Gas Sensor

Abstract

To provide a gas sensor capable of suppressing the occurrence of cracks in a part of an insulator facing a through hole.SOLUTION: A gas sensor 1 includes a solid electrolyte 31, an electrode conductor 310, insulators 33A, 33B, and a heater conductor 34. In the heater through hole 331B formed at a position facing the heater conductor 34 in the insulator 33B, a conductive material 38 is placed. In a portion facing the heater through hole 331B in the heater conductor 34, a recess 343 that recesses from the surface located on the opposite side of the heater through-hole 331B is formed. In recess 343, an insulating material that is a part of insulator 33B is arranged as the convex portion 335.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] The gas sensor is disposed in an exhaust pipe of an internal combustion engine, and is configured to determine the concentration of oxygen, a specific gas, etc. contained in the exhaust gas flowing through the exhaust pipe as a detection target gas. The gas sensor is also configured to determine the air-fuel ratio of the internal combustion engine based on the exhaust gas. The gas sensor may use a laminated type sensor element in which a plate-shaped solid electrolyte body provided with an electrode conductor and an insulator provided with a heater conductor are laminated.

[0003] In a laminated type sensor element, terminal conductors are provided on both sides of the base end in the longitudinal direction of the sensor element in order to wire the electrode conductors and heater conductor to the outside of the sensor element. Furthermore, through holes in which conductive material is disposed are formed in the solid electrolyte body at positions facing the electrode conductors and in the insulator at positions facing the heater conductor. The electrode conductors and the terminal conductors, and the heater conductor and the terminal conductors are electrically connected by the conductive material disposed in the through holes.

[0004] For example, in the sensor element manufacturing method, sensor element, and gas sensor of Patent Document 1, it is described that the inner circumferential surface of the through hole is covered with an insulating paste, and the inside of the insulating paste is filled with a conductive paste. The insulating layer of the insulating paste prevents the insulation of the conductor by the conductive paste from becoming partially insufficient. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-136144 A Summary of the Invention [Problem to be solved by the invention]

[0006] When manufacturing a sensor element, a conductive paste having a predetermined viscosity due to containing a solvent is poured into a through hole penetrating an insulator in an intermediate body of the sensor element. Then, when the intermediate body of the sensor element is fired, etc., a cavity may be generated at the boundary between the surface of the heater conductor located on the opposite side of the through hole and the surface of the insulator due to drying and shrinkage of the conductive paste, and the difference in the amount of shrinkage between the insulating paste and the solid electrolyte body, the insulator, etc.

[0007] Stress is likely to concentrate around the cavity, and the concentration of stress may cause cracks in the insulator. Therefore, further measures are required to prevent cracks from occurring in the insulator at the portion facing the through hole.

[0008] The present invention has been made in view of the above-mentioned problems, and aims to provide a gas sensor capable of preventing cracks from occurring in the portion of the insulator facing the through hole. [Means for solving the problem]

[0009] One aspect of the present invention is a solid electrolyte body (31) made of a solid electrolyte material; an electrode conductor (310) made of a conductive material provided on the solid electrolyte body; an insulator (33A, 33B) made of an insulating material laminated on at least one of a first surface (301) and a second surface (302) of the solid electrolyte body; a heater conductor (34) made of a conductive material embedded in the insulator; a conductive material (38) having the same composition as or different from the conductive material of the electrode conductor or the heater conductor is disposed in a through hole (331A, 331B) formed in the insulator at a position facing the electrode conductor or the heater conductor, A recess (343) is formed in a portion of the electrode conductor or the heater conductor facing the through hole, the recess (343) being recessed from a surface located on the opposite side of the through hole, In the gas sensor (1), a part of an insulating layer (334) made of the insulating material sandwiched between base materials (332, 333) constituting the insulator is filled and arranged in a state of swelling as a protrusion (335) in the recess, and the thickness of the insulating material constituting the insulating layer is 9 μm or more and 30 μm or less. Another aspect of the present invention is a solid electrolyte body (31) made of a solid electrolyte material; an electrode conductor (310) made of a conductive material provided on the solid electrolyte body; an insulator (33A, 33B) made of an insulating material laminated on at least one of a first surface (301) and a second surface (302) of the solid electrolyte body; a heater conductor (34) made of a conductive material embedded in the insulator; a conductive material (38) having the same composition as or different from the conductive material of the electrode conductor or the heater conductor is disposed in a through hole (331A, 331B) formed in the insulator at a position facing the electrode conductor or the heater conductor, a through-hole recess (344) is formed in the electrode conductor or the heater conductor at a portion facing the through-hole, the through-hole penetrating the electrode conductor or the heater conductor; The through recess is provided with the insulator A part of the insulating layer (334) made of the insulating material sandwiched between the base materials (332, 333) constituting the insulating layer (334) is bulged as a protrusion (336). Located in the gas sensor (1). Effect of the Invention

