JP2014149287A - Gas sensor element and gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor element that includes a water permeable electrode and a water non-permeable lead connected to the electrode and can prevent a crack from occurring in itself without reducing oxygen pump performance of the electrode even if water infiltrates into the water permeable electrode and is frozen.SOLUTION: A first electrode 133 includes an exposed-to-space part 133b that is exposed to an internal space 160 of a gas sensor element 10 communicating with the outside of the gas sensor element 10. A first lead 137 is connected to a first electrode 133. The first electrode 133 includes a first connection part 133d that is disposed at a position that is not exposed to the internal space 160, is connected to the first lead 137, and is disposed at a position most distant from the internal space in the first electrode 133. The whole first connection part 133d is positioned in a region A1 separated from the internal space 160 by a distance of 1.0 mm or shorter.

Description

  The present invention relates to a gas sensor element and a gas sensor including the same.

  2. Description of the Related Art Conventionally, gas sensors that are attached to an exhaust passage of an internal combustion engine such as an automobile engine and detect the oxygen concentration and NOx concentration in exhaust gas (measurement target gas) are known (see Patent Documents 1 and 2). Patent Documents 1 and 2 describe a gas sensor element in which a plurality of plate-shaped solid electrolyte bodies are stacked as a gas sensor element constituting the gas sensor. The gas sensor element includes an electrode provided on the front surface side or the back surface side of the solid electrolyte body and a lead provided on the front surface side or the back surface side of the solid electrolyte body and connected to the electrode.

  In patent documents 1 and 2, in order to ensure oxygen pump performance, the electrode is formed porous, and as a result, the electrode has gas permeability and water permeability. On the other hand, in order to improve electrical conductivity, it is preferable to increase the filling degree per unit area, and for this purpose, leads are formed densely. As a result, the lead has non-gas permeability and non-water permeability.

Japanese Patent No. 4165552 JP 2010-122187 A

  Incidentally, in FIGS. 3 and 4 of Patent Document 1, a first electrode having a space exposed portion exposed in an internal space communicating with the outside of the gas sensor element is described as an electrode. Furthermore, a first lead connected to the first electrode is described as the lead. The first lead is connected so as to overlap the first electrode in the internal space. However, when the first electrode and the first lead are a combination of the water-permeable electrode and the non-water-permeable lead as described above, the following problems may occur. In other words, in the portion of the first electrode that overlaps the first lead portion (hereinafter referred to as the first connection portion), the oxygen pump performance is reduced, and the detection accuracy for detecting the oxygen concentration or NOx concentration in the measurement target gas is reduced. There is a fear.

  On the other hand, in consideration of the above-described problem, it is conceivable that the first connection portion is disposed at a position where it is not exposed to the internal space by extending a part of the electrode to a position where it is not exposed to the internal space. Thereby, it can suppress that "the oxygen connection performance falls by the 1st connection part being arranged in interior space, and the detection accuracy which detects the oxygen concentration and NOx concentration in measurement object gas falls."

  However, even if the first connection portion is disposed at a position where it is not exposed to the internal space, there is a possibility that the following problem may occur. For example, in the winter season, the surface of the gas sensor element may condense. Water (condensation water) generated by this condensation may enter the internal space of the gas sensor element, and may further enter the water permeable first electrode through the exposed space. The water that has entered the first electrode reaches the first connection portion that connects to the first lead, but the first lead is impermeable to water, and therefore cannot enter the first lead. It may stay at the first connection. When the condensed water stays in the first connection portion and the volume of the condensed water is expanded by freezing, stress is generated in a direction to separate the layers sandwiching the first connection portion, thereby sandwiching the first connection portion. There was a risk of cracks occurring between the layers.

  The present invention has been made in view of such a situation, and in a gas sensor element including a water-permeable electrode and a non-water-permeable lead connected to the water-permeable electrode without reducing the oxygen pump performance of the electrode. It is an object of the present invention to provide a gas sensor element that can prevent cracks from occurring even when water enters a free electrode and freezes, and a gas sensor including the gas sensor element.

  One aspect of the present invention is a gas sensor element in which a plurality of plate-shaped solid electrolyte bodies are stacked, and an electrode provided on the front surface side or the back surface side of the solid electrolyte body, and the surface side of the solid electrolyte body or And a lead connected to the electrode, the electrode having a space exposed portion exposed to an internal space of the gas sensor element communicating with the outside of the gas sensor element. An electrode, and the lead includes a water-impermeable first lead connected to the first electrode, and the first electrode is disposed at a position not exposed to the internal space and connected to the first lead. 1st connection part, Comprising: The 1st connection part arrange | positioned in the position most distant from the said internal space in the said 1st electrode, The distance from the said internal space is the said 1st connection part as a whole. Within the area of 0mm A gas sensor element formed by.

  The gas sensor element described above has a water permeable first electrode having a space exposed portion exposed in the internal space of the gas sensor element that communicates with the outside of the gas sensor element, and a non-permeable first lead connected to the first electrode. Have. Of these, the first electrode is disposed at a position not exposed to the internal space and includes a first connection portion connected to the first lead (the first electrode is therefore exposed to the space exposed portion and the internal space). A first connection portion that is not exposed to the space). The first connection portion is formed by extending the first electrode in order to connect the first lead to the outside of the internal space. Therefore, the first connection portion is located farthest from the internal space among the first electrodes. Has been placed.

  Conventionally, in the gas sensor element having such a configuration, when water enters the first connection portion and freezes, there is a possibility that the gas sensor element may crack. Specifically, for example, dew condensation water generated on the surface of the gas sensor element may enter the internal space of the gas sensor element and further enter the first electrode through the space exposed portion. The water that has entered the first electrode reaches the first connection portion that is connected to the first lead, but the first lead is impermeable to water and may remain in the first connection portion. Then, in a state where the dew condensation water remains in the first connection part, when the dew condensation water freezes and expands in volume, a stress is generated in a direction to separate the layers sandwiching the first connection part, and thereby, the interlayer of the gas sensor element is generated. There was a possibility that a crack would occur in the (interlayer sandwiching the first connecting portion).

  On the other hand, in the gas sensor element described above, the entire first connection portion is disposed in a region whose distance from the internal space is within 1.0 mm. Thereby, even when water permeates into the first connection portion and the water freezes, it is possible to prevent the gas sensor element from being cracked. The reason is considered as follows.

If the water stays in the first connection part and the water starts to freeze, the fine pores in the first connection part gradually become smaller (closed by ice), so The remaining water moves to the side opposite to the first lead (that is, the inner space side where there is a space where water can enter). At this time, the entire first connection portion is disposed in a region having a distance of 1.0 mm or less from the internal space (that is, from the location farthest from the internal space to the internal space in the first connection portion. The distance of the water in the first connecting portion can be moved (released) to the internal space before freezing in the first connecting portion. it can. Then, even if a lot of water freezes and expands in the internal space, no stress is generated that separates the layers of the gas sensor element. As a result, it is possible to prevent the gas sensor element from being cracked.

  The “internal space of the gas sensor element that communicates with the outside of the gas sensor element” communicates with the interior of the gas sensor directly (without inclusions) or communicates with the outside through a porous body (gas permeation is possible). And an internal space that is permeable to water). Among these, the internal space communicating with the outside through the porous body is not limited to the internal space communicating with the outside through one porous body, but communicates with the outside through a plurality of porous bodies (gas permeable and water permeable). Internal space is also included.

  Moreover, in the gas sensor element described above, the first electrode is connected to the first lead at a position where it is not exposed to the internal space. For this reason, unlike the above-mentioned Patent Document 1 (Japanese Patent No. 4165562), “the first connection portion is disposed in the internal space, so that the oxygen pump performance is reduced, and the oxygen concentration and NOx concentration in the measurement target gas It is possible to suppress “decrease in detection accuracy of detecting”.

  Further, the gas sensor element includes a first insulating layer formed on a front surface or a back surface of the solid electrolyte body, and a part of the first electrode and the first lead are formed on the first insulating layer. The space exposed portion of the first electrode is formed on a layer, and the space exposed portion of the first electrode is in contact with the solid electrolyte body through a through-hole penetrating the first insulating layer in the stacking direction of the solid electrolyte body. The first connection portion of the first electrode may be a gas sensor element connected to the first lead on the first insulating layer.

  In the gas sensor element described above, the space exposed portion of the first electrode (the portion exposed to the internal space of the gas sensor element) has an electrolyte body contact portion that contacts the solid electrolyte body through the through hole of the first insulating layer. . On the other hand, the first lead is formed on the first insulating layer (this prevents contact with the solid electrolyte body). The first connection portion of the first electrode is connected to the first lead on the first insulating layer. Therefore, in the gas sensor element described above, the first connection portion of the first electrode is disposed at a position not exposed to the internal space and is not brought into contact with the solid electrolyte body.

