JP2019007817A - Gas sensor - Google Patents

Abstract

To provide a gas sensor which has improved gas detection accuracy of the gas sensor.SOLUTION: A gas sensor 1 includes casings 11 and 31, a substrate 13, a detection unit 33, and a sealing material 14, and the sealing material 14 contains a catalyst particle capable of converting a first gas component into a second gas component. The substrate 13 includes a surface 13a for introducing the gas to be measured into the interior, and a surface 13b to which the gas to be measured is discharged to the outside. The substrate 13 is configured so as to convert the first gas component into the second gas component by allowing the gas to be measured to flow into the interior of the surface 13a between the surface 13a and the surface 13b. The detection unit 33 detects the second gas component contained in the gas to be measured discharged from the substrate 13. The sealing material 14 is formed of inorganic fibers excluding metal fibers, and is disposed between a portion of the inner wall surface of the chamber of the casing 11 and the outer surface of the casing except the surfaces 13a and 13b of the outer surface of the substrate 13.SELECTED DRAWING: Figure 2

Description

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

  Patent Document 1 is configured such that a constant amount of air as a gas to be measured is always supplied into the chamber, and the gas to be measured is subjected to a pretreatment for burning and removing a combustible gas such as CO by a catalyst in the chamber. Describes a gas sensor that detects NOx concentration by contacting the sensor element with the sensor element.

Japanese Patent Laid-Open No. 10-300702

  In the gas sensor described in Patent Document 1, the chamber is filled with a catalyst so as to cross the flow path through which the gas to be measured flows in the chamber, and the gas to be measured that has passed through the catalyst is brought into contact with the sensor element.

  When a gas permeable catalyst is placed in the chamber in this way, the gap between the inner surface of the chamber and the outer surface of the catalyst is closed with a sealing material, so that the gas to be measured does not leak from the gap and the inside of the catalyst is given priority. Needs to be transparent.

  However, an elastic body such as rubber generally used as a sealing material has low heat resistance. For this reason, the performance of the gas to be measured is in contact with the sealing material, or the temperature of the sealing material to block the flow of the gas to be measured is reduced because the catalyst is heated to a temperature that sufficiently activates the catalyst. There is a possibility that gas may be generated and affect the gas detection accuracy.

  An object of the present disclosure is to improve gas detection accuracy of a gas sensor.

  One aspect of the present disclosure includes a casing, a conversion unit, a detection unit, and a sealing material, and the sealing material contains catalyst particles that can convert the first gas component into the 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 in which the gas to be measured introduced into the internal space is introduced into itself, and a discharge unit from which the gas to be measured introduced into itself is discharged to the outside. The conversion unit is configured to convert the first gas component contained in the measurement gas into the second gas component by circulating the measurement gas between the introduction unit and the discharge unit. Housed in the interior 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 part of the inner wall surface in the internal space of the casing and at least a part of the outer surface of the outer surface of the conversion unit excluding the introduction part and the discharge part. .

  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 with the sealing material, so that the gas to be measured passes through the gap between the casing and the conversion unit instead of the conversion unit. The occurrence of the situation can be suppressed. Thereby, the gas sensor of this indication can improve gas detection accuracy.

  In the gas sensor of the present disclosure, the sealing material is formed of inorganic fibers excluding metal fibers, and thus is flexible and easily deformed. For this reason, the sealing material can easily block the gap between the casing and the conversion unit, and can further suppress the occurrence of a situation in which the gas to be measured passes through the gap between the casing and the conversion unit instead of the conversion unit. Further, in the gas sensor according to the present disclosure, it is not necessary to apply a large load to deform the sealing material, unlike the sealing material formed of metal fiber, in order to close the gap between the casing and the conversion unit. For this reason, in the gas sensor of this indication, in order to block the crevice between a casing and a conversion part, generation | occurrence | production of the situation where a conversion part is damaged can be suppressed.

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

  In the gas sensor according to the present disclosure, specifically, the casing includes a first housing portion and a second housing portion, and the gas to be measured discharged from the first housing portion is introduced into the second housing portion. In order to introduce, you may make it provide the distribution | circulation part comprised so that to-be-measured gas may be distribute | circulated between a 1st accommodating part and a 2nd accommodating part. The first accommodating portion is configured to accommodate the converting portion. The second storage unit is configured to store the detection unit.

