Electrochemical gas sensor, gas detection device, and gas detection system

Abstract

An electrochemical gas sensor 1 includes: a substrate 10; a gas detection part 2 that is disposed on a first surface 10a of the substrate 10; a cover 40 that covers the gas detection part 2; and a wiring 11 that is connected to the gas detection part 2 and is partially exposed from the cover 40. A connection part 15 that is to be connected to an external wiring or an external terminal is formed at a portion of the wiring 11 exposed from the cover 40.

Description

Electrochemical gas sensor, gas detection device, and gas detection system

[0001] The present disclosure relates to an electrochemical gas sensor, a gas detection device using the sensor, and a gas detection system using the gas detection device.

[0002] Electrochemical gas sensors equipped with a catalytic layer and an electrolyte layer have been known. In electrochemical gas sensors, a working electrode (sensing electrode) made of a catalytic layer and a counter electrode are connected via an external circuit. When a target gas such as carbon monoxide flows into the sensor, an oxidation reaction of carbon monoxide occurs at the working electrode, and the concentration of the gas can be detected by measuring the short-circuit current generated during this reaction.

[0003] Patent Document 1 discloses an electrochemical gas sensor including a polymer solid electrolyte membrane, a sensing electrode, a counter electrode, and a gas diffusion layer. The sensor in Patent Document 1 has a laminated structure in which a sensing electrode is formed on one side of a solid electrolyte membrane and a counter electrode is formed on the other side, and the solid electrolyte membrane is sandwiched between gas diffusion layers. This laminated structure functions as a gas detection unit, and the sensor is constructed by being sandwiched between a sealing body and a metal can.

[0004] International Publication No. 2017 / 047316

[0005] As described above, electrochemical gas sensors generate an electrical signal when they detect a target gas, and this electrical signal must be extracted from the gas detection unit. However, electrochemical gas sensors are required to be small and low-cost, so it is undesirable to use a complex signal extraction structure.

[0006] The electrochemical gas sensor according to the present disclosure comprises a substrate including a first surface and a second surface, a gas detection unit disposed on the first surface of the substrate, a cover covering the gas detection unit, and wiring connected to the gas detection unit and a portion of which is exposed from the cover, wherein the portion of the wiring exposed from the cover has a connection portion formed thereon that is connected to an external wiring or an external terminal.

[0007] A gas detection device according to the present disclosure includes the electrochemical gas sensor and a housing that houses the electrochemical gas sensor.

[0008] A gas detection system according to the present disclosure includes the gas detection device and a receiving device that receives the detection result of the gas detection device.

[0009] According to one aspect of the present disclosure, an electrochemical gas sensor having a simple signal extraction structure can be provided, which can, for example, reduce the size and cost of the sensor. Furthermore, the electrochemical gas sensor according to the present disclosure can be easily attached to a gas detection device such as a smoke detector.

[0010] 15 is a diagram showing a state in which the electrochemical gas sensor of the first embodiment is mounted on a circuit board. FIG. 15 is a perspective view of the electrochemical gas sensor of the first embodiment. FIG. 15 is a cross-sectional view taken along line AA in FIG. 2. FIG. 15 is a cross-sectional view taken along line BB in FIG. 2. FIG. 15 is a diagram showing a modified example of the first embodiment. FIG. 15 is a block diagram showing the configuration of a gas detection system of an example embodiment. FIG. 15 is a cross-sectional view of the electrochemical gas sensor of the second embodiment. FIG. 15 is an exploded perspective view of the electrochemical gas sensor of the second embodiment. FIG. 15 is a diagram for explaining a manufacturing method of the electrochemical gas sensor of the second embodiment. FIG. 15 is a diagram showing a modified example of the second embodiment. FIG. 15 is a diagram showing a modified example of the second embodiment. FIG. 15 is a perspective view of the electrochemical gas sensor of the third embodiment. FIG. 15 is an exploded perspective view of the electrochemical gas sensor of the third embodiment. FIG. 15 is a diagram showing the surface of a substrate on which a detection unit is provided. FIG. 15 is a cross-sectional view taken along line CC in FIG. 15. FIG. 15 is a cross-sectional view taken along line DD in FIG. 15. FIG. 15 is a perspective view of a spring member. FIG. 15 is a perspective view of the first housing as seen from the outer surface side. FIG. 15 is a perspective view of the first housing as seen from the inner surface side. FIG. 15 is a perspective view of the second housing as seen from the outer surface side. FIG. 15 is a perspective view of the second housing as seen from the inner surface side. 1A and 1B are perspective views of the lid as seen from the first surface side and the second surface side, respectively;

[0011] Hereinafter, with reference to the drawings, embodiments of an electrochemical gas sensor, a gas detection device, and a gas detection system according to the present disclosure will be described in detail. Note that the embodiments described below are merely examples, and the present disclosure is not limited thereto. Furthermore, selective combinations of multiple embodiments and variations described below are also included in the present disclosure.

[0012] FIG. 1 is a diagram showing a state in which an electrochemical gas sensor 1 according to a first embodiment is mounted on a circuit board 112. As shown in FIG. 1, the electrochemical gas sensor 1 includes a substrate 10, a gas detection unit 2 (see FIG. 2 described later) disposed on the surface of the substrate 10, and a cover 40 that covers the gas detection unit 2. The electrochemical gas sensor 1 further includes wiring 11 connected to the gas detection unit 2. A portion of the wiring 11 is exposed from the cover 40 and functions as an extraction wiring for a signal generated by the gas detection unit 2. As will be described in detail later, a connection portion 15 is formed on the portion of the wiring 11 exposed from the cover 40, for connection to an external wiring or an external terminal. The wiring 11 is, for example, a conductor layer, specifically a metal layer, formed on the surface of the substrate 10.

[0013] The substrate 10 has a plurality of protrusions 14 protruding from the cover 40. In the example shown in FIG. 1 , the protrusions 14 extend from both longitudinal ends of the cover 40, which has a rectangular shape in a plan view, to the outside of the cover 40. In this specification, "plan view" refers to the electrochemical gas sensor 1 and its components viewed from the first surface 10a (see FIG. 3 ) of the substrate 10. Two protrusions 14 extend from one longitudinal end of the cover 40, and one protrusion 14 extends from the other longitudinal end. The three protrusions 14 are formed parallel to each other along the longitudinal direction of the cover 40, and each protrusion 14 has a wiring 11 and a connection portion 15. The wiring 11 extends along the longitudinal direction of each protrusion 14, and the connection portion 15 is formed at the tip of each protrusion 14.

[0014] The electrochemical gas sensor 1 is attached to a circuit board 112 by utilizing a protrusion 14. The circuit board 112 has conductive pins 113 standing on the surface of the board. The pins 113 are, for example, external terminals electrically connected to other electronic devices that constitute the circuit board 112, and have a generally cylindrical shape. The circuit board 112 also has a recess 114 into which the cover 40 of the electrochemical gas sensor 1 fits. The recess 114 is formed by cutting out an end of the circuit board 112 in a generally U-shape in plan view, and is large enough to accommodate the cover 40.

[0015] The electrochemical gas sensor 1 is mounted on the circuit board 112 by connecting the connection portions 15 formed on the protruding portions 14 to the pins 113. In the example shown in Fig. 1, the connection portions 15 include through holes that are semicircular in plan view, and the pins 113 are inserted into the through holes of the connection portions 15. Three pins 113 are provided on the periphery of the recess 114 so that they can be inserted into the connection portions 15 of the protruding portions 14 when the electrochemical gas sensor 1 is accommodated in the recess 114.

[0016] The connection portion 15 constitutes a part of the wiring 11, and has a conductor layer formed on the periphery and inner surface of the through hole. The conductor layer formed on the inner surface of the connection portion 15 abuts on the outer surface of the pin 113 and is electrically connected to the pin 113. The connection portion 15 and the pin 113 may be soldered. A signal generated by the gas detection unit 2 is transmitted to the connection portion 15 via the wiring 11, and then transmitted to the pin 113 via the connection portion 15.

[0017] Fig. 2 is a perspective view of the electrochemical gas sensor 1. In the example shown in Fig. 2, the connection portion 15 includes a through-hole that is circular in plan view, but the other configurations are the same as those of the example shown in Fig. 1. As shown in Figs. 1 and 2, the through-hole of the connection portion 15 may be semicircular or circular in plan view. The shape of the connection portion 15 can be changed depending on the shape of the external wiring or external terminal to which the signal from the gas detection unit 2 is output, etc.

[0018] 2, the substrate 10 of the electrochemical gas sensor 1 includes a base portion 13 that is rectangular in plan view and on which the gas detection portion 2 is disposed, and three protrusions 14 that protrude from opposing short sides of the base portion 13. The substrate 10 is disposed so that the longitudinal direction of the base portion 13 is parallel to the longitudinal direction of the cover 40. The substrate 10 is substantially flat except for, for example, portions where the gas inlet hole 12 (first gas inlet hole) and the connection portion 15 are formed, and the base portion 13 and each of the protrusions 14 are formed on the same plane.

[0019] In this embodiment, two protrusions 14a and 14b protrude from one short side of the base portion 13, and one protrusion 14c protrudes from the other short side of the base portion 13. As will be described in detail below, the wiring 11a formed on the protrusion 14a functions as a wiring for the working electrode, the wiring 11b formed on the protrusion 14b functions as a wiring for the counter electrode, and the wiring 11c formed on the protrusion 14c functions as a wiring for the reference electrode. Connection portions 15a, 15b, and 15c are formed at the tips of the protrusions 14a, 14b, and 14c, respectively. The protrusions 14a, 14b, and 14c have the same shape and size, but may have different shapes and sizes.

[0020] The protrusions 14a and 14b each protrude from between the center and both ends of one short side of the base portion 13, and the protrusion 14c protrudes from the center of the other short side of the base portion 13. The multiple protrusions 14 protrude in two directions from opposite ends of the cover 40. For example, the multiple protrusions 14 may protrude in three directions from the cover 40, but setting the protrusion directions to two directions makes it easier to connect to the circuit board 112. Note that the protrusions 14a and 14c, or the protrusions 14b and 14c, may protrude in the same direction.

[0021] The cover 40 is composed of a first cover 41 and a second cover 42. Each protrusion 14 of the substrate 10 is sandwiched between the first cover 41 and the second cover 42. Each protrusion 14 protrudes from between the first cover 41 and the second cover 42 to the outside of the cover 40. In this embodiment, the cover 40 covers the entire substrate 10 except for the protrusions 14. The cover 40 covers the entire gas detection unit 2 and also covers the short side surfaces of the substrate 10.

[0022] The first cover 41 and the second cover 42 are hard covers formed in the shape of a rectangular tube with a bottom, and the open ends of the covers are overlapped with the substrate 10 sandwiched between them to form the rectangular parallelepiped cover 40. The first cover 41 and the second cover 42 accommodate the portions of the substrate 10 other than the protrusion 14 and are connected to each other. At least one of the first cover 41 and the second cover 42 has a recess formed therein for the protrusion 14 to pass through. A sealing member for sealing the gap between the cover 40 and the protrusion 14 may be provided, or an adhesive may be applied.

[0023] Fig. 3 is a cross-sectional view taken along line AA in Fig. 2, and Fig. 4 is a cross-sectional view taken along line BB in Fig. 2. As shown in Figs. 3 and 4, the electrochemical gas sensor 1 includes wiring 11 formed on a first surface 10a of a substrate 10, a catalyst layer 20, and an electrolyte layer 30. The substrate 10 has a gas inlet hole 12 that connects the first surface 10a and the second surface 10b. The catalyst layer 20 is formed on the first surface 10a of the substrate 10 so as to cover a portion of the wiring 11 and the gas inlet hole 12. The electrolyte layer 30 is formed on the first surface 10a of the substrate 10 so as to be in contact with the catalyst layer 20.

[0024] The electrochemical gas sensor 1 includes a catalyst layer 20, which is a catalyst layer 20a serving as a working electrode and a catalyst layer 20b serving as a counter electrode. The catalyst layers 20a and 20b are formed on the first surface 10a of the substrate 10 so as not to contact each other. The catalyst layer 20 preferably further includes a catalyst layer 20c serving as a reference electrode. The wiring 11 includes a wiring 11a corresponding to the catalyst layer 20a (working electrode), a wiring 11b corresponding to the catalyst layer 20b (counter electrode), and a wiring 11c (see FIG. 2) corresponding to the reference electrode. Similarly, the wirings 11a, 11b, and 11c are formed on the first surface 10a of the substrate 10 so as not to contact each other.

[0025] In the electrochemical gas sensor 1, a laminated structure including wiring 11 formed directly on the first surface 10a of the substrate 10, a catalyst layer 20, and an electrolyte layer 30 functions as the gas detection unit 2. The catalyst layer 20a, which functions as a working electrode, and the catalyst layer 20b, which functions as a counter electrode, are arranged via the electrolyte layer 30 in an ionically conductive manner and are electrically connected via an external circuit (not shown). The working electrode is an electrode into which the gas to be detected flows and is also called a sensing electrode. The electrolyte layer 30 needs to be in contact with at least a portion of the catalyst layers 20a and 20b. Furthermore, if the catalyst layer 20c is formed, the electrolyte layer 30 needs to be in contact with at least a portion of the catalyst layers 20a, 20b, and 20c.

[0026] As will be described in more detail below, forming the catalyst layer 20 directly on the surface of the substrate 10 on which the wiring 11 and the gas inlet hole 12 are formed, and then forming the electrolyte layer 30 directly on the catalyst layer 20, strengthens the adhesion between the layers that make up the gas detection unit, thereby reducing the contact resistance of the laminated structure. Furthermore, with the electrochemical sensor 1, there is no need to press the gas detection unit 2 to keep the contact resistance low, eliminating the need for special fastening jigs and reducing the variation in contact resistance. This means that the resistance value of the sensor is reduced and stabilized. This results in improved sensor reliability, leading to higher sensitivity, smaller size, and lower cost.

[0027] The electrochemical gas sensor 1 detects the gas concentration by introducing a gas to be detected into the working electrode, oxidizing or reducing the gas molecules on the working electrode, and measuring the change in current or potential associated with this redox reaction. The electrochemical gas sensor 1 may be a potential detection type, but this embodiment illustrates a current detection type sensor. When gas molecules are oxidized or reduced at the working electrode, electrons are generated or consumed, causing a current to flow between the working electrode and the counter electrode. This current value is proportional to the gas concentration, so the gas concentration can be detected by measuring the current value. Ions generated by the redox reaction at the working electrode and the counter electrode migrate between the working electrode and the counter electrode via the electrolyte layer 30.

[0028] As described above, the electrochemical gas sensor 1 includes the catalyst layer 20a functioning as a working electrode, the catalyst layer 20b functioning as a counter electrode, and the catalyst layer 20c functioning as a reference electrode. The reference electrode is an electrode that serves as a reference when controlling and measuring the potential of the working electrode, and is also called a reference electrode. The working electrode is connected to the reference electrode via an external circuit, and is configured to maintain a constant potential relative to the reference electrode via the external circuit. The potential of the working electrode is maintained, for example, at a potential that can oxidize the target gas.

[0029] In the following, carbon monoxide (CO) will be taken as an example of a gas to be detected. However, the sensors to which the configuration of the electrochemical gas sensor according to the present disclosure can be applied are not limited to carbon monoxide sensors. The configuration of the electrochemical gas sensor according to the present disclosure can be widely applied to electrochemical gas sensors using a solid electrolyte membrane, and can be used to detect, for example, hydrogen sulfide (H ２ S), nitric oxide (NO), nitrogen dioxide (NO ２ ), sulfur dioxide (SO ２ ), ozone (O ３ ), ammonia (NH ３ The present invention can also be applied to sensors that detect gases such as HCl, HCl, and HCl.

[0030] When the gas to be detected by the electrochemical gas sensor 1 is CO, an oxidation reaction of CO occurs at the working electrode as shown in formula (1): CO + H ２ O → CO ２ +2H ＋ +2e－ ... (1) The CO that flows into the working electrode reacts with water molecules to form CO ２ and generate protons (H ＋ ) and electrons are generated. The protons move to the counter electrode via the electrolyte layer 30, and the electrons move to the counter electrode via an external circuit. At the counter electrode, the reaction shown in formula (2) occurs. ２ +2H ＋ +2e － →H ２ O... (2) The protons and electrons generated at the working electrode react with oxygen in the air at the counter electrode to produce water. At this time, the current flowing in the external circuit is proportional to the amount of CO flowing into the working electrode, so the CO concentration can be detected by measuring this current.

[0031] The electrochemical gas sensor 1 has a structure in which the interior of the sensor, in which the gas detection unit 2 is formed, is sealed by a cover 40. A first cover 41 constituting the cover 40 is disposed on the first surface 10a of the substrate 10 and entirely covers the catalyst layer 20 and the electrolyte layer 30. A second cover 42 is disposed on the second surface 10b of the substrate 10. The first cover 41 is made of a material with low gas permeability that can block gases such as CO and water vapor, and seals the gas detection unit. The second cover 42 is also made of a material with low gas permeability, but has a gas inlet hole 43 formed in the second cover 42. CO, the gas to be detected, is introduced into the gas detection unit 2 only through the gas inlet hole 43 in the second cover 42 and the gas inlet hole 12 in the substrate 10.

[0032] In the electrochemical gas sensor 1, an internal space is formed between the electrolyte layer 30 and the first cover 41. That is, there is a gap between the gas detection unit 2 and the first cover 41, and the gas detection unit 2 is not pressed by the first cover 41. The electrochemical sensor 1 further includes a humidity control member 60 disposed in this internal space. As described above, in the electrochemical sensor 1, the solid electrolyte membrane needs to contain a certain amount of moisture in order to function, and the amount of moisture in the solid electrolyte membrane needs to be controlled. The humidity control member 60 serves to adjust the amount of moisture contained in the solid electrolyte membrane. The humidity control member 60 serves to adjust the amount of moisture contained in the solid electrolyte membrane.

[0033] The humidity control member 60 is housed in the first cover 41 without contacting the catalyst layer 20 and electrolyte layer 30 that constitute the gas detection unit 2. In this embodiment, the humidity control member 60 is layered on the electrolyte layer, but the humidity control member 60 may be placed in a location where it does not overlap with the electrolyte layer 30, such as around the gas detection unit 2. In addition, a gap exists between the humidity control member 60 and the cover 40. The humidity control member 60 may expand in volume when it absorbs moisture, but if a gap exists between the humidity control member 60 and the cover 40, this gap can absorb the volumetric expansion of the humidity control member 60. As a result, the structure of the sensor is stabilized, leading to improved reliability.

