JP2012242112A - Gas sensor and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor that can enhance the airtightness and reduce the effect of thermal stress.SOLUTION: A forth glass layer 34 is formed between a second talc 22 filled in a holder 20 and an inner circumferential face 19 of the holder 20, and a third glass layer 33 is also formed between the second talc 22 and an outer circumferential face 18 of a detection element 10. In addition, a second glass layer 32 is formed between a first talc 26 filled in a main metal fitting 50 and an inner circumferential face 58 of the main metal fitting 50, and a first glass layer 31 is also formed between the first talc 26 and the outer circumferential face 18 of the detection element 10. The first glass layer 31 to the forth glass layer 34 do not melt during a manufacturing process, and are not fixed to respective contact faces. As the second talc 22 and the first talc 26 are packed, the first glass layer 31 to the forth glass layer 34 make contact with respective contact faces, thus securing the airtightness via the inside of the main metal fitting 50.

Description

  The present invention relates to a gas sensor for detecting a specific gas component contained in a detection target gas and a method for manufacturing the same.

  There is known a gas sensor including a detection element whose output changes according to the concentration of a specific gas (oxygen, NOx, etc.) in exhaust gas discharged from an internal combustion engine such as an automobile engine (see, for example, Patent Document 1). For example, a detection element of a NOx sensor capable of detecting NOx concentration has a structure in which at least one cell in which a pair of electrodes are provided on a solid electrolyte body is stacked. In the NOx sensor, oxygen dissociated from NOx remaining in the exhaust gas flows through the solid electrolyte body as oxygen ions, and the NOx concentration is detected based on the current value at that time. For this reason, the current value of the NOx sensor is very small, and as a result, the obtained sensor output is also very small. Therefore, when the humidity inside the sensor changes, the output extraction part (the conductive path connecting the detection element and the external circuit, which is arranged inside the sensor, such as an electrode pad or a metal terminal provided on the element surface) There is a concern about the influence on the accuracy of the sensor output due to the lowering of the insulating property.

  Normally, a NOx sensor is used in a state in which a cylindrical metal shell that holds a detection element inserted is attached to an exhaust pipe, and a tip side where a detection portion of the detection element is disposed is inserted into the exhaust pipe. Exhaust gas contains moisture and the like produced by combustion. Considering the above-mentioned problems, the NOx sensor is installed so that the moisture and the like do not reach the rear end side of the NOx sensor through the metal shell. Therefore, ensuring airtightness in the metal shell is required.

  On the other hand, a gas sensor is known in which a glass layer and a steatite layer are alternately arranged in a metal shell (intermediate shell), and the glass layer is melted by heat treatment to ensure sealing properties (for example, Patent Document 2). reference). In Patent Document 2, a detection element (sensing element) inserted through a cylindrical ceramic body disposed in a metal shell is surrounded by a glass layer and a steatite layer around an intermediate portion. A glass layer melted by heating flows between the outside of the steatite layer and the ceramic body, and between the inside of the steatite layer and the detection element, compressing the molten glass and filling the gap with glass. , Sealability is ensured.

JP 2010-223615 A JP-A-8-114574

  However, in Patent Document 2, since a glass layer melted by heating is caused to flow between the steatite layer, the ceramic main body, and the detection element, the glass layers are fixed to each other like an adhesive. If the glass layer adheres to the steatite layer, ceramic body, or sensing element due to fixation, the gas sensor is used in a high-temperature environment, and when these components undergo thermal expansion, they absorb the thermal expansion difference in the glass layer. I can't. For example, when stress due to thermal expansion is applied to the detection element, there is a possibility that the element may be broken.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a gas sensor that can improve airtightness and reduce the influence of thermal stress.

  According to the first aspect of the present invention, the detection element having a detection portion that extends in the axial direction and detects a specific gas component in the detection target gas on the tip side, and the cylindrical metal shell that passes through the detection element And a first powder material filled between an outer peripheral surface of the detection element and an inner peripheral surface of the metal shell, and is arranged between the first powder material and the detection element, and makes one round in the circumferential direction. The first powder material and the outer peripheral surface of the detection element, respectively, and disposed between the first glass material non-adhering to the detection element, the first powder material and the metal shell, and in the circumferential direction. There is provided a gas sensor comprising: a second glass layer that contacts the first powder material and an inner peripheral surface of the metal shell over one circumference, and is not fixed to the metal shell.

  Since the first glass material and the second glass layer are disposed in contact with each other between the first powder material and the outer peripheral surface of the detection element and the inner peripheral surface of the metal shell, the first powder material and the detection element In addition, it is possible to ensure the airtightness of the metal shell between the metal shell, that is, between the first powder material and the outer peripheral surface of the detection element and the inner peripheral surface of the metal shell. This is because if the gap is filled only with the first powder material, there is a possibility that a slight gap may be formed between the outer peripheral surface of the detection element and the inner peripheral surface of the metal shell and the first powder material. Needs to be more strongly compressed when filled with the first powder material, but the first powder material and the outer peripheral surface of the detection element and the inner peripheral surface of the metal shell in the first glass layer and the second glass layer This is because if the gap between the gaps is filled, the airtightness can be sufficiently secured even if the pressure applied to the first powder material is not strong. Further, the first glass layer and the second glass layer are not fixed to the outer peripheral surface of the detection element and the inner peripheral surface of the metal shell, respectively. That is, it is only in contact and not bonded. Although the gas sensor is used in a high temperature environment, even if the metal shell and the detection element are thermally expanded, the first glass layer and the second glass layer are not fixed to them, so that the difference in thermal expansion can be absorbed. For example, stress applied to the detection element due to thermal expansion can be reduced, and element breakage or the like can be prevented.

  Note that “non-adhesion” means, for example, that there is no glass material on the outer surface of the detection element or the inner surface of the metal shell when the filling of the first powder material is released and the first powder material is physically removed. Refers to that.

  On the other hand, when glass is mixed in the first powder material without providing the first glass layer or the second glass layer, a large amount of the first powder material contacts the outer surface of the detection element or the inner surface of the metal shell. Therefore, the above effect cannot be obtained sufficiently.

  In the first aspect, the metal shell has a step portion protruding radially inward over one circumference in the circumferential direction, and further has a cylindrical shape extending in the axial direction, and is engaged with the step portion. A holder disposed in the metal shell, a second powder material filled between an outer peripheral surface of the detection element and an inner peripheral surface of the holder in the holder, the second powder material, and the A third glass layer disposed between the detection element and in contact with the outer peripheral surface of the second powder material and the detection element over one circumference in the circumferential direction, and non-adhering to the detection element; and the second powder material And a fourth glass layer that is disposed between the second powder material and the inner peripheral surface of the holder and is not fixed to the detection element. Good.

  Furthermore, since the third glass layer and the fourth glass layer are arranged in contact with each other between the second powder material and the outer peripheral surface of the detection element and the inner peripheral surface of the holder, the second powder material and The airtightness of the metal shell between the second powder material between the outer peripheral surface of the detection element and the inner peripheral surface of the holder and the detection element and the holder can also be ensured. Because if the gap between the second powder material and the outer peripheral surface of the detection element and the inner peripheral surface of the holder is filled with the third glass layer and the fourth glass layer, the pressure applied to the compression when filling the second powder material This is because the airtightness can be sufficiently secured even if it is not strong. Further, the third glass layer and the fourth glass layer are not fixed to the outer peripheral surface of the detection element and the inner peripheral surface of the holder, are only in contact with each other, and are not bonded. Therefore, the difference in thermal expansion between the holder and the detection element can be absorbed by the third glass layer and the fourth glass layer, and for example, element breakage or the like can be prevented.

