Gas Sensors

Abstract

To provide a gas sensor that can make it harder for a solid electrolyte body of a sensor element to be deformed.SOLUTION: A sensor element 2 of a gas sensor 1 includes: a solid electrolyte body 31; an exhaust electrode 311 and an atmospheric electrode 312 provided on a surface of the solid electrolyte body 31; a porous atmospheric side protective layer 313 provided on a surface of the atmospheric electrode 312; insulating first buffer layers 331A, 331B and a second buffer layer 332 laminated on both surfaces of the solid electrolyte body 31; an insulating first insulator 33A laminated on the first buffer layers 331A, 331B; and an insulating second insulator 33B laminated on the second buffer layer 332 via an adhesion layer 335. The second buffer layer 332 has a shape surrounding the atmospheric electrode 312 and the atmospheric side protective layer 313 from a side direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a gas sensor. [Background technology]

[0002] A gas sensor is disposed in, for example, an exhaust pipe of an automobile and is used to detect various gases contained in exhaust gas flowing through the exhaust pipe as the detection target gas. In addition to a sensor element for detecting gas, the gas sensor includes a housing for attaching the sensor element to the exhaust pipe or the like.

[0003] The sensor element includes a solid electrolyte body provided with an electrode exposed to the gas to be detected, an insulator laminated on the solid electrolyte body, and a heater embedded in the insulator. A porous protective layer may be provided on the surface of the electrode to protect the electrode from poisoning substances contained in the gas to be detected or the atmosphere. For example, the gas sensor of Patent Document 1 includes a sensor element having an air introduction path through which the atmosphere is introduced, and the air introduction path is provided with a trap layer for capturing poisoning substances of the sensor element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-165663 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the research and development of gas sensors by the inventors, it was found that when a porous protective layer is provided on the surface of the electrode in the solid electrolyte body, the solid electrolyte body may be deformed during the manufacture of the sensor element. Specifically, during the manufacture of the sensor element, pressure is applied to the intermediate body in a state in which the solid electrolyte body and a part of the insulator are laminated, so that the intermediate body is compressed and bonded to prevent the laminated state of the intermediate body from collapsing. At this time, it was found that the portion of the solid electrolyte body where the electrode and the porous layer are provided is deformed so as to be compressed in the cross section of the sensor element in the lamination direction.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a gas sensor capable of making the solid electrolyte body in the sensor element less susceptible to deformation. [Means for solving the problem]

[0007] One aspect of the present invention is A gas sensor (1) comprising a sensor element (2), The sensor element includes: A solid electrolyte body (31, 31A, 31B) having ion conductivity; Electrodes (311, 312, 311A, 312A, 311B, 312B) provided on the surface of the solid electrolyte body; A porous protective layer (313) provided on the surface of the electrode; an insulating buffer layer (332, 333) that is laminated on the solid electrolyte body and has a shape that surrounds the electrodes and the protective layer from the sides; an insulating insulator (33B) laminated on the buffer layer via an adhesive layer (335) and forming a gas introduction path for introducing gas between the solid electrolyte body and the insulating insulator (33B); death, The thickness of the buffer layer is smaller than the thickness of the solid electrolyte body and is within a range of ±25% of the total thickness of the electrode and the protective layer. , in the gas sensor. Another aspect of the present invention is A gas sensor (1) comprising a sensor element (2), The sensor element includes: A solid electrolyte body (31, 31A, 31B) having ion conductivity; Electrodes (311, 312, 311A, 312A, 311B, 312B) provided on the surface of the solid electrolyte body; A porous protective layer (313) provided on the surface of the electrode; an insulating buffer layer (332, 333) that is laminated on the solid electrolyte body and has a shape that surrounds the electrodes and the protective layer from the sides; an insulating insulator (33B) laminated on the buffer layer via an adhesive layer (335) and forming a gas introduction path for introducing a gas between the solid electrolyte body and the insulator (33B); In a cross section perpendicular to the longitudinal direction (L) of the sensor element, a pair of inner wall surfaces (332X) of the buffer layer which form part of the gas introduction path overlap a pair of side surfaces (313X) of the protective layer in the gas sensor. Effect of the Invention

[0008] In the sensor element of the gas sensor of the above-mentioned aspect, a buffer layer having a shape surrounding the electrodes and the protective layer from the sides is laminated on the solid electrolyte body, and an insulator forming a gas introduction path for introducing gas between the solid electrolyte body and the buffer layer is laminated on the buffer layer via an adhesive layer. With this configuration, when pressure is applied to an intermediate body in which the solid electrolyte body provided with the electrodes and the protective layer and the buffer layer are laminated to press the intermediate body during the manufacture of the sensor element, the presence of the buffer layer makes it possible to suppress deformation of the portion of the solid electrolyte body where the electrodes and the protective layer are provided.

[0009] According to the gas sensor of the above aspect, the solid electrolyte body in the sensor element can be made less susceptible to deformation.