  Thereby, in the above-mentioned gas sensor, only the electrolyte body contact part of the 1st electrode can be made to actually function as a sensitive part, and it becomes possible to detect the gas concentration which is a candidate for detection with sufficient accuracy. Since the lead has different electrical characteristics from the first electrode, the gas concentration can be accurately detected when the lead and a part of the first connecting portion connected to the lead are in contact with the solid electrolyte. There are things that cannot be done.

  Furthermore, in any one of the above gas sensor elements, the electrode has gas permeability and water permeability, and has a porous body contact portion in contact with a porous body exposed to the outside of the gas sensor element. The lead includes a non-permeable second lead connected to the second electrode, and the second electrode is porous with respect to a planar direction perpendicular to the stacking direction of the solid electrolyte body. A second connection portion connected to the second lead at a position away from the body, the second connection portion disposed at a position farthest from the porous body in the second electrode, It is preferable that the entire second connection portion be a gas sensor element that is located in a region within a distance of 1.0 mm from the porous body.

The gas sensor element described above has gas permeability and water permeability, and has a porous body exposed to the outside of the gas sensor element. Furthermore, it has the water-permeable 2nd electrode which has a porous body contact part which contacts this porous body, and has the water-impermeable 2nd lead connected with a 2nd electrode. Among these, the second electrode has a second connection portion that is connected to the second lead at a position away from the porous body in the plane direction (therefore, the second electrode is a porous member that contacts the porous body. And a second contact portion that does not contact the porous body). The second connection portion is formed by extending the second electrode so as to be connected to the second lead at a position away from the porous body. Therefore, among the second electrodes, the second connection portion is the most from the porous body. It is located at a distance.

  Even in the gas sensor element having such a configuration, there is a possibility that cracks may occur in the gas sensor element when water enters the second connection portion and freezes. Specifically, for example, dew condensation water generated on the surface of the gas sensor element may enter the second electrode in contact with the porous sensor through the porous body. The water that has entered the second electrode reaches the second connection portion that is connected to the second lead. However, the second lead is impermeable to water and may remain in the second connection portion. Then, when the condensed water stays in the second connecting portion and the condensed water freezes and expands in volume, a stress is generated in a direction separating the layers sandwiching the second connecting portion. There was a possibility that a crack would occur in the (interlayer sandwiching the second connection portion).

  On the other hand, in the gas sensor element described above, the entire second connection portion is disposed within a region whose distance from the porous body is within 1.0 mm. Thereby, it is possible to prevent the gas sensor element from being cracked even when the water that has entered the second connection portion freezes. The reason is considered as follows.

  If the water stays in the second connection part and the water begins to freeze, the fine pores in the second connection part will gradually become smaller (closed by ice), so The remaining water moves to the side opposite to the second lead (that is, the side of the porous body having a space where water can enter). At this time, the entire second connection portion is disposed in a region having a distance of 1.0 mm or less from the porous body (that is, the second connection portion is porous from the portion farthest from the porous body. By keeping the distance to the material body within 1.0 mm, most of the water remaining in the second connection part is moved to the porous body before freezing in the second connection part ( Can escape). Thereafter, even if a large amount of water freezes and expands in the porous body, no stress that separates the layers of the gas sensor element is generated. Since the porous body is exposed to the outside, even if the porous body is filled with water, the water can be released to the outside during freezing. It does not occur. Therefore, it is possible to prevent the gas sensor element from being cracked.

  In addition, the second electrode is connected to the second lead at a position away from the porous body in the planar direction. For this reason, "the second connecting portion is disposed at a position overlapping the porous body, so that the oxygen pump performance is reduced, and the detection accuracy for detecting the oxygen concentration and NOx concentration in the measurement target gas is reduced." Can be suppressed.

  Furthermore, the gas sensor element includes a second insulating layer formed on the front surface or the back surface of the solid electrolyte body, and a part of the second electrode and the second lead are connected to the second insulating layer. The porous body contact portion of the second electrode has an electrolyte body contact portion that comes into contact with the solid electrolyte body through a through-hole penetrating the second insulating layer in the stacking direction. The second connection portion of the second electrode may be a gas sensor element connected to the second lead on the second insulating layer.

  In the gas sensor element described above, the porous body contact portion of the second electrode (the portion in contact with the porous body) has an electrolyte body contact portion that contacts the solid electrolyte body through the through hole of the second insulating layer. . On the other hand, the second lead is formed on the second insulating layer (this prevents contact with the solid electrolyte body). The second connection portion of the second electrode is connected to the second lead on the second insulating layer. Therefore, in the above-described gas sensor element, the second connection portion of the second electrode is disposed at a position away from the porous body in the planar direction, and is not brought into contact with the solid electrolyte body.

  Thereby, in the above-mentioned gas sensor, only the electrolyte body contact portion of the second electrode can actually function as the sensitive portion, and the gas concentration as the detection target can be detected with high accuracy. Since the lead has different electrical characteristics from the second electrode, the gas concentration can be accurately detected when the lead and a part of the second connection part connected to the lead are in contact with the solid electrolyte. There are things that cannot be done.

  Another aspect of the present invention is a gas sensor element formed by laminating a plurality of plate-shaped solid electrolyte bodies, the electrode provided on the surface side or the back side of the solid electrolyte body, and the surface side of the solid electrolyte body Or a lead provided on the back surface side and connected to the electrode, the electrode including a water-permeable third electrode disposed in the internal space of the gas sensor element communicating with the outside of the gas sensor element The lead includes a non-water-permeable third lead connected to the third electrode, and the gas sensor element includes a third insulating layer formed on the front surface or the back surface of the solid electrolyte body, A part of the third electrode and the third lead are formed on the third insulating layer, and the third electrode passes through the through hole penetrating the third insulating layer in the stacking direction of the solid electrolyte body. , Contact with the solid electrolyte body An electrolyte body contact portion that, in and the third insulating layer within the internal space, a gas sensing element having a third connection portion which connects with the third lead.

  The gas sensor element described above has a water-permeable third electrode disposed in the internal space of the gas sensor element that communicates with the outside of the gas sensor element. That is, the entire third electrode is disposed in the internal space (the entire front surface or back surface of the third electrode is exposed in the internal space). Moreover, it has the water-impermeable 3rd lead connected with the 3rd connection part of the 3rd electrode in the said internal space.

  With such a configuration, it is possible to prevent the gas sensor element from being cracked even when the water that has entered the third electrode freezes. Since the entire third electrode including the third connection portion is disposed in the internal space, water remaining in the third electrode including the third connection portion can be frozen (expanded) in the internal space. As a result, the generation of stress that separates the layers of the gas sensor element can be suppressed.

  In addition, the third connection portion of the third electrode is connected to the third lead on the third insulating layer (this prevents contact with the solid electrolyte body). Therefore, even if the third connection portion is disposed in the internal space, the third connection portion does not affect the oxygen pump performance of the third electrode (the oxygen pump performance of the third electrode is not deteriorated). . For this reason, it can suppress that the detection accuracy which detects the oxygen concentration and NOx concentration in measurement object gas falls.

  Further, in the above gas sensor element, the electrode is a water permeable fourth electrode that is in contact with a porous body that has gas permeability and water permeability and is exposed to the outside of the gas sensor element, The whole includes a fourth electrode disposed at a position facing the porous body in the stacking direction of the solid electrolyte body, and the lead includes a water-impermeable fourth lead connected to the fourth electrode, The gas sensor element includes a fourth insulating layer formed on the front surface or the back surface of the solid electrolyte body, and a part of the fourth electrode and the fourth lead are formed on the fourth insulating layer. The fourth electrode includes an electrolyte body contact portion that contacts the solid electrolyte body through a through-hole penetrating the fourth insulating layer in the stacking direction, and a position facing the porous body in the stacking direction. And the fourth insulating layer In, may the gas sensor element having a fourth connecting portion that connects with the fourth lead.

The gas sensor element described above has gas permeability and water permeability, and has a porous body exposed to the outside of the gas sensor element. Furthermore, the fourth electrode is a water-permeable fourth electrode that comes into contact with the porous body, and is entirely disposed at a position facing the porous body in the stacking direction (thickness direction) of the solid electrolyte body. ing. Here, “the whole of the fourth electrode faces the porous body” means that the whole of the porous body faces the porous body while being in contact with it, and a part of the fourth electrode sandwiches the lead. It includes a case where the entire water-permeable electrode faces the porous body in a form in which the other portion contacts the porous body while facing the porous body. Further, the gas sensor element described above has a fourth lead connected to the fourth connection portion of the fourth electrode at a position facing the porous body in the stacking direction.

