阅读说明：本技术 气体传感器 (Gas sensor ) 是由 松仓佑介 北野谷昇治 渡边昌哉 市川大祐 于 2020-01-20 设计创作，主要内容包括：本发明提供在被检测气氛的湿度较大地变化时也能高精度测量出被检测气体浓度的气体传感器。其具有：第1气体检测元件和第2气体检测元件、第1容纳部、第2容纳部、第1膜体,其由使水蒸气透过且不使被检测气体透过的原材料形成以及运算部。气体传感器具有第2膜体,其由与第1膜体同种类的原材料形成。所述第2膜体包括连通孔。在气体传感器中,在水蒸气浓度为2体积％的状态下使被检测气体浓度在25℃的温度条件下从0％快速变化为2％时,被检测气体的响应时间为3秒以内,且在不含被检测气体的状态下使水蒸气浓度在60℃的温度条件下从2体积％快速变化为18体积％时,第1内部空间和第2内部空间之间的水蒸气浓度之差为7体积％以下。(The invention provides a gas sensor capable of measuring the concentration of a gas to be detected with high accuracy even when the humidity of the atmosphere to be detected changes greatly. It has the following components: the gas detection device comprises a1 st gas detection element, a 2 nd gas detection element, a1 st accommodating part, a 2 nd accommodating part and a1 st membrane body, wherein the 1 st gas detection element, the 2 nd accommodating part and the 1 st membrane body are made of raw materials which allow water vapor to permeate through and do not allow detected gas to permeate through, and a calculation part. The gas sensor has a 2 nd film body formed of the same kind of raw material as the 1 st film body. The 2 nd membrane body includes a communicating hole. In the gas sensor, when the concentration of the gas to be detected is rapidly changed from 0% to 2% under a temperature condition of 25 ℃ in a state where the concentration of water vapor is 2% by volume, the response time of the gas to be detected is within 3 seconds, and when the concentration of water vapor is rapidly changed from 2% to 18% by volume under a temperature condition of 60 ℃ in a state where the gas to be detected is not contained, the difference in the concentration of water vapor between the 1 st internal space and the 2 nd internal space is 7% by volume or less.)

1. A gas sensor, having:

a pair of a1 st gas detection element and a 2 nd gas detection element of a heat conduction type;

a1 st housing part having a1 st internal space in which the 1 st gas detection element is disposed, and having a1 st opening connecting the 1 st internal space and an outside exposed to a detected atmosphere;

a 2 nd housing part having a 2 nd internal space in which the 2 nd gas detection element is disposed, and having a 2 nd opening part connecting the 2 nd internal space and the outside;

a1 st film body made of a material that transmits water vapor and does not substantially transmit a gas to be detected, the 1 st film body being disposed so as to close the 1 st opening; and

a calculation unit that calculates a concentration of the gas to be detected contained in the atmosphere to be detected that enters the 2 nd internal space, based on outputs from the 1 st gas detection element and the 2 nd gas detection element,

in the gas sensor,

a 2 nd film body formed of the same kind of material as the 1 st film body and having a thickness larger than that of the 1 st film body, the 2 nd film body being disposed so as to close the 2 nd opening,

the 2 nd film body includes a communication hole penetrating in a thickness direction so as to communicate the outside with the 2 nd internal space,

when the concentration of a gas to be detected contained in the atmosphere to be detected is rapidly changed from 0% to 2% under a temperature condition of 25 ℃ in a state where the concentration of water vapor in the atmosphere to be detected is 2% by volume, the response time of the gas to be detected is within 3 seconds, and when the concentration of water vapor contained in the atmosphere to be detected is rapidly changed from 2% to 18% by volume under a temperature condition of 60 ℃ in a state where the atmosphere to be detected is free from the gas to be detected, the difference in water vapor concentration between the 1 st internal space and the 2 nd internal space is 7% by volume or less.

2. The gas sensor according to claim 1,

the gas to be detected is hydrogen gas,

the difference in water vapor concentration between the 1 st internal space and the 2 nd internal space is 6300ppm or less in terms of hydrogen gas concentration.

3. The gas sensor according to claim 2,

the difference in the water vapor concentration is 6300ppm or less in terms of the hydrogen gas concentration and is calculated by the calculating unit.

Technical Field

The present invention relates to a gas sensor.

Background

As a gas sensor for detecting a combustible gas such as hydrogen gas or methane, a gas sensor capable of suppressing the influence of moisture (i.e., humidity) is known (see patent document 1). In the gas sensor of patent document 1, a gas detection element for inspection is disposed in one space that is open to a detection atmosphere (gas to be inspected), and a gas detection element for reference is disposed in the other space that has an opening portion covered with a film body that transmits water vapor contained in the detection atmosphere but does not transmit the detection gas. The humidity conditions of the pair of gas detection elements are the same as each other, and therefore, the gas sensor can detect gas without being affected by humidity.

Disclosure of Invention

Problems to be solved by the invention

Depending on the environment in which the gas sensor is used, a large amount of water vapor may be generated, and the humidity may be rapidly increased by the water vapor. In such a gas sensor, when the humidity of the atmosphere to be detected changes greatly, the humidity in the space open to the atmosphere to be detected can change immediately in accordance with the change in the humidity of the atmosphere to be detected. On the other hand, the water vapor is not directly introduced into the space where the opening is covered with the film body, but is introduced through the inside of the film body. Therefore, the humidity in the space where the opening is covered with the film body cannot be changed immediately in accordance with the change in the humidity of the atmosphere to be detected, but changes later than the change in the humidity of the atmosphere to be detected. As a result, a large difference may occur between the humidity (i.e., the water vapor concentration) in the two spaces in which the pair of gas inspection elements are arranged. When such a large humidity difference occurs, the influence of water vapor detected by the gas detection element for inspection cannot be ignored in the gas sensor therebetween, and as a result, the concentration of the gas to be detected cannot be accurately measured.

The invention aims to provide a gas sensor which can measure the concentration of a detected gas with high precision even under the condition that the humidity of the detected atmosphere is changed greatly.