  “Non-sticking” means, for example, that there is no glass material on the outer surface of the detection element or the inner surface of the holder when the filling of the second powder material is released and the second powder material is physically removed. Point to.

  On the other hand, when glass is mixed in the second powder material without providing the third glass layer or the fourth glass layer, a large amount of the second powder material contacts the outer surface of the detection element or the inner surface of the holder. The above effects cannot be obtained sufficiently.

  According to the second aspect of the present invention, a detection element that extends in the axial direction and has a detection unit for detecting a specific gas component in the detection target gas on the distal end side, and a cylindrical shape through which the detection element is inserted, A metal shell having a step portion projecting radially inward over one circumference in the circumferential direction, a cylindrical shape extending in the axial direction, and a holder disposed in the metal shell in a state of being engaged with the step portion; In the holder, disposed between the outer peripheral surface of the detection element and the inner peripheral surface of the holder, between the second powder material and the detection element, and arranged in the circumferential direction. It is arranged between the second powder material and the outer peripheral surface of the detection element over one circumference, and is arranged between the second glass material and the holder, and is arranged between the second glass material and the holder. The second powder material and the hor While each of the inner circumferential surface contact, a gas sensor and a fourth glass layer of non-sticking to the detection device is provided.

  Since the third glass layer and the fourth glass layer are arranged in contact with each other between the second powder material and the outer peripheral surface of the detection element and the inner peripheral surface of the holder, the second powder material, the detection element, and Airtightness of the metal shell can be ensured between the holder, that is, between the second powder material, the outer peripheral surface of the detection element, and the inner peripheral surface of the holder. This is because, if the gap is filled only with the second powder material, there is a possibility that a slight gap may be formed between the outer peripheral surface of the detection element and the inner peripheral surface of the holder and the second powder material. The second powder material needs to be compressed more firmly when filled, but the third glass layer and the fourth glass layer are between the second powder material and the outer peripheral surface of the detection element and the inner peripheral surface of the holder. This is because if the gap is filled, the airtightness can be sufficiently secured even if the compression when filling the second powder material is not strong. Further, the third glass layer and the fourth glass layer are not fixed to the outer peripheral surface of the detection element and the inner peripheral surface of the holder, respectively. That is, it is only in contact and not bonded. Although the gas sensor is used in a high temperature environment, even if the holder and the detection element are thermally expanded, the third glass layer and the fourth glass layer are not fixed to them, so that the thermal expansion difference can be absorbed. Stress applied to the detection element due to thermal expansion can be reduced, and element breakage or the like can be prevented.

  “Non-sticking” means, for example, that there is no glass material on the outer surface of the detection element or the inner surface of the holder when the filling of the second powder material is released and the second powder material is physically removed. Point to.

  On the other hand, when glass is mixed in the second powder material without providing the third glass layer or the fourth glass layer, a large amount of the second powder material contacts the outer surface of the detection element or the inner surface of the holder. The above effects cannot be obtained sufficiently.

  In the first aspect and the second aspect, the detection element includes a first measurement chamber into which the detection target gas is introduced, a first solid electrolyte layer, and a pair of first electrodes, and the pair of first electrodes is the first pair. A first oxygen pump cell provided inside and outside the one measurement chamber; and the detection target gas communicated with the first measurement chamber and having an oxygen concentration adjusted by the first oxygen pump cell is introduced from the first measurement chamber. A second oxygen pump cell comprising a second measurement chamber, a second solid electrolyte layer, and a pair of second electrodes, wherein the pair of second electrodes are provided inside and outside the second measurement chamber; May be an element for detecting the concentration of NOx in the detection target gas based on the magnitude of the current flowing through the second oxygen pump cell.

  Since the output of the NOx concentration detected by the gas sensor including the first oxygen pump cell and the second oxygen pump cell is very small and is easily affected by a decrease in insulation of the output extraction portion due to humidity change, the airtightness through the inside of the metal shell is improved. If it can be ensured reliably, the humidity increase inside the sensor can be suppressed, the output is not affected, and the detection accuracy of the NOx concentration can be ensured. Thus, the invention according to the first aspect and the second aspect is particularly effective for a gas sensor that handles a weak current.

  According to the third aspect of the present invention, the detection element having the detection part that extends in the axial direction and detects the specific gas component in the detection target gas on the tip side, and the cylindrical metal shell that passes through the detection element And a first powder material filled between an outer peripheral surface of the detection element and an inner peripheral surface of the metal shell, and is arranged between the first powder material and the detection element, and makes one round in the circumferential direction. The first powder material and the outer peripheral surface of the detection element, respectively, and disposed between the first glass material non-adhering to the detection element, the first powder material and the metal shell, and in the circumferential direction. A gas sensor manufacturing method comprising: a second glass layer that is in contact with an inner peripheral surface of the first powder material and the metal shell over one circumference, and is not fixed to the metal shell, the first powder material Press the powder that is the raw material of A first forming step of forming a cylindrical green compact into which the take-out element is inserted, and at least an outer peripheral surface and an inner peripheral surface in the circumferential direction of the outer surface of the green compact, and the first glass layer and A first attachment step of attaching a liquid glass material as a raw material of the second glass layer; and drying the glass material to form the first glass layer and the second glass layer on the green compact. A first drying step for forming a solid powder material; and the detection element disposed in a state of being inserted through the metal shell. The solid powder material is inserted into the metal powder, and the metal shell and the detection element. A first disposing step disposed between the first powder material, compressing the solid powder material, filling the first powder material obtained by breaking the solid powder material into the metal shell, and holding the detection element; and The first powder material and the detection element include the first With contacting laths layer, method of manufacturing a gas sensor comprising: a first compression step of contacting the second glass layer to said metal shell and said first powder material is provided.

  In forming the first glass layer and the second glass layer on the gas sensor, the first powder material is first molded as a green compact, and a liquid glass material is adhered to the green compact, and further adhered. Using a solid powder material obtained by drying a glass material, filling and compressing between the detection element and the metal shell, the first powder material, and between the outer peripheral surface of the detection element and the inner peripheral surface of the metal shell In addition, the first glass layer and the second glass layer can be disposed in contact with each other. Therefore, the airtightness of the metal shell can be ensured through the space between the first powder material and the outer peripheral surface of the detection element and the inner peripheral surface of the metal shell. In addition, by filling and compressing the solid powder material between the detection element and the metal shell by the above-described method, the first glass layer and the second glass layer are formed between the outer peripheral surface of the detection element and the metal shell. It can be made non-adherent to the peripheral surface. Therefore, even if the metal shell and the detection element are thermally expanded, the first glass layer and the second glass layer are not fixed to them, so that the difference in thermal expansion can be absorbed. For example, the stress applied to the detection element by thermal expansion Can be reduced and element breakage or the like can be prevented.