[0010] In addition, the symbols in parentheses for each component shown in one aspect of the present invention indicate a correspondence with the symbols in the figures in the embodiment, but do not limit each component to only the contents of the embodiment. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram showing a gas sensor according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory view showing a cross section of the sensor element of the gas sensor according to the first embodiment. [Diagram 3] FIG. 3 is an explanatory diagram showing a cross section taken along line III-III of FIG. 2 according to the first embodiment. [Figure 4] FIG. 4 is an explanatory view showing a state in which an intermediate body of the sensor element according to the first embodiment is being pressure-bonded, taken along line III-III of FIG. 2. [Diagram 5]FIG. 5 is an explanatory diagram showing a cross section corresponding to cross section III-III in FIG. 2 according to the second embodiment. [Figure 6] FIG. 6 is an explanatory view showing a state in which an intermediate body of a sensor element according to the second embodiment is being pressure-bonded, in a cross section corresponding to the cross section taken along line III-III in FIG. [Figure 7] FIG. 7 is an explanatory diagram showing a cross section corresponding to cross section III-III in FIG. 2 according to the third embodiment. [Figure 8] FIG. 8 is an explanatory view showing a process of forming an intermediate body of a sensor element according to the third embodiment, in a cross section corresponding to the cross section taken along line III-III in FIG. [Figure 9] FIG. 9 is an explanatory view showing a state in which an intermediate body of a sensor element is being pressure-bonded in a cross section corresponding to the cross section taken along line III-III in FIG. 2 according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A preferred embodiment of the above-mentioned gas sensor will now be described with reference to the drawings. <Embodiment 1> The gas sensor 1 of this embodiment includes a sensor element 2. As shown in Fig. 2 and Fig. 3, the sensor element 2 includes a solid electrolyte body 31 having ion conductivity, an exhaust electrode 311 and an atmosphere electrode 312 provided on the surfaces 301, 302 of the solid electrolyte body 31, a porous atmosphere-side protective layer 313 provided on the surface of the atmosphere electrode 312, insulating first buffer layers 331A, 331B and a second buffer layer 332 laminated on both surfaces 301, 302 of the solid electrolyte body 31, an insulating first insulator 33A laminated on the first buffer layers 331A, 331B, and an insulating second insulator 33B laminated on the second buffer layer 332 via an adhesive layer 335. The second buffer layer 332 has a shape that surrounds the atmosphere electrode 312 and the atmosphere-side protective layer 313 from the sides. Between the second insulator 33B and the solid electrolyte body 31, an air duct 36 is formed as a gas introduction path through which the air A flows in as a gas.

[0013] The gas sensor 1 of this embodiment will be described in detail below. (Gas sensor 1) 1, the gas sensor 1 is disposed at a mounting port 71 of an exhaust pipe 7 of an internal combustion engine of a vehicle, and is used to detect the concentrations of oxygen, specific gases, etc. contained in exhaust gas G flowing through the exhaust pipe 7 as the detection target gas. The gas sensor 1 may be used as an air-fuel ratio sensor (A / F sensor) that determines the air-fuel ratio in the internal combustion engine based on the concentrations of oxygen, unburned gas, etc. in the exhaust gas G.

[0014] A catalyst for purifying harmful substances in the exhaust gas G is disposed in the exhaust pipe 7, and the gas sensor 1 may be disposed either upstream or downstream of the catalyst in the flow direction of the exhaust gas G in the exhaust pipe 7. The gas sensor 1 may also be disposed in a pipe on the intake side of a supercharger that uses the exhaust gas G to increase the density of the air taken in by the internal combustion engine. The pipe in which the gas sensor 1 is disposed may also be a pipe in an exhaust gas recirculation mechanism that recirculates a portion of the exhaust gas G exhausted from the internal combustion engine to the exhaust pipe 7 to the intake pipe of the internal combustion engine.

[0015] (Sensor element 2) As shown in Fig. 2 and Fig. 3, the sensor element 2 of this embodiment includes a solid electrolyte body 31, insulating first buffer layers 331A, 331B laminated on a first surface 301 of the solid electrolyte body 31, an insulating first insulator 33A laminated on the first buffer layers 331A, 331B, an insulating second buffer layer 332 laminated on a second surface 302 of the solid electrolyte body 31, and an insulating second insulator 33B laminated on the second buffer layer 332 via an adhesive layer 335. The first insulator 33A and the first buffer layers 331A, 331B form a gas chamber 35 as a gas introduction path into which exhaust gas G as a gas is introduced. The first buffer layers 331A, 331B include an inner buffer layer 331A laminated on the solid electrolyte body 31, and an outer buffer layer 331B that is thicker than the inner buffer layer 331A and is for forming the gas chamber 35. The second insulator 33B and the second buffer layer 332 form an air duct 36 serving as a gas introduction path through which the air A as a gas is introduced.

[0016] An exhaust electrode 311 exposed to exhaust gas G is provided on a first surface 301 of the solid electrolyte body. An air electrode 312 exposed to the atmosphere A is provided on a second surface 302 of the solid electrolyte body. A porous atmosphere-side protective layer 313 for protecting the air electrode 312 from poisonous substances contained in the atmosphere A is provided on the surface of the air electrode 312.