[0034] The electrochemical sensor 1 further includes a breathable partition layer 70 disposed between the electrolyte layer 30 and the humidity control member 60. When the humidity control member 60 is in contact with the electrolyte layer 30, it is difficult to appropriately adjust the amount of moisture contained in the solid electrolyte membrane. By interposing the partition layer 70 between the electrolyte layer 30 and the humidity control member 60, it becomes easier to adjust the amount of moisture contained in the solid electrolyte membrane, leading to improved reliability and sensitivity of the sensor. The partition layer 70 is preferably water vapor permeable.

[0035] The electrochemical gas sensor 1 further includes activated carbon 80 housed within the second cover 42. An internal space exists between the substrate 10 and the second cover 42, and the activated carbon 80 is disposed in this internal space. The activated carbon 80 adsorbs highly polar gases such as SOx and NOx, and allows CO, the target gas to be detected, to pass through. By providing the activated carbon 80 in the CO introduction path and trapping non-target gases, it is possible to further improve reliability and sensitivity.

[0036] The first cover 41 and the second cover 42 accommodate the entire base portion 13 of the substrate 10 and the root portion of the protrusion 14, and are connected to each other. The first cover 41 and the second cover 42 are formed, for example, in the shape of a rectangular tube with a bottom, and are fixed to each other with their open ends overlapping each other using adhesives, screws, a locking structure, or by welding or the like. As shown in FIG. 3 , the first cover 41 and the second cover 42 may sandwich an end along a long side of the base portion 13. Furthermore, a sealing member 50 may be disposed between the substrate 10 and the first cover 41 and the second cover 42.

[0037] The structures of the substrate 10, catalyst layer 20, electrolyte layer 30, cover 40, humidity control member 60, and partition layer 70 that constitute the electrochemical gas sensor 1 will be described in detail below.

[0038] [Substrate] As described above, the substrate 10 is an insulating base material including the base portion 13 on which the gas detection portion 2 is formed and a plurality of protrusions 14 protruding from the base portion 13, and the base portion 13 and the plurality of protrusions 14 are integrally molded. The protrusions 14 are formed parallel to each other and extend in the longitudinal direction of the base portion 13. Each protrusion 14 has a constant width over its entire length and is formed into a rectangular shape in a plan view. The shape of the substrate 10 in a plan view is not particularly limited and can be changed as appropriate depending on the shape of the electrochemical gas sensor 1, etc.

[0039] The substrate 10 has wiring 11 that functions as wiring and a gas inlet hole 12 that connects the first surface 10a and the second surface 10b. The substrate 10 is made of a material similar to that used for conventionally known printed wiring boards, such as epoxy resin or polyphenylene ether. The substrate 10 may be a dedicated substrate for the electrochemical gas sensor 1, or may be a printed wiring board on which other electronic components are mounted. In this embodiment, the substrate 10 functions as a support member for the gas detection unit 2, and the protrusion 14 of the substrate 10 functions as a fixing portion for the circuit board 112.

[0040] The gas inlet holes 12 of the substrate 10 are preferably formed at positions overlapping with the gas detection unit 2, particularly at positions overlapping with the catalyst layer 20a that functions as the working electrode, and function as paths for introducing gas into the catalyst layer 20a. In other words, the catalyst layer 20a is formed in the region of the first surface 10a of the substrate 10 where the gas inlet holes 12 are formed. In this embodiment, the multiple gas inlet holes 12 are formed only at positions overlapping with the catalyst layer 20a. In other words, in the region of the first surface 10a covered by the first cover 41, there are no through holes for wiring such as through holes, and no through holes other than the gas inlet holes 12 are formed.

[0041] The electrochemical gas sensor 1 is configured so that CO flows into the internal space surrounded by the substrate 10 and the first cover 41 only through the gas inlet 12, and the amount of CO acting on the catalyst layer 20a is controlled. Therefore, the CO concentration can be accurately determined from the proportional relationship between the amount of CO inflow and the current value. The gas inlet 12 is, for example, a through-hole that is perfectly circular in plan view.

[0042] The gas introduction holes 12 have a diameter of, for example, 0.05 to 1 mm, or 0.1 to 0.5 mm. There are no particular limitations on the opening area of ​​the gas introduction holes 12, but the opening area is preferably large enough to prevent the material constituting the catalyst layer 20 from flowing into the gas introduction holes 12 when the material is applied to the first surface 10a of the substrate 10. In other words, it is preferable that a large number of gas introduction holes 12 with small opening areas are formed in the substrate 10. However, there is no particular limitation on the number of gas introduction holes 12.

[0043] Wirings 11a, 11b, and 11c are formed on the first surface 10a of the substrate 10 so as to be spaced apart and not to contact each other. A catalyst layer 20a is formed covering a portion of wiring 11a, a catalyst layer 20b is formed covering a portion of wiring 11b, and a catalyst layer 20c serving as a reference electrode is formed covering a portion of wiring 11c. Wirings 11a, 11b, and 11c function as signal extraction wiring that electrically connects each catalyst layer to an external device. Portions of wirings 11a, 11b, and 11c are exposed to the outside of first cover 41 in a plan view of the substrate 10, and connection portions 15 for connecting to an external circuit are formed in the exposed portions.

[0044] The conductor layer constituting the wiring 11 is formed on the first surface 10a of the substrate 10, for example, by forming copper foil over the entire surface of the insulating substrate, pattern-etching the copper foil, and further plating the remaining copper foil. An example of the wiring 11 is a layer in which the surface of copper is plated with nickel / gold, and has a thickness of 5 μm to 30 μm. Note that the wiring 11 may also be formed by other methods such as vapor deposition or printing. While FIGS. 3 and 4 illustrate the wiring 11 as if it were present within the substrate 10 for clarity, in this embodiment, the wiring 11 is formed on the first surface 10a of the substrate 10.

[0045] The connection portion 15 is formed at the tip of the protrusion 14 and has a through-hole that is circular in plan view and penetrates the protrusion 14 in the thickness direction. When the through-hole has a perfect circular shape in plan view, its diameter is, for example, approximately the same as the diameter of the pin 113, and the pin 113 may be press-fitted into the connection portion 15. The connection portion 15 constitutes part of the wiring 11 connected to the gas detection unit 2, and the above-mentioned conductor layer is formed on the opening periphery and inner surface of the through-hole of the connection portion 15. When the conductor layer of the connection portion 15 abuts against the pin 113, the gas detection unit 2 and the pin 113 are electrically connected, and a signal from the gas detection unit 2 can be output to the outside. Note that when the connection portion 15 has a semicircular shape in plan view (see FIG. 1 ), it can be said that a recess that abuts against the outer circumferential surface of the pin 113 is formed at the tip of the protrusion 14.

[0046] [Catalyst Layer] As described above, the catalyst layer 20 is formed directly on the first surface 10a of the substrate 10, which has the wiring 11 and the gas inlet hole 12. The catalyst layer 20 is preferably a coating formed by applying a catalyst material to the first surface 10a. The catalyst layer 20 is formed on the wiring 11, and a portion of the catalyst layer 20 may be formed in an area of ​​the first surface 10a where the wiring 11 is not present. When the catalyst layer 20 is applied to the first surface 10a, the catalyst layer 20 adheres strongly to the first surface 10a. In this embodiment, the electrolyte layer 30 is also applied to the catalyst layer 20, so that the laminated structure of the gas detection unit 2 has strong adhesion. This reduces the resistance of the gas detection unit 2 without the need for strong pressure on the laminated structure, and the resistance value is stabilized. As a result, the reliability of the sensor is improved, and the sensor can be made more sensitive, smaller, and less expensive.

[0047] The thickness of the catalyst layer 20 is, for example, 1 μm to 500 μm, or 10 μm to 200 μm. The catalyst layers 20a, 20b, and 20c constituting the catalyst layer 20 preferably have the same thickness. The catalyst layers 20a, 20b, and 20c are formed apart from one another on the first surface 10a so as not to overlap with one another. Each catalyst layer has, for example, a rectangular shape in plan view, but the shape of each catalyst layer in plan view is not particularly limited.

[0048] The catalyst constituting the catalyst layer 20 promotes the oxidation reaction of CO. The reaction of formula (1) above occurs in the catalyst layer 20a, which is the working electrode. In this embodiment, each catalyst layer is made of the same material. Examples of catalysts include platinum (Pt), palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), iridium (Ir), cobalt (Co), iron (Fe), and nickel (Ni). Among these, it is preferable to use a noble metal catalyst such as Pt or a PtRu alloy.

[0049] The catalyst layer 20 further includes a conductive support and an ionomer. The conductive support is a conductive material that holds the catalyst. Examples of suitable conductive supports include carbon black such as acetylene black and ketjen black, graphite carbon, and carbon materials such as carbon nanotubes. The catalyst is, for example, adhered to the particle surface of the carbon material. The ionomer is an ionically conductive material that allows the movement of protons generated by the reaction. An example of a suitable ionically conductive material is Nafion (registered trademark: manufactured by DuPont), which has the same composition as the electrolyte membrane.

[0050] [Electrolyte Layer] The electrolyte layer 30 is an ion-conducting membrane that transmits ions generated in the catalyst layer 20a to the catalyst layer 20b, and is an electrically insulating membrane that does not have electronic conductivity. The electrolyte layer 30 may be formed, for example, by absorbing a liquid electrolyte into a support member such as a porous sheet, but is preferably a solid electrolyte membrane made of a polymer material. In this embodiment, a proton-conducting solid electrolyte membrane is used. An example of a proton-conducting solid electrolyte membrane is a polymer membrane in which proton-conducting groups such as sulfonic acid groups are introduced into a hydrocarbon-based polymer or a fluorine-based polymer. A commercially available product such as Nafion (registered trademark: manufactured by DuPont) may be used for the electrolyte layer 30.

[0051] The thickness of the electrolyte layer 30 is not particularly limited, but is, for example, 5 μm to 500 μm. The electrolyte layer 30 is preferably disposed so as to cover the entire catalyst layer 20, and a portion of it is formed directly on the first surface 10 a of the substrate 10. The electrolyte layer 30 is, for example, a coating film formed by applying its constituent materials onto the first surface 10 a on which the wiring 11 and catalyst layer 20 are formed. The electrolyte layer 30 has, for example, a rectangular shape in a plan view, but the shape of the electrolyte layer 30 in a plan view is not particularly limited and can be changed as appropriate depending on the shape of the electrochemical gas sensor 1, etc.

[0052] [Cover] As described above, the cover 40 includes the first cover 41 and the second cover 42 and has a rectangular parallelepiped shape as a whole. The first cover 41 prevents gases, including CO and water vapor, from entering the sensor interior and protects the gas detection unit 2 from damage. The first cover 41 is made of a material with low gas permeability that can block gases such as CO and water vapor. While the first cover 41 may be made of a metal material, it is preferably made of a resin material from the standpoints of weight reduction, productivity, etc. Unlike the second cover 42, the first cover 41 does not have a gas inlet hole.

[0053] The first cover 41 may be a flexible thin-film sealing sheet, but is preferably made of a hard resin material. The first cover 41 is, for example, a hard cover formed in the shape of a bottomed rectangular tube, and is placed on the first surface 10a of the substrate 10 so as to cover the gas detection unit 2 from above. A gap (internal space) is formed between the first cover 41 and the gas detection unit 2 in the thickness direction of the substrate 10, and this internal space serves as an accommodation space for the humidity control member 60. In this embodiment, the first cover 41 is larger than the base portion 13 of the substrate 10, and the entire first surface 10a of the base portion 13 is covered by the first cover 41.

[0054] The second cover 42 covers the second surface 10b of the substrate 10, including the portion where the gas introduction holes 12 are formed. The second cover 42 preferably covers all of the gas introduction holes 12, forming an internal space between the second cover 42 and the second surface 10b. The second cover 42 has a second gas introduction hole 43 for introducing CO to the first gas introduction hole 12 of the substrate 10. CO that flows into the internal space from the gas introduction hole 43 acts on the gas detection unit 2 through the gas introduction hole 12. The gas introduction hole 43 is formed on the surface of the second cover 42 facing the second surface 10b. The shape of the gas introduction hole 43 in a plan view is not particularly limited and may be, for example, a circular shape, a polygonal shape, or a slit shape.

[0055] The second cover 42 may be a flexible thin-film sealing sheet like the first cover 41, but is preferably made of a hard resin material. The second cover 42 is made of a material with low gas permeability that can block gases such as CO and water vapor, and may be made of a metal material, but is preferably made of a resin material. The second cover 42 is, for example, a hard cover formed in the shape of a bottomed rectangular tube, and is arranged on the second surface 10b so as to cover the gas inlet hole 12 of the substrate 10.

[0056] The first cover 41 and the second cover 42 are formed in the shape of a flat, bottomed rectangular tube, but the shape of each cover is not particularly limited. However, from the perspective of miniaturizing the sensor, it is preferable to reduce the height of each cover from the surface of the substrate 10. As described above, the first cover 41 and the second cover 42 are fixed to each other with their open ends overlapping, for example, using adhesives, screws, a locking structure, or by welding. The first cover 41 and the second cover 42 sandwich each of the protrusions 14 of the substrate 10 and also sandwich both ends of the base portion 13 along the long sides via the sealing member 50. The sealing member 50 may be provided between the substrate 10 and each of the protrusions 14.

[0057] In this embodiment, the opening area of ​​each gas inlet hole 12 in the substrate 10 is preferably smaller than the opening area of ​​each gas inlet hole 43 in the second cover 42. When the gas inlet holes 12, 43 have a perfect circular shape, the diameter of the gas inlet hole 12 is preferably smaller than the diameter of the gas inlet hole 43. The opening area of ​​the gas inlet hole 12 needs to be small from the viewpoint of preventing the infiltration of the ink that forms the catalyst layer 20, but it is preferable that the opening area of ​​the gas inlet hole 43 be larger than that of the gas inlet hole 12 to ensure good breathability. For example, when the gas inlet hole 43 is a circular hole, it has a diameter of 0.2 to 2.0 mm or 0.3 to 1.0 mm.

[0058] [Humidity Control Member] The humidity control member 60 has the function of adjusting the amount of moisture contained in the solid electrolyte membrane, absorbing moisture when the humidity inside the sensor is high and releasing moisture when the humidity is low. The humidity control member 60 prevents, for example, an excessive decrease in humidity inside the sensor covered by the cover 40. The humidity control member 60 is preferably disposed in the internal space between the electrolyte layer 30 and the first cover 41 without contacting the first cover 41. The humidity control member 60 may expand when it absorbs moisture, but the gap between the first cover 41 and the humidity control member 60 can absorb the expansion of the humidity control member 60. The gap between the first cover 41 and the humidity control member 60 is preferably large enough so that the first cover 41 and the humidity control member 60 do not come into contact with each other even when the humidity control member 60 expands.

[0059] The humidity control member 60 is, for example, in the form of particles, and is disposed opposite the electrolyte layer 30 with the partition layer 70 interposed therebetween. The shape and size of the humidity control member 60 are not particularly limited. For example, the humidity control member 60 has a volume larger than that of the electrolyte layer 30. In this case, the humidity control member 60 has a sufficient amount of moisture relative to the electrolyte layer, making it possible to adjust the amount of moisture inside the sensor, leading to improved reliability and higher sensitivity of the sensor.

[0060] The humidity control member 60 is, for example, a sheet-like member containing humidity control particles that reversibly absorb and release water vapor. The humidity control member 60 may have a structure in which a plurality of humidity control particles are sandwiched between two base sheets. In this case, the humidity control particles and the humidity control particles and the two base sheets are bound together by a binder. The type of binder is not particularly limited as long as it can maintain the sheet shape of the humidity control member 60. The base sheet may be a general thermoplastic resin sheet, but a porous sheet with breathability is preferable. Nonwoven fabric, woven fabric, etc. may also be used as the base sheet.

[0061] The humidity-conditioning particles may be particles containing a silicon compound such as silica, sepiolite, or zeolite, or may contain alumina, titania, zirconia, or the like instead of or together with the silicon compound. The humidity-conditioning particles may also be particles containing a highly water-absorbent polymer such as cross-linked sodium polyacrylate. As will be described in detail later, the particle size of the humidity-conditioning particles is preferably larger than the diameter of the vent holes in the partition wall layer 70. The average particle size of the humidity-conditioning particles is, for example, 30 μm to 10 mm or 500 μm to 5 mm. The average particle size of the humidity-conditioning particles is calculated by observing the particles with an optical microscope or a scanning electron microscope and averaging the diameters of the circumscribed circles of the particle images. When the humidity-conditioning particles absorb water and expand, it is preferable that the average particle size in the smallest state be within this range.

[0062] [Partition Layer] The partition layer 70 is a sheet-like member that is disposed between the electrolyte layer 30 and the humidity control member 60 in order to prevent contact between the electrolyte layer 30 and the humidity control member 60. If the humidity control member 60 is in contact with the electrolyte layer 30, excess moisture is expected to be supplied to the contact area, and therefore it is preferable to interpose the partition layer 70 between the electrolyte layer 30 and the humidity control member 60. The shape and size of the partition layer 70 are not particularly limited, but it is preferable that the partition layer 70 has the same shape and size as the electrolyte layer 30 and is disposed so as to cover the entire electrolyte layer 30. The thickness of the partition layer 70 is not particularly limited, but is, for example, 30 μm to 1000 μm.

[0063] The partition layer 70 is preferably a breathable sheet. By covering the entire electrolyte layer 30 with the water vapor-permeable partition layer 70, the moisture content of the entire electrolyte layer can be adjusted while preventing contact between the electrolyte layer 30 and the humidity control member 60, leading to improved reliability and sensitivity of the sensor. A porous sheet having ventilation holes can be used for the partition layer 70, and nonwoven fabric, woven fabric, etc. may also be used. When the humidity control member 60 includes a porous substrate sheet, the sheet may function as the partition layer 70.

[0064] The diameter of the air vent holes in the partition wall layer 70 is, for example, less than 50 μm, which is smaller than the particle size of the humidity-conditioning particles in the humidity control member 60. The average particle size of the humidity-conditioning particles needs to be larger than the average diameter of the air vent holes, but the particle sizes of all the humidity-conditioning particles may be larger than the maximum diameter of the air vent holes. In this case, even if the humidity-conditioning particles are present directly on the partition wall layer 70, the humidity-conditioning particles are prevented from penetrating the air vent holes, ensuring the breathability of the partition wall layer 70 and preventing contact between the electrolyte layer 30 and the humidity-conditioning particles. The average diameter of the air vent holes is, for example, 0.1 μm to 30 μm or 0.5 μm to 25 μm. The average diameter of the air vent holes is measured using a mercury porosimeter.

