JP5056723B2 - Gas sensor element - Google Patents

Description

  The present invention relates to an improvement in durability and moisture resistance of a gas sensor element used in a gas sensor for measuring a specific gas component concentration in combustion exhaust gas discharged from an internal combustion engine such as an automobile engine.

Conventionally, a gas sensor for detecting the concentration of a specific gas component such as oxygen, nitrogen oxides, ammonia, and hydrogen contained in the combustion exhaust gas is disposed in the combustion exhaust flow path of the internal combustion engine such as an automobile engine, and the internal combustion engine. Combustion control and exhaust gas purification device control.
As such a gas sensor, for example, in the case of an oxygen sensor, an oxygen ion conductive solid electrolyte layer formed in a flat plate shape, and a measurement electrode layer formed on one surface of the solid electrolyte layer and in contact with the gas to be measured A porous diffusion resistance layer that is formed on the measurement electrode layer side and transmits the gas to be measured; a reference electrode layer that is formed on the other surface of the solid electrolyte layer and is in contact with a reference gas; and the reference electrode layer A laminated gas sensor element is used which is formed by laminating a reference gas chamber forming layer having a reference gas chamber which is formed on the side and into which the reference gas is introduced, and an insulating substrate having a heating element therein.

  On the other hand, the combustion exhaust as the fluid to be measured contains poisonous substances composed of oil-containing components such as P, Ca, Zn, and Si and gasoline-added components such as K, Na, and Pb. The measurement electrode layer and the porous diffusion layer of the element may be contaminated with these poisoning substances, which may cause problems such as deterioration in response of the gas sensor and abnormal output. The combustion exhaust gas also contains water vapor, which may condense and form water droplets that adhere to the stacked gas sensor element.

In addition, in such a stacked gas sensor element, the solid electrolyte layer is heated and activated at a high temperature of, for example, 700 ° C. or higher by a built-in heating element so as to exhibit ionic conductivity with respect to specific ions. in use.
For this reason, adhesion of water droplets in the measurement gas atmosphere (water exposure) may cause a large thermal shock to the stacked gas sensor element and cause water cracking of the element.

  Therefore, by forming a porous protective layer with a predetermined film thickness on the outer peripheral surface of the gas sensor element, the poisoning substance is captured in the porous protective layer to prevent malfunction, or when water droplets adhere, Is dispersed in the porous protective layer to relieve thermal shock and prevent the entire device from cracking (see Patent Documents 1 and 2).

  Such a porous protective layer is, for example, a fluid to be measured of a gas sensor element in a slurry in which a heat-resistant ceramic powder such as alumina having a predetermined particle size distribution is dispersed in a dispersion medium such as water or an organic solvent together with an inorganic binder and a dispersant. It is obtained by immersing (dipping) a portion exposed to the inside to form a film of the slurry on the outer peripheral surface of the gas sensor element, and drying and sintering the film (see Patent Document 1).

For example, as such a conventional gas sensor element, a gas sensor element 10 _Z shown in FIG. 8A has a measurement electrode layer 110 _Z formed on one surface of a solid electrolyte layer 100 _Z formed in a flat plate shape, and the other forms a reference electrode layer 120 _Z in the plane, the reference gas chamber forming layer 131 _Z to form the reference gas chamber 130 _Z for introducing the atmosphere disposed as a reference gas are stacked on the side of the reference electrode layer 120 _Z, further the measurement electrode layer 110 _Z sensor unit 11 disposed diffusion resistance layer 160 _Z made of a porous material laminated on the side of _Z ungated, inside the heating element of the plate-shaped insulator ₁₄₀ is formed on the Z, 141 _Z 150 _Z is provided to form the heater unit 14 _Z, and the sensor unit 11 _Z and the heater unit 14 _Z are laminated and fired to form an integrated gas sensor element.
JP 2006-126077 A JP 2007-121323 A

However, the surface of the gas sensor element 10 _Z of substantially rectangular cross-section, the protective layer forming material such as alumina and dispersant and an inorganic binder or the like are dispersed in a dispersion medium such as water or an organic solvent to adjust the slurry or paste , dipping, brushing, spraying, by wet methods such as printing when you try to form a porous protective layer 170 _Z, as shown in FIG. 8 (a), the porous protective layer 170 under the influence of surface tension _Z The film thicknesses t _HTR Z, t _SN Z, and t _SD Z of the heat generating surface S _HTR Z, the sensor surface S _SN Z, and the side surface S _SD Z are the thickest at the center portions of the respective planes, and the planes intersect. It has been found that the ridge line L _Z , that is, the vicinity of the edge in the longitudinal direction of the gas sensor element 10 _z becomes thin.

