CN101542276A - Oxygen sensor with a protective layer - Google Patents

Abstract

An exhaust gas sensor comprises a planar sensing element, which comprises a ceramic heater, a solid electrolyte electrochemical cell, and a protection layer for the sensing electrode and electrode leads. The protection layer comprises built-in arrays of porous vias.

Description

Oxygen sensor with protective seam

The cross reference of related application

The application's case is advocated the right of priority of the 60/776th, No. 132 U.S. Provisional Patent Application case of application on February 23rd, 2006, and the full text of described application case is incorporated herein by reference.

Technical field

The present invention relates generally to planar oxygen sensor.More particularly, the present invention relates to constructing of this type of oxygen sensor through improving.

Background technology

For the vehicle that is equipped with internal combustion engine, the oxygen sensor of settling along exhaust system can be used for detecting rich and poor air-fuel mixture based on the amount of oxygen in the engine exhaust.The mechanism that is used for detecting most of oxygen sensors of oxygen content relates to the chemical reaction that produces voltage (that is, electromotive force or EMF).The computer control module of described engine (ECM) checks that voltage determines that aspect fuel described potpourri is to be rich in still poor fuel (that is, oxygen content is excessive, low EMF) of fuel (that is, oxygen content reduces, high EMF).When potpourri was rich fuel, voltage level was higher.When potpourri was poor fuel, voltage level was lower.ECM can enter the fuel quantity of engine based on detected voltage level adjustment.Stoichiometric ratio when target realizes normally that engine produces the hydrocarbon (HC) of minimum content, carbon monoxide (CO) and nitrogen oxides (NOx).

Therefore, the function of oxygen sensor is to help engine to move effectively with the discharging that reduces.Traditional engine control algolithm wishes to make sensor to cross the operation lifetime of stoichiometry mid point (for example, approximately the voltage of 450mV) to obtain to prolong with stable status and in power engine operating period under abominable engine operation environment.

Summary of the invention

For conical (that is, sleeve pipe) and plane (for example, flat board) oxygen sensor both, the electrode on the porous ceramics protective layer covering exhaust gas side to protect described electrode in order to avoid directly be exposed to just measured waste gas.In most of planar oxygen sensor, the protective layer of being made by porous ceramic film material (for example, spinel, aluminium oxide etc.) can be deposited on the script exposed electrodes to protect sensing electrode to avoid wearing and tearing and to avoid the waste gas murder by poisoning.This porous layer can make up to realize the more accurate reading of better persistence and waste gas with antitoxin coating.This protective seam is made by the multi-layer ceramics method for making usually, described method relate to lamination of green and subsequently by co-sintering on dense ceramic body 52, to form porous ceramic layer 50, as shown in Figure 1.

Because embolium density mismatch when lamination, so between porous ceramic layer 50, closely knit dielectric ceramic layer 52 and zirconia layer 54, exist sintering to shrink the difference of behavior.Because sintering shrinks the difference of behavior, often form the gap, and on the zirconia layer under the jointing line 54, see the crack usually along the seam between porous ceramic layer 50 and the closely knit ceramic layer 52.Lip-deep these faults of construction of each ceramic layer develop into the main crack that is penetrated into other layer at the sensor element test period and/or in oxygen sensor combination and test period continually.In many cases, minute crack causes at vehicle operation conditions lower sensor element harmful breaking being taken place.

And, the mismatch of the sintering contraction because porous layer 50 (it has relatively low roasting shrinkage factor) and closely knit ceramic layer 52 between (insulator and electrolyte shrink during the sintering bigger) is very difficult to keep rectilinearity and flatness in this part of sensor element.Need rectilinearity and flatness so that the flat surface sensor element is encapsulated in the oxygen sensor metal harness rightly, and be used to prevent because the crooked stress raisers point that causes.

Description of drawings

Now these and other feature of the present invention, aspect and advantage are described referring to the accompanying drawing of preferred embodiment, the set explanation of described embodiment and unrestricted the present invention, and in the accompanying drawings:

Fig. 1 is the prior art planar oxygen sensor construction;

Fig. 2 is the exploded view of the oxygen sensor construction arranging and dispose according to some feature of the present invention, aspect and advantage;

Fig. 3 (a) is the difference configuration that can be used for the through hole in the structure of sensor of Fig. 2 to 3 (f).

Fig. 4 is the exploded view of another oxygen sensor construction of arranging and dispose according to some feature of the present invention, aspect and advantage;

Fig. 5 (a) is schematically showing of a plurality of heater configuration to 5 (b); And

Fig. 6 (a) is additionally schematically showing of other heater configuration to 6 (c).

Embodiment

Now, provide planar oxygen sensor 100 referring to Fig. 2.In some applications, sensor 100 can be used for fuel/air ratio control.Sensor 100 also can be used for other application, such as but not limited to NOx sensor, hydrocarbon sensor, ammoniacal sensor, hydrogen gas sensor, chemical sensor, and the sensing apparatus that contains plate heater.