[0065] Alternatively, the partition layer 70 may be made of a sheet-shaped resin material, which has high strength and therefore improves assembly during manufacturing. In this case, the resin material has through-holes for ventilation, which can adjust the moisture content of the entire electrolyte layer while preventing contact between the electrolyte layer 30 and the humidity control member 60, leading to improved reliability and sensitivity of the sensor. The through-holes formed in the sheet-shaped resin material may have, for example, a perfect circular shape in a plan view and a diameter of less than 1000 μm. In this case, selecting humidity-controlling particles that are larger than the diameter of the through-holes prevents the humidity-controlling particles from penetrating the through-holes, ensuring the breathability of the partition layer 70 and preventing contact between the electrolyte layer 30 and the humidity-controlling particles. The average diameter of the through-holes is, for example, 100 μm to 500 μm, and the average diameter of the through-holes is measured using an optical microscope or the like.

[0066] [Activated Carbon] As described above, activated carbon 80 is disposed between the substrate 10 and the second cover 42. An oxidation reaction of carbon monoxide occurs at the working electrode. By measuring the short-circuit current generated during this reaction, activated carbon 80 adsorbs gases such as SOx and NOx and allows CO, the target gas, to pass through. The activated carbon 80 may be granular or powdered activated carbon formed into a block shape, granular or powdered activated carbon filled in a case with ventilation holes, or activated carbon formed into a cloth shape (activated carbon cloth). From the perspective of sensor miniaturization, the activated carbon 80 is preferably processed into a sheet shape as a whole, and is disposed so as to cover all of the gas inlet holes 12 formed in the substrate 10. Between the second surface 10b of the substrate 10 and the second cover 42, for example, a humidity control member 60 and activated carbon 80 may be layered in this order from the second surface 10b side.

[0067] An example of a method for manufacturing the electrochemical gas sensor 1 having the above configuration will be described below. The electrochemical gas sensor 1 is manufactured, for example, through the following steps: (1) a step of forming wiring 11 on the first surface 10a of a substrate 10 having gas inlet holes 12 connecting the first surface 10a and the second surface 10b; (2) a step of forming a catalyst layer 20 on the first surface 10a of the substrate 10 so as to cover part of the wiring 11 and the gas inlet holes 12; (3) a step of forming an electrolyte layer 30 on the first surface 10a of the substrate 10 so as to cover the catalyst layer 20; and (4) a step of arranging a cover 40 so as to cover the catalyst layer 20 and the electrolyte layer 30 and to expose part of the wiring 11 on the first surface 10a of the substrate 10.

[0068] In step (1), a metal layer such as copper foil is formed on the first surface 10a of the substrate 10, and the wiring 11 including wirings 11a, 11b, and 11c is formed by pattern etching of the copper foil. Alternatively, the wirings 11a, 11b, and 11c may be directly formed by vapor deposition, printing, or the like. The wiring 11 may also have a plating layer of nickel / gold or the like. In this embodiment, there are no through holes other than the gas introduction hole 12 in the area of ​​the substrate 10 covered by the cover 40, and the amount of CO acting on the gas detection unit is controlled.

[0069] In step (2), for example, an ink containing a catalyst, a conductive carrier, and an ionomer is applied to the first surface 10a of the substrate 10 on which the wiring 11 is formed, and the coating is dried to volatilize and remove the dispersion medium, thereby forming the catalyst layer 20. Each catalyst layer is formed to the same thickness using the same type of ink. In this embodiment, the catalyst layer 20a is formed by applying ink to the first surface 10a so as to cover all of the gas inlet holes 12. The opening area of ​​the gas inlet holes 12, the viscosity of the ink, and the like are adjusted so that the ink forming the catalyst layer 20a does not penetrate into the gas inlet holes 12.

[0070] Examples of ink application methods include spray coating, screen printing, inkjet printing, electrolytic spray coating, and dispensing.

[0071] In step (3), for example, an ink containing a constituent material of the solid electrolyte is applied to the first surface 10a of the substrate 10 so as to cover the entire catalyst layer 20, and the coating is dried to volatilize and remove the dispersion medium, thereby forming the electrolyte layer 30. The ink application method is not particularly limited, and a method similar to that in step (2) can be applied. Forming the electrolyte layer 30 by a coating method increases the adhesion of the electrolyte layer 30 to the catalyst layer 20 and the first surface 10a, thereby reducing the contact resistance of the laminated structure of the gas detection unit.

[0072] In step (4), a first cover 41 is placed so as to entirely cover the gas detection unit 2 formed on the first surface 10a, and a second cover 42 is placed so as to cover the portion of the substrate 10 where the gas introduction hole 12 is formed from the second surface 10b side. The first cover 41 and the second cover 42 entirely cover the substrate 10, including the side surfaces of the base portion 13, and are connected to each other by sandwiching three protrusions 14 from both sides in the thickness direction. A sealing member 50 may be provided between the cover 40 and the substrate 10. Each protrusion 14 protrudes outside the cover 40 from between the first cover 41 and the second cover 42, and is connected to an external terminal such as a pin 113 by a connection portion 15 formed on the protrusion 14.

[0073] The cover 40 does not function as a member that presses the gas detection unit 2, and an internal space exists between the gas detection unit 2 and the first cover 41. It is preferable to dispose a humidity control member 60 and a partition layer 70 in this internal space, and the humidity control member 60 is disposed on the gas detection unit via the partition layer 70. It is also possible to form the humidity control layer by applying an ink containing the constituent material of the partition layer 70 onto the electrolyte layer 30 to form the partition layer 70, and then applying an ink containing humidity-control particles onto the partition layer 70.

[0074] FIG. 5 is a diagram showing a modified example of the electrochemical gas sensor 1. The embodiment shown in FIG. 5 differs from the embodiment shown in FIG. 4 and other figures in that a leaf spring 90 is provided to sandwich the first cover 41 and the second cover 42 from the outside and maintain the first cover 41 and the second cover 42 in an integrated state. The first cover 41 and the second cover 42 sandwich the substrate 10, and the leaf spring 90 presses each cover in the thickness direction of the substrate 10. The leaf spring 90 is attached, for example, from both sides of the short side of the cover, which is a direction perpendicular to the direction in which the protrusion 14 extends. The first cover 41 and the second cover 42 may be integrated only by the biasing force of the leaf spring 90, or they may be fixed to each other by adhesive, screws, an engagement structure, welding, etc., and integrated by the biasing force of the leaf spring 90.

[0075] The embodiment shown in FIG. 5 further differs from the embodiment shown in FIG. 4 and other figures in that the side surfaces of the substrate 10 along the thickness direction are exposed from the covers. The side surfaces of the substrate 10 (base portion 13) are exposed to the outside between the first cover 41 and the second cover 42 and are, for example, flush with the side surfaces of the covers. Sealing members 51 are disposed between the first cover 41 and the second cover 42 and the substrate 10, and each cover presses the substrate 10 from both sides in the thickness direction via the sealing members 51 using the biasing force of the leaf springs 90. This seals the connection between the first cover 41 and the second cover 42, and the target gas is introduced only through the gas inlet hole 43 of the second cover 42. The sealing member 51 is preferably disposed in a ring shape surrounding the outer edge of the substrate 10.

[0076] Fig. 6 is a diagram showing another modified example of the electrochemical gas sensor 1. The embodiment shown in Fig. 6 is similar to the embodiment shown in Fig. 5 in that the side surface of the substrate 10 (base portion 13) is exposed to the outside from between the first cover 41 and the second cover 42. As in the above embodiment, the substrate 10 has a protruding portion 95 protruding from between the first cover 41 and the second cover 42, but differs from the above embodiment in that there is only one protruding portion 95. The protruding portion 95 extends from one end of the cover in the width direction and is formed with a constant width over the entire length of the cover.

[0077] On one side of the protrusion 95, a working electrode wire 11a, a counter electrode wire 11b, and a reference electrode wire 11c are formed, each extending from the interior of the sensor covered by the first cover 41. Furthermore, connection portions 15a, 15b, and 15c are formed at the tip of each wire. That is, in the embodiment shown in FIG. 6, multiple connection portions are formed on one protrusion 95. Each connection portion has, for example, a circular through-hole that penetrates the protrusion 95 in the thickness direction and a conductor layer formed on the periphery and inner surface of the through-hole. The connection portions 15a, 15b, and 15c are formed in a row along the length of the protrusion 95.

[0078] 7 is a block diagram showing the configuration of a gas detection system 100 according to an embodiment. As shown in FIG. 7 , the gas detection system 100 includes a gas detection device 110 including an electrochemical gas sensor 1, a receiving device 101 that receives detection information from the gas detection device 110, and a control device 102. The receiving device 101 and the control device 102 may be installed in a location remote from the gas detection device 110, and the receiving device 101 may receive the detection information from the gas detection device 110 via wireless or wired communication, or via a wide area communication network such as the Internet. The control device 102 controls the operation of a predetermined device, for example, based on the detection information from the gas detection device 110.

[0079] The gas detecting device 110 includes an electrochemical sensor 1 and a housing 111 that houses the electrochemical gas sensor 1. The gas detecting device 110 further includes a circuit board 112. As shown in FIG. 1 , the electrochemical gas sensor 1 may be housed in a recess 114 of the circuit board 112, and mounted on the circuit board 112 by inserting pins 113 of the circuit board 112 into connecting portions 15 formed on protruding portions 14 of the circuit board 112. The gas detecting device 110 may also include a holder that holds the electrochemical sensor 1, a speaker that outputs an alarm sound, a warning lamp, etc.

[0080] Gas detection device 110 may further include a detection unit that detects at least one of smoke and heat, and in this case, may also include a speaker that outputs an alarm sound, a warning lamp, etc. Gas detection device 110 may include, for example, a smoke detection unit that detects smoke. The smoke detection unit is configured to be able to detect smoke above a certain amount, and may be mounted on a circuit board together with electrochemical gas sensor 1. The smoke detection unit includes, for example, a light-emitting unit and a light-receiving unit, and detects smoke when light emitted from the light-emitting unit is reflected by smoke particles and reaches the light-receiving unit. Note that, instead of electrochemical sensor 1, an electrochemical sensor according to the embodiments and modifications described below may be used.

[0081] As described above, the electrochemical sensor 1 having the above configuration has a simple signal extraction structure, which, for example, allows for the sensor to be made smaller and less expensive. This facilitates connection to an external device such as the gas detection device 110. Furthermore, the electrochemical sensor 1 is, for example, highly reliable, can be manufactured at low cost, and has high sensitivity. By providing the humidity control member 60, the partition layer 70, and the activated carbon 80, further improvements in reliability and sensitivity can be achieved.

[0082] The above-described embodiments may be modified as appropriate without departing from the scope of the present disclosure. For example, in the above-described embodiments, the reference electrode catalyst layer is formed using the same electrode material as the working electrode catalyst layer 20a and the counter electrode catalyst layer 20b. However, the reference electrode may be made of a different material than the catalyst layers 20a and 20b, and the catalyst layers 20a and 20b may be made of different materials. The electrochemical gas sensor may also have a two-electrode structure including only a working electrode and a counter electrode. Alternatively, a metal layer may serve as the reference electrode, and the counter electrode may also serve as the reference electrode. The electrochemical gas sensor may also include other components, such as a gas diffusion layer.

[0083] Although the electrochemical sensor 1 includes the humidity control member 60, the partition layer 70, and the activated carbon 80, the electrochemical sensor according to the present disclosure is not limited to having the humidity control member 60, the partition layer 70, and the activated carbon 80. The electrochemical sensor according to the present disclosure may, for example, include only the humidity control member 60 or the activated carbon 80, or may have a structure in which the activated carbon 80 is disposed between the gas detection unit 2 and the first cover 41. The humidity control member 60 may also be disposed between the substrate 10 and the second cover 42.

[0084] The electrochemical gas sensor according to the present disclosure includes only a cover that covers the first surface 10a of the substrate 10, and this cover is in close contact with the first surface 10a of the substrate 10 around the gas detection unit 2, for example. In this case, a sealing member may be disposed between the cover and the first surface 10a of the substrate 10, and a leaf spring may be provided that sandwiches the cover and the substrate 10 from the outside and maintains the cover and the substrate 10 in an integrated state.

[0085] The present disclosure will be further described by the following embodiments. Configuration 1: An electrochemical gas sensor comprising: a substrate including a first surface and a second surface; a gas detection unit disposed on the first surface of the substrate; a cover covering the gas detection unit; and wiring connected to the gas detection unit and partially exposed from the cover, wherein a connection portion for connecting to an external wiring or an external terminal is formed on the portion of the wiring exposed from the cover. Configuration 2: The electrochemical gas sensor according to Configuration 1, wherein the substrate has a protrusion protruding from the cover, and the connection portion is formed on the protrusion. Configuration 3: The electrochemical gas sensor according to Configuration 2, wherein a plurality of the connection portions are formed on the protrusion. Configuration 4: The electrochemical gas sensor according to Configuration 2, wherein the electrochemical gas sensor has a plurality of the protrusions, and the connection portion is formed on each of the protrusions. Configuration 5: The electrochemical gas sensor according to any one of Configurations 2 to 4, wherein the cover comprises a first cover covering the first surface of the substrate and a second cover covering the second surface of the substrate, and the protruding portion of the substrate is sandwiched between the first and second covers. Configuration 6: The electrochemical gas sensor according to Configuration 5, wherein the cover covers the entire substrate except for the protruding portion. Configuration 7: The electrochemical gas sensor according to Configuration 5 or 6, wherein the first and second covers accommodate portions of the substrate other than the protruding portion and are connected to each other. Configuration 8: The electrochemical gas sensor according to any one of Configurations 5 to 7, wherein the substrate has a first gas inlet hole connecting the first and second surfaces in a region overlapping with the gas detection unit, and the second cover has a second gas inlet hole and covers the second surface of the substrate including the portion where the first gas inlet hole is formed. The electrochemical gas sensor according to any one of the preceding configurations, wherein the opening area of ​​the first gas inlet hole of the substrate is smaller than the opening area of ​​the second gas inlet hole of the second cover.Configuration 11: The electrochemical gas sensor according to any one of Configurations 1 to 10, further comprising: a sealing member disposed between the cover and the first surface of the substrate; and a leaf spring that sandwiches the cover and the substrate from the outside and maintains the cover and the substrate in an integrated state. Configuration 12: The electrochemical gas sensor according to any one of Configurations 5 to 9, further comprising: a sealing member disposed between at least one of the first cover and the second cover and the substrate; and a leaf spring that sandwiches the first cover and the second cover from the outside and maintains the first cover and the second cover in an integrated state. Configuration 13: The electrochemical gas sensor according to any one of Configurations 5 to 9 and 12, further comprising: a humidity control member housed in the first cover without contacting the gas detection unit. Configuration 14: The electrochemical gas sensor according to Configuration 13, further comprising an air-permeable partition layer disposed between the gas detection unit and the humidity control member. Configuration 15: The electrochemical gas sensor according to any one of Configurations 5 to 9, 12, and 14, further comprising activated carbon disposed within the second cover.

[0086] FIG. 8 is a cross-sectional view of an electrochemical gas sensor 200 according to a second embodiment, and FIG. 9 is an exploded perspective view of the electrochemical gas sensor 200. As shown in FIGS. 8 and 9, the electrochemical gas sensor 200 includes a substrate 210 having a first surface 210a and a second surface 210b, a conductor layer 211 formed as wiring on the first surface 210a of the substrate 210, a catalyst layer 220, and an electrolyte layer 230. The conductor layer 211 is, for example, a metal layer. The substrate 210 has a gas inlet hole 212 connecting the first surface 210a and the second surface 210b. The catalyst layer 220 is formed on the first surface 210a of the substrate 210 so as to cover a portion of the conductor layer 211 and the gas inlet hole 212. The electrolyte layer 230 is formed on the first surface 210a of the substrate 210 so as to be in contact with the catalyst layer 220. The electrochemical sensor 200 further includes a cover 240 that covers the catalyst layer 220 and the electrolyte layer 230 .

[0087] The electrochemical gas sensor 200 includes, as the catalyst layer 220, a catalyst layer 220a serving as a working electrode, a catalyst layer 220b serving as a counter electrode, and a catalyst layer 220c serving as a reference electrode. Note that the catalyst layer 220c can be omitted. The catalyst layers 220a, 220b, and 220c are formed on the first surface 210a of the substrate 210 so as not to contact one another. The conductor layer 211 includes a conductor layer 211a corresponding to the catalyst layer 220a, a conductor layer 211b corresponding to the catalyst layer 220b, and a conductor layer 211c corresponding to the catalyst layer 220c. Similarly, the conductor layers 211a, 211b, and 211c are formed on the first surface 210a of the substrate 210 so as not to contact one another. It is sufficient that the electrolyte layer 230 be in contact with at least a portion of the catalyst layers 220a and 220b. Furthermore, when the catalyst layer 220c is formed, the electrolyte layer 230 only needs to be in contact with at least a portion of the catalyst layers 220a, 220b, and 220c.

[0088] In the electrochemical gas sensor 200, a layered structure including a conductor layer 211, a catalyst layer 220, and an electrolyte layer 230 formed directly on the first surface 210a of the substrate 210 functions as a gas detection unit. The catalyst layer 220a, which functions as a working electrode, and the catalyst layer 220b, which functions as a counter electrode, are arranged via the electrolyte layer 230 to enable ion conduction and are electrically connected via an external circuit (not shown). The working electrode is an electrode into which the gas to be detected flows and is also called a sensing electrode. A portion of the conductor layer 211 is exposed to the outside of the cover 240 on the first surface 210a of the substrate 210. A connection portion to an external circuit is formed in the portion of the conductor layer 211 exposed from the cover 240.

[0089] As will be described in more detail below, by forming the catalyst layer 220 directly on the surface of the substrate 210 on which the conductor layer 211 and the gas inlet hole 212 are formed, and then forming the electrolyte layer 230 directly on the catalyst layer 220, the adhesion between the layers constituting the gas detection unit is strengthened, thereby reducing the contact resistance of the laminated structure. Furthermore, with the electrochemical sensor 200, there is no need to press the gas detection unit to keep the contact resistance low, so no special fastening tool is required, and variations in contact resistance are also suppressed. In other words, the resistance value of the sensor is reduced and stabilized. As a result, the reliability of the sensor is improved, leading to higher sensitivity, smaller size, and lower cost of the sensor.

