JP2015062000A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor capable of suppressing adhesion of water to a gas sensor element and restraining the gas sensor element from being damaged by thermal stress applied to a portion heated by a heater in the gas sensor element.SOLUTION: A gas sensor 100 comprises: a gas sensor element 3 having a solid electrolyte body 3s formed in a bottomed cylindrical shape, an inner electrode 50, an outer electrode 51, a protection layer 60 surrounding a periphery of the outer electrode, and a porous layer 80 surrounding a periphery of the protection layer; and a heater 15 which is inserted into an internal space of the gas sensor element and has a heating element 25 generating heat by energization. The heating element has a heating part 25a formed in a meandering manner. The protection layer and the porous layer are formed to be spaced between each other by a separation part G. The separation part is formed to overlap at least a portion of the heating part in an axial direction. Furthermore, the protection layer and the porous layer are in contact with each other in at least one place on each of tip end and rear end sides with respect to the separation part.

Description

  The present invention relates to a gas sensor that detects the concentration of a gas to be detected.

As a gas sensor for detecting oxygen concentration in an exhaust gas of an automobile or the like, a gas sensor that extends in an axial direction and has a substantially cylindrical gas sensor element with a closed tip is inserted and held inside a cylindrical metal shell is known. (Patent Document 1). This gas sensor element has a cylindrical solid electrolyte body and inner and outer electrodes formed on the inner and outer surfaces of the solid electrolyte body, respectively. Further, a rod-shaped heater for raising the temperature of the gas sensor element to the activation temperature is inserted in the internal space of the gas sensor element.
On the other hand, the outer surface of the solid electrolyte body is covered with a porous protective layer for protecting the outer electrode from poisoning (Patent Document 2).

JP 2012-37445 A Japanese Patent Laid-Open No. 11-72460

  By the way, as described above, when the heater is inserted into the cylindrical gas sensor element and the gas sensor element is heated by the heater, the gas sensor element is heated by the heater when it is flooded by condensed water such as an exhaust pipe. A large thermal stress is applied to the gas sensor element, and the gas sensor element (solid electrolyte body) may be damaged. In particular, in the gas sensor element, a portion in the vicinity of the heat generating portion provided on the front end side of the heater is more susceptible to heat from the heater and is at a higher temperature. That is, if this part is exposed to water, a greater thermal stress is applied and the gas sensor element may be more damaged.

On the other hand, since the protective layer is porous, water can permeate in the protective layer, and direct adhesion to the gas sensor element (solid electrolyte body) can be prevented. Enters and adheres to the gas sensor element, it is difficult to prevent the gas sensor element from being damaged. Even if the protective layer is made thicker, it is possible to delay the adhesion of water to the water by the gas sensor element, but it is difficult to prevent the water from adhering to the gas sensor element.
Accordingly, an object of the present invention is to provide a gas sensor that suppresses the adhesion of water to the gas sensor element and suppresses the gas sensor element from being damaged due to thermal stress applied to the portion heated by the heater of the gas sensor element.