  With such a configuration, it is possible to prevent the gas sensor element from being cracked even when the water that has entered the fourth electrode is frozen. The entire fourth electrode including the fourth connecting portion is disposed to face the porous body, and most of the fourth electrode except the entire portion of the fourth electrode or only the portion in contact with the lead contacts the porous body. Therefore, most of the water remaining in the fourth electrode can be frozen (expanded) in the pores of the porous body, and as a result, the generation of stress separating the layers of the gas sensor element can be suppressed. Because.

  In addition, the fourth connection portion of the fourth electrode is connected to the fourth lead on the fourth insulating layer (this prevents contact with the solid electrolyte body). Therefore, even if the fourth connecting portion is disposed at a position where the fourth connecting portion overlaps the porous body (position facing the stacking direction), the fourth connecting portion does not affect the oxygen pump performance of the fourth electrode (fourth). The oxygen pump performance of the electrode is not degraded). For this reason, it can suppress that the detection accuracy which detects the oxygen concentration and NOx concentration in measurement object gas falls.

  Furthermore, any one of the gas sensor elements described above, wherein the gas sensor element is a gas sensor element that detects a concentration of NOx contained in a measurement target gas, and the first lead or the third lead is configured according to a NOx concentration. A gas sensor element having a lead through which a current flows may be used.

  In order to accurately detect the concentration of NOx contained in the measurement target gas (for example, exhaust gas from an internal combustion engine), it is necessary to form leads with a high current flowing in accordance with the NOx concentration. A densely formed lead is impermeable to water. For this reason, conventionally, when the lead and the electrode through which the current corresponding to the NOx concentration flows are connected, as described above, when water enters the electrode and the water freezes, the gas sensor element is cracked. There was a risk of occurrence.

  However, the gas sensor element described above includes a lead through which a current corresponding to the NOx concentration flows as the first lead or the third lead. As described above, the entire first connection portion of the first electrode connected to the first lead is arranged in a region whose distance from the internal space is within 1.0 mm. About the 3rd connection part of the 3rd electrode connected with a 3rd lead | read | reed, it has arrange | positioned in internal space. Thereby, even when water enters the first (third) electrode and the water freezes, it is possible to prevent the gas sensor element from cracking.

Moreover, the other aspect of this invention is a gas sensor provided with one of the said gas sensor elements.
This gas sensor has any of the gas sensor elements described above. For this reason, in this gas sensor, it is possible to prevent the gas sensor element from cracking even when water enters the permeable electrode and freezes without degrading the oxygen pump performance of the electrode. The gas to be measured can be detected appropriately.

It is sectional drawing of the gas sensor concerning embodiment and modification. It is a perspective view of the gas sensor element concerning embodiment and a modification. It is BB sectional drawing of FIG. It is a perspective view which shows each layer which comprises a gas sensor element. It is an enlarged view of the E section of FIG. It is an enlarged view of the F section of FIG. It is a figure which shows the position of the connection part of Ip2-electrode, and is C arrow line view of FIG. It is a figure which shows the position of the connection part of an Ip1 + electrode, and is a G arrow line view of FIG. It is a correlation diagram of distance D1, D2 and a crack generation rate. It is a figure which shows the position of the connection part of Ip2-electrode about the gas sensor element concerning a deformation | transformation form. It is a figure which shows the position of the connection part of an Ip1 + electrode about the gas sensor element concerning a deformation | transformation form.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a vertical cross-sectional view (a cross-sectional view cut along an axis AX) of a gas sensor 1 according to an embodiment. FIG. 2 is a perspective view of the gas sensor element 10 according to the embodiment. FIG. 3 is a cross-sectional view taken along the line BB in FIG. 2 and shows the internal structure of the gas sensor element 10. FIG. 4 is a perspective view showing each layer constituting the gas sensor element 10 and shows the stacking direction (vertical direction in FIG. 4) in the stacking order. 5 is an enlarged view of a portion E in FIG. 4, and FIG. 6 is an enlarged view of a portion F in FIG.

  The gas sensor 1 includes a gas sensor element 10 that can detect the concentration of a specific gas (NOx) in exhaust gas that is a measurement target gas, and is a NOx sensor that is used by being mounted on an exhaust pipe (not shown) of an internal combustion engine ( (See FIG. 1). This gas sensor 1 includes a cylindrical metal shell 20 in which a screw portion 21 for fixing to an exhaust pipe is formed at a predetermined position on the outer surface. The gas sensor element 10 has an elongated plate shape extending in the direction of the axis AX, and is held inside the metal shell 20 (see FIGS. 1 and 2).

  More specifically, the gas sensor 1 includes a holding member 60 having an insertion hole 62 into which the rear end portion 10k (the upper end portion in FIG. 1) of the gas sensor element 10 is inserted, and six pieces held inside the holding member 60. Terminal members. In FIG. 1, only two terminal members (specifically, terminal members 75 and 76) out of the six terminal members are illustrated.

  A total of six electrode terminal portions having a rectangular shape in plan view are formed at the rear end portion 10k (right end portion in FIG. 2) of the gas sensor element 10. Specifically, electrode terminal portions 13, 14, and 15 are formed on the first surface 10a of the gas sensor element 10, and electrode terminal portions 16, 17, and 18 are formed on the second surface 10b. The above-described terminal members are in elastic contact with and electrically connected to the electrode terminal portions 13 to 18, respectively (see FIG. 1). Specifically, the element contact portion located on the tip side of each terminal member elastically contacts any one of the electrode terminal portions 13 to 18. For example, the element contact portion 75 b of the terminal member 75 is elastically contacted and electrically connected to the electrode terminal portion 14. Further, the element contact portion 76b of the terminal member 76 is elastically contacted and electrically connected to the electrode terminal portion 17 (see FIG. 1).

Furthermore, different lead wires 71 are electrically connected to the six terminal members (terminal members 75, 76, etc.), respectively. Specifically, the lead wire 71 is electrically connected to the terminal member by gripping the core wire of the lead wire 71 by the lead wire gripping portion located at the rear end portion of the terminal member. For example, as shown in FIG. 1, the lead wire 71 is electrically connected to the terminal member 75 by gripping the core wire of the lead wire 71 by the lead wire gripping portion 77 of the terminal member 75. Further, the lead wire gripping portion 78 of the terminal member 76 grips the core wire of the other lead wire 71, whereby the other lead wire 71 is electrically connected to the terminal member 76.

  The metal shell 20 is a cylindrical member having a through hole 23 that penetrates in the direction of the axis AX. The metal shell 20 has a shelf 25 that constitutes a part of the through hole 23 in a form protruding radially inward. The metal shell 20 projects the front end portion 10s of the gas sensor element 10 to the outside of its front end side (downward in FIG. 1), and the rear end portion 10k of the gas sensor element 10 to the outside of its rear end side (upward in FIG. 1). The gas sensor element 10 is held in the through hole 23 in a state where the gas sensor element 10 is protruded to the inside.

  Further, an annular ceramic holder 42, two talc rings 43 and 44 formed by annularly filling talc powder, and a ceramic sleeve 45 are disposed inside the through hole 23 of the metal shell 20. Specifically, the ceramic holder 42, the talc rings 43 and 44, and the ceramic sleeve 45 are arranged in this order in the axial direction front end side (lower end side in FIG. 1) of the metal shell 20 in a state of surrounding the gas sensor element 10 in the radial direction. To the rear end side in the axial direction (upper end side in FIG. 1).

  Further, a metal cup 41 is disposed between the ceramic holder 42 and the shelf 25 of the metal shell 20. A caulking ring 46 is disposed between the ceramic sleeve 45 and the caulking portion 22 of the metal shell 20. The caulking portion 22 of the metal shell 20 is crimped so as to press the ceramic sleeve 45 against the distal end side via the crimping ring 46.

  A metal (specifically, stainless steel) external protector 31 and an internal protector 32 having a plurality of holes are attached to the distal end portion 20b of the metal shell 20 by welding so as to cover the distal end portion 10s of the gas sensor element 10. ing. On the other hand, an outer cylinder 51 is attached to the rear end portion of the metal shell 20 by welding. The outer cylinder 51 has a cylindrical shape extending in the direction of the axis AX and surrounds the gas sensor element 10.

  The holding member 60 is a cylindrical member made of an insulating material (specifically alumina) and having an insertion hole 62 penetrating in the direction of the axis AX. In the insertion hole 62, the six terminal members (terminal members 75, 76, etc.) described above are arranged (see FIG. 1). At the rear end portion of the holding member 60, a flange portion 65 that protrudes radially outward is formed. The holding member 60 is held by the internal support member 53 in such a manner that the collar portion 65 contacts the internal support member 53. The inner support member 53 is held by the outer cylinder 51 by a caulking portion 51g that is caulked toward the radially inner side of the outer cylinder 51.

