WO2018235487A1

WO2018235487A1 - Gas sensor

Info

Publication number: WO2018235487A1
Application number: PCT/JP2018/019453
Authority: WO
Inventors: 雅山崎; 井上　剛; 灘浪　紀彦; 上木　正聡
Original assignee: 日本特殊陶業株式会社
Priority date: 2017-06-23
Filing date: 2018-05-21
Publication date: 2018-12-27
Also published as: JP2019007817A

Abstract

According to the present invention, the gas detection accuracy of a gas sensor is improved. This gas sensor 1 is provided with casings 11, 31, a substrate 13, a detection unit 33, and a seal material 14, wherein the seal material 14 contains catalyst particles capable of converting a first gas component into a second gas component. The substrate 13 is provided with: a surface 13a through which a gas to be measured is introduced to the inside; and a surface 13b through which the gas to be measured is discharged to the outside. The substrate 13 is configured to convert the first gas component into the second gas component by circulating the gas to be measured inside a region between the surface 13a and the surface 13b. The detection unit 33 detects the second gas component contained in the gas to be measured which is discharged from the substrate 13. The seal material 14 is formed of an inorganic fiber other than a metal fiber, and is disposed between a portion of an inner wall surface of a chamber of the casing 11 and outer surfaces of the substrate 13 other than the surfaces 13a, 13b.

Description

Gas sensor

The present disclosure relates to a gas sensor including a conversion unit that converts a first gas component into a second gas component.

In Patent Document 1, the atmosphere as the gas to be measured is always supplied in a constant amount into the chamber, and the catalyst in the chamber is subjected to pretreatment for burning and removing combustible gas such as CO and the like. There is described a gas sensor which detects NOx concentration by contacting the sensor element with the sensor element.

Japanese Patent Application Laid-Open No. 10-300702

In the gas sensor described in Patent Document 1, a catalyst is filled in the chamber so as to cross a flow path through which the measurement gas flows in the chamber, and the measurement gas having permeated through the catalyst is brought into contact with the sensor element.

As described above, when the gas-permeable catalyst is disposed in the chamber, the gap between the inner surface of the chamber and the outer surface of the catalyst is sealed with a sealing material, so that the gas to be measured does not leak from the gap and the inside of the catalyst is prioritized. Need to be transparent.

However, elastic bodies such as rubber generally used as a sealing material have low heat resistance. For this reason, the high temperature gas to be measured contacts the sealing material, and the temperature at which the catalyst is sufficiently activated is decreased, so that the performance of the sealing material blocking the flow of the measurement gas is reduced, and Gas may be generated to affect the gas detection accuracy.

The present disclosure aims to improve the gas detection accuracy of a gas sensor.

One aspect of the present disclosure includes a casing, a conversion unit, a detection unit, and a seal material, and the seal material contains catalyst particles capable of converting a first gas component into a second gas component. It is a gas sensor.

The casing has an internal space into which the gas to be measured can be introduced. The conversion unit includes an introduction unit into which the measurement gas introduced into the internal space is introduced into the interior, and a discharge unit into which the measurement gas introduced into the interior is discharged to the outside. Then, the conversion unit is configured to convert the first gas component contained in the measurement gas into the second gas component by causing the measurement gas to flow inside itself between the introduction unit and the discharge unit. It is housed in the inner space.

The detection unit is configured to detect a second gas component contained in the measurement gas discharged from the conversion unit. The sealing material is formed of inorganic fibers excluding metal fibers, and is disposed between at least a portion of the inner wall surface in the inner space of the casing and at least a portion of the outer surface of the conversion portion excluding the introducing portion and the discharging portion. .

In the gas sensor of the present disclosure configured as described above, at least a part of the gap between the casing and the conversion unit can be closed by the sealing material, and therefore the gas to be measured passes through the gap between the casing and the conversion unit instead of the conversion unit. It is possible to suppress the occurrence of a situation. Thereby, the gas sensor of this indication can improve gas detection accuracy.