Means for solving the problems

The means for solving the problems is as follows,

<1> a gas sensor having: a pair of a1 st gas detection element and a 2 nd gas detection element of a heat conduction type; a1 st housing part having a1 st internal space in which the 1 st gas detection element is disposed, and having a1 st opening connecting the 1 st internal space and an outside exposed to a detected atmosphere; a 2 nd housing part having a 2 nd internal space in which the 2 nd gas detection element is disposed, and having a 2 nd opening part connecting the 2 nd internal space and the outside; a1 st film body made of a material that transmits water vapor and does not substantially transmit a gas to be detected, the 1 st film body being disposed so as to close the 1 st opening; and a calculation unit that calculates a concentration of the gas to be detected contained in the atmosphere to be detected that has entered the 2 nd internal space based on outputs from the 1 st gas detection element and the 2 nd gas detection element, wherein the gas sensor includes a 2 nd film body formed of the same material as the 1 st film body and having a thickness larger than a thickness of the 1 st film body, the 2 nd film body being disposed so as to close the 2 nd opening, the 2 nd film body including a communication hole that penetrates in a thickness direction so as to communicate the outside with the 2 nd internal space, and a response time of the gas to be detected is within 3 seconds when a concentration of the gas to be detected contained in the atmosphere to be detected is rapidly changed from 0% to 2% under a temperature condition of 25 ℃ in a state in which a water vapor concentration of the atmosphere to be detected is 2 vol%, and when the concentration of water vapor contained in the atmosphere to be detected is rapidly changed from 2 vol% to 18 vol% under a temperature condition of 60 ℃ in a state where the atmosphere to be detected does not contain the gas to be detected, the difference in water vapor concentration between the 1 st internal space and the 2 nd internal space is 7 vol% or less.

<2> the gas sensor according to <1>, wherein the gas to be detected is hydrogen gas, and a difference in water vapor concentration between the 1 st internal space and the 2 nd internal space is 6300ppm or less in terms of hydrogen gas concentration.

<3> the gas sensor according to <2>, wherein the difference in the water vapor concentration is 6300ppm or less in terms of the hydrogen gas concentration is calculated by the calculation unit.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a gas sensor capable of measuring the concentration of a gas to be detected with high accuracy even when the humidity of the atmosphere to be detected changes greatly.

Drawings

Fig. 1 is a sectional view schematically showing the structure of a gas sensor according to embodiment 1.

Fig. 2 is a partially enlarged sectional view schematically showing the structure of the gas sensor in the vicinity of the 1 st housing part and the 2 nd housing part.

Fig. 3 is a plan view schematically showing the structure of the 1 st gas detection element included in the gas sensor.

Fig. 4 is a sectional view taken along line a-a of fig. 3.

Fig. 5 is a schematic circuit diagram of the gas sensor.

Fig. 6 is an explanatory view schematically showing the contents (before switching) of the detected gas response test.

Fig. 7 is an explanatory view schematically showing the contents of the detected gas response test (after switching).

Fig. 8 is a graph showing the results of the test for gas response.

Fig. 9 is a partially enlarged cross-sectional view schematically showing the structures of the 1 st and 2 nd housing parts of the gas sensor for the humidity transition test.

Fig. 10 is an explanatory view schematically showing the contents of the humidity transition test.

Fig. 11 is a graph showing the results of the humidity transition test.

FIG. 12 is a graph showing the results of the humidity transition tests of test Nos. 1 to 4.

FIG. 13 is a graph showing the results (hydrogen concentration conversion) of the humidity transition tests of test Nos. 1 to 4.

Fig. 14 is a graph showing the results of the humidity transition tests of test numbers 2 and 5.

Fig. 15 is a graph showing the results of the humidity transition tests (hydrogen concentration conversion) of test nos. 2 and 5.

Fig. 16 is a graph showing the results of the humidity transition tests of test nos. 3 and 6.

Fig. 17 is a graph showing the results of the humidity transition tests (hydrogen concentration conversion) of test nos. 3 and 6.

FIG. 18 is a graph showing the results of the humidity transition tests of test Nos. 7 to 11.

FIG. 19 is a graph showing the results (hydrogen concentration conversion) of the humidity transition tests of test Nos. 7 to 11.

FIG. 20 is a graph showing the results of the hydrogen response tests of test Nos. 7 to 11.

Description of the reference numerals

1. A gas sensor; 2. 1 st gas detection element; 3. a 2 nd gas detecting element; 4. the 1 st accommodating part; 4A, 1 st inner space; 4B, the 1 st opening; 4C, the 1 st membrane body; 5. the 2 nd accommodating part; 5A, 2 nd inner space; 5B, the 2 nd opening part; 5C, the 2 nd film body; 5C1, communication hole; 6. a housing; 7. a base; 8. a protective cover; 10. a circuit substrate; 11. a sealing member; 12. an arithmetic unit.

Detailed Description

[ embodiment mode 1 ]

Embodiment 1 of the present invention will be described below with reference to fig. 1 to 5. Fig. 1 is a cross-sectional view schematically showing the structure of a gas sensor 1 according to embodiment 1, and fig. 2 is a partially enlarged cross-sectional view schematically showing the structure of the vicinity of a1 st housing part 4 and a 2 nd housing part 5 of the gas sensor 1. The gas sensor 1 is a device for detecting hydrogen gas (detected gas) in a detected atmosphere. As shown in fig. 1 and 2, the gas sensor 1 mainly includes a1 st gas detection element 2, a 2 nd gas detection element 3, a1 st housing unit 4, a 2 nd housing unit 5, a case 6, a circuit board 10, and a calculation unit 12.

The 1 st gas detection element 2 is a heat conduction type detection element having a heating resistor whose resistance value changes according to a temperature change of the heating resistor itself. The 1 st gas detection element 2 is used as a detection element on the reference side not exposed to the gas to be detected. Fig. 3 is a plan view schematically showing the structure of the 1 st gas detection element 2 included in the gas sensor 1, and fig. 4 is a cross-sectional view taken along line a-a of fig. 3. As shown in fig. 3 and 4, the 1 st gas detection element 2 includes a heating resistor 20, an insulating layer 21, a wiring 22, a pair of 1 st electrode pads 23A and 23B, and a substrate 26.