  According to the fourth aspect of the present invention, a detection element that extends in the axial direction and has a detection unit for detecting a specific gas component in the detection target gas on the distal end side, and a cylindrical shape through which the detection element is inserted, A metal shell having a step portion projecting radially inward over one circumference in the circumferential direction, a cylindrical shape extending in the axial direction, and a holder disposed in the metal shell in a state of being engaged with the step portion; In the holder, disposed between the outer peripheral surface of the detection element and the inner peripheral surface of the holder, between the second powder material and the detection element, and arranged in the circumferential direction. It is arranged between the second powder material and the outer peripheral surface of the detection element over one circumference, and is arranged between the second glass material and the holder, and is arranged between the second glass material and the holder. The second powder material and the hor A gas sensor manufacturing method comprising: a fourth glass layer that is in contact with the inner peripheral surface of each of the first and second non-adhering glass layers, and compresses the powder that is a raw material of the second powder material, and A second forming step of forming a cylindrical green compact into which the element is inserted; and at least an outer peripheral surface and an inner peripheral surface in the circumferential direction of the outer surface of the green compact; A second attachment step of attaching a liquid glass material that is a raw material of the fourth glass layer; and a solid formed by drying the glass material and forming the third glass layer and the fourth glass layer on the green compact. A second drying step for forming a powder material; and the detection element arranged in a state of being inserted through the holder is inserted into the solid powder material, and the solid powder material is interposed between the holder and the detection element. A second arranging step of arranging, and The shape powder material is compressed, the second powder material obtained by breaking the solid powder material is filled in the holder to hold the detection element, and the second powder material and the detection element are provided with the first powder material. A second compression step of bringing the third glass layer into contact with the second powder material and the holder, and inserting the holder holding the detection element into the metal shell, There is provided a gas sensor manufacturing method comprising: a holding step of engaging a holder with the stepped portion to hold the detection element in the metal shell.

  In forming the third glass layer and the fourth glass layer on the gas sensor, the second powder material was first molded as a green compact, and a liquid glass material was adhered to the green compact, and further adhered. By using a solid powder material obtained by drying a glass material, filling and compressing between the detection element and the holder, the second powder material, between the outer peripheral surface of the detection element and the inner peripheral surface of the holder, The third glass layer and the fourth glass layer can be arranged in contact with each other. Therefore, the airtightness of the metal shell can be ensured between the second powder material, the outer peripheral surface of the detection element, and the inner peripheral surface of the holder. In addition, by filling and compressing the solid powder material between the detection element and the holder by the above-described method, the third glass layer and the fourth glass layer are the outer peripheral surface of the detection element and the inner peripheral surface of the holder. And non-adherent to each other. Therefore, even if the holder and the detection element are thermally expanded, the third glass layer and the fourth glass layer are not fixed to them, so that the difference in thermal expansion can be absorbed. For example, the stress applied to the detection element due to thermal expansion can be absorbed. It can be reduced and element breakage or the like can be prevented.

  In the third aspect or the fourth aspect, a heating step of heating the metal shell holding the detection element at a temperature lower than the flow temperature of the glass material after the first compression step or after the second compression step. Further, it may be provided. The glass material can be softened by heating the first glass layer and the second glass layer, or the third glass layer and the fourth glass layer at a temperature lower than the flow temperature of the glass material. -It can be made to contact more firmly with the surface which contacts the 4th glass layer, and airtightness via a metallic shell can be secured more certainly. Moreover, a glass material does not fuse | melt by setting the heating temperature at this time to the temperature lower than the flow temperature of a glass material. If the glass material melts, it will stick to the inner peripheral surface of the metal shell or holder, leading to an increase in internal stress due to the difference in thermal expansion, which may cause breakage of the detection element, but the glass material will not stick If so, it is possible to absorb such a difference in thermal expansion, and it is possible to reliably maintain contact by softening. Note that “comprising a heating step after the first compression step or after the second compression step” means that the heating step is performed in a step after the first compression step including the first compression step, or It means that the heating step is performed in a step after the second compression step including the time of the two compression steps. Moreover, since it is necessary to soften a glass layer in a heating process, it cannot be overemphasized that it heats at temperature higher than the softening temperature of glass material.

1 is a longitudinal sectional view of a NOx sensor 1. FIG. 3 is a cross-sectional view showing an internal structure of a detection unit 17 of the detection element 10. It is the figure which expanded the part enclosed with the dotted line R of FIG. FIG. 3 is a diagram showing a manufacturing process of the NOx sensor 1. FIG. 3 is a diagram showing a manufacturing process of the NOx sensor 1.

  Hereinafter, an embodiment of a gas sensor and a manufacturing method thereof embodying the present invention will be described with reference to the drawings. First, as an example of a gas sensor, a NOx sensor 1 capable of detecting the concentration of NOx contained in exhaust gas is taken as an example, and the configuration thereof will be described with reference to FIGS. In FIG. 1, the axis O direction (indicated by the alternate long and short dash line) of the NOx sensor 1 is shown as the vertical direction, and the front end 11 side of the detection element 10 held inside is the front end side of the NOx sensor 1 and the rear end 12 side. Will be described as the rear end side of the NOx sensor 1.

  A NOx sensor 1 shown in FIG. 1 is attached to an exhaust pipe (not shown) of an automobile, and a tip portion 11 of a detection element 10 held inside is exposed to exhaust gas flowing in the exhaust pipe, and the exhaust gas is contained in the exhaust gas. The concentration of contained NOx is detected. The detection element 10 has a narrow plate shape extending in the axis O direction. In FIG. 1, the left-right direction on the paper surface is the plate thickness direction of the detection element 10, and the front-back direction of the paper surface is the plate width direction.

  A detection portion 17 for detecting the NOx concentration is formed in the tip portion 11 of the detection element 10. Further, as shown in FIG. 1, six electrode pads 16 (in FIG. 1, of which six are connected to the detection element 10 and an external circuit (not shown)) are provided on the rear end portion 12 of the detection element 10. Are shown).

  Here, the structure of the detection unit 17 of the detection element 10 will be described with reference to FIG. As shown in FIG. 2, the detection element 10 includes a gas detection body 14 that detects NOx concentration and a heater body 15 that is heated to activate the gas detection body 14 at an early stage. It is a thing. In addition, the front end portion 11 of the detection element 10 shown in FIG.

  First, the configuration of the gas detector 14 of the detection element 10 will be described. The gas detector 14 is formed in a layered manner by sandwiching insulators 141 and 146 made of alumina or the like between three plate-like solid electrolyte bodies 111, 121, and 131, respectively. The gas detector 14 includes a first measurement chamber 101, a second measurement chamber 102, a reference oxygen chamber 105, a first oxygen pump cell 110, an oxygen partial pressure detection cell 120, and a second oxygen pump cell 130. Hereinafter, for convenience, the first oxygen pump cell 110, the oxygen partial pressure detection cell 120, and the second oxygen pump cell 130 are referred to as an Ip1 cell 110, a Vs cell 120, and an Ip2 cell 130, respectively.

  The first measurement chamber 101 is a small space in which exhaust gas in an exhaust pipe (not shown) is first introduced into the gas detector 14. The first measurement chamber 101 is formed between the solid electrolyte body 111 and the solid electrolyte body 121. An electrode 113 is disposed on the surface of the first measurement chamber 101 on the solid electrolyte body 111 side, and an electrode 122 is disposed on the surface on the solid electrolyte body 121 side.