[0010] In the gas sensor according to the above embodiment, the shape of the electrode conductor or heater conductor at the position facing the through hole of the insulator is devised. Specifically, a recess recessed from the surface located on the opposite side of the through hole or a through recess penetrating the electrode conductor or heater conductor is formed at the portion of the electrode conductor or heater conductor facing the through hole of the insulator. The recess or the through recess is formed when the heater conductor is provided in the insulator.

[0011] An insulating material that is a part of the insulator is disposed in the recess or the through recess. With this configuration, when the sensor element is heated during manufacture or use of the gas sensor, stress concentration can be prevented from occurring at the interface between the insulator and a surface of the heater conductor that faces the through hole and is located on the opposite side of the through hole.

[0012] Therefore, according to the gas sensor of the above aspect, it is possible to make it difficult for cracks to occur in the portion of the insulator facing the through hole.

[0013] 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]

[0014] [Figure 1] FIG. 1 is an explanatory diagram showing a gas sensor according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing the sensor element according to the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III of FIG. 2, showing the sensor element according to the first embodiment. [Figure 4] FIG. 4 is a perspective view showing the sensor element according to the first embodiment in a state where each component is disassembled. [Diagram 5] FIG. 5 is a cross-sectional view showing the periphery of a heater through hole according to the first embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing the periphery of a heater through hole according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A preferred embodiment of the above-mentioned gas sensor will now be described with reference to the drawings. <Embodiment 1> 1 to 3, the gas sensor 1 of this embodiment includes a solid electrolyte body 31, an electrode conductor 310, insulators 33A and 33B, and a heater conductor 34. The solid electrolyte body 31 is made of a solid electrolyte material. The electrode conductor 310 is made of a conductive material and is provided on the solid electrolyte body 31. The insulators 33A and 33B are made of an insulating material and are laminated on the first surface 301 and the second surface 302 of the solid electrolyte body 31. The heater conductor 34 is made of a conductive material and is embedded in the insulator 33B.

[0016] A conductive material 38 having the same or different composition as the conductive material of the electrode conductor 310 is disposed in an electrode through hole 331A formed in the insulator 33A at a position facing the electrode conductor 310. A conductive material 38 having the same or different composition as the conductive material of the heater conductor 34 is disposed in a heater through hole 331B formed in the insulator 33B at a position facing the heater conductor 34. A recess 343 is formed in the heater conductor 34 at a portion facing the heater through hole 331B, recessed from the surface located on the opposite side to the heater through hole 331B. An insulating material that is part of the insulator 33B is disposed in the recess 343.

[0017] The gas sensor 1 of this embodiment will be described in detail below. (Gas sensor 1) As shown in Fig. 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 oxygen concentration, specific gas concentration, etc., of exhaust gas G flowing through the exhaust pipe 7 as the detection target gas. The gas sensor 1 can be used as an air-fuel ratio sensor (A / F sensor) that determines the air-fuel ratio in an internal combustion engine based on the oxygen concentration, unburned gas concentration, etc., in the exhaust gas G. The air-fuel ratio sensor can quantitatively and continuously detect the air-fuel ratio from a fuel-rich state in which the ratio of fuel to air is higher than the stoichiometric air-fuel ratio to a fuel-lean state in which the ratio of fuel to air is lower than the stoichiometric air-fuel ratio.