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

  Moreover, in the gas sensor of this indication, a heater may be accommodated in the inside of a 2nd accommodating part, and you may make it provide a division member and an adhesive agent. The dividing member is formed of a material that can conduct heat, and is disposed between the first housing portion and the second housing portion in order to separate the first housing portion and the second housing portion. The adhesive is made of a material having a higher thermal conductivity than that of the sealing material, and is disposed between the split member and the conversion portion, thereby bringing the conversion portion into a state of being bonded to the split member. Thereby, the gas sensor of this indication can heat a conversion part still more efficiently.

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

It is a disassembled perspective view of the gas sensor 1 of 1st Embodiment. It is sectional drawing of the gas sensor 1 of 1st Embodiment. It is the 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 material 13, and a sealing material 14.
The casing 11 includes a rectangular bottom plate 21 and four side plates 22, 23, 24, and 25 that protrude perpendicularly from each of the four sides constituting the rectangle of the bottom plate 21, and an opening 26 is formed on the top surface. It is the metal member made.

  The casing 11 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 a flow direction in which gas flows in a 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 includes an inlet 28 and an outlet 29. The inlet 28 extends outward from the opening on the outer side of the through hole 21a perpendicularly to the lower surface plate 21, and is formed in a cylindrical shape. Thereby, gas can be introduced into the inside of the casing 11 from the outer opening of the inlet 28. Similarly, the outlet 29 is formed in a cylindrical shape extending from the outer opening of the through hole 21b toward the outer side perpendicular to the lower surface plate 21. As a result, 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 plan view. The packing 12 is bonded to the flange 27 via an adhesive (not shown).

The base material 13 is a ceramic member formed in a rectangular parallelepiped shape. The base material 13 is formed with a flow path 13c penetrating 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. To convert the first gas component (NO in the present embodiment) contained in the gas to be measured into the second gas component (NO _{2 in the} present embodiment) on the inner wall surface of the flow path 13c at a predetermined activation temperature. The catalyst (in this embodiment, zeolite carrying Pt) is applied.

  The sealing material 14 is a member formed of inorganic fibers (in this embodiment, alumina fibers) excluding metal fibers. Catalyst particles (Pt in this embodiment) are added to the inorganic fibers constituting the sealing material 14. Examples of the method for adding catalyst particles to the inorganic fiber include a method in which the inorganic fiber is immersed in a solution containing the catalyst particle and then dried and fired. Further, instead of immersing the inorganic fiber in the solution containing the catalyst particles, the inorganic fiber may be immersed in a slurry containing zeolite or γ alumina supporting the catalyst particles. The sealing material 14 is disposed so as to come into contact with and cover four surfaces of the six surfaces constituting the rectangular parallelepiped where the flow path 13c is not formed.

  In the base material 13, the sealing materials 14 arranged on three surfaces of the six surfaces constituting the rectangular parallelepiped where the flow path 13 c is not formed are in contact with the lower surface plate 21, the side surface plate 23, and the side surface plate 25, respectively. The sealing material 14 arranged on one surface of the casing 11 is arranged inside the casing 11 so as to be exposed at the opening 26. The base material 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 casing 11 through the through hole 21 a passes through the flow path 13 c of the base material 13 and is discharged from the through hole 21 b to the outside of the casing 11. In addition, when the gas to be measured passes through the flow path 13c of the base material 13, the first gas component contained in the gas to be measured is converted into 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 that includes a rectangular upper surface plate 41 and four side plates that protrude perpendicularly from each of the four sides that form the rectangle of the upper surface plate 41, and an opening 42 is formed on the lower surface. is there. The opening 42 is not shown in FIG. 1 but shown in FIG.

  The casing 31 includes a flange 43. The flanges 43 extend outward from the end portions on the lower surface side of the four side plates perpendicularly to the four side plates, and are formed in a substantially rectangular frame shape 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 includes an inlet 44 and an outlet 45. The inlet 44 extends from the outer opening of the through hole 41a toward the outer side perpendicular to the upper surface plate 41, and is formed in a cylindrical shape. As a result, gas can be introduced into the casing 31 from the outer opening of the inlet 44. Similarly, the outlet 45 extends outward from the outer opening in the through hole 41b perpendicularly to the upper surface plate 41, and is formed in a cylindrical shape. As a result, 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 plan view. The packing 32 is bonded 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 into 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 arranged 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 characteristics that change according to the concentration of the second gas component contained in the gas to be measured. The sensor element 52 is installed on the upper surface 51 a of the substrate 51.