[0090] The electrochemical gas sensor 200 detects the gas concentration by introducing a gas to be detected into the working electrode, oxidizing or reducing the gas molecules on the working electrode, and measuring the change in current or potential associated with this redox reaction. The electrochemical gas sensor 200 may be a potential detection type, but this embodiment illustrates a current detection type sensor. When gas molecules are oxidized or reduced at the working electrode, electrons are generated or consumed, causing a current to flow between the working electrode and the counter electrode. This current value is proportional to the gas concentration, so the gas concentration can be detected by measuring the current value. Ions generated by the redox reaction at the working electrode and the counter electrode migrate between the working electrode and the counter electrode via the electrolyte layer 230.

[0091] As described above, the electrochemical gas sensor 200 includes the catalyst layer 220a functioning as a working electrode, the catalyst layer 220b functioning as a counter electrode, and the catalyst layer 220c functioning as a reference electrode. The reference electrode is an electrode that serves as a reference when controlling and measuring the potential of the working electrode, and is also called a reference electrode. The working electrode is connected to the reference electrode via an external circuit and is configured to maintain a constant potential relative to the reference electrode via the external circuit. The potential of the working electrode is maintained, for example, at a potential that can oxidize the target gas.

[0092] When the gas to be detected by the electrochemical gas sensor 200 is CO, an oxidation reaction of CO occurs at the working electrode as shown in formula (1): CO + H ２ O → CO ２ +2H ＋ +2e － ... (1) The CO that flows into the working electrode reacts with water molecules to form CO ２ and generate protons (H ＋ ) and electrons are generated. The protons move to the counter electrode via the electrolyte layer 230, and the electrons move to the counter electrode via an external circuit. At the counter electrode, the reaction shown in formula (2) occurs. ２ +2H ＋ +2e － →H ２O... (2) The protons and electrons generated at the working electrode react with oxygen in the air at the counter electrode to produce water. At this time, the current flowing in the external circuit is proportional to the amount of CO flowing into the working electrode, so the CO concentration can be detected by measuring this current.

[0093] The electrochemical gas sensor 200 has a structure in which the interior of the sensor, in which a gas detection unit is formed, is sealed by a substrate 210 and a cover 240. The cover 240 is disposed on a first surface 210a of the substrate 210, and entirely covers the catalyst layer 220 and the electrolyte layer 230. The cover 240 is made of a material with low gas permeability that can block gases such as CO and water vapor, and seals the gas detection unit together with the substrate 210, which is also made of a material with low gas permeability. A gas inlet hole 212 is formed in the substrate 210, so that CO, the gas to be detected, is introduced into the sensor only through the gas inlet hole 212.

[0094] In the electrochemical gas sensor 200, an internal space is formed between the electrolyte layer 230 and the cover 240. That is, there is a gap between the gas detection unit and the cover 240, and the gas detection unit is not pressed by the cover 240. The electrochemical sensor 200 further includes a humidity control member 260 disposed in this internal space. As described above, in the electrochemical sensor 200, the solid electrolyte membrane needs to contain a certain amount of moisture in order to function, and the amount of moisture in the solid electrolyte membrane needs to be controlled. The humidity control member 260 serves to adjust the amount of moisture contained in the solid electrolyte membrane.

[0095] The humidity control member 260 is preferably disposed so as not to come into contact with the catalyst layer 220 and electrolyte layer 230 that constitute the gas detection unit. In the example shown in FIG. 8 , the humidity control member 260 is disposed on top of the electrolyte layer, but the humidity control member 260 may also be disposed in a location where it does not overlap with the electrolyte layer 230, such as around the gas detection unit. In addition, a gap exists between the humidity control member 260 and the cover 240. The humidity control member 260 may expand in volume when it absorbs moisture, but if a gap exists between the humidity control member 260 and the cover 240, this gap can absorb the volumetric expansion of the humidity control member 260. As a result, the structure of the sensor is stabilized, leading to improved reliability.

[0096] The electrochemical sensor 200 further includes a breathable partition layer 270 disposed between the electrolyte layer 230 and the humidity control member 260. When the humidity control member 260 is in contact with the electrolyte layer 230, it is difficult to appropriately adjust the amount of moisture contained in the solid electrolyte membrane. By interposing the partition layer 270 between the electrolyte layer 230 and the humidity control member 260, it becomes easier to adjust the amount of moisture contained in the solid electrolyte membrane, leading to improved reliability and sensitivity of the sensor. The partition layer 270 is preferably permeable to water vapor.

[0097] The structures of the substrate 210, catalyst layer 220, electrolyte layer 230, cover 240, humidity control member 260, and partition layer 270 that constitute the electrochemical gas sensor 200 will be described in detail below.

[0098] [Substrate] The substrate 210 is an insulating base material having a conductor layer 211 functioning as wiring and a gas inlet hole 212 connecting the first surface 210a and the second surface 210b. The substrate 210 is made of a material similar to that used for conventionally known printed wiring boards, such as epoxy resin or polyphenylene ether. The substrate 210 may be a substrate dedicated to the electrochemical gas sensor 200, or may be a printed wiring board on which other electronic components are mounted. In this embodiment, the substrate 210 functions as a support member for the gas detection unit and, together with the cover 240, as a sealing member for sealing the gas detection unit. While FIG. 9 illustrates a substrate having a rectangular shape in a plan view, the shape of the substrate 210 is not particularly limited and can be modified as appropriate depending on the shape of the electrochemical gas sensor 200.

[0099] The gas inlet holes 212 of the substrate 210 are formed at positions overlapping the catalyst layer 220a, which functions as a working electrode, and function as paths for introducing gas into the catalyst layer 220a. In other words, the catalyst layer 220a is formed in the region of the first surface 210a of the substrate 210 where the gas inlet holes 212 are formed. In this embodiment, the multiple gas inlet holes 212 are formed only in positions overlapping the catalyst layer 220a. In other words, the region of the first surface 210a covered by the cover 240 does not include any through-holes for wiring, such as through-holes, and no through-holes other than the gas inlet holes 212 are formed.

[0100] The electrochemical gas sensor 200 is configured so that CO flows into the interior of the sensor surrounded by the substrate 210 and cover 240 only through the gas inlet 212, and the amount of CO acting on the catalyst layer 220a is controlled. Therefore, the CO concentration can be accurately determined from the proportional relationship between the amount of CO inflow and the current value. The gas inlet 212 is, for example, a through-hole that is perfectly circular in plan view. In this specification, "plan view" refers to the electrochemical gas sensor 200 and its components viewed from the first surface 210a of the substrate 210.

[0101] The gas introduction holes 212 have a diameter of, for example, 0.05 to 1 mm, or 0.1 to 0.5 mm. There are no particular limitations on the opening area of ​​the gas introduction holes 212, but the opening area is preferably large enough to prevent the material constituting the catalyst layer 220 from flowing into the gas introduction holes 212 when the material is applied to the first surface 210a of the substrate 210. In other words, it is preferable that a large number of gas introduction holes 212 with small opening areas are formed in the substrate 210. However, there is no particular limitation on the number of gas introduction holes 212.

[0102] As described above, conductor layers 211a, 211b, and 211c are formed on the first surface 210a of the substrate 210, spaced apart so as not to contact one another. Catalyst layer 220a is formed covering a portion of conductor layer 211a, catalyst layer 220b is formed covering a portion of conductor layer 211b, and catalyst layer 220c is formed covering a portion of conductor layer 211c. Conductor layers 211a, 211b, and 211c function as extraction electrodes (wiring) that electrically connect each catalyst layer to an external circuit. Portions of conductor layers 211a, 211b, and 211c are exposed to the outside of cover 240 in a plan view of the substrate 210, and connections to the external circuit are formed on these exposed portions.

[0103] When the conductor layer 211 is a metal layer, for example, copper foil is formed on the entire surface of the insulating substrate, the copper foil is pattern-etched, and the remaining copper foil is further plated to form the conductor layer 211 on the first surface 210a of the substrate 210. An example of the conductor layer 211 (metal layer) is a layer in which nickel / gold is plated on the surface of copper, and has a thickness of 5 μm to 30 μm. Note that the conductor layer 211 may also be formed by other methods such as vapor deposition or printing. In FIG. 8 , for clarity of illustration, the conductor layer 211 is illustrated as being present within the substrate 210, but in this embodiment, the conductor layer 211 is formed on the first surface 210a of the substrate 210.

[0104] [Catalyst Layer] As described above, the catalyst layer 220 is formed directly on the first surface 210a of the substrate 210, which has the conductor layer 211 and the gas inlet hole 212. The catalyst layer 220 is preferably a coating formed by applying a catalyst material to the first surface 210a. The catalyst layer 220 is formed on the conductor layer 211, and a portion of the catalyst layer 220 may be formed in an area of ​​the first surface 210a where the conductor layer 211 is not present. When the catalyst layer 220 is applied to the first surface 210a, the catalyst layer 220 adheres strongly to the first surface 210a. In this embodiment, the electrolyte layer 230 is also applied to the catalyst layer 220, so that the laminated structure of the gas detection unit has strong adhesion, and the resistance value of the gas detection unit is reduced and stabilized without the need for strong compression of the laminated structure. As a result, the reliability of the sensor is improved, and the sensor can be made more sensitive, smaller, and less expensive.

[0105] The thickness of the catalyst layer 220 is, for example, 1 μm to 500 μm, or 10 μm to 200 μm. The catalyst layers 220a, 220b, and 220c are formed apart from each other on the first surface 210a so as not to overlap with each other. The areas of the catalyst layers 220b and 220c may be the same or different. In the example shown in FIG. 9 , the catalyst layers 220a, 220b, and 220c have a rectangular shape in a plan view, but the shape of each layer in a plan view is not particularly limited.

[0106] The catalyst constituting the catalytic layer 220 promotes the oxidation reaction of CO. The reaction of formula (1) above occurs in the catalytic layer 220a, which is the working electrode. In this embodiment, the catalytic layers 220a, 220b, and 220c are made of the same material. Examples of catalysts include platinum (Pt), palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), iridium (Ir), cobalt (Co), iron (Fe), and nickel (Ni). Among these, it is preferable to use a noble metal catalyst such as Pt or a PtRu alloy.

[0107] The catalyst layer 220 further includes a conductive support and an ionomer. The conductive support is a conductive material that holds the catalyst. Examples of suitable conductive supports include carbon black such as acetylene black and ketjen black, graphite carbon, and carbon materials such as carbon nanotubes. The catalyst is, for example, adhered to the particle surface of the carbon material. The ionomer is an ionically conductive material that allows the movement of protons generated by the reaction. An example of a suitable ionically conductive material is Nafion (registered trademark: manufactured by DuPont), which has the same composition as the electrolyte membrane.

[0108] [Electrolyte Layer] The electrolyte layer 230 is an ion-conducting membrane that transmits ions generated in the catalyst layer 220a to the catalyst layer 220b, and is an electrically insulating membrane that does not have electronic conductivity. The electrolyte layer 230 may be formed, for example, by absorbing a liquid electrolyte into a support member such as a porous sheet, but is preferably a solid electrolyte membrane made of a polymer material. In this embodiment, a proton-conducting solid electrolyte membrane is used. An example of a proton-conducting solid electrolyte membrane is a polymer membrane in which proton-conducting groups such as sulfonic acid groups are introduced into a hydrocarbon-based polymer or a fluorine-based polymer. A commercially available product such as Nafion (registered trademark: manufactured by DuPont) may be used for the electrolyte layer 230.

[0109] The thickness of the electrolyte layer 230 is not particularly limited, but is, for example, 5 μm to 500 μm. The electrolyte layer 230 is preferably disposed so as to entirely cover the catalyst layers 220 a, 220 b, and 220 c, with a portion of the electrolyte layer 230 being formed directly on the first surface 210 a of the substrate 210. The electrolyte layer 230 is, for example, a coating formed by applying its constituent material onto the first surface 210 a on which the conductor layer 211 and the catalyst layer 220 are formed. In the example shown in FIG. 9 , the electrolyte layer 230 has a rectangular shape in a plan view, but the shape of the electrolyte layer 230 in a plan view is not particularly limited and can be changed as appropriate depending on the shape of the electrochemical gas sensor 200, etc.

[0110] [Cover] Cover 240 prevents gases, including CO and water vapor, from entering the sensor interior and protects the gas detection unit from damage. Cover 240 is fixed to substrate 210 using, for example, adhesives, screws, a locking structure, or by welding or adhesion. Cover 240 is made of a material with low gas permeability that can block gases such as CO and water vapor. While cover 240 may be made of a metal material, it is preferably made of a resin material from the perspectives of weight reduction, productivity, etc. Cover 240 does not have a gas introduction hole like cover 250, which will be described later, and is in close contact with first surface 210a of substrate 210 around the gas detection unit.

[0111] The cover 240 may be a flexible thin-film sealing sheet, but is preferably made of a hard resin material. The cover 240 is, for example, a hard cover formed in a cylindrical shape with a bottom, and is disposed on the first surface 210a of the substrate 210 so as to cover the gas detection unit from above. A gap (internal space) is formed in the thickness direction of the substrate 210 between the cover 240 and the gas detection unit, and the internal space above the gas detection unit serves as an accommodation space for the humidity control member 260. In this embodiment, the cover 240 is smaller than the first surface 210a of the substrate 210, and the entire opening of the cover 240 is blocked by the substrate 210.

[0112] The cover 240 is formed in the shape of a flattened rectangular tube with a bottom, but the shape of the cover 240 is not particularly limited. However, from the perspective of miniaturizing the sensor, it is preferable to reduce the height of the cover 240 from the first surface 210a of the substrate 210. The cover 240 does not cover the entire first surface 210a, and a conductor layer 211 is formed around the periphery of the cover 240 in a plan view. The conductor layer 211 passes between the first surface 210a and the cover 240 and extends from the inside of the sensor covered by the cover 240 to the outside of the cover 240. A sealing member for sealing the gap may be provided between the first surface 210a and the cover 240.

[0113] [Humidity Control Member] The humidity control member 260 has the function of adjusting the amount of moisture contained in the solid electrolyte membrane, absorbing moisture when the humidity inside the sensor is high and releasing moisture when the humidity is low. The humidity control member 260 prevents, for example, an excessive decrease in humidity inside the sensor covered by the cover 240. The humidity control member 260 is preferably disposed in the internal space between the electrolyte layer 230 and the cover 240 without contacting the cover 240. The humidity control member 260 may expand when it absorbs moisture, but the gap between the cover 240 and the humidity control member 260 can absorb the expansion of the humidity control member 260. The gap between the cover 240 and the humidity control member 260 is preferably large enough so that the cover 240 and the humidity control member 260 do not come into contact with each other even when the humidity control member 260 expands.

[0114] The humidity control member 260 is, for example, in the form of particles, and is disposed opposite the electrolyte layer 230 with the partition layer 270 interposed therebetween. The shape and size of the humidity control member 260 are not particularly limited. For example, the humidity control member 260 has a volume larger than that of the electrolyte layer 230. In this case, the humidity control member 260 has a sufficient amount of moisture relative to the electrolyte layer 230, and can adjust the amount of moisture inside the sensor, leading to improved reliability and higher sensitivity of the sensor.

[0115] The humidity control member 260 is, for example, a sheet-like member containing humidity control particles that reversibly absorb and release water vapor. The humidity control member 260 may have a structure in which a plurality of humidity control particles are sandwiched between two base sheets. In this case, the humidity control particles are bound to each other, and to the humidity control particles and the two base sheets, by a binder. The type of binder is not particularly limited, and any binder may be used as long as it can maintain the sheet shape of the humidity control member 260. The base sheet may be a general thermoplastic resin sheet, but a porous sheet with breathability is preferable. Nonwoven fabric, woven fabric, etc. may also be used as the base sheet.

[0116] The humidity-conditioning particles may be particles containing a silicon compound such as silica, sepiolite, or zeolite, or may contain alumina, titania, zirconia, or the like instead of or together with the silicon compound. The humidity-conditioning particles may also be particles containing a highly water-absorbent polymer such as cross-linked sodium polyacrylate. As will be described in detail later, the particle size of the humidity-conditioning particles is preferably larger than the diameter of the vent holes in the partition wall layer 270. The average particle size of the humidity-conditioning particles is, for example, 30 μm to 10 mm, or 500 μm to 5 mm. The average particle size of the humidity-conditioning particles is calculated by observing the particles with an optical microscope or a scanning electron microscope and averaging the diameters of the circumscribed circles of the particle images. When the humidity-conditioning particles absorb water and expand, it is preferable that the average particle size in the smallest state be within this range.

[0117] [Partition Layer] The partition layer 270 is a sheet-like member that is disposed between the electrolyte layer 230 and the humidity control member 260 to prevent contact between the electrolyte layer 230 and the humidity control member 260. If the humidity control member 260 is in contact with the electrolyte layer 230, excess moisture is expected to be supplied to the contact area. Therefore, it is preferable to interpose the partition layer 270 between the electrolyte layer 230 and the humidity control member 260. The shape and size of the partition layer 270 are not particularly limited, but it is preferable that the partition layer 270 has the same shape and size as the electrolyte layer 230 and is disposed so as to cover the entire electrolyte layer 230. The thickness of the partition layer 270 is not particularly limited, but is, for example, 30 μm to 1000 μm.

[0118] The partition layer 270 is preferably a breathable sheet. By covering the entire electrolyte layer 230 with the water vapor-permeable partition layer 270, the moisture content of the entire electrolyte layer can be adjusted while preventing contact between the electrolyte layer 230 and the humidity control member 260, leading to improved reliability and sensitivity of the sensor. A porous sheet having ventilation holes can be used for the partition layer 270, and nonwoven fabric, woven fabric, etc. may also be used. When the humidity control member 260 includes a porous substrate sheet, the sheet may function as the partition layer 270.

[0119] The diameter of the air vent holes in the partition wall layer 270 is, for example, less than 50 μm, which is smaller than the particle size of the humidity-conditioning particles in the humidity control member 260. The average particle size of the humidity-conditioning particles needs to be larger than the average diameter of the air vent holes, but the particle size of all the humidity-conditioning particles may be larger than the maximum diameter of the air vent holes. In this case, even if the humidity-conditioning particles are present directly on the partition wall layer 270, the humidity-conditioning particles are prevented from penetrating the air vent holes, ensuring the breathability of the partition wall layer 270 and preventing contact between the electrolyte layer 230 and the humidity-conditioning particles. The average diameter of the air vent holes is, for example, 0.1 μm to 30 μm, or 0.5 μm to 25 μm. The average diameter of the air vent holes is measured using a mercury porosimeter.