Thus the porous protective layer 170 _Z in a state in which the thickness distribution occurs dried and sintered, stress during drying shrinkage and the sintering shrinkage in the vicinity of the ridge line L _Z within the porous protective layer 170 _Z concentrated, there is a possibility that the porous protective layer 170 _Z is divided into boundary ridgeline L _Z. The porous protective layer 170 _Z decreases adhesion strength between the gas sensing element 10Z and the porous protective layer 170 _Z is by being divided in the ridge line L _Z, was found to be easily peeled off.

In addition, in the heater unit 14 _Z formed in a substantially rectangular cross section, with respect to the heat generating surface direction of the plate thickness _t 141 _{Z 1} and side direction of thickness _{ts 141} Z of the insulator 141 _Z, heating elements incorporated The distance t ₁₄₁ Z ₂ from the edge of 150 _{Z to} the ridgeline L _Z is long.
Therefore, when heating of the heating element 0.99 _Z, a temperature gradient is generated inside the heater unit 14 _Z, the thermal stress. With such gas sensor element 10 _Z state is exposed to water, there is a fear that readily gas sensor element by the synergistic stress of the internal stress of the thermal shock and the heater unit 14 _Z by the water are destroyed.

On the other hand, as shown in FIG. 8B, in the gas sensor element 10 _X , in addition to the same configuration as the gas sensor element 10Z, a C-shaped ridge surface C _X is formed at least on the element tip side along the edge in the longitudinal direction. By forming it in the heat generating region and having a substantially hexagonal or octagonal cross section, the distance from the edge of the heating element 150 _{X to} the surface of the ridge surface C _X is shortened, and the surface of the heating element 150 _X to the heating surface S _HTR achieving uniformity of the heating value and the calorific value of the 2 Sided C _X direction in the X direction, it is expected to alleviate the thermal stress generated inside the heater unit 14 _Z.
However, also in the gas sensor element 10 _X having a structure for reducing such thermal stress, the side surface side ridge line L _1X where the ridge surface C _X and the side surface S _SD X intersect, or the ridge surface C _X and the heat generating surface S _HTR X in the heat generating surface side ridge line L _2X which intersect, as with the gas sensor element 10 _Z of the above-mentioned rectangular section, the thickness of the porous protective layer 170 _X is locally thinner, porous protective layer 170 _X is divided, peeling There is a risk of inviting.

  Therefore, in view of such circumstances, the present invention is a gas sensor element used in a gas sensor for detecting the concentration of a specific gas component in a gas to be measured, and the porous protective layer covering the surface of the gas sensor element is unlikely to peel off. An object of the present invention is to provide a gas sensor element having excellent durability.

According to the first aspect of the present invention, there is provided a sensor unit that is placed in the measured gas flow path and detects the concentration of a specific component in the measured gas, and is formed in a substantially flat plate shape, and the sensor unit stacked on the sensor unit. A heater portion formed in a substantially flat plate shape that heats and activates, and at least along the edge in the longitudinal direction of the heater portion, a multiple ridge surface portion composed of at least two ridge surfaces is provided, In the gas sensor element in which a predetermined range of the outer peripheral surface of the gas sensor element including the multiple ridge surface portion is surrounded by a porous protective layer formed by a wet method, the multiple ridge surface portion is at least a side surface ridge continuous with the heater portion side surface. The porous protective layer is formed on a side-side ridge line where the side-side ridge surface and the side surface of the heater part intersect with each other. Protective layer film Was a side surface side thickness t _1, and the thickness of the porous protective layer formed on the heat generating surface side on the edge line and the heat generating surface side ridge surface and the heater unit heating surface intersects with the heat generating surface side thickness t ₂ At this time, it is set to a range satisfying the relationship of the following formula 1.
1.0 · t ₁ ≦ t ₂ ≦ 1.6 · t ₁ Formula 1

As a result of diligent tests by the present inventors, it has been found that by setting the film thickness of the porous protective layer within the scope of the invention of claim 1, peeling of the porous protective layer can be more effectively suppressed.
According to the first aspect of the present invention, since the angle gradually changes from the heat generation surface of the heater portion to the side surface through the multiple ridge surface portion set in a predetermined range, it is formed using a wet method. Local thinning of the porous protective layer thickness is suppressed, and even if the porous protective layer shrinks during drying and sintering, it is divided at the boundary between the heating surface and the side surface of the heater part. In addition, the adhesion strength between the porous protective layer and the gas sensor element is increased, and peeling is less likely to occur. Therefore, the durability of the gas sensor element used in the gas sensor for detecting the specific gas component concentration in the gas to be measured is improved.