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

  As shown in FIG. 1, the ceramic wiring substrate 34 includes a main body portion 61 and a narrow width portion 62. The main body portion 61 is formed in a rectangular plate shape so that the outer peripheral shape substantially matches the outer peripheral shape of the packings 12 and 32. A recess 61 b for installing the detection unit 33 is formed on the upper surface 61 a of the main body 61.

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

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 surface of the recess 61 b with the adhesive 35.
Further, 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 portion 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 thus closed forms the chamber C1. The lower surface 61 c of the main body 61 of the ceramic wiring board 34 and the portion of the surface of the sealing material 14 covering the base material 13 that is not in contact with the lower surface plate 21, the side surface plates 23 and 25, and the packing 12 are in contact. To 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 body 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 substrate 34. The internal space of the casing 31 thus closed forms the chamber C2.

  Thereby, 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 stacked. For this reason, as indicated by an arrow H <b> 1, the heat generated by the heater 53 is transmitted to the sensor element 52 through the substrate 51. Further, as indicated by an arrow H <b> 2, the heat generated by the heater 53 is transmitted to the base material 13 through the adhesive 35, the ceramic wiring substrate 34 and the sealing material 14.

  The gas flow pipe 4 is made of resin or metal. The outlet 29 is inserted into the opening at one end of the gas circulation pipe 4, and the inlet 44 is inserted into the opening at the other end of the gas circulation pipe 4. Thereby, the measurement gas discharged 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 gas to be measured that has flowed into the chamber C <b> 2 is discharged from the outlet 45 to the outside of the gas sensor 1.

  The gas sensor 1 configured as described above includes casings 11 and 31, a base material 13, a detection unit 33, and a sealing material 14, and the sealing material 14 converts a first gas component into a second gas component. Containing catalyst particles.

The casings 11 and 31 are formed with a chamber C1 into which the gas to be measured can be introduced.
The base material 13 includes a surface 13a through which the gas to be measured introduced into the chamber C1 is introduced into itself, and a surface 13b through which the gas to be measured introduced into itself is discharged to the outside. The base material 13 is configured to convert the first gas component contained in the measured gas into the second gas component by flowing the measured gas between the surface 13a and the surface 13b. And accommodated in the chamber C1.

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

  As described above, in the gas sensor 1, since at least a part of the gap between the casing 11 and the base material 13 can be closed with the sealing material 14, the gas to be measured passes through the gap between the casing 11 and the base material 13 instead of the base material 13. It is possible to suppress the occurrence of the situation. Thereby, the 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 easily closes the gap between the casing 11 and the base material 13, and further suppresses the occurrence of a situation in which the gas to be measured passes through the gap between the casing 11 and the base material 13 instead of the base material 13. Can do. Further, in the gas sensor 1, in order to close the gap between the casing 11 and the base material 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, since the gap between the casing 11 and the base material 13 is closed, the occurrence of a situation where the base material 13 is damaged can be suppressed.

  Furthermore, in the gas sensor 1, the sealing material 14 contains catalyst particles that can convert the first gas component into the second gas component. For this reason, the first gas component is converted into the second gas component in at least a part of the gas to be measured that has passed through the gap between the casing 11 and the base material 13. Thereby, the gas sensor 1 can further improve the gas detection accuracy.

  Further, the gas sensor 1 specifically includes a casing 11 and a casing 31, and in order to introduce the measurement gas discharged from the casing 11 into the casing 31, the gas sensor 1 is covered between the casing 11 and the casing 31. A gas circulation pipe 4 configured to circulate the measurement gas is provided. The casing 11 is configured to accommodate the base material 13. The casing 31 is configured to accommodate the detection unit 33.

  Further, the gas sensor 1 includes a single heater 53 that is accommodated in the casing 31 and heats the base material 13 and the detection unit 33. Thereby, the gas sensor 1 can simplify the structure of the gas sensor 1 and can reduce the gas sensor 1 in size.