[0018] 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.

[0019] (Sensor element 2) 2 and 3, the solid electrolyte body 31, the electrode conductor 310, the second insulators 33A and 33B, and the heater conductor 34 are stacked on one another to form a stacked type sensor element 2. The sensor element 2 is formed in a long rectangular shape, and is held in a housing 41 by an element holding material 42 described later.

[0020] The electrode conductor 310 of this embodiment is composed of an exhaust electrode 311 provided on the first surface 301 of the solid electrolyte body 31, an air electrode 312 provided on the second surface 302 of the solid electrolyte body 31, and an electrode lead portion 313 connected to the exhaust electrode 311 and the air electrode 312. The second insulators 33A and 33B are composed of a first insulator 33A laminated on the first surface 301 of the solid electrolyte body 31 and a second insulator 33B laminated on the second surface 302 of the solid electrolyte body 31. The heater conductor 34 is embedded in the second insulator 33B. The heater conductor 34 may be embedded in the first insulator 33A.

[0021] (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.

[0022] (Solid electrolyte body 31, exhaust electrode 311, and air electrode 312) As shown in FIGS. 2 and 3, the solid electrolyte body 31 converts oxygen ions (O 2- ) conductivity. An exhaust electrode 311 exposed to exhaust gas G is provided on a first surface 301 of the solid electrolyte body 31, and an air electrode 312 exposed to air A is provided on a second surface 302 of the solid electrolyte body 31. The exhaust electrode 311 and the air electrode 312 are arranged in positions overlapping each other in the stacking direction D via the solid electrolyte body 31 at a portion of the tip side L1 exposed to exhaust gas G in the longitudinal direction L of the sensor element 2.

[0023] A sensor cell 21 is formed at a portion on the tip side L1 in the longitudinal direction L of the sensor element 2, which includes an exhaust electrode 311, an atmospheric electrode 312, and a portion of the solid electrolyte body 31 sandwiched between these electrodes 311, 312. In this embodiment, one sensor cell 21 is formed in the sensor element 2 to configure an air-fuel ratio sensor. Alternatively, a plurality of sensor cells 21 may be formed in the sensor element 2 to configure, for example, a NOx (nitrogen oxide) sensor. In this case, a plurality of sets of electrodes are used.

[0024] 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 (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.

[0025] 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. As shown in Figs. 1 and 2, an electrode lead portion 313 is connected to the exhaust electrode 311 and the atmosphere electrode 312 for electrically connecting the electrodes 311, 312 to the outside of the gas sensor 1. The electrode lead portion 313 is drawn out to a portion of the base end side L2 in the longitudinal direction L of the sensor element 2. A terminal connection portion 22 connected to the electrode lead portion 313 is formed on the surface of the first insulator 33A at the end of the base end side L2 in the longitudinal direction L of the electrode lead portion 313.

[0026] (Gas Chamber 35) 2 and 3, a gas chamber 35 surrounded by the first insulator 33A and the solid electrolyte body 31 is formed adjacent to the first surface 301 of the solid electrolyte body 31. The gas chamber 35 is formed at a position on the tip side L1 of the first insulator 33A in the longitudinal direction L, where the gas chamber 35 accommodates the exhaust electrode 311. The gas chamber 35 is formed as a space enclosed by the first insulator 33A, the diffusion resistance portion 32, and the solid electrolyte body 31. Exhaust gas G flowing in the exhaust pipe 7 passes through the diffusion resistance portion 32 and is introduced into the gas chamber 35.