According to a second aspect of the present invention, there is provided a sensor unit that is placed in the measurement gas flow path and that is formed in a substantially flat plate shape for detecting the concentration of a specific component in the measurement gas, and the sensor unit is stacked on the sensor unit. A heater portion formed in a substantially flat plate shape that heats and activates, and at least along the edge in the longitudinal direction of the heater portion, a multiple ridge surface portion composed of at least two ridge surfaces is provided, In the gas sensor element in which a predetermined range of the outer peripheral surface of the gas sensor element including the multiple ridge surface portion is surrounded by a porous protective layer formed by a wet method, the multiple ridge surface portion is at least a side surface ridge continuous with the heater portion side surface. And a heating surface side ridge surface connected to the heating surface of the heater portion, and the height from the heat generation surface of the heater portion to the side surface ridge line where the side surface ridge surface intersects the side surface of the heater portion is the side surface side. Ridge height H ₁ And then, when the heat generating surface side ridge surface height H ₂ the height of the ridge intersects with the heat generating surface side ridge surface and the side surface side ridge surface from the heating surface of the heater unit, the range satisfying the relation of the following formula 2 Provided.
1/2 · H ₁ ≤ H ₂ ≤ 3/4 · H ₁ ... Formula 2

By setting the multiple ridge surface portions within the scope of the invention according to claim 2 through an intensive test by the present inventors, it is possible to suppress peeling of the porous protective layer and effectively prevent water cracking of the gas sensor element. It was found that it can be suppressed.

The gas sensor element of the present invention is provided in a combustion exhaust passage of an internal combustion engine such as an automobile engine, and detects specific gas components such as oxygen, NO _x , NH ₃ , and HC (hydroxycarbon) contained in the combustion exhaust, It is used for a gas sensor used for engine combustion control, combustion exhaust treatment control, and the like.
The gas sensor element 10 used in the oxygen sensor having the most basic configuration as the gas sensor element in the first embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a cross-sectional view of the gas sensor element 10 in the present embodiment, and FIG.

As shown in FIG. 1, the gas sensor element 10 is configured by laminating a sensor portion 11 and a heater portion 14 formed in a substantially flat plate shape, and the outer peripheral surface thereof is covered with a porous protective layer 170.
Between the side surface S _SD of the heater 14 and the heat generating surface S _HTR along the longitudinal direction of the edge, a main part of the present invention, multiple crest surfaces S _1, S ₂ comprising a plurality of ridges surfaces formed Has been.
The side surface _{S SD} side surface side ridge surface _{S 1} is formed in a predetermined edge surface height _{H 1} as a first edge surface with a predetermined angle theta ₁ with respect to the heat generating surface _{S HTR,} heating surface _{S HTR} side Is provided with a predetermined angle θ ₂ with respect to the heat generating surface _SHTR , and a heat generating surface side ridge surface S ₂ is formed with a predetermined ridge surface height H _{2 as a second} ridge surface.
Further, the thickness _{t 1} of the porous protective layer 170 on the side face side ridgeline _{L 1} which is the side surface _{S SD} and the side side edge surface _{S 1} intersects a heat generating surface _{S HTR} and the heat generating surface side ridge surface _{S 2} intersects heating between the film thickness t ₂ on the side ridgeline L _2, the relationship of the following formula 1 is satisfied.
t ₁ ≦ t ₂ ≦ 1.6 · t ₁ Formula 1
Between the side surface side ridge surface height H ₁ and the heat generating surface side ridge surface height H _2, the relationship of the following formula 2 is satisfied.
1/2 · H ₁ ≤ H ₂ ≤ 3/4 · H ₁ ... Formula 2

  The sensor unit 11 is formed by laminating the solid electrolyte layer 100 formed into a flat plate shape, the measurement electrode layer 110 formed on the surface of the solid electrolyte layer 100 on the side in contact with the gas to be measured, and the measurement electrode layer 110 side. A porous diffusion resistance layer 160 that transmits the measured gas under a predetermined diffusion resistance, and a reference electrode layer 120 that is formed on the other surface of the solid electrolyte layer 100 and is in contact with the atmosphere introduced as a reference gas The reference gas chamber forming layer 131 is formed by laminating on the reference electrode layer 120 side to form a reference gas chamber 130 for introducing a reference gas. The heater part 14 is laminated on the inner side of the insulating bases 140 and 141 formed in a flat plate shape to form a heating element 150.