The heating resistor 20 is a conductor patterned in a spiral shape, and is embedded in the center of the insulating layer 21. The heating resistor 20 is electrically connected to the 1 st electrode pads 23A and 23B via the wiring 22.

The 1 st electrode pads 23A, 23B of the 1 st gas detection element 2 are formed on the surface of the insulating layer 21. One of the 1 st electrode pads 23A and 23B is connected to one of the 2 nd electrode pads (not shown) provided in the 2 nd gas detection element 3 (described later). As shown in fig. 4, a substrate 26 made of silicone is laminated on the surface of the insulating layer 21 on the side opposite to the 1 st electrode pads 23A and 23B. The substrate 26 is not present in the region where the heating resistor 20 is disposed. This region is a recess 27 exposing the insulating layer 21, constituting a diaphragm structure.

The heating resistor 20 is a member whose resistance value changes due to its temperature change, and is made of a conductive material having a high resistance temperature coefficient. Platinum (Pt), for example, is used as the material of the heating resistor 20.

The insulating layer 21 may be formed of a single material, or may be formed of a plurality of layers using different materials. Examples of the insulating material constituting the insulating layer 21 include silicon dioxide (SiO)₂) Silicon nitride (Si)₃N₄) And the like.

The 2 nd gas detection element 3 is a heat conduction type detection element having a heating resistor 30 (see fig. 5) as in the 1 st gas detection element 2, and the resistance value of the heating resistor 30 changes due to a change in the temperature thereof. The 2 nd gas detection element 3 is exposed to the gas to be detected and used as an inspection-side detection element for inspecting the gas to be detected. The 2 nd gas detection element 3 includes the heating resistor 30, the insulating layer, the wiring, the pair of 2 nd electrode pads, and the substrate, as in the 1 st gas detection element 2, but these are not illustrated. One of the 2 nd electrode pads is grounded. It is preferable that the heating resistor 20 of the 1 st gas detection element 2 and the heating resistor 30 (see fig. 5) of the 2 nd gas detection element 3 have the same resistance value.

The 1 st housing part 4 is a box-shaped portion that is formed by a base 7 and a protective cover 8 and is open in one direction, and the 1 st housing part 4 has a1 st internal space 4A in which the 1 st gas detection element 2 is disposed, and a1 st opening 4B that connects the 1 st internal space 4A and the outside of the 1 st housing part 4 (internal space 6C described later) exposed to the atmosphere to be detected. Further, similarly to the 1 st housing part 4, the 2 nd housing part 5 is a box-shaped portion which is formed by a base 7 and a protective cover 8 which will be described later and is open in one direction, and the 2 nd housing part 5 has a 2 nd internal space 5A in which the 2 nd gas detection element 3 is disposed and a 2 nd opening part 5B which connects the 2 nd internal space 5A and the outside of the 2 nd housing part 5 (an internal space 6C which will be described later) exposed to the atmosphere to be detected. The 1 st and 2 nd accommodating portions 4 and 5 are formed by attaching the protective cover 8 to the base 7 in a covering manner.

The base 7 has: a recess 7a having an opening 7a1 that opens in one direction and on which the 1 st gas detection element 2 is placed; and a concave portion 7b having an opening portion 7b1 that opens in one direction and is used for disposing the 2 nd gas detection element 3. The two recesses 7a, 7b are arranged adjacent to each other. The base 7 is provided on the surface of the circuit board 10. The base 7 is made of insulating ceramic. Examples of suitable insulating ceramics constituting the susceptor 7 include alumina, aluminum nitride, and zirconia. In the present embodiment, the base 7 is made of the same insulating ceramic as the protective cover 8.

The protective cover 8 is bonded to the base 7 so as to cover the 1 st gas detection element 2 and the 2 nd gas detection element 3 placed in the two concave portions 7a and 7 b.

The material of the protective cover 8 is insulating ceramic. Examples of suitable insulating ceramics constituting the protective cover 8 include alumina. As described above, in the present embodiment, the base 7 and the protective cover 8 are made of the same insulating ceramic.

The base 7 and the protective cover 8 are bonded together by an insulating adhesive. As the insulating adhesive, an insulating adhesive containing a thermosetting resin, a thermoplastic resin, an ultraviolet curable resin, or the like as a main component can be used. Among these, from the viewpoint of improving the adhesion between the base 7 and the protective cover 8, an insulating adhesive containing a thermosetting resin as a main component is preferable. Specific examples of the thermosetting resin include epoxy resins. The term "main component" means a component contained in the insulating adhesive by 80 mass% or more.

The protective cover 8 has a1 st opening 4B serving as a gas inlet/outlet for the 1 st housing part 4 and a 2 nd opening 5B serving as a gas inlet/outlet for the 2 nd housing part 5. The protective cover 8 has a main body portion 8A, and the main body portion 8A includes a portion having a constant thickness and abuts against the opening portion 7a1 of the recess 7a and the opening portion 7b1 of the recess 7b, respectively. The body 8A is formed with a1 st opening 4B and a 2 nd opening 5B penetrating in the thickness direction.

The 1 st opening 4B is opened from the outside to the inside (the recess 7a side) of the 1 st housing part 4 with the same size. Similarly to the 1 st opening 4B, the 2 nd opening 5B is also opened from the outside to the inside (the recess 7B) of the 2 nd housing part 5 with the same size. The opening area of the 1 st opening 4B and the opening area of the 2 nd opening 5B are set to be the same size.

In this specification, the 1 st internal space 4A of the 1 st housing part 4 includes a space surrounded by one of the recesses 7a of the base 7 and the main body part 8A of the protective cover 8 and a space located inside the 1 st opening 4B continuous with the space. The 2 nd internal space 5A of the 2 nd accommodating portion 5 includes a space surrounded by the other recess 7B of the base 7 and the main body portion 8A of the protective cover 8, and a space located inside the 2 nd opening 5B continuous with the space. In the case of the present embodiment, the 1 st internal space 4A and the 2 nd internal space 5A are set to be the same size (volume) as each other.