[0027] (Diffusion resistor 32) 2 and 3, the diffusion resistance portion (gas inlet portion) 32 in this embodiment is provided on both sides in the width direction W of the gas chamber 35. The diffusion resistance portion 32 is formed by disposing a porous body of a metal oxide such as aluminum oxide in an inlet formed in the first insulator 33A. 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 at a portion on the tip side L1 in the longitudinal direction L of the gas chamber 35.

[0028] (Atmospheric Duct 36) 2 to 4, an air duct 36, into which the air A is introduced, is formed adjacent to the second surface 302 of the solid electrolyte body 31 and is surrounded by the second insulator 33B and the solid electrolyte body 31. The air duct 36 is formed from a portion of the second insulator 33B in the longitudinal direction L that houses the air electrode 312 to a base end position in the longitudinal direction L of the sensor element 2.

[0029] (Insulators 33A and 33B) As shown in Fig. 2 to Fig. 4, the first insulator 33A forms the gas chamber 35, and the second insulator 33B forms the air duct 36 and embeds the heater conductor 34. The first insulator 33A and the second insulator 33B are made of a metal oxide such as alumina (aluminum oxide). Each of the insulators 33A and 33B is formed as a dense body through which the exhaust gas G or the air A cannot permeate.

[0030] (Heater conductor 34) As shown in Figs. 3 and 4, the heater conductor 34 is configured as a heating element and is embedded in the second insulator 33B forming the air duct 36. The heater conductor 34 has a heating portion 341 that generates heat when current is applied, and a heater lead portion 342 connected to the base end side L2 of the heating portion 341 in the longitudinal direction L. The heating portion 341 is disposed at a position where at least a part of the heating portion 341 overlaps with the exhaust electrode 311 and the air electrode 312 in the stacking direction D of the solid electrolyte body 31 and the insulators 33A and 33B. The heater conductor 34 is made of a metal material having electrical conductivity. A terminal connection portion 22 connected to the heater lead portion 342 is formed at an end portion of the base end side L2 of the heater lead portion 342 in the longitudinal direction L.

[0031] (Surface protective layer 37) 1, a surface protection layer 37 that covers the sensor cell 21 is formed on a tip side L1 in the longitudinal direction L of the sensor element 2. The surface protection layer 37 is made of a plurality of ceramic particles bonded together as a ceramic material having pores through which exhaust gas G can pass.

[0032] (Configuration of another sensor element 2) Although not shown in the drawings, the sensor element 2 is not limited to having one solid electrolyte body 31, and may have a plurality of solid electrolyte bodies 31. The electrode conductor 310 is provided on each of the plurality of solid electrolyte bodies 31.

[0033] (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.

[0034] 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.

[0035] The contact terminal 44 comes into contact with the terminal connection portion 22 connected to the base end of the electrode lead portion 313 in the sensor element 2, and the terminal connection portion 22 connected to the base end of the heater lead portion 342, to electrically connect the electrode lead portion 313 and the heater lead portion 342 to the lead wire 48. The contact terminal 44 is connected to the lead wire 48 via a connecting metal fitting 441 while being disposed within the terminal holding material 43.

[0036] 1, the tip side cover 45 is provided on the tip side L1 in the longitudinal direction L of the housing 41, and covers the sensor cell 21 of the sensor element 2. The tip side cover 45 is formed with a gas circulation hole 451 through which exhaust gas G contacting the sensor element 2 can flow. The sensor cell 21 of the sensor element 2 and the tip side 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 side cover 45 from the gas circulation hole 451 of the tip side cover 45. Then, the exhaust gas G in the tip side cover 45 passes through the surface protection layer 37 and the diffusion resistance portion 32 of the sensor element 2 and is guided to the exhaust electrode 311.

[0037] 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 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.

[0038] 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.

[0039] (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.

[0040] (Electrode through hole 331A of first insulator 33A) 5, a conductive material 38 is disposed in an electrode through hole 331A formed in the first insulator 33A at a position facing the electrode lead portion 313 of the electrode conductor 310. A terminal connection portion 22 made of a conductive material is provided in a portion facing the electrode through hole 331A on the outer surface of the first insulator 33A. The electrode lead portion 313 of the electrode conductor 310 and the terminal connection portion 22 are electrically connected by the conductive material 38 disposed in the electrode through hole 331A.