In the present embodiment, θ ₁ is provided in the range of 40 degrees to 50 degrees, and θ ₂ is provided in the range of 17.5 degrees to 27.5 degrees.
The thickness _{t 1} of the porous protective layer 170 on the side face side ridgeline _{L 1} is formed in about 125Myuemu～250myuemu, thickness _{t 2} of the porous protective layer 170 on the heating side ridgeline _{L 2} is 200 m to It is formed to about 250 μm. However, the thickness _{t 2} of the porous protective layer 170 on the film thickness _{t 1} and the heating side ridgeline _{L 2} of the porous protective layer 170 on the side face side ridgeline _{L 1,} the heat generating surface side edge line thickness _{t 2} it is desirable to set to the side surface side edge line thickness t ₁ in the range of 1.0 times 1.6 times. On the other hand, edge surface height _{H 1} of the side surface side edge surface _{S 1} is provided in a range of 0.2mm to 0.4 mm, ridge surface height of _{H 2} heat generating surface side ridge surface _{S 2} is from 0 to 0.1 mm. It is provided in a range of 3 mm. However, the heat generating surface side ridge surface height H ₂ relative to the side surface side ridge surface height H ₁ can be set from the third range of 4 minutes from one half.
Further, the plate thicknesses t ₁₄₀ and t ₁₄₁ of the insulating bases ₁₄₀ and ₁₄₁ are formed in the range of 150 μm to 170 μm, and the gas sensor element 10 as a whole is formed to have a plate thickness of 1.4 mm and a width of about 3.4 mm. It is formed in a length corresponding to the measured gas flow path.

The surface temperature of the sensor surface S _SN is lower temperature than the heat generating surface S _HTR of the heater unit 11, furthermore, the solid electrolyte layer 100 and the diffusion resistance layer 160 constituting the sensor unit 11, is porous hardly originally produce the water cracking because of their high resistance to thermal stress for, but further the durability of the sensor portion 11 by forming a similar multi-edge surface also between the side surface S _SD and the sensor surface S _SN It can also be improved.

A method for manufacturing the gas sensor element 10 according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is an _exploded perspective view of the gas sensor element stack 10 _{STK having} the most basic configuration, and FIG. 3 is a perspective view showing an outline of a manufacturing method of the gas sensor element 10 in order from (a) to (d). It is.

  In the solid electrolyte layer 100, an oxygen ion conductive ceramic material such as zirconia is dispersed in a dispersion medium such as toluene and ethanol together with a binder such as polyvinyl butyral (PVB), a plasticizer such as dibutyl phthalate (DBP), and a dispersant. It is obtained by blending the slurry and using it to form a flat plate having a predetermined thickness by the doctor blade method or the like.

  The measurement electrode layer 110 and the measurement electrode lead part 111 are printed on the surface of the solid electrolyte layer 100 on the gas to be measured, and the reference electrode layer 120 and the reference electrode lead part 121 are printed on the other surface. For these print formations, a paste or the like in which a platinum paste and the above-described slurry for forming a solid electrolyte layer are mixed is used.

  The reference gas chamber 130 is formed into a sheet shape by a doctor blade method using a slurry in which an insulating ceramic material such as alumina is dispersed in a dispersion medium together with PBV, DBP, a dispersant, etc. A plurality of reference gas chamber forming layers 131 punched into a U shape are stacked and formed.

Using the above-mentioned insulating ceramic sheet, a flat insulating substrate 141 is formed, and a heating element 150 and a pair of heating element leads 151 and 152 are formed using a paste obtained by mixing platinum paste and alumina slurry on one surface thereof. And a pair of heating element terminal portions 155 and 156 are printed on the other surface, and the heating element lead portions 151 and 152 and the heating element terminal portion 155 are placed in a pair of through holes formed in the insulating base 141. Through-hole electrodes 153 and 154 that are electrically connected to 156 are formed by suction printing or the like.
An insulating base 140 similar to the insulating base 141 is disposed on the printed side of the heat generating body 150 of the insulating base 141 to form the heater unit 14 containing the heat generating body 150.