[0120] Alternatively, the partition layer 270 may be made of a sheet-shaped resin material, which, due to its high strength, improves assembly during manufacturing. In this case, the resin material has through-holes for ventilation, which can adjust the moisture content of the entire electrolyte layer while preventing contact between the electrolyte layer 230 and the humidity control member 260, leading to improved reliability and sensitivity of the sensor. The through-holes in the sheet-shaped resin material may have, for example, a perfect circular shape in a plan view and a diameter of less than 1000 μm. In this case, selecting humidity-controlling particles that are larger than the diameter of the through-holes prevents the humidity-controlling particles from penetrating the through-holes, ensuring the breathability of the partition layer 270 and preventing contact between the electrolyte layer 230 and the humidity-controlling particles. The average diameter of the through-holes is, for example, 100 μm to 500 μm, and the average diameter of the through-holes is measured using an optical microscope or the like.

[0121] Fig. 10 is a diagram illustrating an example of a manufacturing method for the electrochemical gas sensor 200. Fig. 10 illustrates the process of forming the catalyst layer 220 by spray coating the constituent material of the catalyst layer 220 on the first surface 210a of the substrate 210 on which the conductor layer 211 and the gas introduction hole 212 are formed.

[0122] The electrochemical gas sensor 200 is manufactured through, for example, the following steps: (1) a step of forming a conductor layer 211, which is wiring, on a first surface 210a of a substrate 210 having gas inlet holes 212 connecting the first surface 210a and the second surface 210b; (2) a step of forming a catalyst layer 220 on the first surface 210a of the substrate 210 so as to cover a portion of the conductor layer 211 and the gas inlet holes 212 (see FIG. 10(a)); (3) a step of forming an electrolyte layer 230 on the first surface 210a of the substrate 210 so as to cover the catalyst layer 220; and (4) a step of arranging a cover 240 so as to cover the catalyst layer 220 and the electrolyte layer 230 and to expose a portion of the conductor layer 211 on the first surface 210a of the substrate 210 (see FIG. 10(b)).

[0123] In step (1), a conductor layer such as copper foil is formed on the first surface 210a of the substrate 210, and the conductor layer 211 including conductor layers 211a, 211b, and 211c is formed by pattern etching of the copper foil. Alternatively, the conductor layers 211a, 211b, and 211c may be directly formed by vapor deposition, printing, or the like. The conductor layer 211 may also have a plated layer of nickel / gold or the like. In this embodiment, the area of ​​the substrate 210 covered by the cover 240 does not have any through-holes other than the gas introduction hole 212, thereby controlling the amount of CO acting on the gas detection unit. Through-holes or other through-holes for wiring may be formed in the substrate 210 outside the cover 240.

[0124] In step (2), for example, an ink containing a catalyst, a conductive carrier, and an ionomer is applied to the first surface 210a of the substrate 210 on which the conductor layer 211 is formed, and the coating is dried to volatilize and remove the dispersion medium, thereby forming the catalyst layer 220. The catalyst layers 220a, 220b, and 220c are formed to the same thickness using the same type of ink. In this embodiment, the catalyst layer 220a is formed by applying ink to the first surface 210a so as to cover all of the gas introduction holes 212. The opening area of ​​the gas introduction holes 212, the viscosity of the ink, and the like are adjusted so that the ink forming the catalyst layer 220a does not penetrate into the gas introduction holes 212.

[0125] Examples of ink application methods include spray coating, screen printing, inkjet printing, electrolytic spray coating, and dispensing.

[0126] In step (3), for example, an ink containing a constituent material of the solid electrolyte is applied to the first surface 210a of the substrate 210 so as to cover the entire catalyst layer 220, and the coating is dried to volatilize and remove the dispersion medium, thereby forming the electrolyte layer 230. The ink application method is not particularly limited, and a method similar to that in step (2) can be applied. Forming the electrolyte layer 230 by a coating method increases the adhesion of the electrolyte layer 230 to the catalyst layer 220 and the first surface 210a, thereby reducing the contact resistance of the laminated structure of the gas detection unit.

[0127] In step (4), a cover 240 is disposed so as to cover the entire gas detection unit formed on the first surface 210a. The conductor layer 211 functions as an extraction electrode, and therefore a portion of the conductor layer 211 is exposed from the cover 240 on the first surface 210a. The cover 240 is fixed to the substrate 210, for example, using an adhesive, screws, or by welding or adhesion. The cover 240 does not function as a member that presses the gas detection unit, and an internal space exists between the gas detection unit and the cover 240. A humidity control member 260 and a partition layer 270 are preferably disposed in this internal space, and the humidity control member 260 is layered on the gas detection unit via the partition layer 270. It is also possible to form the humidity control layer by first applying an ink containing the constituent material of the partition layer 270 to the electrolyte layer 230 to form the partition layer 270, and then applying an ink containing humidity-conditioning particles to the partition layer 270.

[0128] 11 is a cross-sectional view of an electrochemical sensor 200x according to another embodiment. As shown in FIG. 11 , the electrochemical sensor 200x has a structure in which a conductor layer 211, a catalyst layer 220, an electrolyte layer 230, a partition layer 270, and a humidity control member 260 are layered in this order on a first surface 210a of a substrate 210, and is similar to the electrochemical sensor 200 in that it includes a first cover 240 that covers the catalyst layer 220 and other components. On the other hand, the electrochemical sensor 200x differs from the electrochemical sensor 200 in that it includes a second cover 250 that is provided to cover the gas introduction hole 212 from the second surface 210b side of the substrate 210. The electrochemical sensor 200x has a structure in which the substrate 210 is sandwiched between the two covers 240 and 250.

[0129] The cover 250 covers all of the gas introduction holes 212 formed in the substrate 210, and forms an internal space between the cover 250 and the second surface 210b of the substrate 210. The cover 250 has second gas introduction holes 252 for introducing CO to the first gas introduction holes 212 of the substrate 210. The CO that flows into the internal space from the gas introduction holes 252 passes through the gas introduction holes 212 and acts on the gas detection unit. The shape of the gas introduction holes 252 in a plan view is not particularly limited, and may be, for example, a circular shape, a polygonal shape, or a slit shape.

[0130] The cover 250 is, for example, a hard cover formed in a cylindrical shape with a bottom, and is disposed on the second surface 210b so as to cover the gas introduction hole 212 of the substrate 210. Like the cover 240, the cover 250 may be a flexible thin-film sealing sheet, but is preferably made of a hard resin material. The cover 250 is fixed to the substrate 210 using, for example, an adhesive, screws, a locking structure, or the like, or by welding, adhesion, or the like. The cover 250 may be connected to the cover 240 by sandwiching the substrate 210 together with the cover 240.

[0131] The cover 250 is made of a material with low gas permeability that can block gases such as CO and water vapor. Although it may be made of a metal material, it is preferably made of a resin material from the viewpoint of manufacturing costs. The cover 250 is formed in the shape of a flattened rectangular tube with a bottom, but the shape of the cover 250 is not particularly limited. However, from the viewpoint of miniaturizing the sensor, it is preferable that the height of the cover 250 from the second surface 210b of the substrate 210 be low. A sealing member may be provided between the second surface 210b and the cover 250 to seal the gap.

[0132] In the electrochemical sensor 200x, the opening area of ​​each gas inlet hole 212 in the substrate 210 is preferably smaller than the opening area of ​​each gas inlet hole 252 in the cover 250. When the gas inlet holes 212, 252 are perfectly circular, the diameter of the gas inlet hole 212 is preferably smaller than the diameter of the gas inlet hole 252. While the opening area of ​​the gas inlet hole 212 needs to be small from the standpoint of preventing the infiltration of ink forming the catalyst layer 220, it is preferable that the opening area of ​​the gas inlet hole 252 be larger than that of the gas inlet hole 212 to ensure good ventilation. However, since the gas inlet hole 252 also serves to control the amount of gas flowing into the sensor, similar to the gas inlet hole 212, when the gas inlet hole 252 is a circular hole, it has a diameter of, for example, 0.2 to 2.0 mm or 0.3 to 1.0 mm. The number of gas inlet holes 252 is not particularly limited.

[0133] The electrochemical sensor 200x further includes activated carbon 280 disposed between the substrate 210 and the cover 250. An internal space exists between the second surface 210b of the substrate 210 and the cover 250, and the activated carbon 280 is disposed in this internal space. The activated carbon 280 has a large specific surface area due to its micropores, so that it adsorbs gases such as organic solvents, SOx, and NOx, while allowing CO, the target gas to pass through. By providing the activated carbon 280 in the CO introduction path and trapping non-target gases, it is possible to achieve further improvements in reliability and sensitivity.

[0134] The activated carbon 280 may be granular or powdered activated carbon formed into a block shape, granular or powdered activated carbon filled in a case with ventilation holes, or activated carbon formed into a cloth shape (activated carbon cloth). From the viewpoint of miniaturizing the sensor, the activated carbon 280 is preferably processed into a sheet shape as a whole, and is arranged so as to cover all of the gas introduction holes 212 formed in the substrate 210. Between the second surface 210b of the substrate 210 and the cover 250, for example, a humidity control member 260 and activated carbon 280 may be layered in this order from the second surface 210b side.

[0135] FIG. 12 shows a modified example of electrochemical sensor 200x. As shown in FIG. 12, gas inlet 212 can be formed at a position corresponding to catalyst layer 220a (the working electrode) and at a position overlapping catalyst layer 220b (the counter electrode). In this case, a sealing member 290 such as an O-ring is preferably disposed to surround gas inlet 212 formed corresponding to catalyst layer 220a. Furthermore, gas inlet 252 in cover 250 is formed in a portion surrounded by sealing member 290. Sealing member 290 is in close contact with second surface 210b of substrate 210 and the inner surface of cover 250, and gas inlet 212 formed corresponding to catalyst layer 220b is positioned outside of annular sealing member 290. In this case, CO outside the cover flows only into catalyst layer 220a.

[0136] FIG. 13 is a diagram showing a modified example of the electrochemical sensor 200. As shown in FIG. 13, a portion of the conductor layer 211 functioning as wiring does not need to be exposed to the outside of the cover 240 on the first surface 210a of the substrate 210. In the example shown in FIG. 13, a portion of the conductor layer 211 in contact with the cover 240 extends toward the second surface 210b of the substrate 210 via a through-hole 210c penetrating the substrate 210 in the thickness direction. The through-hole 210c is formed in the portion in contact with the cover 240, and is filled with, for example, a metal constituting the conductor layer 211. The metal filled in the through-hole 210c electrically connects the portion of the conductor layer 211 formed on the first surface 210a with the portion of the conductor layer 211 formed on the second surface 210b. Because the through-hole 210c is blocked by the cover 240, gas leakage is sufficiently suppressed, resulting in a highly reliable sensor.

[0137] FIG. 14 is a diagram showing a modified example of an electrochemical sensor 200x. The configuration shown in FIG. 14 is similar to the configuration shown in FIG. 13 in that a portion of the conductor layer 211 is not exposed to the outside of the cover 240 on the first surface 210a of the substrate 210, but extends toward the second surface 210b of the substrate 210 via a through-hole 210c. In the example shown in FIG. 14, when the second surface 210b of the substrate 210 is viewed from above, a portion of the conductor layer 211 where the through-hole 210c and the conductor layer 211 overlap is covered by a cover 250, which is a covering member. Furthermore, an annular sealing member 290 (e.g., an O-ring) is disposed within the cover 250, and a gas introduction hole 252 of the cover 250 is formed in the portion surrounded by the sealing member 290. Sealing member 290 is in close contact with second surface 210b of substrate 210 and the inner surface of cover 250, and through-hole 210c of substrate 210 is located outside annular sealing member 290. That is, the opening of through-hole 210c on the second surface 210b side is located in a space sealed by cover 250 and sealing member 290, and the second surface 210b side of through-hole 210c is sealed. In this case as well, gas leakage is sufficiently suppressed, and a highly reliable sensor can be realized.

[0138] As described above, the electrochemical sensors 200 and 200x configured as described above have excellent reliability. Furthermore, the electrochemical sensors 200 and 200x can be manufactured at low cost and have high sensitivity. By providing the humidity control member 260, the partition layer 270, and the activated carbon 280, further improvements in reliability and sensitivity can be achieved.

[0139] The above-described embodiment may be modified as appropriate without impairing the objectives of the present disclosure. For example, in the above-described embodiment, the reference electrode catalyst layer 220c is formed using the same electrode material as the working electrode catalyst layer 220a and the counter electrode catalyst layer 220b. However, the catalyst layer 220c may be made of a different material from the catalyst layers 220a and 220b, and the catalyst layers 220a and 220b may be made of different materials. The electrochemical gas sensor may also have a two-electrode structure including only a working electrode and a counter electrode. Alternatively, a conductor layer may serve as the reference electrode, and the counter electrode may also serve as the reference electrode. The electrochemical gas sensor may also include other components, such as a gas diffusion layer.

[0140] Electrochemical sensor 200 includes humidity control member 260 and partition layer 270, and electrochemical sensor 200x further includes activated carbon 280, but electrochemical sensors according to the present disclosure are not limited to those including humidity control member 260, partition layer 270, and activated carbon 280. The electrochemical sensor according to the present disclosure may, for example, include only activated carbon 280, or may have a structure in which activated carbon 280 is disposed between the gas detection unit and cover 240. Furthermore, humidity control member 260 may be disposed between substrate 210 and cover 250.

[0141] The present disclosure will be further described by the following embodiments. Configuration 1: An electrochemical gas sensor comprising: a substrate having a gas inlet hole connecting a first surface and a second surface, wiring formed on the first surface of the substrate, a catalyst layer formed on the first surface of the substrate so as to cover a portion of the wiring and the gas inlet hole, an electrolyte layer formed on the first surface of the substrate so as to cover the catalyst layer, and a cover covering the catalyst layer and the electrolyte layer, wherein a portion of the wiring on the first surface of the substrate is exposed to the outside of the cover, or a portion of the wiring on the first surface of the substrate is not exposed to the outside of the cover and extends to the second surface through the hole in the substrate at a portion where the portion of the wiring contacts the cover, or a portion of the wiring on the first surface of the substrate is not exposed to the outside of the cover and extends to the second surface through the hole in the substrate, and a portion where the hole and the wiring overlap is covered with a covering member when the second surface of the substrate is viewed from above. Configuration 2: The electrochemical gas sensor according to Configuration 1, further comprising: an internal space formed between the electrolyte layer and the cover; and a humidity control member disposed in the internal space. Configuration 3: The electrochemical gas sensor according to Configuration 2, wherein the humidity control member is disposed without contacting the catalyst layer and the electrolyte layer. Configuration 4: The electrochemical gas sensor according to Configuration 3, further comprising: an air-permeable partition layer disposed between the electrolyte layer and the humidity control member. Configuration 5: The electrochemical gas sensor according to Configuration 4, wherein the humidity control member contains humidity control particles that reversibly absorb and release water vapor, the particle size of the humidity control particles being larger than the diameter of the air holes in the partition layer. Configuration 6: The electrochemical gas sensor according to any one of Configurations 1 to 5, further comprising: a second cover provided to cover the gas inlet hole from the second surface side of the substrate, the second cover having a second gas inlet hole. Configuration 7: The electrochemical gas sensor according to Configuration 6, further comprising activated carbon disposed between the second cover and the substrate. Configuration 8: The electrochemical gas sensor according to Configuration 6 or 7, wherein the opening area of ​​the gas inlet hole of the substrate is smaller than the opening area of ​​the second gas inlet hole of the second cover.

[0142] Fig. 15 is a perspective view of an electrochemical gas sensor 300 according to a third embodiment. As shown in Fig. 15, the electrochemical gas sensor 300 includes a first housing 310, a second housing 320 that is assembled to the first housing 310 to form an internal space between the first housing 310 and the second housing 320, and a detection unit 330 (see Fig. 17 , etc., described later) housed in the internal space. The electrochemical gas sensor 300 further includes a plurality of leaf springs 350 that press against and sandwich the first housing 310 and the second housing 320 from both sides in the assembly direction of the first housing 310 and the second housing 320. Two leaf springs 350 are provided, and these spring members maintain the assembled state of the first housing 310 and the second housing 320.

[0143] As will be described in detail later, the first housing 310 and the second housing 320 have rectangular surfaces that are pressed by the leaf spring 350, and the leaf spring 350 is attached to each of the short sides of the rectangle. The first housing 310 and the second housing 320 also have recesses 311 and 321, respectively, on the surfaces that are pressed by the leaf spring 350, into which the leaf spring 350 fits. The second housing 320 has a gas inlet 323, which is a vent hole for introducing the target gas into the detection unit 330. The electrochemical gas sensor 300 has a sealing structure that can effectively prevent the inflow of environmental gases and the outflow of moisture from any source other than the gas inlet 323, and has excellent airtightness despite its small size and simple structure.

[0144] For ease of explanation, the assembly direction of the first housing 310 and the second housing 320, i.e., the direction in which they are pressed by the leaf spring 350, may be referred to as the "Z direction or height direction," the direction along the longitudinal direction of the surface pressed by the leaf spring 350 as the "X direction or longitudinal direction," and the direction perpendicular to the X direction and Z direction as the "Y direction or short direction."

[0145] The electrochemical gas sensor 300 is a small, block-shaped electronic component having an overall, approximately rectangular parallelepiped shape. The electrochemical gas sensor 300 is long in the X direction and has approximately the same lengths in the Y and Z directions. However, the Y direction length may be greater than the Z direction length, or the Y direction length may be less than the Z direction length. For example, the X direction length of the electrochemical gas sensor 300 is 15 mm to 25 mm, and the Y direction length and the Z direction length are 10 mm to 15 mm. The electrochemical gas sensor 300 further includes a substrate 331 on which a detection unit 330 is provided. Most of the substrate 331, including the portion on which the detection unit 330 is provided, is located in the internal space of the electrochemical gas sensor 300, which is surrounded by the first housing 310 and the second housing 320. However, a portion of the substrate 331 protrudes from one end of the housing in the shorter direction.

[0146] A portion of the substrate 331 protruding outward (hereinafter sometimes referred to as a "protrusion") is provided with a connection portion 335 to be connected to an external wiring or an external terminal. The protrusion of the substrate 331 has a rectangular shape in a plan view that is long in the X direction, and three connection portions 335 are provided side by side in the longitudinal direction of the protrusion. Note that the shape, number, etc. of the protrusion of the substrate 331 are not limited to this, and for example, a plurality of protrusions each having a connection portion may protrude from both ends of the housing in the longitudinal direction.