Sensor 100 is preferably the electrolysis oxygen sensor, and it comprises oxygen ion conduction main body 102 to small part.In a configuration, main body 102 is formed by zirconia.Also can use other suitable material.

Main body 102 preferably is inserted between first electrode 104 and second electrode 106.More preferably, first electrode 104 closely contacts main body 102 with second electrode 106.Electrode 104,106 is preferably formed by platinum.Also can use other material.First side 110 of main body 102 will be placed on the exhaust gas side, and second side surface opposite 112 will be placed on environment or the reference air side.

In illustrated configuration, first side 110 of main body 102 (that is, will near the side of waste gas) be preferably by diffusion layer 114 protections.Diffusion layer 114 can comprise ceramic main body 120, and it can mainly be made by aluminium oxide, pure zirconia, partially stabilizedization zirconia, yttria, magnesium oxide, titanium dioxide and rare earth oxide pottery in certain embodiments.Other configuration can mainly be made by aluminium oxide-magnesia spinel pottery, glass ceramics and ceramic complexes.Other configuration also is possible.

Diffusion layer 114 can comprise via-hole array 116, and it is defined in the ceramic main body 120 of otherwise dense.As used herein, through hole 116 is passages.In some configurations, through hole 116 can be formed in the ceramic main body 120 that lacks noble metal catalyst or oxygen storage assembly.Other configuration can be possible.

Diffusion layer 114 preferably comprises poriness, pore size, pore size distribution and the gas diffusion characteristic that is controlled.Therefore, diffusion layer 114 first electrode 104 (that is exhaust gas side electrode) that adequately protects is ideally avoided high-speed thick exhaust gases.In other words, by protectiveness porous surface (for example, diffusion layer 114) is provided, reduce or eliminated the possibility of harmful gas pollution sensing electrode 104 greatly.

In another configuration, the noble heavy metal oxide of platinum, rhodium, palladium, iridium, cadmium, ruthenium, gold, silver, tantalum, molybdenum, niobium, tungsten and alloy and catalysis material (comprising oxide ceramics and metal alloy) (for example, in the loading ratio by about 0-5% of general assembly (TW)) can be added to ceramic main body 120.In some configurations, can be by before ceramic roasting, adding these materials with ceramic powders dry type or wet mixed.In some configurations, can be by based on the dipping of slurries and carry out the back roasting technique subsequently and add these materials.Also can use other technology.Described precious metal and catalysis material can provide the function of catalyzer and/or oxygen storage assembly in the through hole 116 of ceramic main body 120.

Still referring to Fig. 2, the stupalith of available more porous is filled one group of through hole, makes to embed the more ceramic main body 122 of porous in closely knit ceramic main body 120.Through hole 116,122 preferably is arranged on and directly is adjacent to directly over first electrode, 104 places or its.Advantageously, by the more ceramic main body 112 of porous is provided in illustrated configuration, can use monolithic dense ceramic body 120 to replace disposing the closely knit part and the layer of porous part more.Through hole 116 and ceramic main body wherein 122 allow waste gas to penetrate by ceramic main body 120 and arrive the sensor electrode surface in substantially uniform mode.

Porous ceramics main body 122 in the through hole 116 can form in any suitable manner.In a configuration, through hole 116 forms by traditional ceramic process.In another configuration, through hole 116 forms by thin film semiconductor technology.For instance, porous ceramics main body 122 can form and have filler, and described material includes but not limited to based on organic transition material, and it can remove by sintering, back roasting, wet chemical etch or based on the dry etch process of plasma.In other words, through hole can form or fill by traditional ceramic making method, and described method includes but not limited to bore a hole or boring, serigraphy, the filling of pressurization through hole and usefulness have the green adhesive tape replacement of finishing of identical size; Or by other thick film mixing and thin film technique, it includes but not limited to mounted on surface, passes through dry type or the wet type layer building and the photoetching method of silk screen/block printing.In other configuration,, scatter catalyzer and/or oxygen storage material in can be in the through hole 116 contained porosint 122 for example for complicated Abgassensor.

To 3 (f), the various configurations of through hole 116 and relevant porous ceramics main body 122 are described referring to Fig. 3 (a).Preferably, through hole 116 and main body wherein 122 are configured to reflect the size and the shape of the sensor electrode that is placed in through hole and main body 122 belows.As described, through hole 116 and porous ceramics main body 122 can have substantially size and configuration uniformly.Through hole 116 and porous ceramics main body 122 can have all size.In some configurations, through hole 116 and porous ceramics main body 122 can have at approximately 0.1mm and the approximately diameter between the 1.5mm.In some configurations, porous ceramics main body 122 has identical cardinal principle poriness, and in other configuration, poriness can be different.Through hole 116 and porous ceramics main body 122 can be arranged to any required configuration.In more preferably configuration, through hole 116 and porous ceramics main body can be substantially orderly and symmetrical in appearance.This type of is configured in the predictability aspect advantage is provided.Yet, can use other configuration.The through hole and the porous ceramics body design that comprise number, position, pattern, diameter, length, poriness, pore size, pore size distribution, gas penetration and chemical constitution provide desired function as protective seam and diffusion impervious layer, and described protective seam and diffusion impervious layer can be controlled limiting current when exhaust oxygen sensor is operating as the air-fuel linear os sensor; And as waste gas kind sensor with detect (such as but not limited to) NOx, ammonia, CO ₂, CO, hydrocarbon and/or hydrogen.