Using a slurry obtained by laminating the solid electrolyte layer 100 on the side where the measurement electrode layer 110 is formed and dispersing a heat-resistant ceramic material such as alumina having a particle diameter coarser than the above-described alumina sheet together with a binder in a dispersion medium. A diffusion resistance layer 160 is formed. Note that the diffusion resistance layer 160 may be formed by laminating a flat plate as shown in the figure, or may be printed to cover the measurement electrode layer 110.
In addition, an insulating layer 161 is formed of an insulating ceramic sheet similar to the insulating base 141 to be stacked on the side where the measurement electrode lead portion 111 is formed to protect the measurement electrode lead portion 111. The insulating layer 161 protects the measurement electrode lead part 111 and prevents the gas to be measured passing through the diffusion resistance layer 160 from diffusing to the opening end side of the reference gas chamber 130 into which the reference gas is introduced.
The measurement electrode terminal portion 112 and the reference electrode terminal portion 122 are printed on the surface of the protective layer 161, and the measurement electrode lead portion 11 and the measurement electrode terminal portion 112 are electrically connected to each other in the through hole formed in the protective layer 161. A through-hole electrode 123 that conducts the hole electrode 113 and the reference electrode lead 121 and the reference electrode terminal 122 is formed by suction printing or the like.

By laminating the sensor part 11 and the heater part 14 as described above, a bottomed cylindrical gas sensor element laminate 10 _STK as shown in FIG. 3A can be formed. In addition, when laminating each layer, an integral laminate may be formed by adhesive lamination using an adhesive layer paste in which materials of the layers to be laminated are appropriately mixed, or may be integrated by thermocompression bonding. .

The resulting gas sensor element laminate 10 _STK heat generating surface S _HTR both sides of the side surface of the S _SD and four sides of the longitudinal direction of the ridge of the four corners formed by the two faces present invention the sensor surface S _SN The multiple ridge surface portions S ₁ and S ₂ that are essential portions are formed to obtain the gas sensor ridge surface forming body 10 _SPD .
At least, so as to extend in the long lower direction on both sides of the heat generating surface _{S HTR,} a side surface side ridgeline _{L 1} intersects the side surface _{S SD} and the side side edge surface _{S 1,} the heat generating surface _{S HTR} a heat generating surface side ridge surface _{S 2} heat generating surface side ridge line L ₂ intersecting the is formed.

As a specific method of forming the multiple ridge surface portions S ₁ and S ₂ , either a method of forming a ridge surface before firing the gas sensor element laminate 10 _{STK or} a method of forming a ridge surface after firing may be used. When the multiple ridge surface portions S ₁ and S ₂ are formed before firing, the processing accuracy may be inferior, but the time required for processing is short and extremely easy. On the other hand, when the multiple ridge surface portions S ₁ and S ₂ are processed after firing, since the strength of the fired body is high, processing takes time, but the dimensional accuracy is excellent.

For example, in order to form a plurality of gas sensor elements at the same time, when the gas sensor laminate 10 _STK formed by taking a plurality of pieces is laminated, a V-shaped groove is provided, and the gas sensor laminate 10 is divided into individual sides. _A C-shaped first ridge surface S ₁ can be formed at four corners of the _STK . This may be further formed a second edge face S ₂ by polishing.
In the case of processing before firing, it is also possible to form the multiple ridge surface portions S ₁ and S ₂ by heat compression using the thermoplasticity of the sheet molding material.
After the gas sensor element ridge surface forming body 10 _SPD thus obtained is fired, as shown in FIG. 3C, a porous protective layer 170 is formed on the surface using a wet technique. As a more specific wet method, for example, a protective layer forming material such as alumina, a dispersing agent, an inorganic binder, and the like are dispersed in a dispersion medium such as water or an organic solvent, and adjusted to a slurry, and a gas sensor element The ridge surface forming body 10 _SPD is immersed, a predetermined range of the ridge surface forming body 10 _SPD of the gas sensor element is coated with a porous protective layer forming material, and dried and sintered, whereby the gas sensor element 10 can be obtained. .