[0041] The electrode through hole 331A facing the electrode lead portion 313 of the exhaust electrode 311 is formed in a state where it penetrates the first insulator 33A in the stacking direction D. The electrode through hole 331A facing the electrode lead portion 313 of the atmosphere electrode 312 is formed in a state where it penetrates the first insulator 33A and the solid electrolyte body 31 in the stacking direction D. The conductive material 38 in each electrode through hole 331A is arranged in a state where it fills each electrode through hole 331A.

[0042] (Heater through hole 331B of second insulator 33B) 5, a conductive material 38 is disposed in each heater through hole 331B formed in the second insulator 33B at a position facing a pair of heater lead portions 342 of the heater conductor 34. A terminal connection portion 22 made of a conductive material is provided in a portion facing each heater through hole 331B on the outer surface of the second insulator 33B. The heater lead portion 342 of the heater conductor 34 and the terminal connection portion 22 are electrically connected by the conductive material 38 disposed in each heater through hole 331B.

[0043] Heater through hole 331B facing heater lead portion 342 is formed in a state where it penetrates second insulator 33B in stacking direction D. Conductive material 38 in heater through hole 331B is arranged in a state where it fills heater through hole 331B.

[0044] (Recess 343) 5, the recess 343 of the heater conductor 34 is formed in a portion of the heater lead portion 342 of the heater conductor 34 facing the heater through hole 331B. The recess 343 in this embodiment is formed such that a portion of the heater lead portion 342 of the heater conductor 34 is thinner than the other portion. The recess 343 is formed to be recessed in a curved shape.

[0045] (Structure around heater through hole 331B) As shown in Fig. 4 and Fig. 5, the second insulator 33B is formed by joining a plurality of substrates 332, 333 together so as to sandwich the heater conductor 34 therebetween. The heater conductor 34 in this embodiment is embedded between the inner substrate 332 forming the air duct 36 and the outer substrate 333 laminated on the outer side of the inner substrate 332 in the lamination direction D. The heater conductor 34 is provided on the surface of the outer substrate 333 constituting the second insulator 33B. A part of the insulating layer 334 made of an insulating material sandwiched between the inner substrate 332 and the outer substrate 333 is arranged in a bulging state as a protrusion 335 in the recess 343 of the heater lead portion 342 of the heater conductor 34.

[0046] The heater conductor 34 in this embodiment is provided on the outer base material 333 by pattern printing, and is sandwiched between the outer base material 333 and an insulating layer 334 made of insulating paste as an insulating material provided on the surface of the inner base material 332. In other words, the insulating layer 334 is provided between the surface of the inner base material 332, the surface of the outer base material 333, and the surface of the heater conductor 34 on the outer base material 333.

[0047] By arranging the protrusion 335 of the insulating layer 334 in the recess 343 of the heater lead 342, it is possible to prevent a cavity from being generated at the boundary between the second insulator 33B and the heater lead 342 when the sensor element 2 is heated. The sensor element 2 is heated when the sensor element 2 is fired during the manufacture of the sensor element 2, when electricity is passed through the heater conductor 34, or when the sensor element 2 is used as part of the gas sensor 1. In addition, by using the insulating layer 334 made of insulating paste, it is possible to easily fill the recess 343 of the heater lead 342 with a part of the insulating material.

[0048] The insulating paste is made of an insulating material such as aluminum oxide similar to the second insulator 33B. The insulating paste constitutes the insulator 33B after the sensor element 2 is fired. In the intermediate body of the sensor element 2 in which the first insulator 33A, the second insulator 33B, the solid electrolyte body 31, etc. are laminated, a part of the insulating paste is disposed in the recess 343 of the heater lead portion 342 of the heater conductor 34. Then, in the sensor element 2 after firing, the insulating paste is integrated with the inner base material 332 and the outer base material 333, and a part of the second insulator 33B is disposed in the recess 343 of the heater lead portion 342.