  An insulating member 90 is disposed on the rear end surface 61 of the holding member 60. The insulating member 90 is made of an electrically insulating material (specifically, alumina) and has a cylindrical shape. The insulating member 90 is formed with a total of six through holes 91 penetrating in the direction of the axis AX. In the through hole 91, the lead wire gripping portions (lead wire gripping portions 77, 78, etc.) of the terminal member described above are arranged.

  Further, an elastic seal member 73 made of fluororubber is arranged on the radially inner side of the rear end opening 51c located at the rear end portion in the axial direction (the upper end portion in FIG. 1) of the outer cylinder 51 (FIG. 1). reference). The elastic seal member 73 is formed with a total of six cylindrical insertion holes 73c extending in the axis AX direction. Each insertion hole 73 c is configured by an insertion hole surface 73 b (cylindrical inner wall surface) of the elastic seal member 73. One lead wire 71 is inserted through each insertion hole 73c. Each lead wire 71 extends to the outside of the gas sensor 1 through the insertion hole 73 c of the elastic seal member 73. The elastic seal member 73 is elastically compressed and deformed in the radial direction by caulking the rear end opening 51c of the outer cylinder 51 inward in the radial direction, whereby the insertion hole surface 73b and the outer peripheral surface 71b of the lead wire 71 are brought into close contact with each other. Thus, the space between the insertion hole surface 73b and the outer peripheral surface 71b of the lead wire 71 is sealed in a watertight manner.

  On the other hand, as shown in FIG. 3, the gas sensor element 10 includes plate-shaped solid electrolyte bodies 111, 121, 131 and insulators 140, 145 disposed therebetween, which are stacked in the stacking direction (FIG. 3). In the vertical direction). Further, in the gas sensor element 10, a heater 161 is laminated on the back surface 131 c side (the lower surface side in FIG. 3) of the solid electrolyte body 131. The heater 161 includes plate-like insulators 162 and 163 mainly composed of alumina, and a heater pattern 164 (mainly composed of Pt) embedded therebetween (see FIGS. 3 and 6). The heater pattern 164 includes a curved heat generating portion 164d and linear first lead portions 164b and second lead portions 164c connected to both ends of the heat generating portion 164d, respectively. The first lead portion 164b is electrically connected to the electrode terminal portion 16, and the second lead portion 164c is electrically connected to the electrode terminal portion 18 (see FIG. 6).

  The solid electrolyte bodies 111, 121, and 131 are made of zirconia, which is a solid electrolyte, and have oxygen ion conductivity. On the surface 111b side (the upper surface side in FIG. 3) of the solid electrolyte body 111, a porous Ip1 + electrode 112 is provided. A porous Ip1-electrode 113 is provided on the back surface 111c side (the lower surface side in FIG. 3) of the solid electrolyte body 111. The Ip1 + electrode 112 and the Ip1-electrode 113 are formed of cermet containing Pt powder and ceramic powder, and have gas permeability and water permeability.

  In the present embodiment, the Ip1 + electrode 112 and the Ip1− electrode 113 are formed as follows. Specifically, first, 100 parts by weight of Pt powder, 14 parts by weight of ceramic powder, and 10 parts by weight of an organic binder (for example, ethyl cellulose) are mixed, and a predetermined amount of solvent is added to the mixture to form an electrode. Make a paste. Next, this electrode paste is applied to the front surface 111 b side and the back surface 111 c side of the solid electrolyte body 111. Thereafter, the organic binder is eliminated by heating, and the porous electrodes 112 and 113 are formed.

  As shown in FIG. 5, the Ip1 + lead 116 is connected to the connection part 112d of the Ip1 + electrode 112. The Ip1 + lead 116 is electrically connected to the electrode terminal portion 13. In addition, an Ip1-lead 117 is connected to the connection portion 113d of the Ip1-electrode 113. The Ip1-lead 117 is electrically connected to the electrode terminal portion 15. The Ip1 + lead 116 and the Ip1-lead 117 are formed of a cermet containing Pt powder and ceramic powder, but unlike the Ip1 + electrode 112 and the Ip1-electrode 113, they are densely formed. For this reason, the Ip1 + lead 116 and the Ip1-lead 117 are impermeable to water.

In the present embodiment, the Ip1 + lead 116 and the Ip1− lead 117 are formed as follows. Specifically, first, 100 parts by weight of Pt powder, 18 parts by weight of ceramic powder, and 5 parts by weight of an organic binder (for example, ethyl cellulose) are mixed, and a predetermined amount of solvent is added to the mixture, thereby leading to lead. Make a paste. Next, this lead paste is applied to the front surface 111 b side and the back surface 111 c side of the solid electrolyte body 111. Thereafter, the organic binder is eliminated by heating, and leads 116 and 117 are formed.
By the way, the lead paste has an organic binder added in a small amount (about half the amount) compared to the above-mentioned electrode paste. In this way, by reducing the amount of the organic binder added that disappears by heating to form internal vacancies, dense leads 116 and 117 with few internal vacancies are formed.

  Further, a protective layer 115 made of alumina or the like is laminated on the surface side (the upper surface side in FIGS. 3 to 5) of the Ip1 + electrode 112 and the Ip1 + lead 116. A first porous body 114 (corresponding to the porous body in the claims) that is exposed to the outside of the gas sensor element 10 is provided at a position of the protective layer 115 facing the Ip1 + electrode 112 in the stacking direction. Yes. The first porous body 114 has gas permeability and water permeability, and is in contact with a part of the Ip1 + electrode 112. A portion of the Ip1 + electrode 112 that is in contact with the first porous body 114 is referred to as a porous body contact portion 112b.

  The solid electrolyte body 111 and the electrodes 112 and 113 constitute an Ip1 cell 110 (first pump cell) (see FIG. 3). The Ip1 cell 110 has an atmosphere in contact with the electrode 112 (atmosphere outside the gas sensor element 10) and an atmosphere in contact with the electrode 113 (in a first measurement chamber 150 to be described later) according to a pump current Ip1 flowing between the electrodes 112 and 113. Pumping out and pumping oxygen (so-called oxygen pumping).

  The solid electrolyte body 121 is disposed so as to face the solid electrolyte body 111 in the stacking direction with the insulator 140 interposed therebetween. On the surface 121b side (upper surface side in FIG. 3) of the solid electrolyte body 121, a porous Vs-electrode 122 is provided. Further, a porous Vs + electrode 123 is provided on the back surface 121c side (the lower surface side in FIG. 3) of the solid electrolyte body 121. The Vs− electrode 122 and the Vs + electrode 123 are made of cermet containing Pt powder and ceramic powder, and have gas permeability and water permeability.

  As shown in FIG. 5, the Vs-lead 126 is connected to the connection portion 122 d of the Vs-electrode 122. The Vs-lead 126 is electrically connected to the electrode terminal portion 15. The Vs-lead 126 is formed of cermet containing Pt powder and ceramic powder, but unlike the Vs-electrode 122, it is formed densely. For this reason, the Vs-lead 126 has non-water permeability. On the other hand, as shown in FIGS. 5 and 6, the Vs + lead 127 is connected to the connection portion 123 d of the Vs + electrode 123. The Vs + lead 127 is electrically connected to the electrode terminal portion 14. The Vs + lead 127 is formed of a cermet containing Pt powder and ceramic powder. Since the Vs + lead 127 is formed simultaneously with the Vs + electrode 123, the Vs + lead 127 is formed porous. Therefore, the Vs + lead 127 has gas permeability and water permeability.

  A first measurement chamber 150 as an internal space of the gas sensor element is formed between the solid electrolyte body 111 and the solid electrolyte body 121 (see FIG. 3). The first measurement chamber 150 is an internal space in which the exhaust gas flowing through the exhaust passage is first introduced into the gas sensor element 10, and the gas sensor element 10 passes through the second porous body 151 having gas permeability and water permeability. Communicates with the outside. The second porous body 151 is provided on the side of the first measurement chamber 150 as a partition from the outside of the gas sensor element 10, and limits the flow rate of exhaust gas per unit time into the first measurement chamber 150. (See FIGS. 2 and 5).

  On the rear end side (the right side in FIG. 3) of the first measurement chamber 150, as a partition between the first measurement chamber 150 and a second measurement chamber 160 described later, a flow rate of exhaust gas per unit time is limited. A three porous body 152 is provided.

