Abstract: A sensor element 101 includes an element main body 101a that includes oxygen ion-conductive solid electrolyte layers (1 to 6), and a porous protective layer 90 that covers at least part of the element main body 101a. The porous protective layer 90 includes a porous inner protective layer 92 and a porous outer protective layer 91 disposed on the outer side of the inner protective layer 92 and having a smaller average pore diameter than the inner protective layer 92.

Abstract: In a sensor element 101, oxygen contained in a gas to be measured introduced into a first internal space 20 through a first diffusion control part 11 is pumped out by applying voltage between an inner pump electrode 22 and an outer pump electrode 23. After the oxygen is pumped out, NOx in the gas to be measured generates oxygen by being reduced by a measurement electrode 44. This oxygen is pumped by applying voltage between the measurement electrode 44 and the outer pump electrode 23. On the basis of current generated according to the amount of oxygen thus pumped, the NOx gas concentration is calculated. A slit width of the first diffusion control part 11 on an entrance side is larger than a slit width on an exit side.

Abstract: A sensor element 101 includes an element main body 101a that includes oxygen ion-conductive solid electrolyte layers (1 to 6), and a porous protective layer 90 that covers at least part of the element main body 101a. The porous protective layer 90 includes a porous inner protective layer 92 and a porous outer protective layer 91 disposed on the outer side of the inner protective layer 92 and having a smaller average pore diameter than the inner protective layer 92.

Abstract: In a sensor element 101, oxygen contained in a gas to be measured introduced into a first internal space 20 through a first diffusion control part 11 is pumped out by applying voltage between an inner pump electrode 22 and an outer pump electrode 23. After the oxygen is pumped out, NOx in the gas to be measured generates oxygen by being reduced by a measurement electrode 44. This oxygen is pumped by applying voltage between the measurement electrode 44 and the outer pump electrode 23. On the basis of current generated according to the amount of oxygen thus pumped, the NOx gas concentration is calculated. A slit width of the first diffusion control part 11 on an entrance side is larger than a slit width on an exit side.

Abstract: To provide a gas sensor which can stably carry out a securement of an electric continuity between a sensor element and a contact member. A contact member in which an electric connection to a sensor element is obtained by pinching and fixing the sensor element in an inserting port formed by a pair of housing members includes a constraint member which is provided in an outer periphery of a pair of housing members. The constraint member constrains a displacement of a pair of housing members within a predetermined range before the sensor element is pinched and fixed by a pair of housing members, and exists in a state of being pinched between the annular member and a pair of housing member without generating any reaction force with respect to the external force, after the sensor element is pinched and fixed.

Abstract: In a gas sensor, when an arithmetical mean roughness Ra of an inner periphery of a metal tube 95 is 1 ?m or less and end portions 93 and 94 of U-springs 92 are formed as curved contact portions, the end portions 93 and 94 of the U-springs 92 can slide smoothly along the inner periphery of the metal tube 95. Therefore, when vibration is applied to the gas sensor, the U-springs 92 can be prevented from being caught in the inner periphery of the metal tube 95, and the vibration can be absorbed by an elastic function of the U-springs 92. Even if the gas sensor vibrates, defective contact between a sensor element 20 and contact fittings 71 and wear and cracks in the sensor element 20 are less likely to occur. That is, the gas sensor resistant to vibration can be obtained.

Abstract: In a contact member for a gas sensor configured to fix a sensor element by sandwiching the sensor element in an insertion port defined by a pair of housing members to thereby obtain electrical connection with the sensor element, a restraint member provided at an outer circumference of the pair of housing members and having a restraint function for restraining a displacement of the pair of housing members within a predetermined range is used. The restraint member includes: two pressing surface portions to which a compression force that occurs when the annular member shrinkingly deforms is applied; a first side portion coupled perpendicularly to the two pressing surface portions; and a second side portion having an upper side portion coupled perpendicularly to one of the pressing surface portions and a lower side portion coupled perpendicularly to the other of the pressing surface portions.

Abstract: Each of contact fittings is obtained by bending a die-cut member having a metal plate portion of substantially rectangular shape and a metal piece connecting to a long side of the metal plate portion. The metal piece is folded to be accommodated within a region directly above a surface of the metal plate portion opposite a surface in contact with a front-surface electrode or a back-surface electrode. Then, the metal piece is bent along the length of the metal plate portion to form a hook to be retained by a first housing or a second housing. Therefore, as compared to a structure in which hooks are orthogonal to the length of metal plate portions and bend outward from contact fittings, the arrangement width of the contact fittings arranged in a direction substantially orthogonal to the length of the contact fittings can be reduced.

Abstract: To provide a gas sensor which can stably carry out a securement of an electric continuity between a sensor element and a contact member. A contact member in which an electric connection to a sensor element is obtained by pinching and fixing the sensor element in an inserting port formed by a pair of housing members includes a constraint member which is provided in an outer periphery of a pair of housing members. The constraint member constrains a displacement of a pair of housing members within a predetermined range before the sensor element is pinched and fixed by a pair of housing members, and exists in a state of being pinched between the annular member and a pair of housing member without generating any reaction force with respect to the external force, after the sensor element is pinched and fixed.

Abstract: In a contact member for a gas sensor configured to fix a sensor element by sandwiching the sensor element in an insertion port defined by a pair of housing members to thereby obtain electrical connection with the sensor element, a restraint member provided at an outer circumference of the pair of housing members and having a restraint function for restraining a displacement of the pair of housing members within a predetermined range is used. The restraint member includes: two pressing surface portions to which a compression force that occurs when the annular member shrinkingly deforms is applied; a first side portion coupled perpendicularly to the two pressing surface portions; and a second side portion having an upper side portion coupled perpendicularly to one of the pressing surface portions and a lower side portion coupled perpendicularly to the other of the pressing surface portions.

Abstract: In a gas sensor, when an arithmetical mean roughness Ra of an inner periphery of a metal tube 95 is 1 ?m or less and end portions 93 and 94 of U-springs 92 are formed as curved contact portions, the end portions 93 and 94 of the U-springs 92 can slide smoothly along the inner periphery of the metal tube 95. Therefore, when vibration is applied to the gas sensor, the U-springs 92 can be prevented from being caught in the inner periphery of the metal tube 95, and the vibration can be absorbed by an elastic function of the U-springs 92. Even if the gas sensor vibrates, defective contact between a sensor element 20 and contact fittings 71 and wear and cracks in the sensor element 20 are less likely to occur. That is, the gas sensor resistant to vibration can be obtained.

Abstract: Each of contact fittings is obtained by bending a die-cut member having a metal plate portion of substantially rectangular shape and a metal piece connecting to a long side of the metal plate portion. The metal piece is folded to be accommodated within a region directly above a surface of the metal plate portion opposite a surface in contact with a front-surface electrode or a back-surface electrode. Then, the metal piece is bent along the length of the metal plate portion to form a hook to be retained by a first housing or a second housing. Therefore, as compared to a structure in which hooks are orthogonal to the length of metal plate portions and bend outward from contact fittings, the arrangement width of the contact fittings arranged in a direction substantially orthogonal to the length of the contact fittings can be reduced.