In order to solve the above problems, a gas sensor of the present invention includes a solid electrolyte body formed in a bottomed cylindrical shape extending in the axial direction and having a closed tip, and an inner electrode provided on the inner surface of the solid electrolyte body, A gas sensor element having an outer electrode provided on an outer surface of the solid electrolyte body, a protective layer surrounding the outer electrode, and a porous layer surrounding the protective layer; and an internal space of the gas sensor element And a heater having a heating element that generates heat when energized, wherein the heating element includes a heating part formed by meandering, and a pair of lead parts drawn from both ends of the heating part. The protective layer and the porous layer are formed with a spacing portion therebetween, and the spacing portion is formed to overlap with at least a part of the heat generating portion in the axial direction, and Tip side from the spacing Wherein respectively at the rear side the protective layer and the porous layer is in contact with at least a portion.
According to this gas sensor, the separating portion is provided so as to overlap at least a part of the heat generating portion in the axial direction. Thereby, it can suppress that water adheres to the heat generating part vicinity (part of the solid electrolyte body which overlaps with a heat generating part and an axial direction) which receives more the heat | fever from a heater among solid electrolyte bodies. This is because even if the porous layer covering the solid electrolyte body is submerged, it cannot penetrate directly into the part of the protective layer that overlaps the heat generating part and the axial direction beyond the separated part, and in the surface direction of the porous layer. Water diffuses along. Then, water penetrates into the protective layer from the bonding portion between the protective layer and the porous layer at a position away from the heat generating portion in the axial direction, and then the water adheres to the solid electrolyte body. At this time, the water that permeates the porous layer is evaporated by the heat from the heater, and the amount of water that the solid electrolyte body is exposed to can be reduced. Moreover, the site | part which overlaps with a coupling | bond part site | part and an axial direction among solid electrolyte bodies is separated from the heat generating part, and the solid electrolyte body is comparatively low temperature. For this reason, even if water adheres to the solid electrolyte body in a position overlapping with the binding site in the axial direction, excessive thermal stress is not applied to the solid electrolyte body, and damage to the gas sensor element (solid electrolyte body) is suppressed. Can do.

Moreover, in the gas sensor of this invention, the said separation | spacing part may be formed continuously in the circumferential direction.
According to this gas sensor, even if any portion in the circumferential direction outside the gas sensor element is submerged, the spacing part is interposed in the vicinity of the heat generating part, so that the damage of the gas sensor element (solid electrolyte body) can be more effectively suppressed. it can.

Furthermore, in the gas sensor of the present invention, the separation portion may be formed across the position of the front end and the rear end of the heat generating portion in the axial direction.
According to this gas sensor, in the axial direction, the entire vicinity of the heat generating portion is covered with the separation portion, and water adhesion in the vicinity of the heat generating portion is reliably suppressed, and damage to the gas sensor element (solid electrolyte body) is more effectively performed. Can be suppressed.

Furthermore, in the gas sensor of the present invention, the heater has a contact portion that contacts a part of the inner surface of the inner electrode, and the separation portion is formed to overlap the contact portion in the axial direction. Also good.
According to this gas sensor, similarly to the vicinity of the heat generating portion, the separation portion is arranged in the contact portion where the heat of the heater is directly transmitted, so that heat is also applied to the contact portion where excessive thermal stress is easily applied due to water adhesion. Stress can be reduced, and damage to the gas sensor element (solid electrolyte body) can be more effectively suppressed.

Furthermore, in the gas sensor of the present invention, the minimum radial thickness of the porous layer that overlaps the spacing portion in the axial direction may be thicker than the maximum spacing in the radial direction of the spacing portion.
According to this gas sensor, water can be sufficiently retained in the porous layer that is thicker than the separation portion and diffused in the surface direction, water that permeates the protection layer can be reduced, and the protection layer can be formed at the separation portion. The strength of the porous layer floating from the surface can also be improved.

  According to the present invention, it is possible to suppress the adhesion of water to the gas sensor element and to prevent the gas sensor element from being damaged due to thermal stress applied to the portion of the gas sensor element heated by the heater.

It is sectional drawing which cut | disconnected the gas sensor which concerns on embodiment of this invention by the surface which follows an axial direction. It is a fragmentary sectional view which shows the structure of a gas sensor element. It is a disassembled perspective view which shows the structure of a heater. It is a schematic diagram which shows the effect | action of a separation part. It is a schematic diagram which shows an effect | action when a separation part does not intervene. It is a fragmentary sectional view which shows the structure of the gas sensor element of a modification.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 shows a cross-sectional structure of a gas sensor 100 according to an embodiment of the present invention cut along a plane along the axis O direction. In this embodiment, the gas sensor 100 is an oxygen sensor that is inserted into an exhaust pipe of an automobile and has a tip exposed to the exhaust gas to detect the oxygen concentration in the exhaust gas. The gas sensor element 3 provided in the gas sensor 100 is a known oxygen sensor element that constitutes an oxygen concentration cell in which a pair of electrodes are stacked on an oxygen ion conductive solid electrolyte body and outputs a detection value corresponding to the amount of oxygen.
In addition, let the lower side of FIG. 1 be the front end side of the gas sensor 100, and let the upper side of FIG.