In the gas sensor of the present disclosure, the sealing material is made of inorganic fibers other than metal fibers, and thus is flexible and easily deformed. Therefore, the sealing material easily closes the gap between the casing and the conversion unit, and it is possible to further suppress the occurrence of the measured gas passing through the gap between the casing and the conversion unit instead of the conversion unit. Further, in the gas sensor of the present disclosure, it is not necessary to apply a large load to deform the sealing material, unlike the sealing material formed of metal fibers, in order to close the gap between the casing and the conversion unit. For this reason, in the gas sensor of the present disclosure, it is possible to suppress the occurrence of a situation where the converter is damaged in order to close the gap between the casing and the converter.

Furthermore, in the gas sensor of the present disclosure, the seal material contains catalyst particles capable of converting the first gas component into the second gas component. For this reason, the first gas component is converted to the second gas component in at least a part of the measured gas that has passed through the gap between the casing and the conversion unit. Thereby, the gas sensor of this indication can further improve gas detection accuracy.

Further, in the gas sensor of the present disclosure, specifically, the casing includes a first storage portion and a second storage portion, and the gas to be measured discharged from the first storage portion is introduced into the second storage portion. In order to introduce | transduce, you may make it provide the distribution part comprised so that measurement gas could be distribute | circulated between a 1st accommodating part and a 2nd accommodating part. The first accommodating portion is configured to accommodate the conversion portion. The second storage unit is configured to receive the detection unit.

Further, the gas sensor of the present disclosure may be provided with a single heater that is housed inside the casing and heats the conversion unit and the detection unit. Thereby, the gas sensor of this indication can simplify composition of a gas sensor, and can miniaturize a gas sensor.

Further, in the gas sensor of the present disclosure, the heater may be housed inside the second housing portion, and may be provided with a dividing member and an adhesive. The dividing member is formed of a material capable of conducting heat, and is disposed between the first and second accommodating portions in order to separate the first and second accommodating portions. The adhesive is formed of a material having a thermal conductivity higher than that of the sealing material, and is disposed between the dividing member and the converting portion to make the converting portion adhere to the dividing member. Thereby, the gas sensor of this indication can heat a conversion part more efficiently.

In the gas sensor of the present disclosure, specifically, the catalyst particles may be made of at least one of a noble metal and an oxide.

It is an exploded perspective view of gas sensor 1 of a 1st embodiment. It is a sectional view of gas sensor 1 of a 1st embodiment. It is a 1st sectional view in gas sensor 2 of a 2nd embodiment. It is a 2nd sectional view in gas sensor 2 of a 2nd embodiment.

First Embodiment Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings. The gas sensor 1 of this embodiment is provided with the adjustment unit 2, the sensor unit 3, and the gas distribution pipe 4, as shown in FIG.

The adjustment unit 2 includes a casing 11, a packing 12, a base 13, and a seal member 14. The casing 11 includes a rectangular lower surface plate 21 and four

side plates

22, 23, 24, 25 vertically projecting from each of the four sides forming the rectangle of the lower surface plate 21, and an opening 26 is formed on the upper surface Made of metal.

The casing 11 also includes a flange 27. The flange 27 extends outward from the end on the upper surface side of the four

side plates

22, 23, 24, 25 perpendicularly to the

side plates

22, 23, 24, 25 and extends along the periphery of the opening 26. It is formed in a substantially rectangular frame shape.

FIG. 2 is a cross-sectional view of the gas sensor 1 cut along the flow direction in which the gas flows in the flow path 13c described later. As shown in FIG. 2, two through

holes

21 a and 21 b are formed in the lower surface plate 21 of the casing 11. The casing 11 is provided with an inlet 28 and an outlet 29. The inlet 28 is formed in a cylindrical shape so as to extend outward from the outer opening of the through hole 21 a perpendicularly to the bottom plate 21. Thus, the gas can be introduced into the interior of the casing 11 from the outer opening of the inlet 28. Similarly, the outlet 29 is formed in a cylindrical shape, extending perpendicularly outward from the outer opening of the through hole 21 b to the lower surface plate 21. Thereby, the gas can be discharged from the inside of the casing 11 to the outer opening of the inlet 28.

As shown in FIG. 1, the packing 12 is an elastic member formed in a rectangular frame shape substantially the same as the flange 27 in a plan view. The packing 12 is adhered to the flange 27 via an adhesive (not shown).