[0147] The electrochemical gas sensor 300 is mounted on, for example, a circuit board. The circuit board has conductive pins standing on its surface. The pins are external terminals electrically connected to other electronic devices that make up the circuit board. The electrochemical gas sensor 300 is electrically connected to the circuit board by connecting the connection portion 335 to the pins of the circuit board. The connection portion 335 includes, for example, a circular through-hole in a plan view, into which the pin is inserted. The connection portion 335 constitutes part of the wiring 334 (see FIG. 17 described below) and has a conductor layer formed on the periphery and inner surface of the through-hole. The connection portion 335 and the pin may be soldered. A signal generated by the detection unit 330 is transmitted to the connection portion 335 via the wiring 334 and then to the circuit board via the connection portion 335.

[0148] FIG. 16 is an exploded perspective view of the electrochemical gas sensor 300. As shown in FIG. 16, the electrochemical gas sensor 300 includes a humidity control material 340 and a lid 360 disposed between the detection unit 330 and the humidity control material 340. The first housing 310 is a cylindrical case with a bottom and includes a storage section 314, which is a recess for storing the humidity control material 340. The humidity control material 340 is, for example, a spherical member that retains moisture, and multiple humidity control materials 340 are stored in the storage section 314. The electrolyte membrane 332 (see FIG. 17 described below) of the detection unit 330 must contain a certain amount of moisture to function, and therefore, the amount of moisture in the electrolyte membrane 332 must be controlled. The humidity control material 340 serves to adjust the amount of moisture contained in the electrolyte membrane 332.

[0149] The lid 360 covers the storage section 314 in which the humidity conditioner 340 is stored, preventing contact between the detection section 330 and the humidity conditioner 340. If the detection section 330 and the humidity conditioner 340 come into contact, for example, the moisture content of the electrolyte membrane 332 may increase locally at the contact point, which may result in a decrease in the sensitivity and reliability of the sensor. By using the lid 360, the moisture content of the electrolyte membrane 332 can be appropriately controlled. As will be described in detail later, the lid 360 includes a second piece 362 having a protrusion 367, and a locking portion 314a onto which the protrusion 367 of the second piece 362 is hooked is formed on the side surface of the storage section 314.

[0150] The electrochemical gas sensor 300 further includes activated carbon 341 and sealing members 342 and 343. The activated carbon 341 adsorbs highly polar gases such as SOx and NOx and allows CO, the target gas, to pass through. By providing activated carbon 341 in the CO introduction path to trap non-target gases, reliability and sensitivity can be further improved. In the example shown in FIG. 16 , activated carbon 341 is cylindrical. However, activated carbon 341 may be granular or powdered activated carbon formed into a block shape, or activated carbon formed into a cross shape. The sealing members 342 and 343 surround the sensing unit 330 provided on the first surface 331A of the substrate 331 to enhance airtightness and prevent the inflow of environmental gases and the outflow of moisture from sources other than the gas introduction hole 323.

[0151] The electrochemical gas sensor 300 has a structure in which, in order from the first housing 310 side, a humidity conditioner 340, a lid 360, a sealing member 342, a substrate 331 on which a detection unit 330 is provided, a sealing member 343, and activated carbon 341 are arranged in an internal space of the sensor formed by assembling a first housing 310 and a second housing 320. The detection unit 330 is provided on a first surface 331A of the substrate 331 facing the first housing 310 side. A gas to be detected is introduced into the internal space of the electrochemical gas sensor 300 through a gas introduction hole 323 formed in the second housing 320. The gas introduction hole 323 is formed in the longitudinal center of the second housing 320 and penetrates the second housing 320 in the thickness direction.

[0152] The substrate 331 is a plate-like member that is slightly larger than the lid 360, and is held in the housing with the portion where the connection portion 335 is formed protruding outside the housing. The substrate 331 is formed with ventilation holes 336 that penetrate the substrate 331 in the thickness direction from the second surface 331B facing the second housing 320 to the first surface 331A. The ventilation holes 336 are, for example, through-holes with a smaller diameter than the gas introduction holes 323, and a plurality of ventilation holes 336 are formed near the center of the substrate 331, which has a rectangular shape in a plan view. The detection target gas is introduced into the portion where the detection unit 330 is disposed via the gas introduction holes 323 and the ventilation holes 336.

[0153] The sealing member 342 is an annular rubber member that is disposed so as to surround the detection unit 330 of the substrate 331 and is pressed against the inner surface of the first housing 310 facing the substrate 331 and the first surface 331A of the substrate 331. The sealing member 343 is also an annular rubber member that is disposed so as to surround the ventilation hole 336 of the substrate 331 and is pressed against the inner surface of the second housing 320 facing the substrate 331 and the second surface 331B of the substrate 331. The sealing members 342 and 343 are, for example, gaskets having an O-shaped cross section. The sealing members 342 and 343 ensure airtightness around the detection unit 330 and effectively prevent environmental gas from flowing into the portion where the detection unit 330 is disposed from sources other than the gas introduction hole 323.

[0154] A recess 311 into which the leaf spring 350 fits is formed on the outer surface of the first housing 310 facing away from the substrate 331. The recess 311 is formed on each longitudinal side of the first housing 310. A heat conduction suppressing recess 313 is further formed on the outer surface of the first housing 310 in an area sandwiched between the two recesses 311 and not covered by the leaf spring 350. When the electrochemical gas sensor 300 is mounted on a circuit board, it is expected that condensation will occur on the board due to the influence of the sensor, which has a large heat capacity. However, by providing the heat conduction suppressing recess 313, the heat transfer area between the sensor and the circuit board can be reduced. As a result, condensation is effectively suppressed.

[0155] A recess 321 into which the leaf spring 350 fits is formed on the outer surface of the second housing 320 facing away from the substrate 331. The recess 321 is formed on each longitudinal side of the second housing 320. The leaf spring 350 has a generally U-shape or a generally U-shape. The leaf springs 350 are attached to the recesses 311, 321 of each housing and are arranged opposite each other so as to press against both longitudinal ends of each housing and sandwich them. This maintains a stable assembled state of the first housing 310 and the second housing 320. The same leaf springs 350 are used for both housings.

[0156] FIG. 17 is a diagram showing a first surface 331A of a substrate 331 on which a detection unit 330 is provided. As shown in FIG. 17 , the detection unit 330 includes an electrolyte membrane 332, a catalyst layer 333, and wiring 334. The detection unit 330 has a layered structure in which, from the first surface 331A of the substrate 331, wiring 334, catalyst layer 333, and electrolyte membrane 332 are arranged in this order, and detects CO using the function of this layered structure. The wiring 334 is formed directly on the first surface 331A, the catalyst layer 333 is formed on the wiring 334, and the electrolyte membrane 332 is formed on the catalyst layer 333. Note that portions of the electrolyte membrane 332 and the catalyst layer 333 may be formed directly on the first surface 331A.

[0157] The detection unit 330 includes, as catalyst layer 333, catalyst layer 333a which serves as a working electrode and catalyst layer 333b which serves as a counter electrode. Catalyst layers 333a and 333b are formed on the first surface 331A of the substrate 331 so as not to contact each other. Catalyst layer 333 further includes catalyst layer 333c which serves as a reference electrode. The wiring 334 includes wiring 334a which corresponds to catalyst layer 333a, wiring 334b ​​which corresponds to catalyst layer 333b, and wiring 334c which corresponds to catalyst layer 333c. Similarly, wirings 334a, 334b, and 334c are formed on the first surface 331A of the substrate 331 so as not to contact each other.

[0158] The detection unit 330 has a structure in which a catalyst layer 333a functioning as a working electrode and a catalyst layer 333b functioning as a counter electrode are arranged to enable ion conduction via an electrolyte membrane 332, and are electrically connected via an external circuit (not shown). The working electrode is an electrode into which the gas to be detected flows and is also called a sensing electrode. The electrolyte membrane 332 only needs to be in contact with at least a portion of the catalyst layers 333a and 333b. Furthermore, if a catalyst layer 333c is formed, the electrolyte membrane 332 only needs to be in contact with at least a portion of the catalyst layers 333a, 333b, and 333c.

[0159] The electrochemical gas sensor 300 detects the gas concentration by introducing a gas to be detected into the working electrode, oxidizing or reducing the gas molecules on the working electrode, and measuring the change in current or potential associated with this redox reaction. The electrochemical gas sensor 300 may be a potential detection type, but this embodiment illustrates a current detection type sensor. When gas molecules are oxidized or reduced at the working electrode, electrons are generated or consumed, causing a current to flow between the working electrode and the counter electrode. This current value is proportional to the gas concentration, so the gas concentration can be detected by measuring the current value. Ions generated by the redox reaction at the working electrode and the counter electrode migrate between the working electrode and the counter electrode via the electrolyte layer 332.

[0160] As described above, the electrochemical gas sensor 300 includes the catalyst layer 333a functioning as a working electrode, the catalyst layer 333b functioning as a counter electrode, and the catalyst layer 333c functioning as a reference electrode. The reference electrode is an electrode that serves as a reference when controlling and measuring the potential of the working electrode, and is also called a reference electrode. The working electrode is connected to the reference electrode via an external circuit and is configured to maintain a constant potential relative to the reference electrode through the external circuit. The potential of the working electrode is maintained, for example, at a potential that can oxidize the target gas.

[0161] When the gas to be detected by the electrochemical gas sensor 300 is CO, an oxidation reaction of CO occurs at the working electrode as shown in formula (1): CO + H ２ O → CO ２ +2H ＋ +2e － ... (1) The CO that flows into the working electrode reacts with water molecules to form CO ２ and generate protons (H ＋ ) and electrons are generated. The protons move to the counter electrode via the electrolyte membrane 332, and the electrons move to the counter electrode via an external circuit. At the counter electrode, the reaction shown in formula (2) occurs. ２ +2H ＋ +2e － →H ２ O... (2) The protons and electrons generated at the working electrode react with oxygen in the air at the counter electrode to produce water. At this time, the current flowing in the external circuit is proportional to the amount of CO flowing into the working electrode, so the CO concentration can be detected by measuring this current.

[0162] The substrate 331 functions as a support member for the detection unit 330 and is made of a material similar to that of conventionally known printed wiring boards, such as epoxy resin or polyphenylene ether. As described above, the substrate 331 has an air vent 336 formed therethrough in the thickness direction. The air vent 336 is preferably formed at a position overlapping the detection unit 330, particularly at a position overlapping the catalyst layer 333a that functions as the working electrode, and functions as a path for introducing gas to the catalyst layer 333a. In other words, the catalyst layer 333a is formed in the region of the first surface 331A of the substrate 331 where the air vent 336 is formed.

[0163] The electrochemical gas sensor 300 is configured so that CO flows into the detection unit 330 only through the gas inlet 323 of the second housing 320 and the vent 336 of the substrate 331, thereby controlling the amount of CO acting on the catalyst layer 333a. Therefore, the CO concentration can be accurately determined from the proportional relationship between the amount of CO inflow and the current value. The vent 336 is, for example, a through-hole that is perfectly circular in plan view and has a diameter of 0.05 mm to 1 mm, or 0.1 mm to 0.5 mm. In this embodiment, multiple vents 336 are formed only at positions that overlap the catalyst layer 333a.

[0164] The electrolyte membrane 332 is an ion-conducting membrane that transmits ions generated in the catalyst layer 333a to the catalyst layer 333b, and is an electrically insulating membrane that does not have electronic conductivity. The electrolyte membrane 332 may be formed, for example, by absorbing a liquid electrolyte into a support member such as a porous sheet, but is preferably a solid electrolyte membrane made of a polymer material. In this embodiment, a solid electrolyte membrane having proton conductivity is used. An example of a proton-conducting solid electrolyte membrane is a polymer membrane in which proton-conducting groups such as sulfonic acid groups are introduced into a hydrocarbon-based polymer or a fluorine-based polymer.

[0165] The thickness of the electrolyte membrane 332 is not particularly limited, but is, for example, 5 μm to 500 μm. The electrolyte membrane 332 can be formed by applying ink containing a solid electrolyte material to the first surface 331A of the substrate 331 so as to cover the catalyst layer 333, and then drying the applied film to volatilize and remove the dispersion medium. Examples of ink application methods include spray coating, screen printing, inkjet printing, electrolytic spray coating, and dispensing. The electrolyte membrane 332 has, for example, a rectangular shape in a plan view. However, the planar shape of the electrolyte membrane 332 is not particularly limited and can be changed as appropriate depending on the shape of the electrochemical gas sensor 300. Note that commercially available products such as Nafion (registered trademark: manufactured by DuPont) may also be used for the electrolyte membrane 332.

[0166] The catalyst layer 333 is formed, for example, directly on the wiring 334 and the first surface 331A of the substrate 331. The catalyst layer 333 can be formed by applying a catalyst material to the first surface 331A. The thickness of the catalyst layer 333 is not particularly limited, but is, for example, 1 μm to 500 μm, or 10 μm to 200 μm. It is preferable that the catalyst layers 333a, 333b, and 333c have the same thickness. The catalyst layers 333a, 333b, and 333c are formed separately from each other on the first surface 331A of the substrate 331 so as not to overlap each other. Each catalyst layer has, for example, a rectangular shape in a plan view, but the shape of each catalyst layer in a plan view is not particularly limited.

[0167] The catalyst constituting the catalyst layer 333 promotes the oxidation reaction of CO. The reaction of formula (1) above occurs in the catalyst layer 333a, which is the working electrode. In this embodiment, each catalyst layer is made of the same material. Examples of catalysts include platinum (Pt), palladium (Pd), gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), iridium (Ir), cobalt (Co), iron (Fe), and nickel (Ni). Among these, it is preferable to use a noble metal catalyst such as Pt or a PtRu alloy.

[0168] The catalyst layer 333 further includes a conductive support and an ionomer. The conductive support is a conductive material that holds the catalyst. Examples of suitable conductive supports include carbon black such as acetylene black and ketjen black, graphite carbon, and carbon materials such as carbon nanotubes. The catalyst is, for example, adhered to the particle surface of the carbon material. The ionomer is an ionically conductive material that allows the movement of protons generated by the reaction. An example of a suitable ionically conductive material is Nafion (registered trademark: manufactured by DuPont), which has the same composition as the electrolyte membrane.

[0169] The wiring 334 functions as a signal output wiring that electrically connects each catalyst layer to an external device. Portions of the wiring 334a, 334b, and 334c are formed on the protruding portion of the substrate 331 and are connected to the connecting portions 335a, 335b, and 335c, respectively. The conductor layer constituting the wiring 334 is formed on the first surface 331A of the substrate 331, for example, by forming copper foil over the entire surface of the insulating substrate, pattern-etching the copper foil, and further plating the remaining copper foil. One example of the wiring 334 is a layer in which the surface of copper is plated with nickel / gold, and has a thickness of 5 μm to 30 μm. Note that the wiring 334 may also be formed by other methods, such as vapor deposition or printing.

[0170] 18 is a cross-sectional view taken along line CC in FIG. 15 , and FIG. 19 is a cross-sectional view taken along line DD in FIG. 15 . As shown in FIGS. 18 and 19 , the electrochemical gas sensor 300 has a structure in which a substrate 331 is sandwiched between a first housing 310 and a second housing 320, and the periphery of a detection unit 330 is sealed with sealing members 342 and 343. The sealing member 342 is formed in an annular shape to surround the detection unit 330 and is pressed between the inner surface of the first housing 310 and a first surface 331A of the substrate 331. The sealing member 343 is formed in an annular shape to surround the air vent 336 and is pressed between the inner surface of the second housing 320 and a second surface 331B of the substrate 331. This effectively prevents environmental gases from entering and moisture from escaping through gaps between the housings and the substrate 331 in the X and Y directions.

[0171] As described above, the first housing 310 has a storage section 314, which is a recess that stores the humidity-conditioning material 340. The storage section 314 is formed with a depth sufficient to store the humidity-conditioning material 340, for example, a depth exceeding 50% of the Z-direction length of the first housing 310. In this embodiment, two spherical humidity-conditioning materials 340 are stored in the storage section 314, aligned in the X-direction. The first housing 310 is also provided with a lid 360 that covers the opening of the storage section 314 and prevents contact between the detection unit 330 and the humidity-conditioning material 340. A through-hole 364 is formed in the lid 360, and moisture in the humidity-conditioning material 340 is released from the storage section 314 through the through-hole 364. The through-hole 364 is located in an area surrounded by the annular sealing member 342.

[0172] As will be described in detail later, the lid 360 includes a plate-shaped base 363 that covers the storage section 314, a first piece 361 that stands on a first end of the base 363 and extends into the storage section 314, and a second piece 362 that stands on a second end of the base 363 and extends into the storage section 314. As described above, the second piece 362 has a protrusion 367 that protrudes in the opposite direction from the first piece 361, and a locking portion 314a that engages with the protrusion 367 is formed on the side of the storage section 314. In addition, the first housing 310 has a multi-step shape at the edge of the opening of the storage section 314. A first step 315, a second step 316, and a third step 317 are formed on the edge of the opening of the storage section 314, in that order from the storage section 314 side, and the base 363 of the lid 360 is disposed on the first step 315. Furthermore, the sealing member 342 is disposed on the second step portion 316 , and the substrate 331 is disposed on the third step portion 317 .

[0173] The substrate 331 is disposed with a gap between it and the lid 360 in the internal space of the electrochemical gas sensor 300. The base 363 of the lid 360 is placed on the first step 315, for example, so that the surface of the base 363 facing the substrate 331 is flush with the second step 316. The detection unit 330 is provided on a first surface 331A of the substrate 331 facing the lid 360. However, because the detection unit 330 is a thin film, a gap corresponding to the height of the third step 317 is formed between the first surface 331A and the lid 360. By providing a gap between the detection unit 330 and the base 363 of the lid 360, in which the through-holes 364 are formed, moisture can be supplied evenly to the entire electrolyte membrane 332, and the moisture content in the electrolyte membrane 332 can be more appropriately adjusted.

[0174] The second housing 320 has a storage section 324, which is a recess that stores activated carbon 341. The storage section 324 is a space that is widely open toward the substrate 331, and in this embodiment, the storage section 324 is filled with activated carbon 341 without any gaps. In this case, gas that flows in through the gas inlet 323 passes through the activated carbon 341 and flows into the ventilation hole 336 of the substrate 331. As a result, non-detection target gases are trapped by the activated carbon 341, thereby achieving further improvement in reliability and sensitivity. The gas inlet 323 is formed in the center of the bottom of the storage section 324, and the activated carbon 341 is positioned so as to block the path from the gas inlet 323 to the ventilation hole 336, i.e., so that the flowing gas always passes through the activated carbon 341.