  A first diffusion resistance portion 103, which is a porous body made of ceramics such as alumina and having a plurality of continuous pores, is provided on the distal end side of the gas detection body 14 of the first measurement chamber 101. The first diffusion resistance unit 103 functions as a partition inside and outside the first measurement chamber 101 and restricts the amount of exhaust gas flowing into the first measurement chamber 101 per unit time. Similarly, on the rear end side of the gas detection body 14 in the first measurement chamber 101, a second diffusion resistance portion 104, which is a porous body made of ceramics such as alumina and having a plurality of continuous pores, is provided. The second diffusion resistance unit 104 functions as a partition between the first measurement chamber 101 and the second measurement chamber 102, and limits the amount of gas per unit time flowing from the first measurement chamber 101 into the second measurement chamber 102. To do.

  The second measurement chamber 102 includes a solid electrolyte body 111, a second diffusion resistance section 104, an opening 142 of the insulator 141, an opening 124 of the solid electrolyte body 121, an opening 147 of the insulator 146, and a solid. A small space surrounded by the electrolyte body 131. The second measurement chamber 102 communicates with the first measurement chamber 101 via the second diffusion resistance unit 104, and exhaust gas after the oxygen concentration is adjusted by the Ip1 cell 110 is introduced. An electrode 133 is disposed on the surface of the solid electrolyte body 131 exposed in the second measurement chamber 102.

  The reference oxygen chamber 105 is a small space surrounded by an opening provided in the insulator 146 independently of the second measurement chamber 102, and the solid electrolyte body 121 and the solid electrolyte body 131. In the reference oxygen chamber 105, an electrode 123 is disposed on the surface of the solid electrolyte body 121, and an electrode 132 is disposed on the surface of the solid electrolyte body 131. The reference oxygen chamber 105 is filled with a ceramic porous body.

  The Ip1 cell 110 includes a solid electrolyte body 111 and a pair of porous electrodes 112 and 113. The solid electrolyte body 111 is made of, for example, zirconia and has oxygen ion conductivity. The electrodes 112 and 113 are respectively provided on both surfaces of the solid electrolyte body 111 in the stacking direction of the detection elements 10. As described above, the electrode 113 is disposed in the first measurement chamber 101, and the electrode 112 is disposed at a position corresponding to the electrode 113 with the solid electrolyte body 111 interposed therebetween. The electrodes 112 and 113 are formed of a material mainly containing Pt. Examples of the material containing Pt as a main component include Pt, Pt alloy, and cermet containing Pt and ceramics. Porous protective layers 114 and 115 made of ceramic are formed on the surfaces of the electrodes 112 and 113, respectively. The electrode 112 of the Ip1 cell 110 is connected to the Ip1 + electrode of the electrode pad 16, and the electrode 113 is connected to the COM electrode (reference potential).

  The Vs cell 120 includes a solid electrolyte body 121 and a pair of porous electrodes 122 and 123. The solid electrolyte body 121 is made of, for example, zirconia and has oxygen ion conductivity. The solid electrolyte body 121 is disposed so as to face the solid electrolyte body 111 with the insulator 141 interposed therebetween. The electrodes 122 and 123 are respectively provided on both surfaces of the solid electrolyte body 121 in the stacking direction of the detection elements 10. As described above, the electrode 123 is disposed in the reference oxygen chamber 105, and the electrode 122 is disposed in the first measurement chamber 101 at a position corresponding to the electrode 123 with the solid electrolyte body 121 interposed therebetween. The electrodes 122 and 123 are formed of a material containing Pt as a main component. The electrode 122 of the Vs cell 120 is connected to the COM electrode of the electrode pad 16, and the electrode 123 is connected to the Vs + electrode.

  The Ip2 cell 130 includes a solid electrolyte body 131 and a pair of porous electrodes 132 and 133. The solid electrolyte body 131 is made of, for example, zirconia and has oxygen ion conductivity. The solid electrolyte body 131 is disposed so as to face the solid electrolyte body 121 with the insulator 146 interposed therebetween. The electrodes 132 and 133 are provided on the surface of the solid electrolyte body 131 on the solid electrolyte body 121 side in the stacking direction of the detection elements 10. As described above, the electrode 132 is disposed in the second measurement chamber 102, and the electrode 133 is disposed in the reference oxygen chamber 105 so as to be paired with the electrode 132 with the solid electrolyte body 131 interposed therebetween. The electrodes 132 and 133 are formed of the above-described material containing Pt as a main component. The electrode 132 of the Ip2 cell 130 is connected to the Ip2 + electrode of the electrode pad 16, and the electrode 133 is connected to the COM electrode.

  Next, the heater body 15 will be described. The heater body 15 includes insulating layers 152 and 153 and a heater pattern 151. The insulating layers 152 and 153 are made of a sheet mainly composed of alumina. The heater pattern 151 is a single electrode pattern embedded between the insulating layers 152 and 153 and connected in the heater body 15. The heater pattern 151 is formed of a material containing Pt as a main component, and has a correlation between its own temperature and resistance value. One end of the heater pattern 151 is connected to the Htr− electrode of the electrode pad 16 and grounded, and the other end is connected to the Htr + electrode.

  As shown in FIG. 1, the detection element 10 having such a structure is inserted into a cylindrical metal shell 50 and is attached to the metal shell 50 by the second talc 22 and the first talc 26 filled in the cylindrical hole. Is retained. The details of the holding structure of the detection element 10 in the metal shell 50 will be described later.

  The metal shell 50 is for attaching and fixing the NOx sensor 1 to an exhaust pipe (not shown) of an automobile, and an attachment portion 51 having a male screw for attachment to the exhaust pipe is provided on the outer peripheral tip side. Yes. A tip engaging portion 56 to which a protector 8 described later is engaged is formed on the tip side of the mounting portion 51. Further, a tool engaging portion 52 with which a tool for attachment is engaged is formed at the center of the outer periphery of the metal shell 50. On the rear end side of the tool engagement portion 52, a rear end engagement portion 57 with which an outer cylinder 30 described later is engaged is formed. Further, on the rear end side, the detection element 10 is added in the metal shell 50. A caulking portion 53 is formed for tightening and holding. And between the tool engaging part 52 and the attaching part 51, the annular gasket 55 which prevents the gas escape when attaching to an exhaust pipe is inserted.

  The front end engaging portion 56 of the metal shell 50 is formed in a cylindrical shape, and the protector 8 is fitted therein. The protector 8 surrounds the outer periphery of the distal end portion 11 of the detection element 10 to protect the detection element 10 from being damaged by water or physical impact. The protector 8 is fixed to the tip engaging portion 56 by resistance welding or laser welding. The protector 8 includes a double-layered structure including a bottomed cylindrical inner protector 90 and a cylindrical outer protector 80 that surrounds the periphery in the radial direction with a gap between the outer peripheral surface of the inner protector 90. It has a structure.

  The inner protector 90 has a plurality of inner introduction holes 95 at the rear end side of the peripheral wall 92, a plurality of drain holes 96 at the front end side of the peripheral wall 92, and a discharge port 97 at the bottom wall 93. The proximal end portion 91 on the opening end side (rear end side) is engaged with the outer periphery of the distal end engaging portion 56 of the metal shell 50. The outer protector 80 is provided with a plurality of outer introduction holes 85 on the distal end side of the peripheral wall 82. The base end portion 81 on the opening end side is engaged with the outer periphery of the base end portion 91 of the inner protector 90. In this state, laser welding is performed on the outer periphery of the base end portion 81, the base end portion 91 of the inner protector 90 is joined to the front end engaging portion 56 of the metal shell 50, and the outer protector 80 and the inner protector 90 are connected. It is fixed to the metal shell 50. Furthermore, the front-end | tip part 83 of the outer protector 80 is bend | folded inside toward the surrounding wall 92 of the inner protector 90 so that the space | gap between the outer protector 80 and the inner protector 90 may be closed.