The base 13 is a ceramic member formed in a rectangular parallelepiped shape. In the base material 13, a flow passage 13c is formed to pass between two

surfaces

13a and 13b facing each other among the six surfaces constituting the rectangular parallelepiped. The surface 13a is not shown in FIG. 1, but is shown in FIG. In the present embodiment, four flow paths 13c are formed. In the inner wall surface of the flow path 13c, the first gas component (NO in the present embodiment) is converted to the second gas component (NO _{2 in the} present embodiment) at a predetermined activation temperature. The catalyst (in the present embodiment, a Pt supported zeolite) is applied.

The sealing material 14 is a member formed of inorganic fibers (in the present embodiment, alumina fibers) excluding metal fibers. Catalyst particles (Pt in the present embodiment) are added to the inorganic fibers constituting the sealing material 14. Examples of a method of adding catalyst particles to inorganic fibers include a method of immersing inorganic fibers in a solution containing catalyst particles and then drying and calcining. Also, instead of immersing the inorganic fibers in a solution containing catalyst particles, the inorganic fibers may be dipped in a slurry containing catalyst particles or zeolite containing γ-alumina. The sealing material 14 is disposed so as to be in contact with and cover four surfaces in which the flow path 13 c is not formed among the six surfaces forming the rectangular parallelepiped.

In the base material 13, the sealing material 14 disposed on three surfaces not formed with the flow channel 13 c among the six surfaces constituting the rectangular parallelepiped respectively contacts the lower surface plate 21, the side surface plate 23 and the side surface plate 25. The sealing material 14 disposed on one side of the housing 11 is disposed inside the casing 11 so that the sealing material 14 is exposed at the opening 26. The base 13 is disposed between the through hole 21 a and the through hole 21 b inside the casing 11. As a result, the gas to be measured introduced into the interior of the casing 11 through the through hole 21 a is discharged from the through hole 21 b to the outside of the casing 11 through the inside of the flow path 13 c of the substrate 13. In addition, when the to-be-measured gas passes through the inside of the flow path 13c of the base 13, the first gas component contained in the to-be-measured gas is converted to the second gas component.

The sensor unit 3 includes a casing 31, a packing 32, a detection unit 33, and a ceramic wiring board 34. The casing 31 is a metal member having a rectangular upper surface plate 41 and four side plates vertically projected from each of the four sides forming the rectangle of the upper surface plate 41, and having an opening 42 formed on the lower surface. is there. The opening 42 is not shown in FIG. 1, but is shown in FIG.

The casing 31 also includes a flange 43. The flanges 43 extend outward from the lower side end of the four side plates perpendicularly to the four side plates, and are formed in a substantially rectangular frame along the periphery of the opening 42.

Further, as shown in FIG. 2, two through

holes

41 a and 41 b are formed in the upper surface plate 41 of the casing 31. The casing 31 is provided with an inlet 44 and an outlet 45. The inlet 44 is formed in a cylindrical shape so as to extend outward from the outer opening of the through hole 41 a perpendicularly to the top plate 41. Thus, the gas can be introduced into the interior of the casing 31 from the outer opening of the inlet 44. Similarly, the outlet 45 is formed in a cylindrical shape, extending perpendicularly outward from the outer opening of the through hole 41 b to the top plate 41. Thereby, the gas can be discharged from the inside of the casing 31 to the outer opening of the outlet 45.

As shown in FIG. 1, the packing 32 is an elastic member formed in a rectangular frame shape substantially the same as the flange 43 in a plan view. The packing 32 is adhered to the flange 43 via an adhesive (not shown).

As shown in FIG. 2, the detection unit 33 includes a substrate 51, a sensor element 52, and a heater 53. The substrate 51 is a member formed of an insulating material in a rectangular plate shape. Although not shown in detail, the sensor element 52 is a gas sensor including a solid electrolyte body and a pair of electrodes disposed on the solid electrolyte body. The sensor element 52 outputs an electrical signal indicating the concentration of the second gas component based on the electrical characteristic that changes in accordance with the concentration of the second gas component contained in the measurement gas. The sensor element 52 is disposed on the upper surface 51 a of the substrate 51.