The gas sensor 100 is assembled so that a substantially cylindrical (hollow shaft-shaped) gas sensor element (in this example, an oxygen sensor element) 3 having a closed tip is inserted and held inside a cylindrical metal fitting body (main metal fitting) 20. It has been. The sensor element 3 includes a cylindrical solid electrolyte body 3s having a tapered diameter toward the tip, an inner electrode 50 (see FIG. 2) and an outer electrode respectively formed on the inner and outer peripheral surfaces of the solid electrolyte body. 51 (see FIG. 2). Further, a round bar heater 15 is inserted into the hollow portion of the gas sensor element 3 so as to raise the temperature of the solid electrolyte body 3s to the activation temperature.
A cylindrical outer tube 40 that holds lead wires and terminals (described later) provided on the rear end side of the gas sensor element 3 and covers the rear end portion of the sensor element 3 is joined to the rear end portion of the metal fitting body 20. ing. Further, an insulating and cylindrical separator 121 is caulked and fixed inside the outer cylinder 40 on the rear end side of the gas sensor element 3. On the other hand, the detection part at the tip of the gas sensor element 3 is covered with a protector 7. The male screw part 20d of the metal fitting body 20 of the gas sensor 100 manufactured in this way is attached to a screw hole such as an exhaust pipe, so that the detection part at the tip of the gas sensor element 3 is exposed in the exhaust pipe and the gas to be detected (exhaust gas) Gas). A polygonal flange 20c for engaging a hexagon wrench or the like is provided near the center of the metal fitting body 20, and the step between the flange 20c and the male thread 20d is attached to the exhaust pipe. A gasket 14 is inserted to prevent the gas from leaking when it is blown.

On the inner peripheral surface near the tip of the metal fitting body 20, a step portion 20e having a diameter reduced inward is provided. A cylindrical ceramic holder 5 is disposed via a washer 12 on the rear end facing surface of the stepped portion 20e. The gas sensor element 3 is inserted inside the metal fitting body 20 and the ceramic holder 5, and a flange 3 a provided on the center side of the gas sensor element 3 is in contact with the ceramic holder 5 through a washer 13 from the rear end side. .
Further, in the radial gap between the gas sensor element 3 and the metal fitting body 20 on the rear end side of the flange portion 3a, a cylindrical talc powder 6 and a cylindrical ceramic leave 10 are arranged. Then, the metal ring 30 is arranged on the rear end side of the ceramic leave 10, and the rear end portion of the metal fitting body 20 is bent inward to form the crimped portion 20a, whereby the ceramic leave 10 is pressed to the front end side. As a result, the talc ring 6 is crushed and the ceramic leave 10 and the talc powder 6 are caulked and fixed, and the gap between the gas sensor element 3 and the metal fitting body 20 is sealed.

The separator 121 disposed on the rear end side of the gas sensor element 3 is provided with insertion holes (four in this example), and two of the insertion holes are plate-like base portions of the inner terminal fitting 71 and the outer terminal fitting 91, respectively. 74 and 94 are inserted and fixed. Connector portions 75 and 95 are formed at the rear ends of the plate-like base portions 74 and 94, respectively, and lead wires 41 and 41 are crimped to the connector portions 75 and 95, respectively. Further, a heater lead wire 43 (only one is shown in FIG. 1) drawn from the heater 15 is inserted into two insertion holes (heater lead holes) (not shown) of the separator 121.
A cylindrical grommet 131 is caulked and fixed inside the outer cylinder 40 on the rear end side of the separator 121. Two lead wires 41 and two heater lead wires are respectively inserted from four insertion holes of the grommet 131. 43 is pulled out.
A through hole 131 a is formed at the center of the grommet 131 and communicates with the internal space of the gas sensor element 3. A water-repellent ventilation filter 140 is interposed in the through-hole 131a of the grommet 131 so that the reference gas (atmosphere) is introduced into the internal space of the gas sensor element 3 without passing outside water.