  The solid electrolyte body 121 and the electrodes 122 and 123 constitute a Vs cell 120 (see FIG. 3). The Vs cell 120 mainly has an oxygen partial pressure difference between the atmospheres separated by the solid electrolyte body 121 (the atmosphere in the first measurement chamber 150 in contact with the electrode 122 and the atmosphere in the reference oxygen chamber 170 in contact with the electrode 123). In response, an electromotive force is generated.

The solid electrolyte body 131 is disposed so as to face the solid electrolyte body 121 in the stacking direction with the insulator 145 interposed therebetween. On the surface 131b side (upper surface side in FIG. 3) of the solid electrolyte body 131, a porous Ip2 + electrode 132 and a porous Ip2-electrode 133 are provided. The Ip2 + electrode 132 and the Ip2- electrode 133 are made of cermet containing Pt powder and ceramic powder, and have gas permeability and water permeability.

  As shown in FIG. 6, an Ip2 + lead 136 is connected to the Ip2 + electrode 132. The Ip2 + lead 136 is electrically connected to the electrode terminal portion 17. The Ip2 + lead 136 is formed of a cermet containing Pt powder and ceramic powder. Since the Ip2 + lead 136 is formed simultaneously with the Ip2 + electrode 132, the Ip2 + lead 136 is formed porous. Therefore, the Ip2 + lead 136 has gas permeability and water permeability. On the other hand, the Ip2-lead 137 is connected to the connection part 133d of the Ip2-electrode 133. The Ip2-lead 137 is electrically connected to the electrode terminal portion 15. The Ip2-lead 137 is formed of a cermet containing Pt powder and ceramic powder, but unlike the Ip2-electrode 133, the Ip2-lead 137 is densely formed. For this reason, the Ip2-lead 137 has non-water permeability.

A reference oxygen chamber 170 as an isolated small space is formed between the Ip2 + electrode 132 and the Vs + electrode 123 (see FIG. 3). The reference oxygen chamber 170 is constituted by an opening 145 b formed in the insulator 145. In the reference oxygen chamber 170, a ceramic porous body is disposed on the Ip2 + electrode 132 side.
A second measurement chamber 160 as an internal space of the gas sensor element is formed at a position facing the Ip2-electrode 133 in the stacking direction. The second measurement chamber 160 includes an opening 145c that penetrates the insulator 145 in the laminating direction, an opening 125 that penetrates the solid electrolyte body 121 in the laminating direction, and an opening 141 that penetrates the insulator 140 in the laminating direction. It is comprised by.

The first measurement chamber 150 and the second measurement chamber 160 communicate with each other through a third porous body 152 having gas permeability and water permeability. Therefore, the second measurement chamber 160 communicates with the outside of the gas sensor element 10 through the second porous body 151, the first measurement chamber 150, and the third porous body 152.
In the present embodiment, the first measurement chamber 150 and the second measurement chamber 160 correspond to “the internal space of the gas sensor element communicating with the outside of the gas sensor element” recited in the claims.

  The solid electrolyte body 131 and the electrodes 132 and 133 constitute an Ip2 cell 130 (second pump cell) for detecting the NOx concentration. The Ip2 cell 130 moves NOx-derived oxygen (oxygen ions) decomposed in the second measurement chamber 160 to the reference oxygen chamber 170 through the solid electrolyte body 131. At this time, the lead 136 connected to the electrode 132 and the lead 137 connected to the electrode 133 have a current corresponding to the concentration of NOx contained in the exhaust gas (measurement target gas) introduced into the second measurement chamber 160. Flowing.

  In the present embodiment, an alumina insulating layer 118 is formed on the surface 111 b of the solid electrolyte body 111. Further, a part of the Ip1 + electrode 112 and the Ip1 + lead 116 are formed on the alumina insulating layer 118. Furthermore, the porous body contact portion 112b of the Ip1 + electrode 112 has an electrolyte body contact portion 112c that contacts the solid electrolyte body 111 through a through hole 118b that penetrates the alumina insulating layer 118 in the stacking direction.

  Further, an alumina insulating layer 119 is formed on the back surface 111 c of the solid electrolyte body 111. Further, a part of the Ip1-electrode 113 and the Ip1-lead 117 are formed on the alumina insulating layer 119. Furthermore, the space exposed portion 113b exposed to the first measurement chamber 150 (internal space) of the Ip1-electrode 113 is an electrolyte body that contacts the solid electrolyte body 111 through a through hole 119b that penetrates the alumina insulating layer 119 in the stacking direction. A contact portion 113c is provided.

  Furthermore, in this embodiment, an alumina insulating layer 128 is formed on the surface 121 b of the solid electrolyte body 121. Further, a part of the Vs-electrode 122 and the Vs-lead 126 are formed on the alumina insulating layer 128. Furthermore, the space exposed portion 122b exposed to the first measurement chamber 150 (internal space) of the Vs-electrode 122 is an electrolyte body that contacts the solid electrolyte body 121 through a through hole 128b that penetrates the alumina insulating layer 128 in the stacking direction. A contact portion 122c is provided.

  Further, an alumina insulating layer 129 is formed on the back surface 121 c of the solid electrolyte body 121. Further, a part of the Vs + electrode 123 and the Vs + lead 127 are formed on the alumina insulating layer 129. Further, the Vs + electrode 123 has an electrolyte body contact portion 123c that contacts the solid electrolyte body 121 through a through hole 129b that penetrates the alumina insulating layer 129 in the stacking direction.

  Furthermore, in this embodiment, an alumina insulating layer 138 is formed on the surface 131 b of the solid electrolyte body 131. Further, a part of the Ip2 + electrode 132 and the Ip2 + lead 136 are formed on the alumina insulating layer 138. Further, a part of the Ip2-electrode 133 and the Ip2-lead 137 are also formed on the alumina insulating layer 138. The electrode 132 has an electrolyte body contact portion 132c that comes into contact with the solid electrolyte body 131 through a through hole 138b that penetrates the alumina insulating layer 138 in the stacking direction. In addition, the space exposed portion 133b exposed to the second measurement chamber 160 (internal space) of the electrode 133 is an electrolyte body contact portion that contacts the solid electrolyte body 131 through a through hole 138c that penetrates the alumina insulating layer 138 in the stacking direction. 133c.

  With such a configuration, only the electrolyte body contact portions 112c, 113c, 122c, 123c, 132c, and 133c among the electrodes 112, 113, 122, 123, 132, and 133 can actually function as the sensitive portions. It is possible to accurately detect the concentration of the gas to be measured. The leads 116, 117, 126, and 137 have different electrical characteristics from those of the electrodes 112, 113, 122, and 133. Therefore, when the lead and a part of the connecting portion connected thereto are in contact with the solid electrolyte, The gas concentration detection accuracy is inferior to that of the present embodiment in which no contact is made.

  In the present embodiment, the Ip1-electrode 113, the Vs-electrode 122, and the Ip2-electrode 133 correspond to the “first electrode” recited in the claims. Furthermore, the Ip1-lead 117, the Vs-lead 126, and the Ip2-lead 137 correspond to the “first lead” recited in the claims. The Ip1 + electrode 112 corresponds to a “second electrode” recited in the claims. Further, the Ip1 + lead 116 corresponds to a “second lead” recited in the claims.

  In addition, the connection portion 112d of the Ip1 + electrode 112 (second electrode) is disposed at a position away from the first porous body 114 in the plane direction orthogonal to the stacking direction (the left-right direction in FIGS. 3 and 5). It is connected to the Ip1 + lead 116 (second lead). In addition, the connecting portion 112d is disposed at a position farthest from the first porous body 114 in the Ip1 + electrode 112.

  Further, the connection portion 113d of the Ip1-electrode 113 (first electrode) is disposed at a position not exposed to the first measurement chamber 150 (internal space), and is connected to the Ip1-lead 117 outside the first measurement chamber 150. Yes. In addition, the connection portion 113 d is disposed at a position farthest from the first measurement chamber 150 in the Ip 1 -electrode 113. Similarly, the connection part 122 d of the Vs-electrode 122 is also arranged at a position where it is not exposed to the first measurement chamber 150 (internal space), and is connected to the Vs-lead 126 outside the first measurement chamber 150. In addition, the connecting portion 122 d is disposed at a position farthest from the first measurement chamber 150 in the Vs− electrode 122.

  Further, the connection part 133d of the Ip2-electrode 133 is disposed at a position not exposed to the second measurement chamber 160 (internal space), and is connected to the Ip2-lead 137 outside the second measurement chamber 160. In addition, the connecting portion 133d is arranged at a position farthest from the second measurement chamber 160 in the Ip2-electrode 133.