[0175] 18 , the leaf spring 350 has a pair of opposing first portions 351 a, 351 b, a second portion 352 connecting the first portions 351 a, 351 b, and protrusions 353 a, 353 b protruding toward each other at the tips of the first portions 351 a, 351 b, forming a generally U- or C-shape overall. Recesses 311, 321 are formed on both longitudinal ends of the outer surface of each housing, and the leaf spring 350 is attached to the housing by sliding it from both longitudinal sides of the housing with the tips of the first portions 351 a, 351 b facing the housing. The first portions 351 a, 351 b fit into the recesses 311, 321, pressing against the outer surface of each housing.

[0176] In the initial state (when not fastened to the housing), the distance between the first portions 351a and 351b of the leaf spring 350 is smaller than when fastened to the housing. That is, when the leaf spring 350 is fastened to the housing, the distance between the first portions 351a and 351b is wider than when fastened to the housing. In this case, a restoring force that attempts to return to the original shape acts in a direction that brings the first portions 351a and 351b closer together, and the leaf spring 350 presses both longitudinal ends of each housing. The leaf spring 350 sandwiches the first housing 310 and the second housing 320 and crushes the sealing members 342 and 343. As a result, the assembled state of the housings is maintained stably, and good airtightness is achieved.

[0177] As will be described in detail later, the recess 311 of the first housing 310 is formed with a slope 311a and a recess 311b. Similarly, the recess 321 of the second housing 320 is formed with a slope 321a and a recess 321b. When the leaf spring 350 is slid from both sides of the housing in the longitudinal direction, the distance between the first portions 351a and 351b smoothly widens along the slopes 311a and 321a, and eventually the protrusions 353a and 353b fit into the recesses 311b and 321b. Flat surfaces 311c and 321c are formed along the X direction between the slope 311a and the recess 311b, and between the slope 321a and the recess 321b. The leaf spring 350 opens to its maximum when the protrusions 353a and 353b pass through these flat surfaces. The leaf spring 350 is designed to prevent plastic deformation due to stress generated when the leaf spring 350 is fully opened.

[0178] The substrate 331 and the leaf spring 350 overlap in the assembly direction (Z direction) of the first housing 310 and the second housing 320. In this case, the pressing force of the leaf spring 350 is more likely to act on the substrate 331, and the substrate 331 can be more stably fixed. The tips of the first portions 351a and 351b extend beyond the X-direction end of the substrate 331 to a position where they overlap with the detection unit 330 in the Z direction. It is preferable that the recessed portion 311b of the first housing 310 and the recessed portion 321b of the second housing 320 are formed in positions aligned in the Z direction, and the tip positions of the first portions 351a and 351b are substantially aligned in the Z direction.

[0179] Furthermore, at least one of the sealing members 342, 343 and the leaf spring 350 overlap in the Z direction. In this embodiment, both the sealing members 342, 343 and the leaf spring 350 overlap in the Z direction, and the tips of the first portions 351a, 351b are located more inward of the sensor than the sealing members 342, 343. In this case, the pressing force of the leaf spring 350 makes it easier to crush the sealing members 342, 343, improving airtightness. The sealing members 342, 343 are arranged side by side in the Z direction near the ends of the substrate 331 in the X direction.

[0180] As described above, the first housing 310 has the heat conduction suppression recess 313. The heat conduction suppression recess 313 is formed in the longitudinal center portion of the outer surface of the first housing 310 that is pressed by the leaf spring 350 and is not covered by the leaf spring 350. The heat conduction suppression recess 313 is sandwiched between the two recesses 311 and is formed over the entire length of the outer surface of the first housing 310 in the Y direction. The heat conduction suppression recess 313 reduces the heat transfer area between the electrochemical gas sensor 300 and the circuit board, thereby suppressing the occurrence of condensation. It is also possible to flatten the longitudinal center portion of the outer surface of the first housing 310 without forming the heat conduction suppression recess 313.

[0181] The second portion 352 of the leaf spring 350 is located further outward in the Y direction than the side surfaces of the respective housings and covers most of the side surfaces of the respective housings. The first portion 351a does not protrude beyond the first housing 310 in the Z direction, and most of the first portion 351a is substantially flush with the outermost surface of the first housing 310. The recess 311 into which the first portion 351a fits has a depth equal to or greater than the thickness of the leaf spring 350 (first portion 351a), preventing the first portion 351a from protruding in the Z direction. Similarly, the first portion 351b does not protrude beyond the second housing 320 in the Z direction, and most of the first portion 351b is substantially flush with the outermost surface of the second housing 320. With this configuration, the leaf spring 350 does not get in the way when mounting the electrochemical gas sensor 300 on a circuit board, facilitating mounting the sensor on the circuit board.

[0182] 20 to 22B, the first housing 310, the second housing 320, and the leaf spring 350 will be described in further detail. Fig. 20 is a perspective view of the leaf spring 350 in an initial state, Figs. 21A and 21B are perspective views of the first housing 310, and Figs. 22A and 22B are perspective views of the second housing 320.

[0183] As shown in FIG. 20 , the leaf spring 350 has a structure in which a pair of opposing first portions 351 a, 351 b are connected by a second portion 352, and the boundary between the first portions 351 a, 351 b and the second portion 352 is significantly curved. Note that the boundary between the first portions 351 a, 351 b and the second portion 352 does not need to be clearly defined. The leaf spring 350 is formed by bending a single metal plate. In the initial state of the leaf spring 350, the first portions 351 a, 351 b are bent so that their tips approach each other. As described above, the leaf spring 350 can clamp the housing by fastening to the housing with the distance between the first portions 351 a, 351 b wider than in the initial state.

[0184] The direction in which the first portion 351 a, the second portion 352, and the first portion 351 b are aligned along the surface of the leaf spring 350 is the length direction of the leaf spring 350, and the direction perpendicular to the length direction is the width direction of the leaf spring 350. The leaf spring 350 has a constant width and thickness except for, for example, the tip portions of the first portions 351 a and 351 b.

[0185] Protrusions 353a and 353b that protrude toward each other are formed at the tips of the first portions 351a and 351b, respectively. The leaf spring 350 is prevented from coming off the housings by fitting the protrusion 353a into the recess 311b of the first housing 310 and the protrusion 353b into the recess 321b of the second housing 320. The protrusion 353a of the first portion 351a is curved so as to be convex toward the first portion 351b. The protrusion 353b of the first portion 351b is similarly curved so as to be convex toward the first portion 351a and is formed in a position opposite the protrusion 353a.

[0186] The tips of the first portions 351a and 351b are curved so that the distance between them increases. In this case, when fastening the leaf spring 350 to the housing, the tips of the first portions 351a and 351b are less likely to get caught on the housing, making it easier to fasten the leaf spring 350. In this embodiment, the protrusions 353a and 353b are curved so that the distance between them increases from their most protruding portions toward their tips. Therefore, when fastening the leaf spring 350, the curved surfaces of the protrusions 353a and 353b come into contact with the housing, and the tips of the first portions 351a and 351b do not get caught on the housing. Furthermore, because the protrusions 353a and 353b that come into contact with the housing are curved rather than angular, fastening the leaf spring 350 is easier.

[0187] Further, notches 354a and 354b are formed at the tips of the first portions 351a and 351b, respectively. The notches 354a are formed at both widthwise ends of the tip of the first portion 351a, and no protrusions 353a are formed at these widthwise ends. In other words, both widthwise ends of the protrusions 353a are removed by the notches 354a. Similarly, the first portion 351b has notches 354b formed at both widthwise ends of the tip. By forming the notches 354a and 354b, it is possible to prevent both widthwise ends of the tips of the first portions 351a and 351b from interfering with the housing.

[0188] A protrusion 353a is formed at the tip of the first portion 351a, spanning the notches 354a at both widthwise ends. That is, the protrusion 353a extends in the widthwise direction of the leaf spring 350 and is continuous from the notch 354a on one side to the notch 354b on the other side (the same applies to the protrusion 353b). Note that a plurality of protrusions 353a, 353b may be provided in the widthwise direction of the leaf spring 350. In this case, the protrusions are formed intermittently at intervals in the widthwise direction of the leaf spring 350, and, for example, the protrusions and the notches are arranged alternately in the widthwise direction of the leaf spring 350.

[0189] The leaf spring 350 is preferably symmetrical with respect to a plane along the width direction that passes through the center of the length direction of the second portion 352. In other words, the leaf spring 350 has a rotationally symmetric shape with respect to an axis that passes through the length direction and width direction of the second portion 352 and is perpendicular to the second portion 352, and when the leaf spring 350 is rotated 180° around this axis, it matches its original shape. In this case, there is no need to consider the orientation of the leaf spring 350 when attaching it to a housing, and the pressing force of the leaf spring 350 acting on each housing is stabilized.

[0190] As shown in FIG. 21A , the outer surface of the first housing 310 has a rectangular shape in a plan view, with two recesses 311 formed on each short side of the rectangle and a heat conduction suppressing recess 313 sandwiched between the recesses 311. The first housing 310 has a shape that is rotationally symmetrical with respect to an axis that passes through the center in the longitudinal and lateral directions and is perpendicular to the outer surface of the first housing 310. As described above, the recess 311 is a portion into which the leaf spring 350 fits, and preferably has a depth equal to or greater than the thickness of the leaf spring 350. The recess 311 has an inclined surface 311a that gradually decreases in height toward the short side of the rectangle. The recess 321 of the second housing 320 also has an inclined surface 321a, and the inclined surfaces 311a, 321a are inclined toward each other toward the short side of the rectangle.

[0191] The slope 311a of the first housing 310 allows the leaf spring 350 to be smoothly fastened to the housing. The leaf spring 350 is fastened to the housing by sliding it in the X direction, but at this time, the gap between the first portions 351a and 351b must be widened from its initial state. That is, a restoring force acts on the first portion 351a to return it to its original shape. If the first housing 310 has sharp corners, the first portion 351a may get caught on the corners of the housing, making smooth sliding difficult. By chamfering the corners of the first housing 310 to form the slope 311a, the first portion 351a slides along the slope 311a, gradually widening the gap between the first portion 351a and the first portion 351b, allowing the leaf spring 350 to be smoothly fastened.

[0192] The recess 311 also has a recess 311b into which the protrusion 353a of the leaf spring 350 fits, and a flat surface 311c located between the slope 311a and the recess 311b. The recess 311b is preferably formed deeper than the flat surface 311c so that the entire protrusion 353a can be accommodated. The protrusion 353a fitting into the recess 311b effectively prevents the leaf spring 350 from coming off the first housing 310. The flat surface 311c is a flat surface that is parallel to the X and Y directions and has no irregularities. The provision of the flat surface 311c facilitates stable application of the pressing force of the leaf spring 350 in the housing assembly direction (Z direction).

[0193] In a cross-sectional view of the first housing 310 in the X direction (see FIG. 18 ), the angle of the inclined surface 311a with respect to an extension line of the flat surface 311c is, for example, 20° or more, and preferably 30° to 45°. In this embodiment, the angle of the inclined surface 311a is the same as the angle of the inclined surface 321a with respect to an extension line of the flat surface 321c of the second housing 320. In this case, the leaf spring 350 can be fastened more smoothly.

[0194] The first housing 310 further has guide walls 312 that guide the insertion of the leaf spring 350 into the recess 311. A pair of guide walls 312 are formed on both sides of the recess 311 in the Y direction, and together with the inclined surfaces 311a, enable smooth fastening of the leaf spring 350. If the guide walls 312 were not present, it would be expected that the leaf spring 350 would be fastened in a state in which the first portion 351a protrudes from the outer surface of the first housing 310 in the Y direction. However, the presence of the guide walls 312 on both sides of the recess 311 in the Y direction prevents this fastening state. The guide walls 312 are formed from the inclined surfaces 311a to the recessed portions 311b, in other words, from both ends of the first housing 310 in the X direction to the heat conduction suppressing recess 313.

[0195] The width (length in the Y direction) of the recess 311 is slightly larger than the width of the leaf spring 350, and is preferably 80% to 95% of the width of the leaf spring 350. In this case, the leaf spring 350 can be smoothly fastened along the pair of guide walls 312, and the assembled state of the first housing 310 and the second housing 320 is maintained stably.

[0196] 21B , first housing 310 has storage section 314, which is a first recess that stores humidity conditioner 340, and a multi-step shape formed on the opening edge of storage section 314. The opening edge of storage section 314 includes first step 315, which is a second recess in which base 363 of lid 360 is disposed, second step 316, which is a third recess in which sealing member 342 is disposed, and third step 317, which is a fourth recess in which substrate 331 is disposed. The heights of first step 315, second step 316, and third step 317 increase in this order, and the distance from storage section 314 increases. Therefore, sealing member 342 is disposed so as to surround lid 360, and a gap is formed between substrate 331 and lid 360.

[0197] The first step portions 315 are formed on both sides of the storage portion 314 in the Y direction with a depth corresponding to the thickness of the base portion 363 of the lid 360. The first surface of the base portion 363, which is placed on the first step portion 315 and faces the substrate 331, is flush with, for example, the second step portion 316. The first step portions 315 are not formed along the Y direction on both sides of the storage portion 314 in the X direction. That is, the first step portions 315 are formed separately on both sides of the storage portion 314 in the Y direction. The second step portion 316 is formed in an annular shape surrounding the storage portion 314 and the first step portion 315. The second step portion 316 is formed shallower than the thickness of the sealing member 342 and crushes the sealing member 342 together with the substrate 331. In other words, a sealing member 342 having a thickness greater than the depth of the second step portion 316 is disposed on the second step portion 316.

[0198] The third step portion 317 is formed in a ring shape surrounding the second step portion 316. The third step portion 317 is surrounded by walls on three sides except for one end in the Y direction, and supports the ends of the substrate 331 along three sides. That is, the third step portion 317 is formed up to one end in the Y direction of the first housing 310. At one end in the Y direction of the first housing 310, no wall is formed on the third step portion 317, and an opening 319 is formed through which a portion of the substrate 331 protrudes. The third step portion 317 is narrower than the second step portion 316 and is formed to a depth corresponding to the substrate 331. A second surface 331B of the substrate 331 placed on the third step portion 317 is, for example, flush with the walls surrounding the third step portion 317 on three sides.

[0199] Convex portions 318 that protrude toward the second housing 320 are formed on both ends of the first housing 310 in the X direction. Concave portions 326 (see FIG. 22B described below) into which the convex portions 318 fit are formed in the second housing 320, and fitting the convex portions 318 into the concave portions 326 makes the assembled state of the first housing 310 and the second housing 320 more stable.

[0200] As shown in FIG. 22A , the outer surface of the second housing 320 has a rectangular shape in a plan view and two recesses 321 formed from each short side of the rectangle. Like the recess 311 of the first housing 310, the recess 321 has a depth equal to or greater than the thickness of the leaf spring 350. The recess 321 has a slope 321a that gradually decreases in height toward the short side of the rectangle. Together with the slope 311a of the first housing 310, this enables smooth fastening of the leaf spring 350 to the housing. The recess 321 also has a recess 321b into which the protrusion 353b of the leaf spring 350 fits, and a flat surface 321c located between the slope 321a and the recess 321b. The second housing 320 further has a guide wall 322 that guides the insertion of the leaf spring 350 into the recess 321.

[0201] The recessed portion 321b is formed deeper than the flat surface 321c, effectively preventing the leaf spring 350 from coming off the second housing 320. The flat surface 321c is a smooth surface parallel to the X and Y directions, allowing the pressing force of the leaf spring 350 to stably act in the direction in which the housing is assembled (Z direction). A pair of guide walls 322 are formed on both sides of the recessed portion 311 in the Y direction, and together with the inclined surface 321a, enable the leaf spring 350 to be fastened smoothly and stably. The guide walls 322 are formed from the inclined surface 321a to the recessed portion 321b.

[0202] As shown in FIG. 22B , the second housing 320 is formed with a storage section 324 that stores activated carbon 341. The periphery of the storage section 324 is formed flat and abuts against the second surface 331B of the substrate 331. The second housing 320 also has a gas introduction hole 323 that penetrates the housing from the longitudinal center of the outer surface to the bottom of the storage section 324. The second housing 320 further has an annular groove 325 in which the sealing member 343 is disposed, and a recess 326 into which the protrusion 318 of the first housing 310 fits. The groove 325 is shallower than the thickness of the sealing member 343 and is formed in an annular shape surrounding the flat surface around the storage section 324. The recess 326 is formed at both ends of the second housing 320 in the X direction, with a size that is just large enough to fit the protrusion 318.

[0203] According to the above-described configuration of the first housing 310, the second housing 320, and the leaf spring 350, the leaf spring 350 can be easily fastened to the housing without using a special jig by sliding the leaf spring 350 from both sides of the housing in the X direction. Furthermore, the fastening load of the leaf spring 350 compresses the sealing members 342 and 343, ensuring good airtightness and maintaining a stable assembled state of the first housing 310 and the second housing 320. According to this embodiment, processing costs can be reduced, and a sealing structure with excellent airtightness can be realized at low cost.

[0204] 23A and 23B, the lid 360 will be described in further detail. Fig. 23A is a perspective view of the lid 360 as seen from the first surface (the surface facing the substrate 331), and Fig. 23B is a perspective view of the lid 360 as seen from the second surface (the surface facing the storage section 314).

[0205] 23A and 23B , the lid 360 has a first piece 361, a second piece 362, and a rib 365 that are erected on a second surface of the base 363 facing the storage section 314 (see FIG. 18 , etc.). The first piece 361, the second piece 362, and the rib 365 are all formed perpendicular to the base 363 and are inserted into the storage section 314, enabling the lid 360 to be stably fixed to the first housing 310. As described above, the second piece 362 has a protrusion 367, and the side surface of the storage section 314 is formed with a locking portion 314a onto which the protrusion 367 can be hooked. By fitting the protrusion 367 into the locking portion 314a, the lid 360 is firmly fixed to the first housing 310 without coming off from the first housing 310.

[0206] The base 363 has a rectangular shape in a plan view and completely covers the opening of the storage section 314. The base 363 functions as a partition wall that prevents contact between the detection unit 330 and the humidity conditioner 340. It is preferable that the base 363 be the same size as the opening of the storage section 314, as long as it does not interfere with installation in the storage section 314. The base 363 also has a thickness that is substantially the same as the depth of the first step 315 of the first housing 310. In this case, the first surface of the base 363 is flush with the second step 316, and no significant step is formed around the base 363. The lid 360 has a through-hole 364 that penetrates the base 363 in the thickness direction, and moisture in the humidity conditioner 340 is released from the storage section 314 through the through-hole 364.