  On the other hand, a cylindrical protector 7 is fitted on the distal end side of the metal fitting body 20, and the distal end side of the gas sensor element 3 protruding from the metal fitting body 20 is covered with the protector 7. The protector 7 is configured by attaching a bottomed cylindrical metal (for example, stainless steel, etc.) double outer protector 7b and an inner protector 7a having a plurality of holes (not shown) by welding or the like.

Next, the configuration of the gas sensor element 3 will be described with reference to FIG. As shown in FIG. 2, an inner electrode 50 is formed on the distal end side of the inner peripheral surface of the solid electrolyte body 3s over the entire circumference in the circumferential direction including the distal end surface. A lead portion (not shown) extends from the inner electrode 50 toward the rear end side. On the other hand, an outer electrode 51 is formed on the outer peripheral surface of the solid electrolyte body 3s over the entire circumference in the circumferential direction including the front end surface. A lead portion (not shown) extends from the outer electrode 51 toward the rear end side.
The inner electrode 50 is exposed to a reference gas atmosphere introduced into the internal space of the gas sensor element 3. On the other hand, the outer electrode 51 formed on the outer surface of the gas sensor element 3 is exposed to the gas to be detected, and the gas is detected between the inner electrode 50 and the outer electrode 51 through the solid electrolyte body 3s. .
The inner electrode 50 and the outer electrode 51 are electrically connected to the inner terminal fitting 71 and the outer terminal fitting 91, respectively, via lead portions.

Furthermore, a protective layer 60 that covers the outer electrode 51 is formed in a region from the distal end surface of the outer peripheral surface of the solid electrolyte body 3s to the vicinity of the flange portion 3a. The protective layer 60 is formed of a ceramic sprayed layer such as spinel and is a porous layer. The protective layer 60 has a function of protecting the outer electrode 51.
The porous layer 80 covers at least the outer surface of the protective layer 60 that covers the outer electrode 51. Here, in the present embodiment, the rear end portion of the porous layer 80 extends to the rear end side with respect to the outer electrode 51 and is located on the front end side with respect to the protective layer 60.
The porous layer 80 can be formed by bonding, for example, one or more ceramic particles selected from the group consisting of alumina, spinel, zirconia, mullite, zircon, and cordierite by firing or the like. By sintering the slurry containing these particles, pores having a three-dimensional network structure can be formed so as to allow gas permeation between the ceramic particles. A slurry obtained by adding a burnable pore former to the slurry containing the particles may be sintered so that a portion where the pore former is burnt out becomes pores. As the pore former, for example, carbon, resin beads, organic or inorganic binder particles can be used.

On the other hand, a round bar heater 15 is inserted into the hollow portion of the gas sensor element (solid electrolyte body 3s). The heater 15 has a heating element 25 that generates heat when energized from outside via a heater lead wire 43. The heating element 25 has a heating part 25a formed by meandering a conductor in the axial direction, and a pair of lead parts 25b made of a conductor drawn from both ends of the heating part 25a.
More specifically, the heater 15 can be manufactured as shown in FIG. That is, the heating element 25 includes a heating part 25a, both lead parts 25b, and an electrode pattern 25c formed on the other end of both lead parts 25b. The heating element 25 includes two ceramic green sheets 16b, 16c. Note that alumina is used as the ceramic green sheet. Further, tungsten, rhenium, or the like is used for the heat generating portion 25a and the lead portion 25b. Two electrode pads 15p to which a heater lead terminal (not shown) is brazed are formed on the surface of the first ceramic green sheet 16c, and the electrode pattern 25c is connected to the electrode pad 15p through a through hole to make the ceramic green sheet. Is formed. Furthermore, the heater 15 can be manufactured by winding this laminated body around the rod-like base material 16a whose main component is alumina or the like with the first ceramic green sheet 16c on the front side and firing.