The 1 st and 2 nd accommodating parts 4 and 5 are provided adjacent to each other so as to share 1 wall as shown in fig. 2. The 1 st internal space 4A located inside the 1 st housing part 4 and the 2 nd internal space 5A located inside the 2 nd housing part 5 are in a state of being close to each other. Therefore, the temperature difference between the 1 st internal space 4A and the 2 nd internal space 5A is reduced. With the gas sensor 1 having such a configuration, the output variation due to the temperature change is reduced, and the error in the sensor output can be suppressed.

The 1 st membrane 4C is a membrane made of a material (solid polymer electrolyte) having a property of transmitting water vapor and substantially not transmitting a gas to be detected (a combustible gas such as hydrogen gas or methane gas). In the present specification, "substantially impermeable" means that the amount of gas (hydrogen gas or the like) to be detected that has passed through is 50 min to 1 min of water vapor on a volume basis. As shown in fig. 2, the 1 st film 4C is a film having a predetermined thickness (constant thickness), and is fixed to the main body 8A of the protective cover 8 with an adhesive or the like so as to close the 1 st opening 4B as a whole. The main body 8A of the protective cover 8 is provided with two recesses 8A, 8b that open to the outside (an internal space 6C described later), and the 1 st film body 4C is attached to the main body 8A so as to be accommodated in one of the recesses 8A.

A fluororesin-based ion-exchange membrane can be applied to the 1 st membrane 4C. Specifically, for example, Nafion (registered trademark), Flemion (registered trademark), Aciplex (registered trademark), and the like can be given. Further, as the 1 st membrane 4C, a hollow fiber membrane capable of separating the gas to be detected and the water vapor may be used.

The 1 st film body 4C can allow moisture (water vapor) contained in the atmosphere to be detected located outside the 1 st housing part 4 (the internal space 6C described later) to pass through toward the 1 st internal space 4A. The 1 st film body 4C can also transmit moisture (water vapor) in the 1 st internal space 4A toward the outside of the 1 st housing part 4.

Further, a catalyst layer 14 for oxidizing the gas to be detected (hydrogen gas or the like) is laminated on the 1 st membrane 4C of the present embodiment. The catalyst layer 14 is laminated on the surface of the 1 st membrane 4C on the 1 st internal space 4A side. The catalyst layer 14 also has a function of allowing water vapor to pass therethrough.

The 2 nd film 5C is formed of the same kind of material (solid polymer electrolyte) as the 1 st film 4C. The 2 nd film body 5C is formed of a film body having a thickness larger than that of the 1 st film body 4C. The 2 nd film body 5C has a constant thickness. As a specific material of the 2 nd film 5C, a material exemplified as a material of the 1 st film 4C can be used. Similarly to the 1 st membrane 4C, the 2 nd membrane 5C also has a property of transmitting water vapor and substantially not transmitting a gas to be detected (a combustible gas such as hydrogen gas or methane gas).

The 2 nd film body 5C has a humidity control function of absorbing and releasing moisture (water vapor) according to humidity. The greater the thickness of the 2 nd film body 5C, the greater the effect (humidity control effect) is obtained. In addition, the 2 nd film 5C has a larger thickness than the 1 st film 4C, and therefore, the effect of the humidity control function can be remarkably exhibited.

As shown in fig. 2, the 2 nd film 5C is fixed to the main body 8A of the protective cover 8 with an adhesive or the like so as to close the entire 2 nd opening 5B. The 2 nd film body 5C is attached to the main body portion 8A so as to be housed in the other recess portion 8b provided in the main body portion 8A.

The 2 nd film body 5C has a communication hole 5C1, and the communication hole 5C1 communicates between the outside of the 2 nd container 5 (the internal space 6C described later) exposed to the atmosphere to be detected and the 2 nd internal space 5A, and penetrates in the thickness direction. The 2 nd film 5C is attached to the main body 8A of the protective cover 8 so that the communication hole 5C1 communicates with the 2 nd opening 5B. The communication hole 5C1 is a hole having a size such that the 2 nd internal space 5A of the 2 nd housing unit 5 can be seen from the outside, and can directly introduce the gas to be detected and the water vapor contained in the atmosphere to be detected from the outside of the 2 nd housing unit 5 into the 2 nd internal space 5A. Conversely, the communication hole 5C1 can discharge the gas to be detected and the water vapor in the 2 nd internal space 5A to the outside of the 2 nd accommodating portion 5. In the present embodiment, the opening area of the communication hole 5C1 is smaller than the opening area of the 2 nd opening 5B. The communication hole 5C1 of the present embodiment has a circular opening in plan view, and is formed to have the same size in the thickness direction. The communication hole 5C1 is disposed substantially at the center of the 2 nd opening 5B in plan view. In a plan view, the 2 nd opening 5B overlaps the 2 nd film body 5C at a portion not overlapping the communication hole 5C 1.

In the case of the 2 nd film body 5C, the water vapor between the outside of the 2 nd container 5 and the 2 nd internal space 5A can be introduced and withdrawn through the communication hole 5C1, and can be introduced and withdrawn through the inside of the 2 nd film body 5C. That is, the 2 nd film body 5C can transmit the water vapor located outside the 2 nd accommodating portion 5 toward the 2 nd internal space 5A, and can transmit the water vapor located in the 2 nd internal space 5A toward the outside of the 2 nd accommodating portion 5.

The case 6 is a member for housing the 1 st housing part 4 and the 2 nd housing part 5. The case 6 has an opening 6A for introducing a detection atmosphere containing a detection target gas into the inside, and a filter 6B disposed in the opening 6A.

Specifically, the 1 st and 2 nd accommodating portions 4 and 5 (i.e., the base 7 and the protective cover 8) are accommodated in an internal space 6C, and the internal space 6C is provided between the housing 6 and the circuit board 10. The circuit board 10 is fixed to the inner frame 6D protruding into the housing 6 through the sealing member 11, thereby forming the internal space 6C. That is, the internal space 6C is a space surrounded by the case 6, the circuit board 10, and the sealing member 11 that fixes the case 6 and the circuit board 10.