  In the present embodiment, the connection portion 112d of the Ip1 + electrode 112 corresponds to a “second connection portion” recited in the claims. Further, the connection portion 113d of the Ip1-electrode 113, the connection portion 122d of the Vs-electrode 122, and the connection portion 133d of the Ip2-electrode 133 correspond to the “first connection portion” recited in the claims.

As described above, in this embodiment, the connection portions 113d, 122d, and 133d (first connection portion) are not exposed to the first measurement chamber 150 and the second measurement chamber 160 (internal space), and the Ip1-lead 117 is exposed. , Vs-lead 126 and Ip2-lead 137 (first lead). Thereby, unlike the above-mentioned patent document 1 (Japanese Patent No. 4165552), “the first connection portion is disposed in the internal space, so that the oxygen pump performance is reduced, and the oxygen concentration and NOx concentration in the measurement target gas. It is possible to suppress “decrease in detection accuracy for detecting“
Further, the connecting portion 112d (second connecting portion) is connected to the Ip1 + lead 116 (second lead) at a position away from the first porous body 114 in the planar direction (left and right direction in FIGS. 3 and 5). Yes. Thereby, “the second connecting portion is arranged at a position overlapping the porous body, so that the oxygen pump performance is lowered and the detection accuracy for detecting the oxygen concentration and the NOx concentration in the measurement target gas is lowered”. Can be suppressed.

Here, the NOx concentration detection by the gas sensor 1 of the present embodiment will be briefly described.
The solid electrolyte bodies 111, 121, 131 of the gas sensor element 10 are heated and activated as the heater pattern 164 is heated. As a result, the Ip1 cell 110, the Vs cell 120, and the Ip2 cell 130 are operated.

  Exhaust gas (measurement target gas) flowing in the exhaust passage (not shown) is introduced into the first measurement chamber 150 while being restricted by the second porous body 151. At this time, a weak current Icp flows through the Vs cell 120 from the electrode 123 side to the electrode 122 side. For this reason, oxygen in the exhaust gas can receive electrons from the electrode 122 in the first measurement chamber 150 on the negative electrode side, flows as oxygen ions in the solid electrolyte body 121, and moves into the reference oxygen chamber 170. To do. That is, when the current Icp flows between the electrodes 122 and 123, oxygen in the first measurement chamber 150 is sent into the reference oxygen chamber 170.

  When the oxygen concentration of the exhaust gas introduced into the first measurement chamber 150 is lower than a predetermined value, a current Ip1 is passed through the Ip1 cell 110 so that the electrode 112 side becomes a negative electrode, and the gas sensor element 10 has an inside of the first measurement chamber 150. Pump oxygen into the water. On the other hand, when the oxygen concentration of the exhaust gas introduced into the first measurement chamber 150 is higher than a predetermined value, the current Ip1 is supplied to the Ip1 cell 110 so that the electrode 113 side becomes a negative electrode, and the gas sensor element 10 is supplied from the first measurement chamber 150. Pump out oxygen to the outside.

  In this way, the exhaust gas whose oxygen concentration is adjusted in the first measurement chamber 150 is introduced into the second measurement chamber 160 through the third porous body 152. NOx in the exhaust gas in contact with the electrode 133 in the second measurement chamber 160 is decomposed (reduced) into nitrogen and oxygen on the electrode 133 by being applied with the voltage Vp2 between the electrodes 132 and 133 and decomposed. Oxygen flows as oxygen ions through the solid electrolyte body 131 and moves into the reference oxygen chamber 170. At this time, the residual oxygen remaining in the first measurement chamber 150 is similarly moved into the reference oxygen chamber 170 by the Ip2 cell 130. As a result, a current derived from NOx and a current derived from residual oxygen flow through the Ip2 cell 130.

  Here, since the concentration of the residual oxygen remaining in the first measurement chamber 150 is adjusted to a predetermined value as described above, the current derived from the residual oxygen can be regarded as substantially constant, and is derived from NOx. The influence on the current fluctuation is small, and the current flowing through the Ip2 cell 130 is proportional to the NOx concentration. Therefore, the current Ip2 flowing through the Ip2 cell 130 can be detected, and the NOx concentration in the exhaust gas can be detected based on the current value.

  By the way, in the conventional gas sensor element, when water infiltrates into the 1st electrode (for example, Ip1-electrode 113) and this freezes, there exists a possibility that a crack may generate | occur | produce in a gas sensor element. Specifically, for example, condensed water generated on the surface of the gas sensor element may enter the internal space of the gas sensor element through the second porous body 151 and further enter the first electrode. The water that has entered the first electrode reaches the first connection portion (for example, the connection portion 113d) connected to the first lead (for example, Ip1-lead 117), but the first lead is impermeable to water. It may stay at the first connection. When the condensed water stays in the first connection portion and the volume expands due to the freezing of the condensed water, a stress is generated in a direction separating the layers sandwiching the first connection portion. There was a risk of cracks occurring between the layers sandwiching one connecting portion.

  On the other hand, in the gas sensor element 10 of the present embodiment, the entire first connection portion (specifically, the connection portions 113d, 122d, and 133d) is the internal space (the first measurement chamber 150 or the second measurement chamber 160). It arrange | positions in the area | region within 1.0 mm from the distance. For example, as shown in FIG. 7, the entire connection portion 133d (first connection portion) is arranged in a region A1 within a distance of 1.0 mm from the second measurement chamber 160 (internal space) (two-dot chain line K1 in FIG. 7). (Area surrounded by). Similarly, the entire connection portions 113d and 122d are arranged inside a region whose distance from the first measurement chamber 150 (internal space) is within 1.0 mm.

  Thereby, even when water permeates into the Ip2-electrode 133 (first electrode) and the water freezes, it is possible to prevent the gas sensor element 10 from being cracked. The same applies when water enters the Ip1-electrode 113 and the Vs-electrode 122. These are clear from the results of the freezing test described later. The reason why cracks can be prevented is considered as follows.

  For example, when the water stays in the connection part 133d of the Ip2-electrode 133 and the water starts to freeze, the fine pores in the connection part 133d gradually become smaller (closed by ice). Therefore, the water remaining in the connection part 133d moves to the side opposite to the Ip2-lead 137 (first lead) (that is, the second measurement chamber 160 side where there is a space where water can enter, left side in FIG. 7). I will do it. At this time, the entire connection portion 133d is disposed in the region A1 whose distance from the second measurement chamber 160 is 1.0 mm or less (that is, from the portion of the connection portion 133d that is farthest from the second measurement chamber 160). The distance D1 to the second measurement chamber 160 is shortened to within 1.0 mm), so that most of the water remaining in the connection portion 133d is frozen in the connection portion 133d before the second measurement chamber 160d is frozen. It is possible to move up to 160. Thereafter, even if a large amount of water freezes and expands in the second measurement chamber 160, no stress that separates the layers of the gas sensor element 10 is generated. As a result, it is possible to prevent the gas sensor element 10 from being cracked. The same applies to the case where water accumulated in the connecting portion 113d of the Ip1-electrode 113 and the connecting portion 122d of the Vs-electrode 122 freezes.

  Further, in the conventional gas sensor element, there is a possibility that cracks may occur in the gas sensor element even when water enters the second electrode (Ip1 + electrode 112) and freezes. Specifically, for example, condensed water generated on the surface of the gas sensor element may enter the second electrode in contact with the first porous body 114 through the first porous body 114. The water that has entered the second electrode reaches the second connecting portion (connecting portion 112d) connected to the second lead (Ip1 + lead 116). However, since the second lead is impermeable to water, May stay. When the condensed water stays in the second connection portion and the volume of the condensed water is expanded by freezing, stress is generated in a direction to separate the layers sandwiching the second connection portion. There was a risk of cracks occurring in the layer between the two connecting portions.

  On the other hand, in the gas sensor element 10 of the present embodiment, as shown in FIG. 8, the entire connection portion 112d (second connection portion) is a region A2 whose distance from the first porous body 114 is within 1.0 mm. (A region surrounded by a two-dot chain line K2 in FIG. 8). In other words, the distance D2 from the portion farthest from the first porous body 114 to the first porous body 114 in the connecting portion 112d (second connecting portion) is set to be within 1.0 mm. Thereby, even when water permeates into the Ip1 + electrode 112 (second electrode) and the water freezes, it is possible to prevent the gas sensor element 10 from being cracked. This is clear from the results of the freezing test described later. Therefore, in the gas sensor 1 including such a gas sensor element 10, even when water enters the permeable electrode and freezes, it is possible to prevent the gas sensor element from cracking, and to measure the gas to be measured. Can be detected appropriately.