The heater 53 includes, for example, a heating resistor formed of a material mainly composed of platinum, and heats the sensor element 52 by power supplied from a power supply (not shown). The heater 53 is disposed on the lower surface 51 b of the substrate 51.

As shown in FIG. 1, the ceramic wiring board 34 includes a main body portion 61 and a narrow portion 62. The main body portion 61 is formed in a rectangular plate shape such that the shape of the outer periphery thereof substantially matches the shape of the outer periphery of the packing 12, 32. The upper surface 61 a of the main body 61 is formed with a recess 61 b for installing the detection unit 33.

The narrow portion 62 extends outward from one of four sides of the main body 61 and is formed in a rectangular plate shape. The narrow portion 62 has a length (i.e., width) along a direction perpendicular to the direction in which the narrow portion 62 extends outward is shorter than the length of the side (width) of the main portion 61. It is formed. Wirings electrically connected to the sensor element 52 and the heater 53 are formed on the narrow portion 62 with respect to the front and back surfaces.

Then, as shown in FIG. 2, the detection unit 33 is installed in the recess 61 b by bonding the lower surface 51 b of the substrate 51 to the bottom of the recess 61 b with the adhesive 35. The lower surface 12a of the packing 12 and the upper surface 27a of the flange 27 are bonded by an adhesive, and the upper surface 12b of the packing 12 and the outer peripheral portion of the lower surface 61c of the main body 61 of the ceramic wiring board 34 are bonded by an adhesive. As a result, the opening 26 of the casing 11 is closed by the main body 61 of the ceramic wiring board 34. The internal space of the casing 11 closed in this manner forms a chamber C1. The lower surface 61c of the main body portion 61 of the ceramic wiring substrate 34 is in contact with the surface of the sealing material 14 covering the base material 13 which is not in contact with the lower surface plate 21, the

side plates

23, 25 and the packing 12 Do.

Further, the upper surface 32a of the packing 32 and the lower surface 43a of the flange 43 are bonded by an adhesive, and the lower surface 32b of the packing 32 and the outer peripheral portion of the upper surface 61a of the main portion 61 of the ceramic wiring board 34 are bonded by an adhesive. As a result, the opening 42 of the casing 31 is closed by the main body 61 of the ceramic wiring board 34. The internal space of the casing 31 closed in this way forms a chamber C2.

As a result, the base material 13, the sealing material 14, the ceramic wiring substrate 34, the adhesive 35, the heater 53, the substrate 51, and the sensor element 52 are sequentially laminated. Therefore, as indicated by the arrow H1, the heat generated by the heater 53 is transmitted to the sensor element 52 through the substrate 51. Further, as indicated by the arrow H2, the heat generated by the heater 53 is transmitted to the base 13 through the adhesive 35, the ceramic wiring board 34 and the sealing material 14.

The gas flow pipe 4 is formed of resin or metal. Then, the outlet 29 is inserted into the opening at one end of the gas flow pipe 4, and the inlet 44 is inserted into the opening at the other end of the gas flow pipe 4. Thereby, the measurement gas exhausted from the chamber C1 flows into the chamber C2 through the gas flow pipe 4. And the detection part 33 installed in the chamber C2 detects the density | concentration of the 2nd gas component contained in the to-be-measured gas which flowed in in the chamber C2. The measured gas flowing into the chamber C2 is discharged from the outlet 45 to the outside of the gas sensor 1.

The gas sensor 1 configured in this manner includes the

casings

11 and 31, the base material 13, the detection unit 33, and the seal member 14. The seal member 14 converts the first gas component into the second gas component. Can contain catalyst particles.

The

casings

11 and 31 each have a chamber C1 into which a gas to be measured can be introduced. The base 13 includes a surface 13a into which the gas to be measured introduced into the chamber C1 is introduced into the substrate 13 and a surface 13b into which the gas to be measured introduced into the chamber C1 is discharged to the outside of the substrate C1. The substrate 13 is configured to convert the first gas component contained in the gas to be measured into the second gas component by circulating the gas to be measured inside between the surface 13 a and the surface 13 b. And housed in the chamber C1.

The detection unit 33 detects a second gas component contained in the measurement gas discharged from the substrate 13. The sealing material 14 is formed of inorganic fibers excluding metal fibers, and is disposed between a part of the inner wall surface of the chamber C1 of the casing 11 and the outer surface of the base 13 excluding the

surfaces

13a and 13b.