In addition, the opening 6A is formed to communicate the atmosphere to be detected with the internal space 6C. That is, the outer sides of the 1 st and 2 nd accommodating parts 4 and 5 are exposed to the atmosphere to be detected. The atmosphere to be detected introduced from the opening 6A into the internal space 6C is supplied to both the 1 st internal space 4A and the 2 nd internal space 5A.

The filter 6B is a water-repellent filter that allows the gas to be detected and the like to pass therethrough but does not allow liquid water to pass therethrough (i.e., removes water droplets contained in the gas to be detected). The filter 6B can suppress the entry of water droplets and other foreign matter into the internal space 6C from the opening 6A. In the present embodiment, the filter 6B is attached to the inner surface of the housing 6 so as to close the opening 6A.

Fig. 5 is a schematic circuit diagram of the gas sensor 1. The circuit board 10 is a plate-shaped board disposed in the case 6, and has a circuit shown in fig. 5. The circuit is electrically connected to the 1 st electrode pads 23A and 23B of the 1 st gas detection element 2 and the 1 st electrode pad of the 2 nd gas detection element 3.

The calculation unit 12 calculates the concentration of the gas to be detected contained in the atmosphere to be detected entering the 2 nd internal space 5A based on the respective outputs from the 1 st gas detection element 2 and the 2 nd gas detection element 3. Specifically, as shown in fig. 5, the calculation unit 12 calculates the concentration from the potential between the heating resistor 20 of the 1 st gas detection element 2 and the heating resistor 30 of the 2 nd gas detection element 3 when a constant voltage Vcc is applied to the heating resistor 20 of the 1 st gas detection element 2 and the heating resistor 30 of the 2 nd gas detection element 3 connected in series.

More specifically, the calculation unit 12 obtains the potential difference Vd obtained by amplifying, by the operational amplifier circuit, the potential difference between the potential between the heating resistor 20 of the 1 st gas detection element 2 and the heating resistor 30 of the 2 nd gas detection element 3 and the potential between the fixed resistor R3 and the fixed resistor R4 arranged in parallel with the heating resistors 20 and 30. Then, the computing unit 12 calculates the concentration D of the gas to be detected (hydrogen gas) from the potential difference Vd and outputs the calculated concentration D.

Further, a current is supplied from the dc power supply 40 to the arithmetic unit 12 and the circuit board 10. The dc power supply 40 applies a voltage to the heating resistor 20 of the 1 st gas detection element 2 and the heating resistor 30 of the 2 nd gas detection element 3.

The gas sensor 1 of the present embodiment sets the response time of the gas to be detected to be within 3 seconds when the response test of the gas to be detected is performed. The test gas response test is a test in which the concentration of a test gas (for example, hydrogen gas concentration) contained in a test atmosphere is rapidly changed from 0% to 2% under a temperature condition of 25 ℃ in a state where the water vapor concentration of the test atmosphere is 2% by volume, and the response time Y (seconds) of the gas sensor 1 to the test gas is measured. In the gas sensor 1, for example, the size (particularly, the opening area) of the communication hole 5C1 of the 2 nd membrane 5C is appropriately adjusted so that the response time Y (second) is within 3 seconds. The details of the test for the response of the gas to be detected will be described later.

In the gas sensor 1, when the humidity transition test is performed, the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A (the maximum water vapor concentration difference X) is set to 7 vol% or less. The humidity transition test is a test in which the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A is measured by rapidly changing the water vapor concentration contained in the atmosphere to be detected from 2 vol% to 18 vol% under the temperature condition of 60 ℃ in a state in which the atmosphere to be detected does not contain a gas to be detected (for example, hydrogen gas). In the gas sensor 1, for example, the thickness of the 2 nd film 5C, the size (particularly, the opening area) of the communication hole 5C1 of the 2 nd film 5C, the thickness of the 1 st film 4C, and the like are appropriately adjusted so that the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A (the maximum water vapor concentration difference X) is 7 vol% or less. The humidity transition test will be described in detail later.

When the humidity transition test is performed in the case where the gas to be detected is hydrogen gas, the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A is preferably 6300ppm or less in terms of hydrogen gas concentration. The value obtained by converting the hydrogen concentration (converted hydrogen concentration) is a value outputted from the calculation unit 12 after the calculation unit 12 calculates the difference between the water vapor concentrations.

The gas sensor 1 of the present embodiment having the above-described configuration can accurately measure the concentration of the gas to be detected (hydrogen gas concentration or the like) even when a large amount of water vapor or the like is generated around the gas sensor 1 and the humidity of the atmosphere to be detected changes greatly from a low state to a high state. The principle thereof is explained below.

In the case where the water vapor concentration in the atmosphere to be detected changes greatly from a low state to a high state (for example, in the case where the water vapor concentration in the atmosphere to be detected changes from 2% by volume to 18% by volume under the temperature condition of 60 ℃), in the 1 st internal space 4A of the 1 st housing unit 4 for housing the 1 st gas sensor element 2 on the reference side, the water vapor in the atmosphere to be detected located outside the 1 st housing unit 4 passes through the 1 st film body 4C and the 1 st opening 4B, and enters the 1 st internal space 4A. As a result, the water vapor concentration in the 1 st internal space 4A becomes higher than that before the entrance. Moreover, the gas to be detected in the atmosphere to be detected substantially cannot pass through the 1 st film body 4C, and the gas to be detected is prevented from entering the 1 st internal space 4A.

Further, as described above, when the water vapor concentration in the atmosphere to be detected greatly changes from a low state to a high state, in the 2 nd internal space 5A of the 2 nd housing part 5 for housing the 2 nd gas detection element 3 on the detection side, the water vapor in the atmosphere to be detected located outside the 2 nd housing part 5 mainly passes through the communication hole 5C1 provided in the 2 nd film 5C and the 2 nd opening 5B, and directly enters the 2 nd internal space 5A. It is expected that the amount of water vapor passing through the communication hole 5C1 is larger than the amount of water vapor passing through the 1 st membrane 4C. However, since the 2 nd film body 5C of the present embodiment has a humidity control function according to the thickness thereof as described above, the water vapor concentration in the 2 nd internal space 5A is adjusted so as not to become excessively higher than the water vapor concentration in the 1 st internal space 4A by appropriately absorbing the water vapor or the like entering the 2 nd internal space 5A with the 2 nd film body 5C. The gas to be detected in the atmosphere to be detected passes through the communication hole 5C1 provided in the 2 nd film 5C and the 2 nd opening 5B, and directly enters the 2 nd internal space 5A.