  In the gas sensor 1, the catalyst particles contained in the sealing material 14 are Pt. Thereby, the gas sensor 1 can be removed by oxidizing the miscellaneous gas (for example, hydrogen, carbon monoxide, etc.) contained in the gas to be measured.

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

The casing 11 corresponds to a first housing part, the casing 31 corresponds to a second housing part, and the gas flow pipe 4 corresponds to a flow 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. Common components are denoted by the same reference numerals.

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

As shown in FIGS. 3 and 4, the gas sensor 1 according to the second embodiment is different from the first embodiment in that the range in which the base material 13 is covered with the sealing material 14 is changed and the adhesive 17 is provided. .
As shown in FIG. 3, the sealing material 14 is disposed so as to come into contact with and cover three surfaces facing the lower surface plate 21 and the side surface plates 23 and 25 among the six surfaces constituting the rectangular parallelepiped of the base material 13. The Therefore, the sealing material 14 is not disposed on the surface of the base material 13 exposed at the opening 26.

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

  In the gas sensor 1 configured as described above, the heater 53 is housed in the casing 31 and includes the main body 61 of the ceramic wiring board 34 and the adhesive 17. The main body 61 is made 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 higher thermal conductivity than the sealing material 14 and is disposed between the main body 61 and the base 13 so that the base 13 is bonded 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 split member.
As mentioned above, although one embodiment of this indication was described, this indication is not limited to the above-mentioned embodiment, and can carry out various modifications.

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

In the said embodiment, although the sealing material 14 showed the form formed with the alumina fiber, a silica fiber or glass fiber etc. may be sufficient, for example.
Moreover, in the said embodiment, although the structure which fixes the casing 11, the packing 12, the ceramic wiring board 34, the packing 32, and the casing 31 via an adhesive material was respectively employ | adopted, each member 11, 12, 34, 32, 31 is taken. The fixing structure is not limited to this. For example, without using an adhesive, a pair of fixing plates with screw holes formed at the four corners are arranged so as to be positioned on the outer circumferences of the casings 11 and 31 and on the flanges 27 and 43, and the pair of fixing members By inserting screws through the screw holes and applying a force (biasing force) from each fixing member toward the ceramic wiring substrate 34, each member 11, 12, 34, 32, 31 is fixed so as not to be displaced. It may be.
In addition, the function of one component in the above embodiment may be shared by a plurality of components, or the function of a plurality of components may be exhibited by one component. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

  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 (5)

A casing in which an internal space into which the gas to be measured can be introduced is formed;
The introduction includes the introduction portion into which the gas to be measured introduced into the internal space is introduced into the inside, and the discharge portion from which the measurement gas introduced into the inside is discharged to the outside. The first gas component contained in the measured gas is converted into the second gas component by flowing the measured gas between itself and the discharge unit, and the internal space A conversion unit housed in
A detection unit configured to detect the second gas component contained in the gas to be measured discharged from the conversion unit;
It is formed of inorganic fibers excluding metal fibers, and is disposed between at least a part of the inner wall surface in the internal space of the casing and at least a part of the outer surface of the outer surface of the conversion part excluding the introduction part and the discharge part. Sealing material,
The said sealing material is a gas sensor containing the catalyst particle which can convert the said 1st gas component into the said 2nd gas component. The gas sensor according to claim 1,
The casing includes a first accommodating portion configured to accommodate the conversion portion, and a second accommodating portion configured to accommodate the detection portion,
In order to introduce the measured gas discharged from the first accommodating portion into the second accommodating portion, the measured gas is circulated between the first accommodating portion and the second accommodating portion. A gas sensor comprising a circulation part configured as described above. The gas sensor according to claim 1 or 2, wherein
A gas sensor comprising a single heater housed in the casing and heating the conversion part and the detection part. The gas sensor according to claim 3,
The heater is housed in the second housing portion;
A split member formed of a material capable of conducting heat and disposed between the first housing portion and the second housing portion in order to separate the first housing portion and the second housing portion;
A gas sensor comprising: an adhesive formed of a material having a higher thermal conductivity than the sealing material, and disposed between the dividing member and the converting portion so that the converting portion is bonded to the dividing member. . The gas sensor according to any one of claims 1 to 4,
The gas sensor, wherein the catalyst particles are composed of at least one of a noble metal and an oxide.