As described above, in the gas sensor 1, at least a part of the gap between the casing 11 and the base material 13 can be closed by the sealing material 14, the gas to be measured passes through the gap between the casing 11 and the base material 13 instead To prevent the occurrence of Thereby, gas sensor 1 can improve gas detection accuracy.

In the gas sensor 1, since the sealing material 14 is formed of inorganic fibers excluding metal fibers, it is flexible and easily deformed. For this reason, the sealing material 14 is likely to close the gap between the casing 11 and the base material 13 and to further suppress the occurrence of the measured gas passing through the gap between the casing 11 and the base material 13 instead of the base material 13. Can. Further, in the gas sensor 1, in order to close the gap between the casing 11 and the base 13, unlike the sealing material formed of metal fibers, it is not necessary to apply a large load to deform the sealing material. For this reason, in the gas sensor 1, it is possible to suppress the occurrence of a situation where the base material 13 is broken in order to close the gap between the casing 11 and the base material 13.

Furthermore, in the gas sensor 1, the seal material 14 contains catalyst particles capable of converting the first gas component into the second gas component. Therefore, the first gas component is converted to the second gas component in at least a part of the measurement gas that has passed through the gap between the casing 11 and the base 13. Thereby, the gas sensor 1 can further improve the gas detection accuracy.

Further, specifically, the gas sensor 1 includes a casing 11 and a casing 31, and in order to introduce the gas to be measured discharged from the casing 11 into the interior of the casing 31, the gas sensor 1 is placed between the casing 11 and the casing 31. A gas flow pipe 4 configured to flow the measurement gas is provided. The casing 11 is configured to receive the base material 13. The casing 31 is configured to receive the detection unit 33.

Further, the gas sensor 1 is provided with a single heater 53 which is accommodated inside the casing 31 and heats the base 13 and the detection unit 33. Thus, the gas sensor 1 can simplify the configuration of the gas sensor 1 and can miniaturize the gas sensor 1.

In the gas sensor 1, the catalyst particles contained in the sealing material 14 are Pt. Thereby, the gas sensor 1 can remove the miscellaneous gases (for example, hydrogen and carbon monoxide etc.) contained in the measured gas by oxidation.

In the embodiment described above, the chamber C1 corresponds to the internal space, the surface 13a corresponds to the introduction part, the surface 13b corresponds to the discharge part, and the substrate 13 coated with the catalyst corresponds to the conversion part.

Moreover, the casing 11 corresponds to a 1st accommodating part, the casing 31 corresponds to a 2nd accommodating part, and the gas flow pipe 4 corresponds to a distribution | circulation part. Second Embodiment Hereinafter, a second embodiment of the present disclosure will be described with reference to the drawings. In the second embodiment, parts different from the first embodiment will be described. The same reference numerals are given to the common configurations.

FIG. 3 is a cross-sectional view of the gas sensor 1 of the second embodiment cut along the direction perpendicular to the flow direction. FIG. 4 is a cross-sectional view of the gas sensor 1 of the second embodiment taken along the above flow direction.

The gas sensor 1 of the second embodiment is different from the first embodiment in that the range in which the base material 13 is covered is changed by the sealing material 14 and that the adhesive 17 is provided as shown in FIGS. 3 and 4. . As shown in FIG. 3, the sealing material 14 is disposed so as to contact and cover three surfaces facing the lower surface plate 21 and the

side surface plates

23 and 25 among the six surfaces forming the rectangular parallelepiped of the base material 13. Ru. Therefore, the sealing material 14 is not disposed on the surface of the base 13 exposed by the opening 26.

The adhesive 17 is formed of a material having a thermal conductivity higher than that of the sealing material 14 and has gas impermeability in a cured state. The adhesive 17 is disposed between the surface of the base 13 exposed at the opening 26 and the lower surface 61 c of the main portion 61 of the ceramic wiring substrate 34. That is, the substrate 13 is bonded to the main portion 61 of the ceramic wiring substrate 34 via the adhesive 17.