As described above, the gas sensor 1 of the present embodiment can accurately measure the concentration of the gas to be detected (hydrogen gas concentration, etc.) even when a large amount of water vapor or the like is generated around the gas sensor and the humidity of the atmosphere to be detected changes greatly from a low state to a high state. Further, the gas sensor 1 of the present embodiment can measure the concentration of the gas to be detected (hydrogen gas concentration, etc.) with high accuracy even when the humidity of the atmosphere to be detected changes greatly from a high state to a low state.

The gas sensor 1 of the present embodiment is used, for example, by being installed in an engine room (e.g., a hood back surface) of an automobile.

Next, the detected gas response test will be described with reference to fig. 6 to 8. The test gas response test is a test in which the concentration of a test gas (for example, hydrogen gas concentration) contained in a test atmosphere is rapidly changed from 0% to 2% under a temperature condition of 25 ℃ in a state where the water vapor concentration of the test atmosphere is 2% by volume, and the response time Y of the gas sensor 1 to the test gas is measured. In the test of response to gas to be detected, the gas sensor 1 was used in which the opening area of the reference-side 1 st opening 4B and the opening area of the inspection-side 2 nd opening 5B were set to 3.4mm²(1.7mm × 2.0mm), and the volume of the 1 st internal space 4A on the reference side and the volume of the 2 nd internal space 5A on the inspection side are both set to 8.1mm³. The contents of the specific test method are as follows.

Fig. 6 and 7 are explanatory views schematically showing the contents of the test for the response of the gas to be detected, fig. 6 and 7 show a gas sensor 1 provided in a predetermined measurement chamber 100, 2 lines L1, L2 for supplying the gas to the measurement chamber 100, and two three-way valves (electromagnetic valves) 101, 102 for switching the kind of the gas to be supplied to the measurement chamber 100, a line L1 for supplying Air (Air) having a concentration of 0% of the gas to be detected (hydrogen gas in this case), and in contrast, a line L2 for supplying Air (Air) having a concentration of 2% of the gas to be detected (hydrogen gas) is shown in fig. 6, that is, Air (Air) having a concentration of 0% of the gas to be detected (hydrogen gas) is supplied to the measurement chamber 100 by a line L1, and fig. 7 for supplying Air (Air) having a concentration of 2% of the gas to be detected (hydrogen gas) to the measurement chamber 100 by a line L2, and the Air supplied to the measurement chamber 100 is appropriately discharged.

In the detected gas response test, the three-way valves 101 and 102 are switched from a state in which a predetermined amount of air (detected gas concentration: 0%) is supplied to the measurement chamber 100 by the line L1 as shown in fig. 6, and a predetermined amount of air (detected gas concentration: 2%) containing a detected gas is supplied to the measurement chamber 100 by the line L2 as shown in fig. 7, and the detected gas response time Y (seconds) at that time is measured.

Further, during the test of the response of the gas to be detected, the water vapor concentration (absolute humidity) in the measurement chamber 100 was set to 2% by volume, and in addition, the gas flow rates of the line L1 and the line L2 were both set to 5L/min.

Fig. 8 is a graph showing the results of the test for gas response. The vertical axis of fig. 8 represents the sensor output (H) of the gas sensor 1₂As shown in fig. 8, the response time Y (sec) is obtained by using the start point a (sec) and the end point b (sec) shown below, the start point a (sec) is the time (the time at which the sensor output starts to increase) at which the gas sensor 1 starts to react with hydrogen (detected gas) when the three-way valves 101 and 102 are switched from the line L1 to the line L2 as described above, and when the sensor output of the gas sensor 1 is stabilized at a constant value (stabilization point S) in a state where a predetermined gas (hydrogen concentration: 2%) is supplied to the measurement chamber 100 by the line L2 after the switching by the three-way valves 101 and 102, the time (sec) at which the sensor output reaches a value (S × 0.9) of 90% of the stabilized sensor output is the end point b (sec).

Next, the humidity transition test will be described with reference to fig. 9 to 11. The humidity transition test is a test in which the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A is measured by rapidly changing the water vapor concentration contained in the atmosphere to be detected from 2 vol% to 18 vol% under the temperature condition of 60 ℃ in a state in which the atmosphere to be detected does not contain a gas to be detected (for example, hydrogen gas). Fig. 9 is a partially enlarged cross-sectional view schematically showing the structures of the 1 st housing part 4 and the 2 nd housing part 5 of the gas sensor 1T for a humidity transition test. In the humidity transition test, a gas sensor 1T having temperature and humidity sensors 2T and 3T mounted thereon is used instead of the 1 st gas detection element 2 and the 2 nd gas detection element 3 of the gas sensor 1. The temperature/humidity sensors 2T and 3T are constituted by capacitance type semiconductor elements or the like for detecting relative humidity. The basic structure of the gas sensor 1T other than the temperature/humidity sensors 2T and 3T is the same as that of the gas sensor 1 described above. In fig. 9, the same components as those of the gas sensor 1 are denoted by the same reference numerals as those of the gas sensor 1 in the gas sensor 1T, and the description thereof is omitted.

In the gas sensor 1T for the humidity transient test, the opening area of the 1 st opening 4B on the reference side and the opening area of the 2 nd opening 5B on the inspection side are set to 3.4mm in the same manner as in the gas sensor 1 for the detected gas response test described above²(1.7mm × 2.0mm), and the volume of the 1 st internal space 4A on the reference side and the volume of the 2 nd internal space 5A on the inspection side are both set to 8.1mm³。

Fig. 10 is an explanatory view schematically showing the content of the humidity transition test, and fig. 10 shows a gas sensor 1T for the humidity transition test provided in a predetermined measurement chamber 200, a thermostatic bath 201 for housing the gas sensor 1T for the humidity transition test provided in the measurement chamber 200, a line L3 for supplying Air (Air) to the measurement chamber 200, a line L4 for supplying Air (Air) containing water vapor to the measurement chamber 200, a mass flow controller 202 provided in the middle of the line L3 and adjusting the flow rate of the Air (Air) supplied by the line L3, and a mass flow controller 203 provided in the middle of the line L4 and adjusting the flow rate of the Air (Air) containing water vapor supplied by the line L4.