(Freezing test)
Next, a freezing test performed on the gas sensor element will be described.
Specifically, from the location farthest from the internal space (first measurement chamber 150 or second measurement chamber 160) in the first connection portion (connection portions 113d, 122d, or connection portion 133d) to the internal space. A gas sensor element (hereinafter, also referred to as a test element) in which the distance D1 and the distance D2 from the portion farthest from the second porous body to the second porous body in the second connecting portion (connecting portion 112d) are different. 20) were produced. The distances D1 and D2 are different at intervals of 0.2 mm in the range of 0 to 2.0 mm for the respective connecting portions.

  Next, a freezing test was performed using the produced test element. Specifically, first, the tip of the test element (the end including the second porous body 151 and the first porous body 114) is submerged and left in this state for 24 hours. As a result, water enters the test element (in the electrodes 112, 113, 122, 133) through the second porous body 151 and the first porous body 114. Next, the test element is taken out from the water, and the water adhering to the surface of the test element is wiped off. Next, the test element is placed in a thermostatic bath set at −20 ° C. and left for 2 minutes. This freezes the water that has entered the test element. Thereafter, the test element is taken out from the thermostat and allowed to stand at room temperature for 1 minute. After being left in the constant temperature bath and left at room temperature 10 times, a red liquid is applied to the surface of the test element. After a certain time has elapsed after application, the surface of the test element is wiped off. The presence or absence of cracks was confirmed by checking the appearance of the test element surface after wiping.

  Specifically, since the red liquid penetrates into the cracked portion, the red liquid remains even after the surface of the test element is wiped off. Therefore, when a crack is generated between the first connection part (connection part 113d, 122d or connection part 133d) and the second connection part (connection part 112d), red liquid remains between the layers. Will do. Based on this idea, the presence or absence of cracks was determined. The result is shown in FIG.

  As shown in FIG. 9, when the distance D1 was 1.0 mm or less, no crack occurred in the gas sensor element. Similarly, no cracks occurred in the gas sensor element even when the distance D2 was 1.0 mm or less.

  On the other hand, when the distance D1 was larger than 1.0 mm, a crack occurred in the gas sensor element. Specifically, when the distance D1 was 1.2 mm, the crack generation rate was 15%. That is, cracks occurred in three of the 20 test elements. When the distance D1 was 1.4 mm, the crack generation rate was 25%. That is, cracks occurred in 5 of the 20 test elements. Moreover, when the distance D1 was 1.6 mm, the crack generation rate was 50%. That is, cracks occurred in 10 test elements out of 20 test elements. When the distance D1 was 1.8 mm, the crack generation rate was 85%. That is, cracks occurred in 17 test elements out of 20 test elements. When the distance D1 was 2.0 mm, the crack generation rate was 100%. That is, cracks occurred in all 20 test elements.

  Further, when the distance D2 was larger than 1.0 mm, a crack occurred in the gas sensor element. The occurrence rate of cracks was equivalent to the occurrence rate with respect to the distance D1 (see FIG. 9).

  From the above results, the electrodes 113 and 122 are arranged by disposing the entire connection portions 113d and 122d (first connection portion) in a region whose distance from the first measurement chamber 150 (internal space) is within 1.0 mm. It can be said that even when water enters the inside and freezes, cracks can be prevented from occurring between the layers sandwiching the connection portions 113d and 122d. Further, the entire connection portion 133d (first connection portion) is disposed in a region within a distance of 1.0 mm from the second measurement chamber 160 (internal space), so that water enters the electrode 133. Even when this water freezes, it can be said that cracks can be prevented from occurring between the layers sandwiching the connecting portion 133d. Further, the entire connection portion 112d (second connection portion) is disposed in a region within a distance of 1.0 mm from the first porous body 114, so that water enters the electrode 112, and this water It can be said that cracks can be prevented from occurring between the layers sandwiching the connecting portion 112d even when the battery freezes.

(Deformation)
Next, modifications of the present invention will be described. The gas sensor 201 of the modified embodiment is different from the gas sensor 1 of the embodiment only in the gas sensor element, and the other parts are the same (see FIG. 1). Therefore, here, a different point from embodiment is demonstrated and description is abbreviate | omitted or simplified about the same point.
In the gas sensor element 10 of the embodiment, as shown in FIG. 7, the distance from the second measurement chamber 160 (internal space) to the entire connection portion 133 d (first connection portion) of the Ip2-electrode 133 is within 1.0 mm. In the region A1 (region surrounded by a two-dot chain line K1 in FIG. 7).

  On the other hand, in the gas sensor element 210 of this modification, as shown in FIG. 10, the Ip2-electrode 233 is disposed in the second measurement chamber 260 (internal space). That is, the entire Ip2-electrode 233 including the connection portion 233d is disposed in the second measurement chamber 260 (internal space). Thus, the entire Ip2-electrode 233 including the connection portion 233d is exposed in the second measurement chamber 260 (internal space). The Ip2-lead 237 is connected to the connection part 233d of the Ip2-electrode 233 in the second measurement chamber 260 (internal space).

  With such a configuration, it is possible to prevent the gas sensor element from being cracked even when the water that has entered the Ip2-electrode 233 freezes. Since the entire Ip2-electrode 233 (third electrode) including the connection portion 233d is disposed in the second measurement chamber 260 (internal space), the Ip2-electrode 233 including the connection portion 233d (third connection portion) This is because the water remaining in the gas chamber can be frozen (expanded) in the second measurement chamber 260, and as a result, the generation of stress separating the layers of the gas sensor element can be suppressed.

  Further, the Ip2-electrode 233 has an electrolyte body contact portion 233c that comes into contact with the solid electrolyte body 131 on which the alumina insulating layer 238 is formed through the through hole 238c of the alumina insulating layer 238 (see FIG. 10). On the other hand, the Ip2-lead 237 is formed on the alumina insulating layer 238 (this prevents contact with the solid electrolyte body 131). Further, the connection part 233d of the Ip2-electrode 233 is connected to the Ip2-lead 237 on the alumina insulating layer 238 (this prevents the contact with the solid electrolyte body 131). Thereby, even if the connection part 233d is arrange | positioned in the 2nd measurement chamber 260 (internal space), the connection part 233d does not affect the oxygen pump performance of the Ip2-electrode 233 (oxygen of the Ip2-electrode 233) Pump performance will not be reduced). For this reason, it can suppress that the detection accuracy which detects the oxygen concentration and NOx concentration in measurement object gas falls. In addition, only the electrolyte contact portion 233c of the Ip2-electrode 233 can actually function as a sensitive portion, and the gas concentration that is the detection target can be detected with high accuracy.

  In this modification, the Ip2-electrode 233 corresponds to a “third electrode” recited in the claims. The connection portion 233d corresponds to a “third connection portion” recited in the claims. The Ip2-lead 237 corresponds to a “third lead” recited in the claims. The alumina insulating layer 238 corresponds to a “third insulating layer” recited in the claims. The electrolyte body contact portion 233c corresponds to a “third electrolyte body contact portion” recited in the claims.

  In addition, as for the Ip1-electrode and the Vs-electrode, similarly to the Ip2-electrode 233, the entire structure including the connection portion with the lead is arranged in the first measurement chamber (internal space), thereby generating cracks. Can be suppressed.

  Further, in the gas sensor element 10 of the embodiment, as shown in FIG. 8, the entire connection portion 112 d (second connection portion) of the Ip1 + electrode 112 is a region whose distance from the first porous body 114 is within 1.0 mm. It arrange | positioned in A2 (area | region enclosed with the dashed-two dotted line K2 in FIG. 8).

  On the other hand, in the gas sensor element 210 of the present modified embodiment, as shown in FIG. 11, the Ip1 + electrode 212 is brought into contact with the first porous body 214, and the whole is laminated in the stacking direction of the solid electrolyte body (thickness direction, In FIG. 11, it is arranged at a position facing the first porous body 214 in a direction perpendicular to the paper surface. Specifically, a part of the Ip1 + electrode 212 faces the first porous body 214 with the Ip1 + lead 216 interposed therebetween, and the other part (the part where the lead 216 does not exist in the stacking direction) is the first porous body. The entire Ip1 + electrode 212 is opposed to the first porous body 214 in a form in contact with 214. The Ip1 + lead 216 is connected to the connection part 212d of the Ip1 + electrode 212 at a position facing the first porous body 214 in the stacking direction.

  With such a configuration, it is possible to prevent the gas sensor element from being cracked even when the water that has entered the Ip1 + electrode 212 freezes. The entire Ip1 + electrode 212 including the connecting portion 212d is disposed to face the first porous body 214, and most of the electrode 212 excluding only the portion in contact with the Ip1 + lead 216 of the Ip1 + electrode 212 is the first porous body 214. Since it is in contact with the body 214, much of the water remaining in the Ip1 + electrode 212 can be frozen (expanded) in the pores of the first porous body 214, and as a result, the stress separating the layers of the gas sensor element It is because generation | occurrence | production of this can be suppressed.