[0017] The sensor element 2 is a laminated type in which a solid electrolyte body 31, insulators 33A and 33B, buffer layers 331A, 331B and 332, an adhesive layer 335, etc. are laminated. The sensor element 2 is formed in a long rectangular shape, and is held in a housing 41 by an element holding material 42, which will be described later.

[0018] (Longitudinal direction L, stacking direction D, width direction W) In this embodiment, the longitudinal direction L of the gas sensor 1 and the sensor element 2 refers to the direction in which the sensor element 2 extends in an elongated shape. A direction perpendicular to the longitudinal direction L, in which the solid electrolyte body 31 and the insulators 33A and 33B are stacked, is referred to as a stacking direction D. A direction perpendicular to the longitudinal direction L and the stacking direction D is referred to as a width direction W. In the longitudinal direction L of the sensor element 2, a side exposed to the exhaust gas G is referred to as a tip side L1, and a side opposite to the tip side L1 is referred to as a base side L2.

[0019] (Solid electrolyte body 31, electrodes 311, electrodes 312, and atmosphere-side protective layer 313) As shown in FIGS. 2 and 3, the solid electrolyte body 31 converts oxygen ions (O 2- ) The exhaust electrode 311 and the atmosphere electrode 312 are arranged at a position where they overlap in the stacking direction D via the solid electrolyte body 31 at a portion of the tip side L1 in the longitudinal direction L of the sensor element 2 exposed to exhaust gas G. A sensor cell is formed at the portion of the tip side L1 in the longitudinal direction L of the sensor element 2 by the exhaust electrode 311, the atmosphere electrode 312, and a portion of the solid electrolyte body 31 sandwiched between these electrodes 311, 312.

[0020] The solid electrolyte body 31 is made of a zirconia-based oxide, and is made of stabilized zirconia or partially stabilized zirconia, which is mainly composed of zirconia (zirconium oxide) (containing 50 mass% or more) and in which a rare earth metal element or an alkaline earth metal element has substituted for a part of the zirconia. A part of the zirconia constituting the solid electrolyte body 31 is substituted for by yttria, scandia, or calcia.

[0021] The exhaust electrode 311 and the atmosphere electrode 312 contain platinum as a precious metal exhibiting catalytic activity against oxygen, and zirconia-based oxide as a common material with the solid electrolyte body 31. The exhaust electrode 311 and the atmosphere electrode 312 are connected to electrode lead portions for electrically connecting these electrodes 311, 312 to the outside of the gas sensor 1.

[0022] The atmosphere-side protective layer 313 is provided so as to cover the surface of the atmosphere electrode 312. The atmosphere-side protective layer 313 is made of a porous ceramic material such as alumina, and captures poisoning substances contained in the atmosphere A to prevent the poisoning substances from reaching the atmosphere electrode 312.

[0023] A porous exhaust-side protective layer may be provided on the surface of the exhaust electrode 311 to protect the exhaust electrode 311 from poisonous substances contained in the exhaust gas G. In this case, the exhaust-side protective layer is made of a porous ceramic material such as alumina, and captures the poisonous substances contained in the exhaust gas G to prevent the poisonous substances from reaching the exhaust electrode 311.

[0024] (Gas Chamber 35) 2 and 3, a gas chamber 35 is formed on the first surface 301 of the solid electrolyte body 31, surrounded by the first insulator 33A, the first buffer layers 331A and 331B, and the solid electrolyte body 31, and into which exhaust gas G is introduced. The gas chamber 35 is formed at a position on the tip side L1 in the longitudinal direction L of the sensor element 2, where the exhaust electrode 311 is accommodated. The gas chamber 35 is formed as a space portion closed by the first insulator 33A, the first buffer layers 331A and 331B, the diffusion resistance portion 32, and the solid electrolyte body 31. The exhaust gas G flowing through the exhaust pipe 7 is introduced into the gas chamber 35 through the diffusion resistance portion 32.

[0025] (Diffusion resistor 32) As shown in Figs. 2 and 3, the diffusion resistance portion (gas inlet portion) 32 of this embodiment is provided at a portion on the tip side L1 in the longitudinal direction L of the gas chamber 35 in order to introduce the exhaust gas G into the gas chamber 35. The diffusion resistance portion 32 is formed by disposing a porous body of a metal oxide such as alumina (aluminum oxide) in an inlet formed in the first buffer layers 331A, 331B. The diffusion speed (flow rate) of the exhaust gas G introduced into the gas chamber 35 is determined by limiting the speed at which the exhaust gas G passes through the pores of the porous body in the diffusion resistance portion 32. The diffusion resistance portion 32 may be provided on both sides of the gas chamber 35 in the width direction W.