The temperature in the thermostatic bath 201 was set to 60 ℃, the line L3 and the line L4 were connected to each other at positions downstream of the mass flow controllers 202 and 203, respectively, air supplied from the line L3 and having a flow rate adjusted by the mass flow controller 202 and air containing steam supplied from the line 4 and having a flow rate adjusted by the mass flow controller 203 were merged and mixed with each other, and the resulting air was supplied to the measurement chamber 200. by operating each of the mass flow controllers 202 and 203 to appropriately adjust the flow rate of each of the lines L3 and L4, the concentration of steam in the air supplied to the measurement chamber 200 could be adjusted, in this humidity transition test, the gas to be detected (hydrogen gas) was not supplied into the measurement chamber 200, the concentration of the gas to be detected (hydrogen gas concentration) was 0%, the flow rate of the air supplied to the measurement chamber 200 was constant and set to 5L/min, and the air supplied to the measurement chamber 200 was appropriately discharged.

In the humidity transition test, first, air containing water vapor is supplied to the measurement chamber 200 in the thermostatic bath 201 set at 60 ℃ to stabilize the water vapor concentration (absolute humidity) in the measurement chamber 200 at 2 vol%, then, the mass flow controller 203 is operated to change the setting of the flow rate of the line L4 for supplying air containing water vapor to supply air having a water vapor concentration (absolute humidity) of 18 vol% into the measurement chamber 200, and in the humidity transition test, the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A in the gas sensor 1T when the water vapor concentration changes rapidly from the 2 vol% state to the 18 vol% state is measured.

Fig. 11 is a graph showing the results of the humidity transition test. In fig. 11, the vertical axis represents the water vapor concentration (vol%) of the atmosphere to be detected, and the horizontal axis represents time. The water vapor concentration (% by volume) in the air (i.e., the atmosphere to be detected) supplied to the measurement chamber 200 is shown in fig. 11. Fig. 11 shows a difference in concentration of water vapor between the two inner spaces (the 1 st inner space 4A and the 2 nd inner space 5A) by a curve W. Fig. 11 shows the maximum difference X in water vapor concentration between the two internal spaces (the 1 st internal space 4A and the 2 nd internal space 5A). In the humidity transition test, as described above, the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A when the water vapor concentration (% by volume) in the air supplied to the measurement chamber 200 (i.e., the atmosphere to be detected) is rapidly changed from 2% by volume to 18% by volume under the temperature condition of 60 ℃ is measured, and the maximum water vapor concentration difference X (% by volume) is obtained from the measurement result.

[ verification based on thickness difference of No. 2 film ]

Next, the effect of the thickness of the 2 nd film body of the gas sensor 1 on the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A was examined. Specifically, the gas sensors 1T for testing the 1 st film and the 2 nd film having the conditions of the test numbers 1 to 4 shown in table 1 were prepared and subjected to a humidity transition test. The results of the humidity transition test are shown in fig. 12 and 13.

[ TABLE 1 ]

In addition, "kind" in table 1 indicates the kind of raw material constituting the 1 st film body and the 2 nd film body. "type a" in table 1 means a perfluorosulfonic acid membrane (commercially available product) containing a teflon (registered trademark) skeleton having extensibility and a sulfonic acid group. The starting material (commercially available product) having the catalyst layer formed on the perfluorosulfonic acid membrane of type a is referred to as "type a (with catalyst layer)". In tables other than table 1, the types of raw materials constituting the 1 st film body and the 2 nd film body are also shown in the same manner.

In the gas sensor 1 having the 1 st membrane and the 2 nd membrane under each condition of test numbers 1 to 4, a test gas response test using hydrogen gas as a test gas was performed, and the size of the communication hole formed in each of the 2 nd membrane was set so that the response time Y was within 3 seconds. The results of the response times Y of test numbers 1 to 4 are shown in Table 1.

Fig. 12 and 13 are graphs showing the results of the humidity transition tests of test numbers 1 to 4. The vertical axis of fig. 12 represents the difference in water vapor concentration (vol%) between the 1 st internal space 4A and the 2 nd internal space 5A, and the horizontal axis represents time (sec). The vertical axis of fig. 13 shows the sensor output (H) obtained by converting the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A into the hydrogen gas concentration₂ppm), and the horizontal axis represents time (seconds). As shown in fig. 12 and 13, it was confirmed that the thickness of the 2 nd film body on the inspection side was larger than that of the 1 st film body on the reference side, and as the difference between the thicknesses was larger, the difference in water vapor concentration between the 1 st internal space 4A on the reference side and the 2 nd internal space 5A on the inspection side in the humidity transition test was smaller.

[ verification of differences in raw Material based on No. 1 film ]

Next, the influence of the difference in the raw material of the 1 st film body of the gas sensor 1 on the difference in the water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A was verified. Specifically, the gas sensors 1T for testing the 1 st film and the 2 nd film having the conditions of the test numbers 2 and 5 shown in table 2 were prepared and subjected to the humidity transition test. Test No. 2 is the same as test No. 2 described above. The results of the humidity transition test are shown in fig. 14 and 15.

[ TABLE 2 ]

"type B" in table 2 refers to a perfluorosulfonic acid membrane (Nafion (registered trademark)) manufactured by Du Pont.

In the gas sensor 1 having the 1 st membrane and the 2 nd membrane under the respective conditions of the test numbers 2 and 5, the test gas response test using hydrogen gas as the test gas was performed, and the size of the communication hole formed in each of the 2 nd membrane was set so that the response time Y was within 3 seconds. The results of the response times Y of test numbers 2 and 5 are shown in table 2.