  Further, the Ip1 + electrode 212 has an electrolyte body contact portion 212c that comes into contact with the solid electrolyte body 111 on which the alumina insulating layer 218 is formed through the through hole 218b of the alumina insulating layer 218 (see FIG. 11). On the other hand, the Ip1 + lead 216 is formed on the alumina insulating layer 218 (this prevents contact with the solid electrolyte body 111). In addition, the connecting portion 212d of the Ip1 + electrode 212 is connected to the Ip1 + lead 216 on the alumina insulating layer 218 (this prevents contact with the solid electrolyte body 111). By doing in this way, even if the connection part 212d (4th connection part) is arrange | positioned in the position (position which opposes a lamination direction) which overlaps with the 1st porous body 214, the connection part 212d becomes Ip1 + electrode 212 (1st electrode). (4 electrodes) oxygen pump performance is not affected (the oxygen pump performance of the Ip1 + electrode 212 is not deteriorated). For this reason, it can suppress that the detection accuracy which detects the oxygen concentration and NOx concentration in measurement object gas falls. Moreover, only the electrolyte body contact portion 212c of the Ip1 + electrode 212 can actually function as a sensitive portion, and the gas concentration that is the detection target can be detected with high accuracy.

  In this modification, the Ip1 + electrode 212 corresponds to the “fourth electrode” recited in the claims. Further, the connecting portion 212d corresponds to a “fourth connecting portion” recited in the claims. Further, the Ip1 + lead 216 corresponds to a “fourth lead” recited in the claims. The alumina insulating layer 218 corresponds to the “fourth insulating layer” recited in the claims. The electrolyte body contact portion 212c corresponds to a “fourth electrolyte body contact portion” recited in the claims.

In the above, the present invention has been described with reference to the embodiments and modifications. However, the present invention is not limited to the above-described embodiments and the like, and can be appropriately modified and applied without departing from the gist thereof. Needless to say.
For example, in the embodiment and the modification, the gas sensor element (NOx sensor element) capable of detecting the NOx concentration is exemplified as the gas sensor element. However, the present invention can be applied not only to NOx sensor elements but also to gas sensor elements that can detect gases other than NOx (for example, oxygen sensor elements that detect oxygen).

  In a modified form, a part of the Ip1 + electrode 212 faces the first porous body 214 with the Ip1 + lead 216 interposed therebetween, and the other part (part where the lead 216 does not exist in the stacking direction) is the first porous. The entire Ip1 + electrode 212 is made to face the first porous body 214 in a form in contact with the mass body 214. However, the position in the stacking direction of the Ip1 + electrode 212 and the Ip1 + lead 216 may be reversed (upside down) so that the entire Ip1 + electrode 212 is in contact with the first porous body 214.

1,201 Gas sensor 10, 210 Gas sensor element 111, 121, 131 Solid electrolyte body 111b, 121b, 131b Front surface 111c, 121c, 131c of solid electrolyte body 112 Ip1 + electrode (second electrode) of solid electrolyte body
112b Porous body contact part 112c Electrolyte body contact part 112d Connection part (2nd connection part)
113 Ip1-electrode (first electrode)
113b, 122b, 133b Space exposed portion 113c, 122c, 133c Electrolyte body contact portion 113d, 122d, 133d Connection portion (first connection portion)
114 1st porous body 116 Ip1 + lead (2nd lead)
117 Ip1-lead (first lead)
118 Alumina insulating layer (second insulating layer)
118b, 119b, 128b, 138c Through hole 119, 128, 138 Alumina insulating layer (first insulating layer)
122 Vs-electrode (first electrode)
123 Vs + electrode 126 Vs-lead (first lead)
127 Vs + lead 132 Ip2 + electrode 133 Ip2- electrode (first electrode)
136 Ip2 + lead 137 Ip2- lead (first lead)
150 1st measurement chamber (internal space)
151 2nd porous body 160 2nd measurement chamber (internal space)
212 Ip1 + electrode (fourth electrode)
212c Electrolyte body contact portion (fourth electrolyte body contact portion)
212d Connection part (fourth connection part)
216 Ip1 + lead (4th lead)
218 Alumina insulating layer (fourth insulating layer)
233 Ip2-electrode (third electrode)
233c Electrolyte body contact portion (third electrolyte body contact portion)
233d connection part (third connection part)
237 Ip2-lead (3rd lead)
238 Alumina insulating layer (third insulating layer)

Claims (8)

A gas sensor element in which a plurality of plate-shaped solid electrolyte bodies are laminated,
An electrode provided on the front or back side of the solid electrolyte body;
Provided on the front side or the back side of the solid electrolyte body, and connected to the electrode,
The electrode is
A water permeable first electrode having a space exposed portion exposed in the internal space of the gas sensor element that communicates with the outside of the gas sensor element;
The lead includes a water-impermeable first lead connected to the first electrode,
The first electrode is disposed at a position that is not exposed to the internal space, and is a first connection portion that is connected to the first lead, and is disposed at a position farthest from the internal space in the first electrode. Including a first connecting portion,
The gas sensor element in which the whole said 1st connection part is located in the area | region where the distance from the said interior space is 1.0 mm or less. The gas sensor element according to claim 1,
A first insulating layer formed on the front or back surface of the solid electrolyte body;
A part of the first electrode and the first lead are formed on the first insulating layer,
The space exposed portion of the first electrode has an electrolyte body contact portion that contacts the solid electrolyte body through a through-hole penetrating the first insulating layer in the stacking direction of the solid electrolyte body,
The gas sensor element, wherein the first connection portion of the first electrode is connected to the first lead on the first insulating layer. The gas sensor element according to claim 1 or 2,
The electrode is
A porous body having gas permeability and water permeability, exposed to the outside of the gas sensor element, and a water permeable second electrode having a porous body contact portion in contact with the porous body,
The lead includes a water-impermeable second lead connected to the second electrode,
The second electrode is a second connection portion connected to the second lead at a position away from the porous body in a plane direction orthogonal to the stacking direction of the solid electrolyte body, A second connecting portion disposed at a position farthest from the porous body,
A gas sensor element in which the entire second connection portion is located within a region having a distance of 1.0 mm or less from the porous body. The gas sensor element according to claim 3,
A second insulating layer formed on the front or back surface of the solid electrolyte body;
A part of the second electrode and the second lead are formed on the second insulating layer,
The porous body contact portion of the second electrode has an electrolyte body contact portion that contacts the solid electrolyte body through a through-hole penetrating the second insulating layer in the stacking direction,
The gas sensor element, wherein the second connection portion of the second electrode is connected to the second lead on the second insulating layer. A gas sensor element in which a plurality of plate-shaped solid electrolyte bodies are laminated,
An electrode provided on the front or back side of the solid electrolyte body;
A lead provided on the front side or the back side of the solid electrolyte body and connected to the electrode;
With
The electrode is
A water permeable third electrode disposed in the internal space of the gas sensor element communicating with the outside of the gas sensor element;
The lead includes a water-impermeable third lead connected to the third electrode,
The gas sensor element has a third insulating layer formed on the front surface or the back surface of the solid electrolyte body,
A part of the third electrode and the third lead are formed on the third insulating layer,
The third electrode is
An electrolyte body contact portion that comes into contact with the solid electrolyte body through a through-hole penetrating the third insulating layer in the stacking direction of the solid electrolyte body;
A gas sensor element comprising: a third connection portion connected to the third lead in the internal space and on the third insulating layer. The gas sensor element according to claim 5,
The electrode is
A porous electrode having gas permeability and water permeability that is exposed to the outside of the gas sensor element, and a water permeable fourth electrode that is in contact with the porous body in the stacking direction of the solid electrolyte body. Including a fourth electrode disposed at a position facing the body,
The lead includes a water-impermeable fourth lead connected to the fourth electrode,
The gas sensor element has a fourth insulating layer formed on the front surface or the back surface of the solid electrolyte body,
A part of the fourth electrode and the fourth lead are formed on the fourth insulating layer,
The fourth electrode is
An electrolyte body contact portion in contact with the solid electrolyte body through a through hole penetrating the fourth insulating layer in the stacking direction;
A gas sensor element comprising: a fourth connection portion connected to the fourth lead at a position facing the porous body in the stacking direction and on the fourth insulating layer. The gas sensor element according to any one of claims 1 to 6,
The gas sensor element is a gas sensor element that detects the concentration of NOx contained in the measurement target gas,
A gas sensor element comprising a lead through which a current corresponding to a NOx concentration flows as the first lead or the third lead. A gas sensor comprising the gas sensor element according to any one of claims 1 to 7.

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