[0026] (Atmospheric Duct 36) 2 and 3, an air duct 36 is formed on the second surface 302 of the solid electrolyte body 31, and is surrounded by the second insulator 33B, the second buffer layer 332, and the solid electrolyte body 31, and into which the air A is introduced. The air duct 36 is formed from a portion of the sensor element 2 on the tip side L1 in the longitudinal direction L that houses the air electrode 312, to a base end position of the sensor element 2 in the longitudinal direction L.

[0027] (Each insulator 33A, 33B, each buffer layer 331A, 331B, 332 and adhesive layer 335) As shown in FIG. 2 and FIG. 3, the first insulator 33A and the first buffer layers 331A, 331B form the gas chamber 35, and the second insulator 33B and the second buffer layer 332 form the air duct 36 and embed the heater 34. The first buffer layers 331A, 331B are sandwiched between the solid electrolyte body 31 and the first insulator 33A, and have a notch along the shape of a plane perpendicular to the stacking direction D of the gas chamber 35. The second buffer layer 332 is sandwiched between the solid electrolyte body 31 and the second insulator 33B, and has a notch along the shape of a plane perpendicular to the stacking direction D of the air duct 36. The second buffer layer 332 has a shape that surrounds the air electrode 312 and the air side protective layer 313 from three sides, namely, the tip side L1 in the longitudinal direction L and both sides in the width direction W.

[0028] Each of the insulators 33A, 33B and each of the buffer layers 331A, 331B, 332 is formed of a metal oxide such as alumina (aluminum oxide). Each of the insulators 33A, 33B and each of the buffer layers 331A, 331B, 332 is formed as a dense body that cannot be permeated by gas such as exhaust gas G or air A.

[0029] The thickness of the second buffer layer 332 in the stacking direction D is thinner than the thickness of the solid electrolyte body 31 in the stacking direction D, and is within a range of ±25% of the total thickness of the atmosphere electrode 312 and the atmosphere-side protective layer 313 in the stacking direction D. Hereinafter, the term "thickness" refers to the thickness in the stacking direction D. This configuration makes it possible to make the solid electrolyte body 31 less likely to deform when pressure is applied in the stacking direction D to the intermediate body 20 of the sensor element 2 to compress the intermediate body 20 during the manufacturing process of the sensor element 2.

[0030] If the thickness of the second buffer layer 332 is smaller than −25% of the total thickness of the atmosphere electrode 312 and the atmosphere-side protective layer 313, the effect of suppressing deformation due to crushing of the solid electrolyte body 31 by the second buffer layer 332 may not be obtained. On the other hand, if the thickness of the second buffer layer 332 is larger than the total thickness of the atmosphere electrode 312 and the atmosphere-side protective layer 313 by more than +25%, the pressure applied to the solid electrolyte body 31 when the intermediate body 20 is compressed may become uneven, and the effect of suppressing deformation of the solid electrolyte body 31 may not be obtained.

[0031] When the thickness of the second buffer layer 332 is t1 and the total thickness of the atmosphere electrode 312 and the atmosphere-side protective layer 313 is t2, the relationship between the thickness ratio t1 / t2×100[%] and the amount of crushing occurring in the solid electrolyte body 31 is such that the amount of crushing exponentially increases as the thickness ratio t1 / t2 deviates from 100[%] to the increasing or decreasing side. It was also found that the allowable range for the thickness variation occurring in the solid electrolyte body 31 is a range of 75[%] to 125[%] for the thickness ratio t1 / t2.

[0032] It is preferable that the thickness of the second buffer layer 332 is as close as possible to the total thickness of the atmosphere electrode 312 and the atmosphere-side protective layer 313. It is more preferable that the thickness of the second buffer layer 332 is within a range of ±5% of the total thickness of the atmosphere electrode 312 and the atmosphere-side protective layer 313.

[0033] The first buffer layers 331A, 331B and the first insulator 33A are made of alumina, which is the same ceramic material. With this configuration, when the intermediate body 20 of the sensor element 2 is fired to manufacture the sensor element 2, the first buffer layers 331A, 331B and the first insulator 33A are firmly adhered to each other. In addition, the second buffer layer 332 and the second insulator 33B are made of alumina, which is the same ceramic material. With this configuration, when the intermediate body 20 of the sensor element 2 is fired to manufacture the sensor element 2, the second buffer layer 332 and the second insulator 33B are firmly adhered to each other.

[0034] The adhesive layer 335 is made of the same type of ceramic material as the second buffer layer 332 and the second insulator 33B. The adhesive layer 335 contains a solvent when bonding the second buffer layer 332 and the second insulator 33B of the intermediate body 20 of the sensor element 2. When the laminate of the sensor element 2 in which the first insulator 33A, the first buffer layers 331A and 331B, the solid electrolyte body 31, the second buffer layer 332, the adhesive layer 335, and the second insulator 33B are laminated is fired, the solvent in the adhesive layer 335 volatilizes, and the intermediate body 20 of the sensor element 2 and the second insulator 33B are firmly bonded by the adhesive layer 335.