[0049] In the sensor element 2, the heater lead portion 342 of the heater conductor 34 and the conductive material 38 are integrated. Therefore, the recess 343 may be formed in a state where it is recessed in the heater lead portion 342 and the conductive material 38. In addition, the outer base material 333 is formed by laminating two sheets, and a part 381 of the conductive material 38 filled in the heater through hole 331B permeates the gap between the outer base materials 333 and the outer surface of the outer base material 333.

[0050] The thickness of the insulating paste of the insulating layer 334 may be set within a range of, for example, 9 μm to 30 μm. With this configuration, the insulating paste is appropriately filled into the recesses 343 of the heater lead portions 342 of the heater conductor 34. Furthermore, the thickness of the heater lead portions 342 of the heater conductor 34 may be set within a range of, for example, 10 μm to 30 μm. With this configuration, the conductivity of the heater lead portions 342 can be ensured and the recesses 343 can be easily formed. Furthermore, the size (diameter) of the heater through holes 331B may be set within a range of φ200 μm to φ300 μm.

[0051] The recess 343 of the heater lead portion 342 of the heater conductor 34 is formed to have a depth of 5 μm or more and a maximum diameter of 100 μm or more and 300 μm or less in a central portion facing the heater through hole 331B. The maximum diameter refers to the length of the portion where the diameter is largest. In other words, the depth of the deepest portion of the recess 343 is 5 μm or more, and the maximum diameter of the recess 343 is 100 μm or more and 300 μm or less. The planar shape of the recess 343 does not necessarily have to be circular.

[0052] If the depth of the deepest part of the recess 343 is less than 5 μm, the cavity will become larger so that the recess 343 becomes deeper when the sensor element 2 is heated, and there is a risk that the effect of preventing stress concentration from occurring at the interface between the heater lead portion 342 of the heater conductor 34 and the insulating layer 334 will not be obtained. The depth of the deepest part of the recess 343 is set to be within the range of 5 μm to 450 μm, regardless of the thickness of the heater lead portion 342. The recess 343 is filled with an insulating paste that constitutes the insulating layer 334 by applying pressure to the stack of green sheets to press the green sheets together.

[0053] By setting the maximum diameter of the recess 343 to be equal to or greater than 100 μm and equal to or less than 300 μm, it is easy to form the recess 343 in relation to the size of the heater through hole 331B.

[0054] (Method of manufacturing sensor element 2) A method for manufacturing the sensor element 2 will be described below. In manufacturing the sensor element 2, the green sheet of the solid electrolyte body 31 and the green sheets of the first insulator 33A and the second insulator (base material) 33B are molded by extrusion molding, doctor blade molding, or the like. Next, the heater through-holes 331B are formed in the green sheets of the first insulator 33A and the second insulator 33B by a punching device, or the like. Next, the electrode conductor 310 is formed in the green sheet of the solid electrolyte body 31 by pattern printing. Also, the electrode through-holes 331A in the green sheet of the first insulator 33A and the heater through-holes 331B in the green sheet of the second insulator 33B are filled with a conductive material 38, and the heater conductor 34 is formed in the green sheet of the second insulator 33B by pattern printing.

[0055] In addition, the surface of the heater lead portion 342 of the heater conductor 34 facing the heater through hole 331B is pressed to form a recess 343 on the surface of the heater lead portion 342. Next, the green sheet of the solid electrolyte body 31 and the green sheets of the first insulator 33A and the second insulator 33B are stacked on top of each other. At this time, an insulating paste is applied to the green sheet constituting the inner base material 332 of the second insulator 33B so that the insulating paste is sandwiched between the inner base material 332 and the outer base material 333 of the second insulator 33B. Then, pressure is applied to the stack of green sheets so that the green sheets are in close contact with each other, and the green sheets are pressed together. At this time, the insulating paste in the inner base material 332 of the second insulator 33B becomes the insulating layer 334 and fills the recess 343 of the heater lead portion 342.