At this time, the angle change of the ridge surface is moderated by the multiple ridge surface portions S ₁ and S ₂ . For this reason, the porous protective layer 170 can be formed while maintaining a relatively uniform film thickness without being divided by the ridgelines L ₁ , L ₂ , and L ₃ .
The present invention exhibits a particularly excellent effect when the porous protective layer 170 is formed by dipping. However, in the present invention, the method for forming the porous protective layer 170 is not limited to dipping. .
For example, the porous protective layer material may be adjusted to a paste form, and the porous protective layer 170 may be formed by brushing or printing, or the porous protective layer material may be formed into a slurry form and sprayed to form a porous layer. A protective layer 170 may be formed. Alternatively, a porous protective layer material adjusted to a slurry shape is formed into a sheet shape by a doctor blade method or the like, and is attached so as to cover the portion exposed to the gas to be measured of the gas sensor element ridge surface forming body 10 _SPD. Layer 170 may be formed.
Even when the porous protective layer 170 is formed by any method, the angle of the ridge surface is gradually changed by the multiple ridge surface portions S ₁ and S ₂ . Thus, there is no possibility that the porous protective layer 170 is divided at the ridgelines L ₁ and L ₂ .
The multiple ridge surface portions S ₁ and S ₂ may be formed by a plurality of flat ridge surfaces formed of two or more, or may be formed by a curved surface that is continuously curved.

The effects of the present invention will be described with reference to FIGS.
4, the thickness _{t 2} of the porous protective layer 170 on the heat generating surface side ridge line _{L 2} is formed to a predetermined thickness (e.g. 200 [mu] m), the thickness of the porous protective layer 170 on the side face side ridgeline _{L 1} t It is a characteristic view which shows the test result which investigated the generation | occurrence | production frequency of protective layer peeling at the time of forming ₁ changing (for example, 110-250 micrometers).
As shown in FIG. 4, when the heat generating surface side ridge line thickness t ₂ is formed relatively thin with respect to the side surface ridge line thickness t ₁ , that is, t ₂ / t ₁ is smaller than 1. If the separation of the porous protective layer 170 on the heat generating surface side ridge surface S ₂ is generated, the heat generating surface side edge line thickness t ₂ to the side surface side edge line thickness t ₁ is from 1.6 times In other words, when t ₂ / t ₁ is larger than 1.6, the porous protective layer 170 is peeled on the side surface ridge surface S ₁ . Therefore, it is desirable to set the heating side edge line thickness t ₂ in the range of 1.0 times the lateral side edge line thickness t ₁ 1.6-fold was found.

As shown in FIG. 5A, the side surface side ridge surface S _{1 is formed} to a predetermined value (for example, θ ₁ = 45 degrees, H ₁ = 0.4 mm), and the heat generation surface side ridge surface S ₂ is θ _{2 is set} to 22.5 degrees, and S ₂ (1), S ₂ (2), and S ₂ (so that H ₂ is 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, and 0.3 mm. 3), S ₂ (4), S ₂ (5) were changed, and water cracking test was performed on Sample 1, Sample 2, Sample 3, Sample 4, and Sample 5 provided with the porous protective layer 170 under the same conditions. The results are shown in FIG. In this figure (a), in order to clarify the characteristics of each sample, the porous protective layer 170 is omitted.
Further, the method of the water cracking test, the heater unit 11 and the energization, dropwise 0.5μl of water droplets on the heat generating surface side ridge surface S ₂ of the gas sensor element 10 heated to a temperature on the heat generating surface S _HTR to 700 ° C. And it was done by investigating the occurrence of water cracking.
As shown in this figure (b), by providing multiple ridge surface portions S ₁ and S ₂ , water cracking is reduced, and the ridge surface height H ₂ of the heat generating surface side ridge surface S ₂ is set to the side surface ridge surface S ₁ . It has been found that water cracking can be further suppressed by setting the ridge surface height H ₁ to be in the range of 1/2 or more and 3/4 or less.

FIG. 6 shows the overall configuration of the gas sensor 1 including the gas sensor element 10 of the present invention.
The gas sensor 1 includes a gas sensor element 10, a housing 30 that holds the gas sensor element 10 inside the insulating holding member 20, cover bodies 50 and 51 that cover a portion of the gas sensor element 10 that is exposed to the gas to be measured, and the gas sensor element. And a casing 40 holding a pair of signal lines 115 and 125 for taking out an output signal from the gas sensor element 10.
The housing 30 is made of a metal such as stainless steel and is formed in a substantially cylindrical shape. A casing 40 is fitted on the boss portion 32 on the proximal end side, and a double tubular shape is formed on the caulking portion 34 on the distal end side. Cover bodies 50 and 51 are fixed.
A screw portion 33 is formed on the middle outer peripheral portion of the housing 30 and is screwed to a flow path wall 60 of an annual combustion exhaust flow path 600 of an internal combustion engine (not shown) via a gasket 37, so that the gas sensor detection element 10. The distal end side is disposed in the gas flow channel 600 to be measured and is fixed in a state covered with the cover bodies 50 and 51.
The housing 30 is formed with a hexagonal portion 35 for tightening the screw portion 33.