  Returning to FIG. 2, a separation portion G that separates the protective layer 60 and the porous layer 80 is formed in a region R <b> 1 that straddles the position of the front end 25 p and the rear end 25 s of the heat generating portion 25 a in the axis O direction. Further, the protective layer 60 and the porous layer 80 are in contact (bonded in the case of this embodiment) on the front end side and the rear end side from the separation portion G, respectively. Specifically, the spacing portion G is formed only in part (only on the left side in FIG. 2) in the circumferential direction. On the other hand, the protective layer 60 and the porous layer 80 are in contact with each other in the circumferential direction on the rear end side with respect to the separation portion G. Further, the protective layer 60 and the porous layer 80 are in contact with each other in the circumferential direction on the distal end side with respect to the separation portion G. Note that the protective layer 60 and the porous layer 80 are also in contact at the tip portion (bottomed portion) of the solid electrolyte body 3s. Further, in the present embodiment, the protective layer 60 and the porous layer 80 are in contact with each other in the region that overlaps the separation portion G in the axial direction.

When the heat generating part 25a generates heat, the portion 3sa (the heat generating part vicinity 3sa) of the solid electrolyte body 3s that overlaps the heat generating part 25a in the axis O direction is further heated to a higher temperature. For this reason, when the gas sensor element 3 gets wet, a large thermal stress is applied to the heat generating portion vicinity 3sa, and the solid electrolyte body 3s may be damaged. Therefore, the separation portion G is provided in at least a part of the heat generating portion 25a so as to overlap with the direction of the axis O (in the present embodiment, the region region R1). As a result, as shown in FIG. 4, even when water W is applied to the porous layer 80 covering the solid electrolyte body 3 s, the portion 60 a of the protective layer 600 that overlaps the heat generating portion 25 a and the axis O direction beyond the spacing portion G is applied. It cannot penetrate directly, and the water W diffuses along the surface direction of the porous layer 80 (the direction of the arrow in FIG. 4). Then, at a position away from the heat generating portion 25aa in the axis O direction, water W permeates into the protective layer 60 from the bonded portions (portions 60b and 60c in FIG. 4) of the protective layer 60 and the porous layer 80, and then solids Water W adheres to the electrolyte body 3s. At this time, the water W penetrating the porous layer 80 is evaporated by the heat from the heater 15, and the amount of water that the solid electrolyte body 3s is exposed to can be reduced. Further, in the solid electrolyte body 3s, the portions (3sb and 3sc in FIG. 4) that overlap with the binding portions 60b and 60c in the axial direction are separated from the heat generating portion 25a, and the solid electrolyte body 3s is at a relatively low temperature. . For this reason, excessive thermal stress is not applied to the solid electrolyte body 3s, and damage to the gas sensor element (solid electrolyte body 3s) can be suppressed.
On the other hand, as shown in FIG. 5, when the separation portion G is not formed so as to overlap the heat generation portion 25 a in the axis O direction, when water W is applied to the porous layer 80, it directly penetrates into the protective layer 60 as it is, The vicinity of the heat generating portion 3sa heated by the heat generating portion 25a gets wet. For this reason, excessive thermal stress is applied to the solid electrolyte body 3s, and the gas sensor element (solid electrolyte body 3s) is easily damaged.

  As shown in FIGS. 2 and 4, in the present embodiment, the separation portion G is formed across the position of the front end 25 p and the position of the rear end 25 s of the heat generating portion 25 a in the axis O direction. As a result, in the direction of the axis O, the entire vicinity of the heat generating portion 3sa is covered with the separation portion G, and adhesion of water W in the vicinity of the heat generating portion 3sa is reliably suppressed, and the gas sensor element 3 (solid electrolyte body 3s) is damaged. Can be suppressed more effectively.