In the gas sensor 1 configured as described above, the heater 53 is housed inside the casing 31, and includes the main body portion 61 of the ceramic wiring board 34 and the adhesive 17. The main body portion 61 is formed of a material that can conduct heat, and is disposed between the casing 11 and the casing 31 in order to separate the casing 11 and the casing 31. The adhesive 17 is formed of a material having a thermal conductivity higher than that of the sealing material 14, and is disposed between the main body 61 and the base 13 so that the base 13 is adhered to the main body 61. Thereby, the gas sensor 1 can heat the catalyst of the base material 13 more efficiently.

In the embodiment described above, the main body 61 corresponds to a dividing member. As mentioned above, although one Embodiment of this indication was described, this indication is not limited to the said embodiment, It can deform | transform variously and can be implemented.

For example, in the above embodiment, the catalyst particles contained in the sealing material 14 are in the form of Pt, but the catalyst particles may be made of at least one of a noble metal and an oxide.

In the above embodiment, the sealing material 14 is formed of alumina fibers, but it may be, for example, silica fibers or glass fibers. In the above embodiment, the casing 11, the packing 12, the ceramic wiring board 34, the packing 32, and the casing 31 are fixed via the adhesive, respectively. However, the

members

11, 12, 34, 32, 31 are used. The fixed structure of is not limited to this. For example, a pair of fixing plates having screw holes formed at the four corners are disposed without using an adhesive and located on the outer periphery of the

casings

11 and 31 and on the

flanges

27 and 43. By inserting a screw into the screw hole and applying a force (biasing force) from each fixing member to the ceramic wiring board 34, the

members

11, 12, 34, 32, 31 are fixed so as not to be displaced. You may Further, the function possessed by one component in the above embodiment may be shared by a plurality of components, or the function possessed by a plurality of components may be exhibited by one component. In addition, part of the configuration of the above embodiment may be omitted. In addition, at least a part of the configuration of the above-described embodiment may be added to or replaced with the configuration of the other above-described embodiment. In addition, all the aspects contained in the technical thought specified from the wording as described in a claim are an embodiment of this indication.

DESCRIPTION OF SYMBOLS 1 ... Gas sensor, 11 ... Casing, 13 ... Base material, 13a, 13b ... Surface, 14 ... Sealing material, 31 ... Casing, 33 ... Detection part, C1 ... Chamber

Claims

A casing in which an inner space into which a gas to be measured can be introduced is formed;

The system includes an introduction unit into which the measurement gas introduced into the internal space is introduced into the interior, and a discharge unit into which the measurement gas introduced into the interior is discharged out of the interior. The first gas component contained in the gas to be measured is configured to be converted into a second gas component by circulating the gas to be measured inside between itself and the discharge part, and the internal space A converter housed in the

A detection unit configured to detect the second gas component contained in the measurement gas discharged from the conversion unit;

It is formed of inorganic fibers excluding metal fibers, and is disposed between at least a portion of the inner wall surface in the inner space of the casing and at least a portion of the outer surface of the conversion portion excluding the introduction portion and the discharge portion. Seal material, and

The said sealing material is a gas sensor containing the catalyst particle which can convert said 1st gas component into said 2nd gas component.
The gas sensor according to claim 1, wherein

The casing includes a first accommodating portion configured to accommodate the conversion portion, and a second accommodating portion configured to accommodate the detection portion.

The measurement gas is caused to flow between the first storage portion and the second storage portion in order to introduce the measurement gas discharged from the first storage portion into the inside of the second storage portion. A gas sensor comprising a distribution unit configured as above.
A gas sensor according to claim 1 or 2, wherein

A gas sensor comprising a single heater housed inside the casing and heating the conversion unit and the detection unit.
The gas sensor according to claim 3, wherein

The heater is housed inside the second housing portion,

A dividing member formed of a material capable of conducting heat and disposed between the first housing and the second housing to separate the first housing and the second housing;

A gas sensor comprising: an adhesive which is formed of a material having a thermal conductivity higher than that of the sealing material, and which is disposed between the dividing member and the converting part to make the converting part adhere to the dividing member. .
The gas sensor according to any one of claims 1 to 4, wherein

The said catalyst particle is a gas sensor comprised with at least one of a noble metal and an oxide.