The cover bodies 50 and 51 are made of a heat-resistant metal such as stainless steel and have a double cylinder structure including a substantially bottomed cylindrical inner cover 50 and an outer cover 51.
The inner cover 50 and the outer cover 51 are respectively formed with openings 501, 503, 511, 512 for introducing the gas to be measured into the gas sensor element 10 to prevent the gas sensor element 10 from being exposed to water, and a flange portion 503 provided on the base end side. 513 is fixed to the caulking portion 34 of the housing 30 by caulking.

  The gas sensor element 10 is fixed inside the housing 30 by the insulator 20 while ensuring insulation from the housing 30. The tip of the gas sensor element 10 exposed to the gas to be measured is covered with a porous protective layer 170.

  The pair of signal lines 115 and 125 and the pair of energization lines 158a and 158b are held in the casing base end part 411 by the base end insulating sealing material 420, and are connected to the sensor via the connection fittings 114, 124, 157a and 157b. The element 10 is connected to the measurement electrode terminal 112, the reference electrode terminal 122, and the heating element energization terminals 155 and 156, respectively.

  A reference gas inlet 412 is formed in the base end insulating sealing material 420, and the atmosphere introduced from the reference gas inlet 412 through the water repellent filter 421 is introduced into the reference gas chamber 130 of the gas sensor element 10. Has been.

  When the heating element 150 is energized by an energization control device (not shown) and the solid electrolyte layer 100 is activated by the heating element 150, the oxygen concentration in the measurement gas that is in contact with the measurement electrode layer 110 via the diffusion resistance layer 160. And the difference in oxygen concentration in the atmosphere introduced into the reference gas chamber 130 in contact with the reference electrode layer 120 causes a potential difference between the two electrodes. By measuring this, the oxygen concentration in the gas to be measured can be detected. .

The present invention is not limited to the above-described embodiment. As shown in FIG. 7A, the gas sensor element 10a includes a heater part 14a and a sensor part 11a, and at least the heater part 14a side of the gas sensor element 10a. The present invention is intended to suppress peeling of the porous protective layer 170 and prevent water sensor cracking of the gas sensor element 10a by forming at least two or more ridge surfaces S ₁ and S ₂ at the longitudinal edges of the gas sensor element 10a. The present invention can be changed as appropriate without departing from the spirit of the invention, and any sensor function can be applied to the sensor unit 11a.

  For example, as shown in FIG. 5B, oxygen pump cells 100a, 110a, 120a, 180, and 181 that adjust oxygen concentration in the gas chamber 133a to be pumped by oxygen, and oxygen in the gas chamber 133a to be measured. Oxygen monitor cells 100b, 110b, 110d for detecting concentrations, sensor cells 100b, 110c, 110d for detecting specific gas component concentrations in the gas to be measured, air-fuel ratio detection cells 120a, 110d for detecting the air-fuel ratio of the gas to be measured, The measurement gas side electrode 120a in the air-fuel ratio detection cells 120a, 110d and the pump electrode 120a in the oxygen pump cells 100a, 110a, 120a, 180, 181 are made common, and the reference gas in the oxygen monitor cells 100b, 110b, 110d The side electrode 110d and the sensor cells 100b and 110 , A reference gas side electrode 110d in 110d, it is capable of applying to an air-fuel ratio detection cell 120a, the composite gas sensor element 10a or the like in common the three electrodes of the reference gas side electrode 110d in 110d.

  In the above embodiment, the case where an oxygen ion conductive solid electrolyte is used as the solid electrolyte constituting the sensor unit 11 used in an oxygen sensor, a NOx sensor, an air-fuel ratio sensor, and the like has been described. The present invention is not limited to such a gas sensor that detects an oxygen-derived gas component, but can be applied to any gas sensor such as a gas sensor that detects a hydrogen component-containing gas such as ammonia or hydrocarbon using a proton conductive solid electrolyte.