[0056] Thereafter, the laminate of green sheets is fired to produce the sensor element 2. When the laminate of green sheets is fired, the inner base material 332, the outer base material 333 and the insulating layer 334 are bonded together to form the second insulator 33B.

[0057] The recess 343 on the surface of the heater lead 342 may be formed not by application of external pressure, but by a part of the heater lead 342 being drawn into the heater through hole 331B when the conductive material 38 filled in the heater through hole 331B thermally shrinks. The conductive material 38 contains a solvent. When the green sheet laminate is dried or fired, the solvent in the conductive material 38 volatilizes, forming the recess 343.

[0058] (Action and effect) In the gas sensor 1 of this embodiment, the shape of the heater conductor 34 at a position facing the heater through hole 331B of the second insulator 33B is devised. Specifically, a recess 343 recessed from the surface located on the opposite side to the heater through hole 331B is formed in the heater lead portion 342 of the heater conductor 34 at a portion facing the heater through hole 331B of the second insulator 33B. The recess 343 is formed when the heater conductor 34 is provided on the green sheet of the second insulator 33B.

[0059] An insulating material that is a part of the second insulator 33B is disposed in the recess 343. With this configuration, when the sensor element 2 is heated during the manufacture or use of the gas sensor 1, stress concentration can be prevented from occurring at the interface between the second insulator 33B and a surface of the heater conductor 34 that faces the heater through hole 331B and is located on the opposite side of the heater through hole 331B.

[0060] Therefore, according to the gas sensor 1 of this embodiment, it is possible to make it difficult for cracks to occur in the portion of the second insulator 33B facing the heater through hole 331B.

[0061] 5, a portion of the heater lead portion 342 of the heater conductor 34 that forms the recess 343 may protrude into the heater through hole 331B along a depression 383 formed on the inner end surface of the conductive material 38 filled in the heater through hole 331B. In this case, the recess 343 is formed by bending a portion of the heater lead portion 342 toward the heater through hole 331B.

[0062] In this case, the recess 343 is formed by at least one of the following: when the conductive material 38 filled in the heater through hole 331B thermally shrinks, a part of the heater lead portion 342 is attracted to the heater through hole 331B; and when the solvent in the conductive material 38 volatilizes, the conductive material 38 dries and shrinks. In the sensor element 2, the heater lead portion 342 of the heater conductor 34 and the conductive material 38 are integrated. Therefore, in the sensor element 2, it is not necessary to clearly distinguish between the heater lead portion 342 and the conductive material 38.

[0063] <Embodiment 2> 6, this embodiment shows a case where a through recess 344 is formed in a heater lead portion 342 of a heater conductor 34, and a conductive material 38 is formed on the inner peripheral surface of a heater through hole 331B. A part of an insulating layer 334 made of an insulating material sandwiched between an inner base material 332 and an outer base material 333 is arranged in a bulging state as a protrusion 336 in the through recess 344 of the heater lead portion 342 of the heater conductor 34.

[0064] The through recess 344 is formed by a hole penetrating the heater lead portion 342 in the stacking direction D, and a tapered opening 345 is formed at the edge of the surface of the through recess 344 located on the opposite side to the heater through hole 331B. The conductive material 38 is disposed on the inner circumferential surface of the heater through hole 331B, so that a through center portion 382 penetrating the conductive material 38 is formed at the center of the heater through hole 331B. A part of the insulating layer 334 of the second insulator 33B is disposed as a protrusion 336 in the through recess 344 of the heater lead portion 342 and the through center portion 382 of the heater through hole 331B.

[0065] In this embodiment, since the through recess 344 is formed in the heater lead portion 342, the conductive material 38 is disposed in the heater through hole 331B by penetrating the heater lead portion 342. This makes it possible to prevent cracks from occurring in the portion of the second insulator 33B facing the heater through hole 331B.