[0035] Between the surface of the atmosphere-side protective layer 313 provided on the atmosphere electrode 312 and the second insulator 33B, a gap S is formed which is exposed to the atmosphere A flowing into the atmosphere duct 36. This configuration makes it easier for the atmosphere A to reach the surface of the atmosphere-side protective layer 313 from the gap S, and to reach the atmosphere electrode 312 via the atmosphere-side protective layer 313. This improves the detection accuracy of the air-fuel ratio, specific gases, etc. by the gas sensor 1.

[0036] (Heater 34) As shown in Figs. 2 and 3, the heater 34 is configured as a heating element for heating the solid electrolyte body 31, the exhaust electrode 311, and the atmosphere electrode 312, and is embedded in the second insulator 33B forming the atmosphere duct 36. The heater 34 has a heating part 341 that generates heat when energized, and a heater lead part connected to the base end side L2 of the heating part 341 in the longitudinal direction L. At least a part of the heating part 341 is disposed at a position overlapping the exhaust electrode 311 and the atmosphere electrode 312 in the stacking direction D. The heater 34 is configured of a metal material having electrical conductivity. The heater 34 may be embedded in the first insulator 33A.

[0037] (Outer protective layer 37) 2 and 3, a peripheral protective layer 37 for protecting the sensor element 2 from cracks due to exposure to water is provided on the outer periphery of the tip side L1 in the longitudinal direction L of the sensor element 2. The peripheral protective layer 37 is made of a ceramic material such as alumina (aluminum oxide) having pores through which exhaust gas G can pass.

[0038] (Method of manufacturing sensor element 2) As shown in Fig. 4, the sensor element 2 of this embodiment is formed by forming an intermediate body 20 in which a solid electrolyte body 31 provided with an exhaust electrode 311, an atmosphere electrode 312, and an atmosphere side protective layer 313, a first insulator 33A, first buffer layers 331A and 331B, and a second buffer layer 332 are laminated, and then laminating a second insulator 33B on the second buffer layer 332 in the intermediate body 20 via an adhesive layer 335. In order to properly maintain the laminated state of the components, the intermediate body 20 is compressed by applying pressure in the stacking direction D by a pressure-bonding member 8 or the like. At this time, the solid electrolyte body 31, the first insulator 33A, the first buffer layers 331A and 331B, the second buffer layer 332, and the like in the intermediate body 20 are compressed in the stacking direction D and come into close contact with each other.

[0039] When the intermediate body 20 is compressed, the second buffer layer 332 is formed to an appropriate thickness, which makes it difficult for the solid electrolyte body 31 to deform. In addition, an adhesive constituting an adhesive layer 335 is applied to at least one of the surface in the stacking direction D of the second buffer layer 332 of the intermediate body 20 after compression and the surface in the stacking direction D of the second insulator 33B, and the intermediate body 20 and the second insulator 33B are bonded together by the adhesive to form the stack of the sensor element 2. At this time, since the surface in the stacking direction D of the second buffer layer 332 of the intermediate body 20 is flat, the intermediate body 20 and the second insulator 33B can be firmly bonded together. Thereafter, when the stack of the sensor element 2 is fired, the adhesive becomes the adhesive layer 335, and the sensor element 2 is manufactured.

[0040] (Another configuration of gas sensor 1) As shown in FIG. 1, the gas sensor 1 has a housing 41, an element holding material 42, a terminal holding material 43, a contact member 431, a contact terminal 44, a tip end cover 45, a base end cover 46, a bush 47, lead wires 48, etc., for disposing the sensor element 2 in the exhaust pipe 7 and electrically wiring it to the sensor control device 5.

[0041] The housing 41 is used to fasten the gas sensor 1 to the mounting port 71 of the exhaust pipe 7. The housing 41 holds the sensor element 2 via the element holding material 42 and the like. The sensor element 2 is held by the element holding material 42 via glass 421, and the element holding material 42 is held by the housing 41 via crimping materials 422, 423, and 424. A terminal holding material 43 that holds a contact terminal 44 is connected to the base end side L2 of the element holding material 42 in the longitudinal direction L. The terminal holding material 43 is supported by the base end cover 46 by a contact member 431.

[0042] The contact terminal 44 electrically connects the electrodes 311, 312 and the heater 34 in the sensor element 2 to the lead wire 48. The contact terminal 44 is disposed in the terminal holding material 43 and is connected to the lead wire 48 via a connecting metal fitting 441.

[0043] As shown in FIG. 1, the tip cover 45 is provided on the tip side L1 in the longitudinal direction L of the housing 41, and covers the detection tip 21 of the sensor element 2. The tip cover 45 is formed with a gas circulation hole 451 through which the exhaust gas G contacting the sensor element 2 can flow. The detection tip 21 of the sensor element 2 and the tip cover 45 are disposed in an exhaust pipe 7 of an internal combustion engine. A part of the exhaust gas G flowing in the exhaust pipe 7 flows into the tip cover 45 from the gas circulation hole 451 of the tip cover 45. Then, the exhaust gas G in the tip cover 45 passes through the outer circumferential protective layer 37 and the diffusion resistance portion 32 of the sensor element 2 and is guided to the exhaust electrode 311.