Further, as shown in FIGS. 2 and 4, in the present embodiment, a contact portion 15 c where the side wall of the heater 15 and the inner surface of the inner electrode 50 come into contact is provided. Thereby, the heat generated by the heater 15 can be effectively transferred to the solid electrolyte body 3s. In the present embodiment, the separation portion G is formed so as to overlap the contact portion 15c in the axis O direction. In this way, as in the heat generating part vicinity 3sa, excessive heat is generated due to adhesion of the water W by arranging the separation part G in the contact part 15c where the heat of the heater 15 is directly transmitted to the solid electrolyte body 3s. Thermal stress can be reduced even in the contact portion 15c where stress is easily applied, and damage to the gas sensor element (solid electrolyte body 3s) can be more effectively suppressed.
Furthermore, as shown in FIG. 2, in the present embodiment, the minimum radial thickness t1 of the porous layer 80 that overlaps the spacing portion G and the axis O direction is greater than the maximum radial spacing t2 of the spacing portion G. thick. In this way, water can be sufficiently retained in the porous layer 80 thicker than the spacing portion G to diffuse in the surface direction, the water W penetrating into the protective layer 60 can be reduced, and the spacing portion G can be reduced. The strength of the porous layer 80 floating from the protective layer 60 can also be improved.

Next, an example of a method for manufacturing a gas sensor element according to an embodiment of the present invention will be described.
First, a material of a predetermined solid electrolyte (for example, partially stabilized zirconia in which 5 mol% of Y ₂ O ₃ is added to ZrO ₂ ) is used as a slurry, and this slurry is dried and granulated by a spray drying method. The powder is formed into a bottomed cylindrical shape by a hydraulic press method, ground into a predetermined shape, and then fired at, for example, 1500 ° C. to form a solid electrolyte body 3s.
Next, the inner electrode 50 made of Pt is formed on the inner peripheral surface of the solid electrolyte body 3s by an electroless plating method, and similarly, the front end side of the outer peripheral surface of the solid electrolyte body 3s is formed by an electroless plating method. The outer electrode 51 made of Pt is formed.
Next, a protective layer 60 made of a ceramic (spinel or the like) sprayed layer is formed so as to cover the outer electrode 51.

Next, in the protective layer 60, a burnable sheet is pasted on the position where the separation part G is formed, and a paste that becomes the porous layer 80 is applied on the protective layer 60 from above the burnable sheet. Bake. At this time, it is preferable to sinter a slurry for forming a paste to which a burnable pore-forming material is added so that the porous layer 80 becomes porous, and the portion where the pore-forming material is burned out is a three-dimensional network structure. Of relatively large pores. The paste can be applied by a dip method, a spray method or the like.
By baking, the burnable sheet between the protective layer 60 and the porous layer 80 disappears, and a gap serving as a separation portion G is formed. As the burnout sheet, for example, a carbon sheet can be used.

It goes without saying that the present invention is not limited to the above-described embodiment, but extends to various modifications and equivalents included in the spirit and scope of the present invention. For example, the shape of the heat generating portion 25a is not limited to the above, and can be formed by meandering in the radial direction of the gas sensor element 3 (direction orthogonal to the axis O) as an example.
Further, the separation portion G only needs to be formed so as to overlap with at least a part of the heat generating portion 25a in the axis O direction. However, as in the present embodiment, when the separation portion G is formed across the front end position 25p and the rear end position 25s of the heat generation portion 25a in the axis O direction, the separation portion G and the heat generation portion in the axis O direction. This is preferable because the entire 25a always overlaps and the solid electrolyte body 3s heated by the heat generating portion 25a is reliably prevented from being wetted. Further, the separation portion G may not straddle only the position 25p at the front end of the heat generating portion 25a in the axis O direction and may not extend over the position 25s at the rear end, or the separation portion G may follow the heat generating portion 25a in the axis O direction. It does not have to straddle only the end position 25s and not the end position 25p.
Further, at least a part (one place) of the protective layer 60 and the porous layer 80 may be in contact with each other on the front end side and the rear end side from the separation portion G.
Further, in the present embodiment, the separation portion G has a substantially circular cross section, but is not limited thereto, and may have a substantially rectangular cross section or a substantially triangular cross section.

