JP7600914B2 - Gas Sensors - Google Patents

Description

The present invention relates to a gas sensor.

The gas sensor is disposed in the exhaust pipe of an internal combustion engine, and is configured to determine the concentration of oxygen, specific gases, etc. contained in the exhaust gas flowing through the exhaust pipe as the 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.

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

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.

JP 2016-136144 A

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

Stress tends to concentrate around this cavity, and this concentration of stress can cause cracks in the insulator. Therefore, further ingenuity is required to prevent cracks from occurring in the area of the insulator facing the through hole.

The present invention was made in consideration of these problems, and aims to provide a gas sensor that can reduce the likelihood of cracks occurring in the portion of the insulator facing the through hole.

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 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) is configured such that 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 protrusion (335) in the recess, and the insulating material constituting the insulating layer has a thickness of 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 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;
The gas sensor (1) has a through recess in which 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 gas sensor of 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, in the portion of the electrode conductor or heater conductor facing the through hole of the insulator, a recess is formed that is recessed from the surface located on the opposite side of the through hole, or a through recess that penetrates the electrode conductor or heater conductor is formed. This recess or through recess is formed when the heater conductor is provided in the insulator.

An insulating material that is part of the insulator is disposed in the recess or through recess. This configuration makes it possible to prevent stress concentration from occurring at the interface between the insulator and the surface of the heater conductor that faces the through hole and is located on the opposite side of the through hole when the sensor element is heated during manufacture or use of the gas sensor.

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

Note that the reference numerals in parentheses for each component shown in one aspect of the present invention indicate the corresponding reference numerals in the figures in the embodiment, but do not limit each component to only the contents of the embodiment.

FIG. 1 is an explanatory diagram showing a gas sensor according to a first embodiment. FIG. 2 is a cross-sectional view showing the sensor element according to the first embodiment. FIG. 3 is a cross-sectional view of the sensor element according to the first embodiment taken along line III-III of FIG. FIG. 4 is a perspective view showing the sensor element according to the first embodiment in a state where each component is disassembled. FIG. 5 is a cross-sectional view showing the periphery of a heater through hole according to the first embodiment. FIG. 6 is a cross-sectional view showing the periphery of a heater through hole according to the second embodiment.

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.

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

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.

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.

(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 the stacked sensor element 2. The sensor element 2 is formed in a long rectangular shape, and is held in the housing 41 by an element holding material 42, which will be described later.

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.

(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, 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 addition, in the longitudinal direction L of the sensor element 2, the side exposed to the exhaust gas G is referred to as a tip side L1, and the opposite side of the tip side L1 is referred to as a base side L2.

(Solid electrolyte body 31, exhaust electrode 311, and air electrode 312)
2 and 3, the solid electrolyte body 31 has oxygen ion (O ²⁻ ) conductivity at a predetermined activation temperature. 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 tip side L1 exposed to exhaust gas G in the longitudinal direction L of the sensor element 2.

At the tip end L1 of the sensor element 2 in the longitudinal direction L, a sensor cell 21 is formed, which is made up of 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 form an air-fuel ratio sensor. In addition, multiple sensor cells 21 may be formed in the sensor element 2 to form, for example, a NOx (nitrogen oxide) sensor. In this case, multiple sets of electrodes are used.

The solid electrolyte body 31 is made of a zirconia-based oxide, and is composed of stabilized zirconia or partially stabilized zirconia, with zirconia as the main component (containing 50% by mass or more) and with a rare earth metal element or an alkaline earth metal element replacing a portion of the zirconia. A portion of the zirconia constituting the solid electrolyte body 31 is replaced by yttria, scandia, or calcia.

The exhaust electrode 311 and the air electrode 312 contain platinum as a precious metal that exhibits 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, the exhaust electrode 311 and the air electrode 312 are connected to an electrode lead portion 313 for electrically connecting these electrodes 311, 312 to the outside of the gas sensor 1. The electrode lead portion 313 is drawn out to the base end side L2 of 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 of the longitudinal direction L of the electrode lead portion 313.

(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 in the longitudinal direction L of the first insulator 33A, 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 through the exhaust pipe 7 passes through the diffusion resistance portion 32 and is introduced into the gas chamber 35.

(Diffusion resistance portion 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.

(Atmospheric duct 36)
2 to 4, an air duct 36, into which 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 the base end position in the longitudinal direction L of the sensor element 2.

(Insulators 33A and 33B)
2 to 4, the first insulator 33A forms the gas chamber 35, and the second insulator 33B forms the atmospheric 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 atmospheric air A cannot pass.

(Heater conductor 34)
As shown in Fig. 3 and Fig. 4, the heater conductor 34 is configured as a heating element and is embedded in the second insulator 33B forming the atmospheric 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 the exhaust electrode 311 and the atmospheric 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 of the base end side L2 of the heater lead portion 342 in the longitudinal direction L.

(Surface protective layer 37)
1, a surface protection layer 37 is formed on a tip end side L1 in the longitudinal direction L of the sensor element 2 to cover the sensor cell 21. 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.