[0044] The base-end cover 46 is provided on the base-end side L2 of the housing 41 in the longitudinal direction L, and covers the wiring portion located on the base-end side L2 of the gas sensor 1 in the longitudinal direction L to protect the wiring portion from water and the like contained in the atmosphere A. The wiring portion is composed of a contact terminal 44, which is a portion electrically connected to the sensor element 2, a connection portion (connection metal fitting 441) between the contact terminal 44 and the lead wire 48, and the like.

[0045] A bushing 47 that holds a plurality of lead wires 48 is held on the inner periphery of the base end cover 46 at a portion of the base end side L2 in the longitudinal direction L. The base end cover 46 is formed with an air inlet hole 461 for introducing air A from the outside of the gas sensor 1. The air inlet hole 461 is covered with a water-repellent filter 462. The base end position of the air duct 36 in the sensor element 2 is open to the space within the base end cover 46, and the air A is led to the air electrode 312 within the air duct 36.

[0046] (Sensor control device 5) As shown in Fig. 1, the lead wires 48 in the gas sensor 1 are electrically connected to a sensor control device 5 that controls gas detection in the gas sensor 1. The sensor control device 5 performs electrical control of the gas sensor 1 in cooperation with an engine control device 6 that controls the combustion operation of the engine. The sensor control device 5 is configured using various control circuits, a computer, etc. The sensor control device 5 may be built in the engine control device 6. The sensor control device 5 is configured using a circuit 511 that applies a DC voltage between the exhaust electrode 311 and the atmospheric electrode 312, a circuit 512 that detects a current flowing between the exhaust electrode 311 and the atmospheric electrode 312, etc.

[0047] (Action and effect) In the sensor element 2 of the gas sensor 1 of this embodiment, the second buffer layer 332 having a shape surrounding the atmosphere electrode 312 and the atmosphere-side protective layer 313 from the sides is laminated on the solid electrolyte body 31, and the second insulator 33B forming the atmosphere duct 36 for introducing the atmosphere A between the solid electrolyte body 31 and the second buffer layer 332 is laminated on the second buffer layer 332 via an adhesive layer 335. With this configuration, when pressure is applied to the intermediate body 20 in which the first insulator 33A, the first buffer layers 331A and 331B, the solid electrolyte body 31 and the second buffer layer 332 are laminated during the manufacture of the sensor element 2, the presence of the second buffer layer 332 makes it possible to suppress deformation of the portion of the solid electrolyte body 31 where the atmosphere electrode 312 and the atmosphere-side protective layer 313 are provided.

[0048] Moreover, the second buffer layer 332 and the second insulator 33B of the intermediate body 20 are firmly bonded together by the adhesive layer 335. With this configuration, the sensor element 2 is formed in a state in which deformation of the solid electrolyte body 31, in which the atmosphere-side protective layer 313 is provided on the atmosphere electrode 312, is suppressed. Deformation of the atmosphere-side protective layer 313 is also suppressed, making it possible to make it difficult for residual stress to occur in the sensor element 2.

[0049] According to the gas sensor 1 of this embodiment, the solid electrolyte body 31 in the sensor element 2 can be made less susceptible to deformation.

[0050] Furthermore, the sensor cell consisting of the solid electrolyte body 31, the exhaust electrode 311 and the atmosphere electrode 312 may be used as a temperature detection unit when controlling the temperature of the sensor element 2 by the heater 34, utilizing the relationship between the impedance value of the sensor cell and the temperature of the sensor cell. In this case, since the solid electrolyte body 31 is hardly deformed, it is possible to maintain good temperature detection and controllability.

[0051] <Embodiment 2> In this embodiment, as shown in FIG. 5, a sensor element 2 in which two solid electrolyte bodies 31A and 31B are stacked in a stacking direction D is shown. In this embodiment, a gas chamber 35 is formed between the inner surface of the first solid electrolyte body 31A and the inner surface of the second solid electrolyte body 31B, a first atmosphere duct 36A is formed on the outer surface of the first solid electrolyte body 31A, and a second atmosphere duct 36B is formed on the outer surface of the second solid electrolyte body 31B. In addition, the first solid electrolyte body 31A is provided with a first exhaust electrode 311A ​​accommodated in the gas chamber 35 and a first atmosphere electrode 312A accommodated in the first atmosphere duct 36A, and the second solid electrolyte body 31B is provided with a second exhaust electrode 311B accommodated in the gas chamber 35 and a second atmosphere electrode 312B accommodated in the second atmosphere duct 36B.

[0052] A first insulator 33A and first buffer layers 331A, 331B which form a first atmospheric duct 36A are arranged on one surface of the first solid electrolyte body 31A, a second buffer layer 332 which forms a gas chamber 35 is arranged between the first solid electrolyte body 31A and the second solid electrolyte body 31B, and a third buffer layer 333 and a second insulator 33B which form a second atmospheric duct 36B are arranged on the other surface of the second solid electrolyte body 31B via an adhesive layer 335.