  On the other hand, the rear end portion 12 of the detection element 10 held by the metal shell 50 protrudes rearward from the rear end (caulking portion 53) of the metal shell 50. The rear end portion 12 is covered with a cylindrical separator 60 made of insulating ceramics (in this embodiment, alumina). The separator 60 includes a front end side separator 61 and a rear end side separator 66, and the rear end side separator 66 is engaged with a flange portion 62 provided on the front end side separator 61 and projecting radially outward. . The front-side separator 61 includes six electrode pads 16 formed at the rear end portion 12 of the detection element 10 and six connection terminals (metal terminals) 44 (in FIG. 1) that are electrically connected to the electrode pads 16. The connection parts (contact points) with four of them are housed inside. In other words, the electrical connection between the connection terminal 44 and the electrode pad 16 is performed in the front end side separator 61. The rear end side separator 66 accommodates the connection portion of each connection terminal 44 and the six lead wires 41 drawn out of the NOx sensor 1 inside.

  A metallic outer cylinder 30 is disposed so as to surround the periphery of the rear end portion 12 of the detection element 10 in which the separator 60 is fitted. The outer cylinder 30 has an opening end 35 on the front end side engaged with the outer periphery of the rear end engaging portion 57 of the metal shell 50. The open end 35 is crimped from the outer peripheral side, and further, laser welding is performed around the outer periphery, and is joined to the rear end engaging portion 57, whereby the outer cylinder 30 and the metal shell 50 are integrated. It has become.

  Further, in the gap between the outer cylinder 30 and the front end side separator 61, a metal-made cylindrical holding metal fitting 42 is disposed. The holding metal fitting 42 has a support portion 43 configured by bending its rear end inward. The flange portion 62 of the front end side separator 61 inserted into the holding metal fitting 42 is engaged with the support portion 43, so that the front end side separator 61 is held by the holding metal fitting 42. In this state, the outer peripheral surface of the outer cylinder 30 at the portion where the holding metal fitting 42 is disposed is crimped inward, whereby the holding metal fitting 42 that supports the front end side separator 61 is fixed to the outer cylinder 30.

  Next, a grommet 45 made of fluorine rubber is fitted into the opening on the rear end side of the outer cylinder 30 to seal the inside of the outer cylinder 30. The grommet 45 has six insertion holes 46 (two of which are shown in FIG. 1), and the six lead wires 41 drawn from the separator 60 are inserted into the insertion holes 46. . In this state, the grommet 45 is clamped from the outer periphery of the outer cylinder 30 and is fixed to the rear end of the outer cylinder 30 while pressing the rear end side separator 66 against the front end side separator 61.

  Next, details of the holding structure of the detection element 10 in the metal shell 50 will be described. As described above, the detection element 10 is inserted into the cylindrical hole of the metal shell 50. A metal holder 20 having a bottomed cylindrical shape and a hole 25 in the bottom wall is disposed at a position slightly on the tip side from the center of the body portion 13 of the detection element 10. The detection element 10 is inserted through the holder 20 through the hole 25, and the distal end portion 11 protrudes further toward the distal end side in the axis O direction than the hole 25. The holder 20 is a member for positioning and holding the detection element 10 in the metal shell 50. The edge portion of the bottom wall of the holder 20 is formed with a tip peripheral portion 23 that is tapered from the bottom wall to the outer peripheral wall. The holder 20 is disposed in the metal shell 50 in a state in which the distal end peripheral edge portion 23 is engaged with a stepped portion 54 that protrudes radially inward over the circumference of the metal shell 50.

  In the holder 20, a ceramic ring 21 made of alumina is disposed on the bottom wall side, and the powder of the second talc 22 is filled on the opening end side. The second talc 22 is hardened by compression, and the gap between the powders is filled in a dense state. As shown in FIG. 3, a fourth glass layer 34 mainly composed of glass is formed between the second talc 22 and the inner peripheral surface 19 of the holder 20. Similarly, a third glass layer 33 is also formed between the second talc 22 and the outer peripheral surface 18 of the detection element 10. The third glass layer 33 and the fourth glass layer 34 are obtained by drying water glass and are not melted. The second talc 22, the outer peripheral surface 18 of the detection element 10, and the inner peripheral surface 19 of the holder 20. Not glued to. In other words, the third glass layer 33 and the fourth glass layer 34 are not fixed to the second talc 22, the outer peripheral surface 18 of the detection element 10, and the inner peripheral surface 19 of the holder 20. When the second talc 22 is compressed in the holder 20, the third glass layer 33 and the fourth glass layer 34, respectively, the second talc 22 and the outer peripheral surface 18 of the detection element 10, the second talc 22 and It is in contact with the inner peripheral surface 19 of the holder 20. The detection element 10 is positioned by the ceramic ring 21 in the holder 20 and is held by the second talc 22.

  In addition, the 3rd glass layer 33 and the 4th glass layer 34 are glass layers in which the second talc 22 is partially included in the present embodiment. In the case of the glass layer partially including the second talc, the boundary between the third glass layer 33, the fourth glass layer 34, and the second talc 22 in a part where the glass component is present in a large amount and a part where the glass component is present in a very small amount. Can be separated. Moreover, like the 3rd glass layer 33 and the 4th glass layer 34, it may not be a glass layer in which the 2nd talc 22 is partially contained, but may be formed only with glass.

  Further, in the present embodiment, the third glass layer 33 and the fourth glass layer 34 are the same material (water glass), but the third glass layer 33 and the fourth glass layer 34 are formed of different materials. May be.

  As described above, the detection element 10 integrated with the holder 20 is held by the peripheral edge 23 of the holder 20 being engaged with the step 54 of the metal shell 50 and surrounded by the metal shell 50. The metal shell 50 is filled with the powder of the first talc 26 from the rear end side of the holder 20. The first talc 26 is further compressed and hardened by a cylindrical sleeve 27 inserted into the metal shell 50 from the rear end side, and the gap between the powders is filled in a dense state. A second glass layer 32 similar to the above is formed between the first talc 26 and the inner peripheral surface 58 of the metal shell 50, and also between the first talc 26 and the outer peripheral surface 18 of the detection element 10. A first glass layer 31 is formed. The first glass layer 31 and the second glass layer 32 are not melted, and similarly to the third glass layer 33 and the fourth glass layer 34, the first talc 26, the outer peripheral surface 18 of the detection element 10, and the metal shell 50. It is not fixed to the inner peripheral surface 58. When the first talc 26 is pressed and hardened in the metal shell 50, the first glass layer 31 and the second glass layer 32 are, respectively, the first talc 26 and the outer peripheral surface 18 of the detection element 10, and the first talc 26. The metal shell 50 is in contact with the inner peripheral surface 58.

  As shown in FIG. 1, the sleeve 27 is inserted into the metal shell 50 while allowing the detection element 10 to pass therethrough, and presses the first talc 26 from the rear end side. The sleeve 27 has a shoulder portion 28 formed in a step shape on the outer periphery on the rear end side, and an annular packing 29 is disposed on the shoulder portion 28. In this state, the crimping portion 53 of the metal shell 50 is crimped inward, and the crimping portion 53 presses the shoulder portion 28 of the sleeve 27 toward the distal end side through the packing 29. The first talc 26 is pressed against the sleeve 27 by caulking, and the second talc 22 is further pressed by the first talc 26 and is compressed tightly in the metal shell 50. The holder 20 and the detection element 10 are positioned and held in the metal shell 50 by the second talc 22 and the first talc 26.