(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.

(Other configurations 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 an exhaust pipe 7 and electrically wiring it to a sensor control device 5.

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 to the element holding material 42 via glass 421, and the element holding material 42 is held to 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.

The contact terminal 44 contacts 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, and electrically connects 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 the connection fitting 441 while being disposed within the terminal holding material 43.

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

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 the contact terminal 44, which is electrically connected to the sensor element 2, and the connection portion (connection metal fitting 441) between the contact terminal 44 and the lead wire 48.

A bushing 47 that holds multiple lead wires 48 is held on the inner periphery of the base end cover 46 at 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 outside 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 inside the base end cover 46, and the air A is led to the air electrode 312 in the air duct 36.

(Sensor control device 5)
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.

(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.

The electrode through hole 331A facing the electrode lead portion 313 of the exhaust electrode 311 is formed in a state in which it penetrates the first insulator 33A in the stacking direction D. The electrode through hole 331A facing the electrode lead portion 313 of the air electrode 312 is formed in a state in which 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 in which it fills each electrode through hole 331A.

(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.

The heater through hole 331B facing the heater lead portion 342 is formed in a state in which it penetrates the second insulator 33B in the stacking direction D. The conductive material 38 in the heater through hole 331B is arranged in a state in which it fills the heater through hole 331B.

(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.

(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 atmospheric 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. In the recess 343 of the heater lead portion 342 of the heater conductor 34, 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.

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

By arranging the protrusion 335 of the insulating layer 334 in the recess 343 of the heater lead portion 342, it is possible to prevent a cavity from being generated at the boundary between the second insulator 33B and the heater lead portion 342 when the sensor element 2 is heated. The sensor element 2 is heated when the sensor element 2 is baked during the manufacture of the sensor element 2, when electricity is passed through the heater conductor 34, etc., 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 a portion of the insulating material into the recess 343 of the heater lead portion 342.

The insulating paste is made of an insulating material such as aluminum oxide, similar to the second insulator 33B. The insulating paste forms the insulator 33B after the sensor element 2 is fired. In the intermediate sensor element 2 in which the first insulator 33A, the second insulator 33B, the solid electrolyte body 31, etc. are laminated, a portion 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 portion of the second insulator 33B is disposed in the recess 343 of the heater lead portion 342.

In addition, 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 made up of two laminated sheets, and a portion 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.

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

The recess 343 of the heater lead portion 342 of the heater conductor 34 is formed with a depth of 5 μm or more and a maximum diameter of 100 μm or more and 300 μm or less in the central portion facing the heater through hole 331B. The maximum diameter refers to the length of the portion with the largest diameter. 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.

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 in 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.

By having the maximum diameter of the recess 343 be 100 μm or more and 300 μm or less, it is easy to form the recess 343 in relation to the size of the heater through hole 331B.

(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 (substrate) 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. In addition, 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.

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 provided on 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 multiple green sheets are in close contact with each other, and the green sheets are pressed together. At this time, the insulating paste on 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.

Then, the green sheet stack is fired to produce the sensor element 2. When the green sheet stack 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.

In addition, the recess 343 on the surface of the heater lead portion 342 may be formed not by applying external pressure, but by a part of the heater lead portion 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.

(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 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 being recessed from the surface located on the opposite side to the heater through hole 331B. The recess 343 is formed when the heater conductor 34 is provided on the green sheet of the second insulator 33B.

An insulating material that is part of the second insulator 33B is disposed in the recess 343. This configuration makes it possible to prevent stress concentration from occurring at the interface between the 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, and the second insulator 33B when the sensor element 2 is heated during the manufacture or use of the gas sensor 1.

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.

5, the 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.

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 evaporates, 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.

<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.

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 of the heater through hole 331B. The conductive material 38 is disposed on the inner peripheral 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.

In this embodiment, the heater lead portion 342 is provided with a through recess 344, so that the conductive material 38 passes through the heater lead portion 342 and is disposed in the heater through hole 331B. This makes it possible to prevent cracks from occurring in the portion of the second insulator 33B facing the heater through hole 331B.

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 first embodiment. Other configurations, functions, effects, etc. of the gas sensor 1 of this embodiment are the same as those of the first embodiment. Also, in this embodiment, components denoted by the same reference numerals as those in the first embodiment are the same as those in the first embodiment.

<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.

The present invention is not limited to the embodiments, and further different embodiments can be constructed without departing from the gist 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 the various components envisioned from the present invention are also included in the technical concept of the present invention.

REFERENCE SIGNS LIST 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 (6)

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. The gas sensor according to claim 1, wherein the recess is formed in a central portion of the portion facing the through hole with a depth of 5 μm or more and a maximum diameter of 100 μm or more and 300 μm or less. 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. The gas sensor according to any one of claims 1 to 3, wherein the portion of the heater conductor that forms the recess protrudes into the through hole along a depression (383) formed in the inner end surface of the conductive material filled in the through hole. 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. 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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