[0053] An atmosphere-side protective layer 313 is provided on the surface of the first atmosphere electrode 312A and the surface of the second atmosphere electrode 312B. In this embodiment, as shown in FIG. 6, the intermediate body 20 in which the first solid electrolyte body 31A, the second solid electrolyte body 31B, the first insulator 33A, the second insulator 33B, the first buffer layers 331A and 331B, the second buffer layer 332, and the third buffer layer 333 are laminated is compressed by a compression member 8 or the like. Then, the third buffer layer 333 of the intermediate body 20 and the second insulator 33B are bonded by an adhesive that constitutes an adhesive layer 335. Then, the laminate of the sensor element 2 is fired.

[0054] 5, the thickness of the third buffer layer 333 is thinner than each of the first solid electrolyte body 31A and the second solid electrolyte body 31B, and is within a range of ±25% of the total thickness of the second atmosphere electrode 312B and the atmosphere-side protective layer 313 provided on the second atmosphere electrode 312B. With this configuration, when pressure is applied to the intermediate body 20 of the sensor element 2 in the stacking direction D to compress the intermediate body 20 during the manufacturing process of the sensor element 2, it is possible to make the second solid electrolyte body 31B less likely to deform.

[0055] A gap S exposed to the atmosphere A flowing into the atmosphere duct 36 is formed between the surface of the atmosphere side protective layer 313 provided on the first atmosphere electrode 312A and the first insulator 33A, and between the surface of the atmosphere side protective layer 313 provided on the second atmosphere electrode 312B and the second insulator 33B. This configuration makes it easier for the atmosphere A to reach the surface of the atmosphere side protective layer 313 from the gap S, and to reach each of the atmosphere electrodes 312A and 312B via the atmosphere side protective layer 313. This improves the detection accuracy of the air-fuel ratio, specific gases, etc. by the gas sensor 1.

[0056] Other configurations, functions, and effects of the sensor element 2 of this embodiment are similar to those of the sensor element 2 of embodiment 1. In this embodiment, the components denoted by the same reference numerals as those of embodiment 1 are similar to those of embodiment 1.

[0057] <Embodiment 3> This embodiment shows a sensor element 2 in which the relationship between the second buffer layer 332 and the protective layer is further improved. In the sensor element 2 of this embodiment, as shown in FIG. 7, in a cross section perpendicular to the longitudinal direction L, a pair of inner wall surfaces 332X of the second buffer layer 332 that form a part of the atmosphere duct 36 overlap a pair of side surfaces 313X of the atmosphere-side protective layer 313. In other words, a state is formed in which the atmosphere-side protective layer 313 contacts a pair of inner wall surfaces 332X in the width direction W that form a part of the atmosphere duct 36 in the second buffer layer 332. With this configuration, as shown in FIG. 8, when the intermediate body 20 of the sensor element 2 is pressure-bonded in the stacking direction D, the atmosphere-side protective layer 313 is supported by the pair of inner wall surfaces 332X of the second buffer layer 332, and pressure due to pressure bonding can be applied more uniformly to the intermediate body 20 of the sensor element 2.

[0058] In addition, the pair of inner wall surfaces 332X of the second buffer layer 332 in this embodiment are tapered in the stacking direction D of a cross section perpendicular to the longitudinal direction L, such that the spacing in the width direction W becomes narrower as the distance increases from the atmosphere electrode 312, in other words, as the distance increases toward the second insulator 33B. The atmosphere-side protective layer 313 is in close contact with the pair of tapered inner wall surfaces 332X of the second buffer layer 332 in the width direction W.

[0059] 8 shows a state in which the paste material constituting the atmosphere-side protective layer 313 is placed in the cutout of the second buffer layer 332. In this state, the paste material is received by a pair of tapered inner wall surfaces 332X, thereby preventing it from sagging downward due to gravity.

[0060] 9, when the intermediate body 20 of the sensor element 2 is pressure-bonded in the stacking direction D by the pressure-bonding member 8 or the like, the paste material constituting the atmosphere-side protective layer 313 is received by a pair of tapered inner wall surfaces 332X, and is therefore less likely to come into contact with the pressure-bonding member 8 or the like. Therefore, the surface of the second buffer layer 332 that overlaps with the second insulator 33B in the stacking direction D is appropriately contacted with the pressure-bonding member 8 or the like and is formed flat. As a result, when the second buffer layer 332 and the second insulator 33B of the intermediate body 20 of the sensor element 2 are bonded to each other via the adhesive layer 335, the second buffer layer 332 and the second insulator 33B are appropriately adhered to each other and can be firmly bonded to each other.