  Next, the manufacturing process of the NOx sensor 1 of the present embodiment will be described with reference to FIGS. 4 and 5, focusing on the process of assembling the element unit 230 to the metal fitting assembly 235. In the manufacturing process of the NOx sensor 1, as shown in FIG. 4, the second talc 22 and the first talc 26 are solid talc pressed into a cylindrical shape in order to facilitate the handling thereof. Supplied as a ring 225. The talc ring 225 is produced by the following process.

  By flowing the talc powder 205 into the mold 210 and compressing it, the cylindrical green compact 200 in which the insertion hole through which the detection element 10 is inserted is formed (first forming step, second forming step). . The formed green compact 200 is immersed in a water glass aqueous solution 215 prepared by, for example, dissolving sodium silicate in water and heating. Water glass is attached to the outer surface including the outer peripheral surface and the inner peripheral surface in the circumferential direction of the cylindrical green compact 200 (first attaching step, second attaching step). The green compact 200 to which the water glass is attached is put into a drying furnace 220, and the water glass attached to the surface is dried (first drying step, second drying step). The green compact 200 is coated with a glass material. That is, a glass layer that functions as the second glass layer 32 and the fourth glass layer 34 is formed on the outer peripheral surface of the green compact 200 after the NOx sensor 1 is assembled, and the first glass layer 31 and the third glass layer 34 are formed on the inner peripheral surface. A glass layer that functions as the glass layer 33 is formed. The green compact 200 on which the glass layer is formed is supplied to the assembly line of the NOx sensor 1 as a talc ring 225.

  The detection element 10 of the NOx sensor 1 includes an unfired gas detector 14 and an unfired heater body 15 stacked in the thickness direction (plate thickness direction) and, after firing, has an elongated plate-like detection as shown in FIG. The device 10 is produced. In another process, the holder 20, the ceramic ring 21, the sleeve 27, and the packing 29 are produced. The metal shell 50 and the protector 8 are also produced in separate processes. In the assembly line of the NOx sensor 1, a metal fitting assembly 235 (see FIG. 5) is assembled by joining the protector 8 to the tip engaging portion 56 of the metal shell 50. Supplied.

  Next, as shown in FIG. 5, the ceramic ring 21 and the talc ring 225 through which the detection element 10 is inserted are accommodated in the holder 20. A talc ring 225 is disposed between the inner peripheral surface 19 of the holder 20 and the outer peripheral surface 18 of the detection element 10 (second disposing step).

  The holder 20 is fixed, and the talc ring 225 is compressed from the opening side of the holder 20 by a compression jig (not shown) (second compression step). The talc ring 225 is crushed, the shape is broken, and the powdered second talc 22 is formed, and the gap in the holder 20 is filled. At this time, the glass layer formed on the outer peripheral surface of the talc ring 225 is sandwiched between the second talc 22 and the inner peripheral surface 19 of the holder 20, and both are used as a fourth glass layer 34 (see FIG. 3). To touch. Similarly, the glass layer formed on the inner peripheral surface of the talc ring 225 is sandwiched between the second talc 22 and the outer peripheral surface 18 of the detection element 10, and as a third glass layer 33 (see FIG. 3), Contact both. In this way, the element unit 230 is formed by holding the detection element 10 in the holder 20 by the second talc 22.

  The element unit 230 is inserted into the metal shell 50 from the rear end side (clamping portion 53 side) of the metal fitting assembly 235. The front end peripheral edge portion 23 of the holder 20 is engaged with the stepped portion 54, and the detection element 10 held by the holder 20 is held in the metal shell 50 (holding step). Further, the talc ring 225, the sleeve 27, and the packing 29 are inserted into the detection element 10 from the rear end 12 side, and are accommodated in the metal shell 50 (first arrangement step).

  The bracket assembly 235 is fixed, the crimping portion 53 of the metal shell 50 is crimped by a crimping jig (not shown), and the sleeve 27 is pressed downward (to the front end side of the metal shell 50) through the packing 29. Is done. This caulking is performed by heat caulking performed while removing the residual stress by heating the caulking portion 53. The sleeve 27 presses the first talc 26 downward, whereby the talc ring 225 is compressed in the metal shell 50 (first compression step). The talc ring 225 is crushed and its shape is lost to form the first talc 26 in powder, and the gap in the metal shell 50 is filled. At this time, the glass layer formed on the outer peripheral surface of the talc ring 225 is sandwiched between the first talc 26 and the inner peripheral surface 58 of the metal shell 50, and as the second glass layer 32 (see FIG. 3), Contact both. Similarly, the glass layer formed on the inner peripheral surface of the talc ring 225 is sandwiched between the first talc 26 and the outer peripheral surface 18 of the detection element 10, and as the first glass layer 31 (see FIG. 3), Contact both.

  Moreover, by performing heat caulking, heat is transmitted to the first glass layer 31 to the fourth glass layer 34, and the first glass layer 31 to the fourth glass layer 34 are heated (heating step). The heating temperature and heating time of the caulking portion 53 in the heat caulking are adjusted so that the heating temperature at this time is higher than the softening temperature at which the glass material softens and lower than the flow temperature. Although the glass material which forms the 1st glass layer 31-the 4th glass layer 34 softens, it does not fuse | melt and it contacts firmly with respect to the surface which each contacts. Therefore, the clearances between the second talc 22 and the first talc 26 and the outer peripheral surface 18 of the detection element 10, the inner peripheral surface 19 of the holder 20, and the inner peripheral surface 58 of the metal shell 50 are the first glass layer 31 to the fourth glass. It is completely sealed by the glass layer 34.

  In addition, the second talc 22 and the first talc 26 are also compressed so that the gap between the powders is filled in a dense state. Therefore, the airtightness through the metal shell 50 is ensured. In this manner, the detection element 10 is positioned in the metal shell 50 and is held by the second talc 22 and the first talc 26 so as to be integrated with the metal shell 50. In addition, since the pressing force is further applied to the second talc 22 that has been compressed in the holder 20 in the heat caulking, the body portion 13 of the detection element 10 is further strengthened by the second talc 22. Retained. Thus, the outer cylinder 30, the separator 60, the grommet 45, etc. shown in FIG. 1 are assembled to the metal shell 50 holding the detection element 10, and the NOx sensor 1 is completed.

  As described above, the first glass layer 31 and the second glass layer 32 are in contact with each other between the first talc 26 and the outer peripheral surface 18 of the detection element 10 and the inner peripheral surface 58 of the metal shell 50. Since the first talc 26 is disposed between the detection element 10 and the metal shell 50, that is, between the first talc 26 and the outer peripheral surface 18 of the detection element 10 and the inner peripheral surface 58 of the metal shell 50. The airtightness of the metal shell 50 can be ensured. This is because if the gap between the first talc 26 and the outer peripheral surface 18 of the detecting element 10 and the inner peripheral surface 58 of the metal shell 50 is filled with the first glass layer 31 and the second glass layer 32, the first talc 26 is filled. This is because the airtightness can be sufficiently secured even if the pressure applied to the compression is not strong. The first glass layer 31 and the second glass layer 32 are not fixed to the outer peripheral surface 18 of the detection element 10 and the inner peripheral surface 58 of the metal shell 50, respectively. That is, it is only in contact and not bonded. Although the NOx sensor 1 is used in a high temperature environment, even if the metallic shell 50 and the detection element 10 are thermally expanded, the first glass layer 31 and the second glass layer 32 are not fixed to them, so that a difference in thermal expansion is generated. For example, stress applied to the detection element 10 due to thermal expansion can be reduced, and element breakage or the like can be prevented.