  Furthermore, in the present embodiment, the separation portion G is formed only in a part (only on the left side in FIG. 2) in the circumferential direction. However, as shown in FIG. 6, the separation portion G is continuous in the circumferential direction. It may be formed. FIG. 6 is a partial cross-sectional view showing a configuration of a gas sensor element according to a modification, and corresponds to FIG. As shown in FIG. 6, when the separation portion G is continuously formed in the circumferential direction, the separation portion G is interposed in the heat generating portion vicinity 3sa regardless of which portion of the outer circumferential direction of the gas sensor element 3 is flooded. Damage to the gas sensor element (solid electrolyte body 3s) can be more effectively suppressed.

  Furthermore, in the present embodiment, the contact portion 15c and the vicinity of the heat generating portion 3sa (the portion 3sa of the solid electrolyte body 3s overlapping the heat generating portion 25a and the axis O direction) partially overlap, but not limited thereto, As shown in FIG. 6, the contact part 150c and the heat generating part vicinity 3sa may have shifted | deviated. In the present embodiment, as shown in FIG. 2, the side wall of the heater 15 and the inner surface of the inner electrode 50 are in contact with each other to form a contact portion 15 c, and the contact portion 15 c and the heat generating portion vicinity 3 sa are partly formed. It was overlapping. However, as shown in FIG. 6, the edge 150 z that is a stepped portion whose diameter increases from the front end to the rear end of the heater 150 and the inner surface of the inner electrode 50 come into contact with each other to form the contact portion 150 c. is there. In this case, the contact portion 150c and the heat generating portion vicinity 3sa are provided to be shifted from each other. However, also in this case, the separation portion Ga is formed so as to overlap the contact portion 150c in the axis O direction. . In this way, as in the heat generating portion vicinity 3sa, excessive heat is generated due to adhesion of the water W by arranging the separation portion Ga in the contact portion 150c where the heat of the heater 150 is directly transmitted to the solid electrolyte body 3s. Thermal stress can be reduced even in the contact portion 150c where stress is easily applied, and damage to the gas sensor element (solid electrolyte body 3s) can be more effectively suppressed.

3 Gas Sensor Element 3s Solid Electrolyte Body 15, 150 Heater 15c, 150c Contact Part 25 Heating Element 25a Heating Part 25b Lead Part 25p Tip of Heating Part 25s Rear End of Heating Part 50 Inner Electrode 51 Outer Electrode 60 Protective Layer 80 Porous Layer 100 Gas sensor G, Ga separation part O Axial direction t1 Minimum radial thickness of porous layer t2 Maximum radial distance of separation part

Claims (5)

A solid electrolyte body formed in a bottomed cylindrical shape extending in the axial direction and having a closed tip, an inner electrode provided on the inner surface of the solid electrolyte body, and an outer electrode provided on the outer surface of the solid electrolyte body A gas sensor element having a protective layer surrounding the periphery of the outer electrode, and a porous layer surrounding the protective layer;
A gas sensor comprising a heater inserted into the internal space of the gas sensor element and having a heating element that generates heat when energized,
The heating element has a heating portion formed by meandering and a pair of lead portions drawn from both ends of the heating portion,
The protective layer and the porous layer are formed with a spacing portion therebetween, and the spacing portion is formed so as to overlap with at least a part of the heat generating portion in the axial direction, and the tip side from the spacing portion. A gas sensor in which the protective layer and the porous layer are in contact with each other at least partially on the rear end side.   The gas sensor according to claim 1, wherein the separation portion is formed continuously in the circumferential direction.   The gas sensor according to claim 1, wherein the separation portion is formed across the position of the front end and the rear end of the heat generating portion in the axial direction.   The contact part which the said heater and a part of inner surface of the said inner side electrode contact | abut, The said separation | spacing part is formed so that it may overlap with the said contact part in an axial direction. The gas sensor described in 1.   The gas sensor according to any one of claims 1 to 4, wherein a minimum radial thickness of the porous layer that overlaps the separation portion in the axial direction is thicker than a maximum distance in a radial direction of the separation portion.

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