[0061] In this embodiment, as shown in FIG. 7, the atmosphere-side protective layer 313 is in contact with the second surface 302 of the solid electrolyte body 31 and a pair of inner wall surfaces 332X of the second buffer layer 332. In addition, in the stacking direction D of the sensor element 2, the position of the surface of the atmosphere-side protective layer 313 is substantially the same as the position of the surface of the second buffer layer 332. In addition, when the thickness of the atmosphere-side protective layer 313 in the stacking direction D is t3 and the thickness of the second buffer layer 332 in the stacking direction D is t4, the thickness ratio t3 / t4×100[%] may be within a range of 75[%] to 100[%]. In this case, when the intermediate body 20 of the sensor element 2 is pressure-bonded in the stacking direction D by the pressure-bonding member 8 or the like, it is possible to make the solid electrolyte body 31 less likely to deform.

[0062] In addition, a configuration in which this thickness ratio t3 / t4×100[%] is within the range of 75[%] to 100[%] may be applied to the relationship between the atmosphere-side protective layer 313 and the second buffer layer 332 in embodiment 1, or the relationship between the atmosphere-side protective layer 313 and the third buffer layer 333 in embodiment 2.

[0063] The configurations of the second buffer layer 332 and the atmosphere-side protective layer 313 of this embodiment may be applied to the third buffer layer 333 and the atmosphere-side protective layer 313 provided on the third buffer layer 333 shown in the second embodiment.

[0064] Other configurations, functions, and effects of the sensor element 2 of this embodiment are similar to those of the sensor element 2 of embodiment 1. In this embodiment, the components denoted by the same reference numerals as those of embodiment 1 are similar to those of embodiment 1.

[0065] The present invention is not limited to the respective embodiments, and further different embodiments can be configured without departing from the scope of the present invention. The present invention also includes various modified examples, modifications within the scope of equivalents, etc. Furthermore, the combinations and forms of various components envisioned from the present invention are also included in the technical spirit of the present invention. [Explanation of symbols]

[0066] 1 Gas sensor 2 Sensor element 31 Solid electrolyte body 311 Exhaust Electrode 312 Air Electrode 313 Atmospheric side protective layer 33A, 33B Insulator 331A,331B,332,333 Buffer layer 335 Adhesive layer 36 Air Duct

Claims

1. A gas sensor (1) comprising a sensor element (2), The sensor element includes: A solid electrolyte body (31, 31A, 31B) having ion conductivity; Electrodes (311, 312, 311A, 312A, 311B, 312B) provided on the surface of the solid electrolyte body; A porous protective layer (313) provided on the surface of the electrode; an insulating buffer layer (332, 333) having a shape surrounding the electrodes and the protective layer from the sides and laminated on the solid electrolyte body; an insulating insulator (33B) laminated on the buffer layer via an adhesive layer (335) and forming a gas introduction path for introducing a gas between the solid electrolyte body and the insulating insulator (33B); A gas sensor, wherein the thickness of the buffer layer is smaller than the thickness of the solid electrolyte body and is within a range of ±25% of the total thickness of the electrode and the protective layer.

2. A gas sensor (1) comprising a sensor element (2), The sensor element includes: A solid electrolyte body (31, 31A, 31B) having ion conductivity; Electrodes (311, 312, 311A, 312A, 311B, 312B) provided on the surface of the solid electrolyte body; A porous protective layer (313) provided on the surface of the electrode; an insulating buffer layer (332, 333) having a shape surrounding the electrodes and the protective layer from the sides and laminated on the solid electrolyte body; an insulating insulator (33B) laminated on the buffer layer via an adhesive layer (335) and forming a gas introduction path for introducing a gas between the solid electrolyte body and the insulating insulator (33B); A gas sensor, wherein in a cross section perpendicular to a longitudinal direction (L) of the sensor element, a pair of inner wall surfaces (332X) of the buffer layer forming a part of the gas introduction path overlap a pair of side surfaces (313X) of the protective layer.

3. 3. The gas sensor according to claim 2, wherein in a cross section perpendicular to the longitudinal direction of the sensor element, the pair of inner wall surfaces of the buffer layer are formed in a tapered shape such that the distance therebetween becomes narrower with increasing distance from the electrode.

4. 4. The gas sensor according to claim 2, wherein the thickness of the buffer layer is smaller than the thickness of the solid electrolyte body and is within a range of ±25% of the total thickness of the electrode and the protective layer.

5. The electrodes include exhaust electrodes (311, 311A, 311B) provided on a first surface (301) of the solid electrolyte body and exposed to exhaust gas (G), and air electrodes (312, 312A, 312B) provided on a second surface (302) of the solid electrolyte body and exposed to air (A) as the gas, the protective layer is provided on a surface of the air electrode, the buffer layer is laminated on the second surface of the solid electrolyte body, 5. The gas sensor according to claim 1, wherein an air duct (36, 36A, 36B) serving as the gas introduction path for introducing the air is formed between the insulator and the buffer layer and the second surface of the solid electrolyte body.

6. 6. The gas sensor according to claim 1, wherein a gap exposed to the gas introduced into the gas introduction path is formed between the surface of the protective layer and the insulator.

7. 7. The gas sensor according to claim 1, wherein the buffer layer and the insulator are made of the same ceramic material.

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