Fig. 14 and 15 are graphs showing the results of the humidity transition tests of test numbers 2 and 5. The vertical axis of fig. 14 represents the difference in water vapor concentration (vol%) between the 1 st internal space 4A and the 2 nd internal space 5A, and the horizontal axis represents time (sec). The vertical axis of fig. 15 shows the sensor output (H) obtained by converting the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A into the hydrogen gas concentration₂ppm), and the horizontal axis represents time (seconds). In test nos. 2 and 5, the thickness of the 1 st film body and the thickness of the 2 nd film body are set to be the same value as each other. In test No. 2 and test No. 5, the types of raw materials constituting the 2 nd film body on the inspection side were different from each other. However, the 2 nd membrane 5C of type A of test No. 2 and the 2 nd membrane 5C of type B of test No. 5 are both one type of fluororesin-based ion exchange membrane, becauseAs shown in fig. 14 and 15, the results of the humidity transition tests were almost the same in test No. 2 and test No. 5.

[ verification based on thickness difference of No. 1 film ]

Next, the effect of the thickness of the 1 st film body 4C of the gas sensor 1 on the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A was examined. Specifically, the gas sensors 1T for testing the 1 st film and the 2 nd film having the conditions of the test numbers 3 and 6 shown in table 3 were prepared and subjected to the humidity transition test. Test No. 3 is the same as test No. 3 described above. The results of the humidity transition test are shown in fig. 16 and 17.

[ TABLE 3 ]

In the gas sensor 1 having the 1 st membrane and the 2 nd membrane under each condition of each test No. 3 and 6, a gas response test using hydrogen gas as a gas to be detected was performed, and the size of the communication hole formed in each 2 nd membrane was set so that the response time Y was within 3 seconds. The results of the response times Y of test numbers 3 and 6 are shown in table 3.

Fig. 16 and 17 are graphs showing the results of the humidity transition tests of test nos. 3 and 6. The vertical axis of fig. 16 represents the difference in water vapor concentration (vol%) between the 1 st internal space 4A and the 2 nd internal space 5A, and the horizontal axis represents time (sec). The vertical axis of fig. 17 shows the sensor output (H) obtained by converting the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A into the hydrogen gas concentration₂ppm), and the horizontal axis represents time (seconds). As shown in fig. 16 and 17, it was confirmed that when the thickness of the reference-side 1 st film body was reduced, the time during which the water vapor (water molecules) moved through the 1 st film body was also shortened, and therefore, if the thickness of the inspection-side 2 nd film body was the same, the difference in water vapor concentration between the reference-side 1 st internal space 4A and the inspection-side 2 nd internal space 5A in the humidity transition test was reduced.

[ verification of connected pore diameter difference based on 2 nd membrane ]

Next, the influence of the size (communication hole diameter) of the communication hole of the 2 nd film body of the gas sensor 1 on the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A was examined. Specifically, the gas sensors 1T for testing the 1 st film and the 2 nd film having the conditions of the test numbers 7 to 11 shown in table 4 were prepared and subjected to the humidity transition test. The results of the humidity transition test are shown in fig. 18 and 19.

In the gas sensor 1 having the 1 st membrane and the 2 nd membrane under each condition of test numbers 7 to 11, a test gas response test (hydrogen response test) using hydrogen as a test gas was performed, and the response time Y was measured. The results of the response times Y of test Nos. 7 to 11 are shown in Table 5 and FIG. 20.

[ TABLE 4 ]

[ TABLE 5 ]

FIGS. 18 and 19 are graphs showing the results of the humidity transition tests of test Nos. 7 to 11. The vertical axis of fig. 18 represents the difference in water vapor concentration (vol%) between the 1 st internal space 4A and the 2 nd internal space 5A, and the horizontal axis represents time (sec). The vertical axis of fig. 19 shows the sensor output (H) obtained by converting the difference in water vapor concentration between the 1 st internal space 4A and the 2 nd internal space 5A into the hydrogen gas concentration₂ppm), and the horizontal axis represents time (seconds). FIG. 20 is a graph showing the results of the hydrogen response tests of test Nos. 7 to 11. The vertical axis of fig. 20 represents the sensor output (H) of the gas sensor 1₂ppm), and the horizontal axis represents time (seconds).

As shown in table 5 and fig. 19 to 20, it was confirmed that the larger the size (communication hole diameter) of the communication hole of the 2 nd film body on the inspection side, the more easily the hydrogen gas enters the 2 nd internal space 5A on the inspection side, and therefore the response time Y of the hydrogen gas becomes shorter, but the difference in water vapor concentration (maximum water vapor concentration difference X) between the 1 st internal space 4A on the reference side and the 2 nd internal space 5A on the inspection side in the humidity transition test becomes larger. That is, it can be understood that the response time Y of hydrogen and the maximum water vapor concentration difference X are a so-called trade-off relationship.

< other embodiment >

The present invention is not limited to the embodiments described above and illustrated in the drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

(1) In the gas sensor 1 of embodiment 1, the communication hole 5C1 formed in the 2 nd film 5C has a circular shape in plan view, but the shape of the communication hole is not particularly limited as long as the object of the present invention is not impaired. The number of the communicating holes formed in the 2 nd film body 5C is not particularly limited as long as it does not depart from the object of the present invention, and may be two or more (plural).

(2) In the gas sensor 1 of embodiment 1 described above, the catalyst layer 14 is formed on the 1 st membrane 4C, but in other embodiments, the 1 st membrane on which the catalyst layer 14 is not formed may be used.

(3) In embodiment 1 described above, the difference in water vapor concentration (maximum water vapor concentration difference X) between the 1 st internal space 4A and the 2 nd internal space 5A is set to 7% by volume or less, but in other embodiments, it may be set to 6.5% by volume or less, or may be set to 6% by volume or less. When the maximum difference X of the water vapor concentration is 6.5 vol% or less, the difference between the water vapor concentrations in the 1 st internal space and the 2 nd internal space is 5900ppm or less in terms of the hydrogen gas concentration, and therefore, the concentration of the gas to be detected can be measured with higher accuracy. Further, if the maximum difference X of the water vapor concentration is 6% by volume or less, the difference between the water vapor concentrations in the 1 st internal space and the 2 nd internal space is 5400ppm or less in terms of the hydrogen gas concentration, and therefore the concentration of the gas to be detected can be measured with further high accuracy.