[0207] The through-holes 364 are formed at a position facing the detection unit 330. In this embodiment, two small through-holes 364 with a diameter of 1 mm or less are formed. The amount of moisture supplied to the detection unit 330 can be controlled by adjusting the size and number of the through-holes 364. A gap may exist between the opening of the storage unit 314 and the base 363, and moisture from the humidity conditioner 340 may be released through this gap. Alternatively, a sealing member may be provided around the base 363 to close the gap, so that moisture is released only through the through-holes 364.

[0208] The locking portion 314a into which the protrusion 367 of the second piece 362 fits is an undercut portion formed in the lower part of the side surface of the storage portion 314. To form the undercut portion, a mold with a slider is required, and one slider is required for each undercut portion. Increasing the number of sliders increases manufacturing costs and restricts the structure of the molded body, such as requiring a width of approximately 10 mm when removing the slider. In this embodiment, the locking portion 314a is formed in only one location on the side surface located at one longitudinal end of the storage portion 314, so only one slider is required, and it is easy to remove the slider from the molded body. As a result, manufacturing costs can be reduced and the first housing 310 can be made smaller.

[0209] An example of the dimensions of the storage section 314 is a length of approximately 10 mm and a width of approximately 5 mm. By providing only one undercut portion, such a small storage section 314 can be formed at low cost. The depth of the locking portion 314a is, for example, 2 mm or less. On the other hand, if there is only one locking portion 314a, the strength of the lid 360 is insufficient, and it is expected that the lid 360 will come off the locking portion 314a. Therefore, in this embodiment, the first piece 361 is provided in a position opposite the second piece 362 having the protrusion 367 to suppress deformation of the lid 360. Furthermore, by providing the rib 365, the deformation suppression effect becomes more pronounced.

[0210] The first piece 361 stands on one longitudinal end of the base 363 and is arranged along the side surface of the storage section 314 (see FIG. 18 ). The first piece 361 functions as a beam without a protrusion (claw) that can hook onto the first housing 310, effectively preventing the lid 360 from deforming inward in the longitudinal direction. The first piece 361 may abut against the side surface of the storage section 314, or may abut against the side surface of the storage section 314 when a load is applied to the lid 360. In this embodiment, the first piece 361 has the same length as the second piece 362, a width greater than that of the second piece 362, and is formed parallel to the second piece 362. The provision of the first piece 361 effectively prevents the lid 360 from coming off the first housing 310 even when only one claw hooks onto the locking portion 314a.

[0211] As described above, the second piece 362 has a protrusion 367 that hooks onto the locking portion 314a, and functions as a beam with a claw. The protrusion 367 is formed at the tip of the second piece 362 and protrudes in the opposite direction from the first piece 361. Like the first piece 361, the second piece 362 is arranged along the side surface of the storage section 314 and may abut against the side surface of the storage section 314, or may abut against the side surface of the storage section 314 when a load is applied to the lid 360. The second piece 362 hooking onto the locking portion 314a securely fixes the lid 360 to the first housing 310.

[0212] At least one of the first piece 361 and the second piece 362 has a tapered slope formed on the tip thereof on the side facing the side of the storage section 314. In this embodiment, both pieces have this slope. The protrusion 367 of the second piece 362 has a flat surface facing the substrate 331 to easily hook onto the locking portion 314a, but the surface facing the bottom of the storage section 314 has a slope formed that gradually slopes toward the first piece 361 toward the tip of the second piece 362. Forming slopes on the tip portions of the first piece 361 and the second piece 362 makes it easier to insert the lid 360 into the storage section 314, improving productivity.

[0213] The rib 365 is a reinforcing wall that is lower than the first piece 361 and the second piece 362, and effectively suppresses deformation of the lid 360, such as lifting of the end on the first piece 361 side. The rib 365 extends from the first piece 361 toward the second piece 362, i.e., in the longitudinal direction of the base 363, so as to be connected to the first piece 361 but not to the second piece 362. Connecting the rib 365 to the first piece 361 reinforces the base of the first piece 361 and increases the rigidity of the lid 360, thereby more significantly suppressing deformation of the lid 360. On the other hand, not connecting the first piece 361 to the rib 365 makes it easier for the first piece 361 to fit into the locking portion 314a.

[0214] A plurality of ribs 365 are provided facing each other, extending from both widthwise sides of the first piece 361 toward the second piece 362. While a single rib 365 may be provided, providing multiple ribs more significantly suppresses deformation of the lid 360. The ribs 365 are formed parallel to each other at the same height on both widthwise sides of the base 363. Preferably, a pair of ribs 365 are formed along the entire length of the base 363 and connected to both widthwise ends of the first piece 361. The end of the rib 365 on the second piece 362 side may have a slope that gradually slopes toward the first piece 361 toward the tip of the rib 365 to facilitate insertion of the lid 360 into the storage section 314.

[0215] The pair of ribs 365 include, on the surfaces that do not face each other, inclined portions 366 that are tapered toward the tips of the ribs 365. The inclined portions 366 are provided at multiple locations on each rib 365, for example, one on each side of the longitudinal center of the rib 365. The inclined portions 366 are molded integrally with the rib 365, and it can be said that the rib 365 is widened at the portions where the inclined portions 366 are present. The inclined portions 366 have the function of centering and guiding the lid 360 to an appropriate position when the lid 360 is inserted into the storage section 314.

[0216] The above-described configuration of the lid 360 effectively suppresses deformation of the lid 360 and prevents the lid 360 from coming off the first housing 310. In a vibration test in accordance with European Standard EN54-31, it was confirmed that the protrusion 367 of the second piece 362 does not come off the locking portion 314a.

[0217] As described above, the electrochemical sensor 300 having the above configuration has a small and simple structure, yet has excellent airtightness and can appropriately control the amount of moisture in the electrolyte membrane 332. The pair of leaf springs 350 stably maintain the assembled state of the first housing 310 and the second housing 320, and effectively suppress the inflow of environmental gas and the outflow of moisture from any location other than the gas inlet hole 323. Furthermore, the lid 360 disposed between the detection unit 330 and the humidity conditioner 340 is securely fixed to the first housing 310, preventing contact between the detection unit 330 and the humidity conditioner 340. As a result, the amount of moisture contained in the electrolyte membrane 332 is appropriately controlled, and the electrochemical gas sensor 300 can be improved in sensitivity and reliability.

[0218] The above-described embodiments may be modified as appropriate without departing from the scope of the present disclosure. For example, in the above-described embodiments, the reference electrode catalyst layer is formed using the same electrode material as the working electrode catalyst layer 333a and the counter electrode catalyst layer 333b. However, the reference electrode may be formed from a different material than the catalyst layers 333a and 333b, or the catalyst layers 333a and 333b may be formed from different materials. The electrochemical gas sensor may also have a two-electrode structure including only a working electrode and a counter electrode. Alternatively, a metal layer may serve as the reference electrode, and the counter electrode may also serve as the reference electrode. The electrochemical gas sensor may also include other components, such as a gas diffusion layer.

[0219] In the above-described embodiment, a protrusion is formed at the tip of the spring member, and a recess is formed in the housing into which the protrusion fits, but it is also possible to form a recess in the spring member and a protrusion in the housing. In this case, the spring member has a pair of first portions facing each other, a second portion connecting the first portions, and recesses recessed in directions away from each other at the tip sides of each first portion, and protrusions that fit into the recesses are formed in the recesses of the first and second housings.

[0220] The present disclosure will be further described by the following embodiments. Configuration 1: An electrochemical gas sensor comprising: a first housing having a recess; a second housing assembled to the first housing to form an internal space between it and the first housing; a humidity control material housed in the recess; a detection unit housed in the internal space; and a lid disposed between the humidity control material and the detection unit and covering the recess, wherein the lid includes a plate-shaped base covering the recess, a first piece erected on a first end side of the base and extending into the recess, and a second piece erected on a second end side of the base and extending into the recess and having a protrusion protruding in the opposite direction from the first piece, and a locking portion formed on a side surface of the recess to engage with the protrusion of the second piece. Configuration 2: An electrochemical gas sensor according to Configuration 1, wherein a tip of at least one of the first piece and the second piece is formed with a slope that is inclined toward the side facing the side surface of the recess so that the tip becomes narrower. Configuration 3: The electrochemical gas sensor according to Configuration 1, further comprising a rib erected on the base and extending into the recess, the rib extending from the first piece toward the second piece so as to be connected to the first piece but not to the second piece. Configuration 4: The electrochemical gas sensor according to Configuration 3, wherein a plurality of the ribs are provided facing each other and extend from both sides in the width direction of the first piece toward the second piece. Configuration 5: The electrochemical gas sensor according to Configuration 4, wherein the plurality of ribs include inclined portions on the sides not facing each other that are tapered toward the tips of the ribs. Configuration 6: The electrochemical gas sensor according to any one of Configurations 3 to 5, wherein the inclined portions are provided at a plurality of locations on the rib. Configuration 7: The electrochemical gas sensor according to any one of Configurations 1 to 6, further comprising a substrate on which the detection unit is provided, the substrate being disposed in the internal space with a gap between it and the lid. Configuration 8: The electrochemical gas sensor according to any one of Configurations 1 to 7, wherein the recess includes a first recess for accommodating the humidity conditioner and a second recess formed on an opening edge of the first recess, and the base of the lid is disposed in the second recess.Configuration 9: The electrochemical gas sensor according to Configuration 8, further comprising a sealing member surrounding the detection section, wherein the recess has a third recess formed in an annular shape surrounding the first recess and the second recess, and the sealing member is disposed in the third recess.Configuration 10: A gas detection device comprising the electrochemical gas sensor according to any one of Configurations 1 to 9 and a housing that houses the electrochemical gas sensor.Configuration 11: The gas detection device according to Configuration 10, further comprising a smoke detection section housed in the housing and that detects smoke.Configuration 12: A gas detection system comprising the gas detection device according to Configuration 10 or 11 and a receiving device that communicates with the gas detection device.

[0221] The present disclosure will be further described with reference to the following embodiments. Configuration 1: An electrochemical gas sensor comprising: a first housing; a second housing assembled to the first housing to form an internal space between the first housing and the second housing; a detection unit housed in the internal space; and a plurality of spring members pressing against and sandwiching the first and second housings from both sides in the assembly direction of the first and second housings. Configuration 2: The electrochemical gas sensor according to Configuration 1, in which the first and second housings have rectangular surfaces pressed by the spring members, and the spring members are attached to each of the short sides of the rectangle. Configuration 3: The detection device according to Configuration 1 or 2, in which the first and second housings have recesses on their surfaces pressed by the spring members, into which the spring members fit. Configuration 4: The electrochemical gas sensor according to Configuration 3, in which the first and second housings have guide walls that guide the insertion of the spring members into the recesses. Configuration 5: The electrochemical gas sensor according to Configuration 3 or 4, wherein the spring member has a pair of first portions facing each other, a second portion connecting the first portions to each other, and protruding portions that protrude toward each other at the tip ends of the first portions, and the recesses of the first and second housings are formed with recesses into which the protruding portions fit.Configuration 6: The electrochemical gas sensor according to Configuration 5, wherein a plurality of the protruding portions are provided in the width direction of the spring member.Configuration 7: The electrochemical gas sensor according to any one of Configurations 3 to 6, wherein the spring member has a pair of first portions facing each other, a second portion connecting the first portions to each other, and recessed portions that are recessed away from each other at the tip ends of the first portions, and the recesses of the first and second housings are formed with protruding portions that fit into the recessed portions. The electrochemical gas sensor according to any one of the preceding configurations, wherein the first housing and the second housing have a surface that is pressed by the spring member, the surface having a slope that is inclined so that the height of the surface decreases toward the short side of the rectangle. The electrochemical gas sensor according to any one of the preceding configurations, wherein the spring member has a pair of first portions that face each other and a second portion that connects the first portions, and the tips of the first portions are bent so that the distance between them increases.Configuration 10: The electrochemical gas sensor according to any one of Configurations 1 to 9, wherein the spring member has a pair of first portions facing each other and a second portion connecting the first portions, and wherein notches are formed on both widthwise ends of the tips of the first portions.Configuration 11: The electrochemical gas sensor according to any one of Configurations 1 to 10, wherein the spring member has a pair of first portions facing each other and a second portion connecting the first portions, and wherein the spring member is symmetrical with respect to a plane along the widthwise direction passing through the center in the longitudinal direction of the second portions.Configuration 12: The electrochemical gas sensor according to any one of Configurations 1 to 11, further comprising a substrate on which the detection unit is provided, wherein the substrate and the spring member overlap in the assembly direction of the first housing and the second housing.Configuration 13: The electrochemical gas sensor according to any one of Configurations 1 to 12, further comprising a sealing member surrounding the detection unit, wherein the sealing member and the spring member overlap in the assembly direction of the first housing and the second housing. Configuration 14: The electrochemical gas sensor according to any one of Configurations 1 to 13, wherein one of the first and second housings has a vent hole for introducing a gas to be detected into the detection unit, and the other of the first and second housings has a recess in a region of a surface pressed by the spring member that is not covered by the spring member.Configuration 15: A gas detection device comprising the electrochemical gas sensor according to any one of Configurations 1 to 14 and a housing that houses the electrochemical gas sensor.Configuration 16: The gas detection device according to Configuration 15, further comprising a smoke detection unit housed in the housing that detects smoke.Configuration 17: A gas detection system comprising the gas detection device according to Configuration 15 or 16 and a receiving device that communicates with the gas detection device.

[0222] 1 Electrochemical gas sensor, 10 Substrate, 10a First surface, 10b Second surface, 11, 11a, 11b, 11c Wiring, 12, 43 Gas inlet hole, 13 Base portion, 14, 14a, 14b, 14c Protrusion, 15, 15a, 15b, 15c Connection portion, 20, 20a, 20b, 20c Catalyst layer, 30 Electrolyte layer, 40 Cover, 41 First cover, 42 Second cover, 50, 51 Sealing member, 60 Humidity control member, 70 Partition layer, 80 Activated carbon, 90 Leaf spring, 100 Gas detection system, 101 Receiving device, 102 Control device, 110 Gas detection device, 111 Housing, 112 Circuit board, 113 Pin

[0223] 200, 200x Electrochemical gas sensor, 210 Substrate, 210a First surface, 210b Second surface, 211, 211a, 211b, 211c Conductor layer, 212, 252 Gas inlet hole, 220, 220a, 220b, 220c Catalyst layer, 230 Electrolyte layer, 240, 250 Cover, 260 Humidity control member, 270 Partition layer, 280 Activated carbon, 290 Sealing member

[0224] 300 Electrochemical gas sensor, 310 First housing, 311 Recess, 311a Slope, 311b Indented portion, 311c Flat surface, 312 Guide wall, 313 Recess for suppressing heat conduction, 314 Storage portion, 314a Locking portion, 315 First step portion, 316 Second step portion, 317 Third step portion, 318 Convex portion, 319 Opening portion, 320 Second housing, 321, 326 Recess, 321a Slope, 321b Indented portion, 321c Flat surface, 322 Guide wall, 323 Gas introduction hole, 324 Storage portion, 325 Groove, 330 Detection portion, 331 Substrate, 331A First surface, 331B Second surface, 332 Electrolyte membrane, 333, 333a, 333b, 333c Catalyst layer, 334, 334a, 334b, 334c Wiring, 335, 335a, 335b, 335c Connection portion, 336 Ventilation hole, 340 Humidity conditioner, 341 Activated carbon, 342, 343 Sealing member, 350 Leaf spring, 351a, 351b First portion, 352 Second portion, 353a, 353b Protrusion, 354a, 354b Notch, 360 Lid, 361 First piece, 362 Second piece, 363 Base portion, 364 Through hole, 365 Rib, 366 Inclined portion, 367 Protrusion

Claims

1. An electrochemical gas sensor comprising: a substrate including a first surface and a second surface; a gas detection unit disposed on the first surface of the substrate; a cover covering the gas detection unit; and wiring connected to the gas detection unit and a portion exposed from the cover, wherein a connection portion is formed on the portion of the wiring exposed from the cover to be connected to an external wiring or an external terminal.

2. The electrochemical gas sensor according to claim 1, wherein the substrate has a protrusion that protrudes from the cover, and the connection portion is formed on the protrusion.

3. The electrochemical gas sensor according to claim 2, wherein a plurality of said connection portions are formed on said protrusion.

4. The electrochemical gas sensor according to claim 2, wherein the electrochemical gas sensor has a plurality of the protrusions, and the connection portion is formed on each of the protrusions.

5. The electrochemical gas sensor according to claim 2, wherein the cover comprises a first cover covering the first surface of the substrate and a second cover covering the second surface of the substrate, and the protruding portion of the substrate is sandwiched between the first cover and the second cover.

6. The electrochemical gas sensor according to claim 5, wherein the cover covers the entire substrate except for the protruding portion.

7. The electrochemical gas sensor according to claim 5, wherein the first cover and the second cover accommodate the portion of the substrate other than the protruding portion and are connected to each other.

8. The electrochemical gas sensor according to claim 5, wherein the substrate has a first gas inlet hole that connects the first surface and the second surface in a region overlapping with the gas detection section, and the second cover has a second gas inlet hole and covers the second surface of the substrate including the portion where the first gas inlet hole is formed.

9. The electrochemical gas sensor according to claim 8, wherein the opening area of ​​the first gas inlet hole of the substrate is smaller than the opening area of ​​the second gas inlet hole of the second cover.

10. The electrochemical gas sensor according to claim 1, further comprising: a sealing member disposed between the cover and the first surface of the substrate; and a leaf spring that sandwiches the cover and the substrate from the outside and maintains the cover and the substrate in an integrated state.

11. The electrochemical gas sensor according to claim 5, further comprising: a sealing member disposed between at least one of the first cover and the second cover and the substrate; and a leaf spring that sandwiches the first cover and the second cover from the outside and maintains the first cover and the second cover in an integrated state.

12. The electrochemical gas sensor according to claim 5, further comprising: a humidity control member housed within the first cover without contacting the gas detection unit; and a breathable partition layer disposed between the gas detection unit and the humidity control member.

13. The electrochemical gas sensor according to claim 5, further comprising activated carbon disposed within said second cover.

14. A gas detection device comprising the electrochemical gas sensor according to any one of claims 1 to 13 and a housing that houses the electrochemical gas sensor.

15. A gas detection system comprising the gas detection device according to claim 14 and a receiving device for receiving detection information from the gas detection device.

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