  Furthermore, since the 3rd glass layer 33 and the 4th glass layer 34 are arrange | positioned and contacted between the 2nd talc 22 and the outer peripheral surface 18 of the detection element 10, and the inner peripheral surface 19 of the holder 20, respectively. The airtightness of the metal shell 50 between the second talc 22 and the detection element 10 and the holder 20 between the second talc 22 and the outer peripheral surface 18 of the detection element 10 and the inner peripheral surface 19 of the holder 20 is also. Can be secured. This is because if the gap between the second talc 22 and the outer peripheral surface 18 of the detection element 10 and the inner peripheral surface 19 of the holder 20 is filled with the third glass layer 33 and the fourth glass layer 34, the second talc 22 is filled. This is because sufficient airtightness can be secured even if the pressure applied to the compression is not strong. In addition, the third glass layer 33 and the fourth glass layer 34 are not fixed to the outer peripheral surface 18 of the detection element 10 and the inner peripheral surface 19 of the holder 20, and are only in contact with each other, and are not adhered to each other. Absent. Therefore, the difference in thermal expansion between the holder 20 and the detection element 10 can be absorbed by the third glass layer 33 and the fourth glass layer 34, and for example, element breakage or the like can be prevented as described above.

  In addition, the output of the NOx concentration detected by the NOx sensor 1 including the first oxygen pump cell 110 and the second oxygen pump cell 130 is very small, and is easily affected by a decrease in insulation properties of the electrode pad 16 and the connection terminal 44 due to a change in humidity. If airtightness through the metal shell 50 can be reliably ensured, the humidity increase in the NOx sensor 1 can be suppressed, the output is not affected, and the detection accuracy of the NOx concentration can be ensured. Thus, the present invention is particularly effective for a gas sensor such as the NOx sensor 1 that handles a weak current.

  Further, in forming the first glass layer 31 to the fourth glass layer 34 on the NOx sensor 1, the talc powder 205 is first formed as a green compact 200 in advance, and a liquid water glass aqueous solution 215 is formed on the green compact 200. To attach. Further, the talc ring 225 obtained by drying the attached water glass is used for filling and compression between the detection element 10 and the metal shell 50 or between the detection element 10 and the holder 20. By doing so, the first glass layer 31 and the second glass layer 32 are brought into contact with each other between the first talc 26 and the outer peripheral surface 18 of the detection element 10 and the inner peripheral surface 58 of the metal shell 50, respectively. Can be arranged. Further, the third glass layer 33 and the fourth glass layer 34 can be arranged in contact with each other between the second talc 22 and the outer peripheral surface 18 of the detection element 10 and the inner peripheral surface 19 of the holder 20. Therefore, the airtightness of the metal shell 50 can be ensured. In addition, by filling and compressing the talc ring 225 between the detection element 10 and the metal shell 50 or between the detection element 10 and the holder 20 by the above-described method, the first glass layer 31 to the fourth glass. The layer 34 can be non-adhered to the outer peripheral surface 18 of the detection element 10, the inner peripheral surface 58 of the metal shell 50, and the inner peripheral surface 19 of the holder 20.

  Moreover, in a heating process, a glass material can be softened by heating the 1st glass layer 31-the 4th glass layer 34 at the temperature lower than the flow temperature of a glass material. Therefore, the first glass layer 31 to the fourth glass layer 34 are contacted with the first glass on the outer peripheral surface 18 of the detection element 10, the inner peripheral surface 19 of the holder 20, and the inner peripheral surface 58 of the metal shell 50. The layers 31 to the fourth glass layer 34 can be contacted more firmly, and the airtightness through the metal shell 50 can be ensured more reliably. Moreover, a glass material does not fuse | melt by setting the heating temperature at this time to the temperature lower than the flow temperature of a glass material.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. When forming the talc ring 225, the green compact 200 is immersed in the water glass aqueous solution 215. For example, the surface of the green compact 200 may be adhered by applying water glass using a brush or spray. Good. Further, the water glass does not have to be attached to the green compact 200 on the entire outer peripheral surface of the green compact 200 as long as it is attached to at least the outer peripheral surface and the inner peripheral surface. Furthermore, if water glass is attached to each of the outer peripheral surface and the inner peripheral surface of the green compact 200 over one circumference in the circumferential direction, it does not have to be attached to the entire outer peripheral surface and inner peripheral surface.

  In the heating process, the first glass layer 31 to the fourth glass layer 34 are heated by the residual heat in the caulking portion 53, and after the first talc 26 is compressed, the first glass is separately provided. A step of heating the layer 31 to the fourth glass layer 34 may be provided. Alternatively, it is not necessary to heat the first glass layer 31 to the fourth glass layer 34. By compressing the second talc 22 and the first talc 26, the first glass layer 31 to the fourth glass layer 34 include the second talc 22, the first talc 26, the outer peripheral surface 18 of the detection element 10, and the holder 20. Between the inner peripheral surface 19 and the inner peripheral surface 58 of the metal shell 50. Therefore, even without heating the first glass layer 31 to the fourth glass layer 34, it is possible to sufficiently ensure the airtightness through the metal shell 50.

  In the present embodiment, the detection element 10 is held in the holder 20 by the second talc 22 and the detection element 10 is held in the metal shell 50 together with the holder 20 by the first talc 26. For example, the configuration of the holder 20 and the second talc 22 may be omitted, and the metal shell 50 may be directly filled with the first talc 26 to hold the detection element 10. Alternatively, the configuration of the first talc 26 may be omitted, the holder 20 may be held in the metal shell 50, and the detection element 10 may be held by the second talc 22 filled in the holder 20. In this case, the front end peripheral edge 23 of the holder 20 may be engaged with the stepped portion 54 of the metal shell 50 via packing, and the airtightness between the metal shell 50 and the holder 20 may be ensured by packing.

  In the present embodiment, a so-called NOx sensor is taken as an example of a gas sensor, and the present invention is applied. Not limited to this, a one-cell oxygen sensor of a type that detects the oxygen concentration in a binary manner (the output changes suddenly at a specific air-fuel ratio such as a theoretical air-fuel ratio), an all-region air-fuel ratio sensor, an HC sensor The present invention may be applied to various gas sensors using sensor elements such as the above.

  In the present invention, the first talc 26 corresponds to the “first powder material”, and the second talc 22 corresponds to the “second powder material”. Further, the first glass layer 31 to the fourth glass layer 34 correspond to “first to fourth glass layers”, respectively. The solid electrolyte body 111 corresponds to a “first solid electrolyte layer”, and the electrodes 112 and 113 correspond to “a pair of first electrodes”. The solid electrolyte body 131 corresponds to a “second solid electrolyte layer”, and the electrodes 132 and 133 correspond to “a pair of second electrodes”. The talc powder 205 corresponds to “powder”. The water glass aqueous solution 215 corresponds to a “liquid glass material”. The talc ring 225 corresponds to a “solid powder material”.