[0066] In the gas sensor 1 of this embodiment, the configurations of the inner substrate 332, the outer substrate 333, the insulating layer 334, etc. of the second insulator 33B are the same as those in the embodiment 1. Other configurations, functions, effects, etc. of the gas sensor 1 of this embodiment are the same as those of the embodiment 1. Also, in this embodiment, components denoted by the same reference numerals as those in the embodiment 1 are the same as those in the embodiment 1.

[0067] <Other embodiments> Although details are omitted, a recess recessed from the surface located on the opposite side of the electrode through hole 331A, or a penetrating recess penetrating the electrode lead portion 313, may be formed in a portion of the electrode lead portion 313 of the exhaust electrode 311 serving as the electrode conductor 310 facing the electrode through hole 331A. In this case, an insulating material that is a part of the first insulator 33A is disposed in the recess or the penetrating recess.

[0068] 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]

[0069] 1 Gas sensor 2 Sensor element 31 Solid electrolyte body 310 Electrode conductor 33A, 33B Insulator 331A,331B Through hole 34 Heater conductor 343 Recess 344 Through recess

Claims

1. A solid electrolyte body (31) made of a solid electrolyte material; An electrode conductor (310) made of a conductive material provided on the solid electrolyte body; an insulator (33A, 33B) made of an insulating material laminated on at least one of a first surface (301) and a second surface (302) of the solid electrolyte body; a heater conductor (34) made of a conductive material embedded in the insulator; a conductive material (38) having the same or different composition as the conductive material of the electrode conductor or the heater conductor is disposed in a through hole (331A, 331B) formed in the insulator at a position facing the electrode conductor or the heater conductor, A recess (343) is formed in a portion of the electrode conductor or the heater conductor facing the through hole, the recess being recessed from a surface located on the opposite side of the through hole, The gas sensor (1) has a recess in which a portion of an insulating layer (334) made of the insulating material sandwiched between base materials (332, 333) constituting the insulator is filled and arranged in a bulging state as a convex portion (335), and the insulating material that becomes the insulating layer has a thickness of 9 μm or more and 30 μm or less.

2. 2. The gas sensor according to claim 1, wherein the recess is formed at a central portion facing the through hole with a depth of 5 μm or more and a maximum diameter of 100 μm to 300 μm.

3. The heater conductor is composed of a heat generating portion (341) that generates heat when current is applied and a heater lead portion (342) connected to the heat generating portion, 3. The gas sensor according to claim 1, wherein the recess is formed in the heater lead at a portion facing the through hole.

4. 4. The gas sensor according to claim 1, wherein a portion of the heater conductor that forms the recess protrudes into the through hole along a depression (383) formed in an inner end surface of the conductive material filled in the through hole.

5. A solid electrolyte body (31) made of a solid electrolyte material; An electrode conductor (310) made of a conductive material provided on the solid electrolyte body; an insulator (33A, 33B) made of an insulating material laminated on at least one of a first surface (301) and a second surface (302) of the solid electrolyte body; a heater conductor (34) made of a conductive material embedded in the insulator; a conductive material (38) having the same or different composition as the conductive material of the electrode conductor or the heater conductor is disposed in a through hole (331A, 331B) formed in the insulator at a position facing the electrode conductor or the heater conductor, a through-hole recess (344) is formed in the electrode conductor or the heater conductor at a portion facing the through-hole, the through-hole penetrating the electrode conductor or the heater conductor; In the gas sensor (1), a portion of the insulating layer (334) made of the insulating material, which is sandwiched between the base materials (332, 333) constituting the insulator, is arranged in a bulging state as a convex portion (336) in the through recess.

6. The heater conductor is composed of a heat generating portion (341) that generates heat when current is applied and a heater lead portion (342) connected to the heat generating portion, 6. The gas sensor according to claim 5, wherein the through recess is formed in a portion of the heater lead portion facing the through hole.

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