These show the outline | summary of the gas sensor element in the 1st Embodiment of this invention, (a) is sectional drawing, (b) is a principal part enlarged view which shows the characteristic part of this invention. The expansion | deployment perspective view of the laminated body which comprises the gas sensor element in the 1st Embodiment of this invention. The perspective view which shows the outline | summary of the manufacturing process of the gas sensor element in the 1st Embodiment of this invention later on in order of (a) to (d). The characteristic view which shows the result of the test done about the effect with respect to peeling of this invention. The effect with respect to the moisture crack of this invention is shown, (a) is principal part sectional drawing which shows the outline | summary of each sample, (b) is a characteristic view which shows the test result of each sample. Sectional drawing which shows the whole structure of the gas sensor using the gas sensor element in the 1st Embodiment of this invention. (A) is sectional drawing which shows the characteristic of the gas sensor element in other embodiment of this invention, (b) is a perspective view shown as the example. The problems of the conventional gas sensor element are shown. (A) is a sectional view when the longitudinal edge of the gas sensor element is not chamfered, and (b) is the chamfered edge of the gas sensor element. Sectional drawing when being done.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Gas sensor element 11 Sensor part 100 Solid electrolyte layer 110 Measurement electrode 120 Reference electrode 130 Reference gas chamber 14 Heater part 140, 141 Insulating base | substrate 150 Heating body 160 Diffusion resistance layer 170 Porous protective layer L ₁ 1st ridgeline (side surface side) Edge)
L ₂ 2nd ridge line (heat generation surface side ridge line)
S _SD side surface S ₁ first ridge surface (side surface ridge surface)
S2 _2nd ridge surface (heating surface side ridge surface)
S _HTR heating surface H ₁ 1st ridge surface height (side surface ridge surface height)
H ₂ 2nd ridge surface height (heating surface side ridge surface height)
t ₁ First film thickness on the ridge line (film thickness on the side ridge line)
t ₂ Second ridge line thickness (heat generation surface side ridge line thickness)
θ ₁ First ridge surface angle (side surface ridge surface angle)
θ ₂ Second ridge surface angle (heating surface side ridge surface angle)

Claims (2)

A sensor unit that is placed in the measurement gas flow path and detects the concentration of a specific component in the measurement gas, and a sensor unit that is formed in a substantially flat plate shape, and that is stacked on the sensor unit to heat and activate the sensor unit. A heater portion formed in a flat plate shape ,
At least along the edge in the longitudinal direction of the heater portion, a multiple ridge surface portion including at least two ridge surfaces is provided, and a predetermined range of the outer peripheral surface of the gas sensor element including the multiple ridge surface portion is formed by a wet method. In the gas sensor element surrounded by the formed porous protective layer ,
The multiple ridge surface portion includes at least a side surface ridge surface continuous with the heater portion side surface and a heat generation surface side ridge surface continuous with the heat generation surface of the heater portion, and the porous protective layer includes the side surface ridge surface and the heater. the thickness of the side surface and the above porous protective layer formed on the side face side on the edge line intersecting parts and side surface side thickness t _1, the heat generating surface side ridge surface and the heater unit heating surface and the heating surface on the edge line intersects when the film thickness of the formed the porous protective layer was changed to the heat generating surface side thickness t _2, the gas sensor element, characterized in that set in a range satisfying the relation of the following formula 1.
1.0 · t ₁ ≦ t ₂ ≦ 1.6 · t ₁ Formula 1 A sensor unit that is placed in the measurement gas flow path and detects the concentration of a specific component in the measurement gas, and a sensor unit that is formed in a substantially flat plate shape, and that is stacked on the sensor unit to heat and activate the sensor unit. A heater portion formed in a flat plate shape,
At least along the edge in the longitudinal direction of the heater portion, a multiple ridge surface portion including at least two ridge surfaces is provided, and a predetermined range of the outer peripheral surface of the gas sensor element including the multiple ridge surface portion is formed by a wet method. In the gas sensor element surrounded by the formed porous protective layer,
The multiple ridge surface portion includes at least a side surface ridge surface continuous with the heater portion side surface and a heat generation surface side ridge surface continuous with the heat generation surface of the heater portion,
The height from the heat generating surface of the heater portion to the side surface side ridge intersection between the side surface of the side surface side ridge surface and the heater portion and the side surface side ridge surface height H _1, the heat generating surface side ridge from the heating surface of the heater unit A gas sensor element, wherein a height to a ridge line where the surface and the side surface side ridge surface intersect is set to a range satisfying the relationship of the following formula 2 when the heat generation surface side ridge surface height H ₂ is set .
1/2 · H ₁ ≤ H ₂ ≤ 3/4 · H ₁ ... Formula 2

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