DESCRIPTION OF SYMBOLS 1 NOx sensor 10 Detection element 17 Detection part 18 Outer peripheral surface 19 Inner peripheral surface 20 Holder 22 2nd talc 26 First talc 27 Sleeve 31-34 First glass layer-4th glass layer 50 Main metal fitting 54 Step part 58 Inner peripheral surface 101 1st measurement chamber 102 2nd measurement chamber 110 1st oxygen pump cell 111,131 Solid electrolyte body 112,113,132,133 Electrode 130 2nd oxygen pump cell 200 Green compact 205 Talc powder 215 Water glass aqueous solution 225 Talc ring

Claims (7)

A detection element that extends in the axial direction and has a detection unit for detecting a specific gas component in the detection target gas on the tip side;
A cylindrical metal shell for inserting the detection element;
A first powder material filled between an outer peripheral surface of the detection element and an inner peripheral surface of the metal shell;
A first glass layer that is disposed between the first powder material and the detection element, contacts the outer peripheral surface of the first powder material and the detection element over one circumference in the circumferential direction, and is not fixed to the detection element. When,
A second glass that is disposed between the first powder material and the metal shell, contacts the inner peripheral surface of the first powder material and the metal shell over one circumference in the circumferential direction, and is not fixed to the metal shell. Layers,
A gas sensor comprising: The metal shell has a stepped portion projecting radially inward over one circumference in the circumferential direction,
Furthermore, a cylindrical shape extending in the axial direction, a holder disposed in the metal shell in a state of being engaged with the stepped portion,
In the holder, a second powder material filled between the outer peripheral surface of the detection element and the inner peripheral surface of the holder,
A third glass layer that is disposed between the second powder material and the detection element, contacts the outer peripheral surface of the second powder material and the detection element over one circumference in the circumferential direction, and is not fixed to the detection element. When,
A fourth glass layer disposed between the second powder material and the holder, contacting the second powder material and the inner peripheral surface of the holder over one circumference in the circumferential direction, and non-adhering to the detection element; ,
The gas sensor according to claim 1, comprising: A detection element that extends in the axial direction and has a detection unit for detecting a specific gas component in the detection target gas on the tip side;
A metal fitting having a cylindrical shape through which the detection element is inserted and having a step portion protruding radially inward over one circumference in the circumferential direction;
A holder extending in the axial direction, in a state of being engaged with the stepped portion and disposed in the metal shell,
In the holder, a second powder material filled between the outer peripheral surface of the detection element and the inner peripheral surface of the holder,
A third glass layer that is disposed between the second powder material and the detection element, contacts the outer peripheral surface of the second powder material and the detection element over one circumference in the circumferential direction, and is not fixed to the detection element. When,
A fourth glass layer disposed between the second powder material and the holder, contacting the second powder material and the inner peripheral surface of the holder over one circumference in the circumferential direction, and non-adhering to the detection element; ,
A gas sensor comprising: The detection element is
A first measurement chamber into which the detection target gas is introduced;
A first oxygen pump cell comprising a first solid electrolyte layer and a pair of first electrodes, wherein the pair of first electrodes are provided inside and outside the first measurement chamber;
A second measurement chamber that communicates with the first measurement chamber and into which the detection target gas whose oxygen concentration is adjusted by the first oxygen pump cell is introduced from the first measurement chamber;
A second oxygen pump cell comprising a second solid electrolyte layer and a pair of second electrodes, wherein the pair of second electrodes are provided inside and outside the second measurement chamber;
Provided in the detection unit,
The gas sensor according to any one of claims 1 to 3, wherein the gas sensor is an element for detecting a concentration of NOx in the detection target gas based on a magnitude of a current flowing through the second oxygen pump cell. A detection element that extends in the axial direction and has a detection unit for detecting a specific gas component in the detection target gas on the tip side;
A cylindrical metal shell for inserting the detection element;
A first powder material filled between an outer peripheral surface of the detection element and an inner peripheral surface of the metal shell;
A first glass layer that is disposed between the first powder material and the detection element, contacts the outer peripheral surface of the first powder material and the detection element over one circumference in the circumferential direction, and is not fixed to the detection element. When,
A second glass that is disposed between the first powder material and the metal shell, contacts the inner peripheral surface of the first powder material and the metal shell over one circumference in the circumferential direction, and is not fixed to the metal shell. Layers,
A method of manufacturing a gas sensor comprising:
A first forming step of compacting powder as a raw material of the first powder material to form a cylindrical green compact into which the detection element is inserted;
A first attachment step of attaching a liquid glass material, which is a raw material of the first glass layer and the second glass layer, to at least an outer peripheral surface and an inner peripheral surface in the circumferential direction of the outer surface of the green compact; ,
A first drying step of drying the glass material and forming a solid powder material in which the first glass layer and the second glass layer are formed on the green compact;
A first arrangement step of inserting the detection element arranged in a state of being inserted through the metal shell, through the solid powder material, and arranging the solid powder material between the metal shell and the detection element;
The solid powder material is compressed, the metal powder is filled with the first powder material formed by breaking the solid powder material, the detection element is held, and the first powder material and the detection element A first compression step of contacting the first glass layer and contacting the second glass layer to the first powder material and the metallic shell;
A method of manufacturing a gas sensor, comprising: A detection element that extends in the axial direction and has a detection unit for detecting a specific gas component in the detection target gas on the tip side;
A metal fitting having a cylindrical shape through which the detection element is inserted and having a step portion protruding radially inward over one circumference in the circumferential direction;
A holder extending in the axial direction, in a state of being engaged with the stepped portion and disposed in the metal shell,
In the holder, a second powder material filled between the outer peripheral surface of the detection element and the inner peripheral surface of the holder,
A third glass layer that is disposed between the second powder material and the detection element, contacts the outer peripheral surface of the second powder material and the detection element over one circumference in the circumferential direction, and is not fixed to the detection element. When,
A fourth glass layer disposed between the second powder material and the holder, contacting the second powder material and the inner peripheral surface of the holder over one circumference in the circumferential direction, and non-adhering to the detection element; ,
A method of manufacturing a gas sensor comprising:
A second forming step of compacting powder as a raw material of the second powder material to form a cylindrical green compact into which the detection element is inserted;
A second attachment step of attaching a liquid glass material, which is a raw material of the third glass layer and the fourth glass layer, to at least an outer peripheral surface and an inner peripheral surface in the circumferential direction of the outer surface of the green compact; ,
A second drying step of drying the glass material and forming a solid powder material in which the third glass layer and the fourth glass layer are formed on the green compact;
A second arrangement step of inserting the detection element arranged in a state of being inserted through the holder into the solid powder material, and arranging the solid powder material between the holder and the detection element;
The solid powder material is compressed, the second powder material formed by breaking the solid powder material is filled in the holder to hold the detection element, and the second powder material and the detection element are A second compression step of bringing the fourth glass layer into contact with the second powder material and the holder, while contacting the third glass layer;
Inserting the holder for holding the detection element into the metal shell, engaging the holder with the stepped portion, and holding the detection element in the metal shell; and
A method of manufacturing a gas sensor, comprising:   The heating process of heating the metallic shell holding the detection element at a temperature lower than the flow temperature of the glass material after the first compression process or after the second compression process. A method for producing the gas sensor according to 5 or 6.

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