Electric resistance heater 124 can be placed in main body 102 belows.Illustrated well heater 124 is installed to ceramic main body 126.Other configuration also is possible.In a configuration, air reference channel 130 is placed between main body 102 and the well heater 124.Air reference channel 130 preferably becomes fluid to be communicated with surrounding air, and can be arranged in the ceramic main body 128.Therefore, well heater 124 can be inserted between two ceramic main bodies 126,128.Other configuration is possible.

Can be the together common roasting of diffusion layer 114, main body 102, electrode 104 and well heater 124, perhaps roasting and each can use the high-temp glue glue to lump together through the roasting assembly to each assembly (for example, protective seam, sensed layer, zone of heating) separately.

With respect to above-described sensor 100, the sintered porous ceramic main body 122 in the through hole 116 preferably has the poriness between about 10% and about 40%, and wherein pore size distribution arrives in about 20 microns scope at about 1 micron.Preferably, porous ceramics main body 122 and through hole 116 roughly or fully extend through the thickness of diffusion layer 114, and the diameter of each the porous ceramics main body 122 and the through hole 116 that is associated arrives in about 2 millimeters scope at about 50 microns.Believing that this is configured under the normal vehicle operation conditions works rightly.

The solid section that is used to form the packing material of porous ceramics main body 122 can comprise the main part that is formed by the pottery of aluminium oxide, pure zirconia, partially stabilizedization zirconia, yttria, magnesium oxide, titanium dioxide, rare earth oxide, aluminium oxide-magnesia spinel pottery, glass ceramics and ceramic complexes.In some configurations, can add platinum, rhodium, palladium, iridium, cadmium, ruthenium, gold, silver, tantalum, molybdenum, niobium, tungsten by any suitable technique

Precious metal and alloy and catalysis material (comprising oxide ceramics and metal alloy) (quantitative) in about 0% to about 10% loading by general assembly (TW).For instance, in some configurations, by before ceramic roasting with ceramic powders dry type or wet mixed or by based on the dipping of slurries and carry out the back roasting technique subsequently and add these materials.Also can use other technology.

In some applications, the coating on protective coating can be coated with by slurry, the two dimension or three-dimensional block printing, flame spraying or plasma spray coating apply.Described coating preferably provides thermal barrier to reduce the possibility that ceramic sensor element is caused thermal shock.Protective coating can be identical with the through hole packing material on composition, and perhaps protective coating can be different from the through hole packing material and replenish the functional of through hole packing material aspect gaseous diffusion control, the catalytic reaction on composition.Preferably, protective coating can be in the thermal property that enhancing is provided aspect the thermal barrier of serving as waste-gas heat.More preferably, protective coating can improve because water splashes etc. the resistance to sudden heating that causes aspect the thermal property of enhancing is provided.

Fig. 4 illustrates another embodiment of the planar oxygen sensor 200 of arranging and disposing according to some feature of the present invention, aspect and advantage.Illustrated sensor 200 can be used for open circuit to be used, and can be used for the automobile exhaust gas sensor when making up with any suitable closed circuit heater voltage controlling mechanism.

Sensor 200 comprises plane sensing element 202.Plane sensing element 202 can have any suitable configuration.As discussed above, the plane sensing element can comprise solid electrolyte electrochemical cell 204, diffusion layer 206 and ceramic heater 210.

Electrochemical cell 204 can comprise electrolyte layers, wherein is mounted with an electrode on each side of described electrolyte layers.Diffusion layer 206 preferably comprises the diffusion restriction through hole, its in above-described mode for example near the electrode and the contact conductor of battery 204.

Ceramic heater 210 is preferably integrated isothermal thick film heater, and it comprises a plurality of well heaters 212,214.Advantageously, well heater 212,214 can heat Electrochemical Detection part 204.Isothermal thick film heater 210 can be by realizing and keeping temperature required distribution curve to alleviate the thermal stress on the ceramic sensor element 200 during sensor is lighted a fire around the peripheral part of sensing electrode.Isothermal thick film heater 210 also can provide the height of the per unit area of heating surface well heater wattage of flashing.Therefore, can obtain quick igniting.Thereby some aspect of illustrated sensor 200 can reduce the possibility of local overheating, can reduce heter temperature and change during high-temperature operation, and can prolong the well heater life-span by the wattage density that reduces on the platinum serpentine (serpentine).

Ceramic heater 210 allows to create predetermined temperature profiles.For instance, by changing the heater pattern design at each indivedual well heater serpentine 216,220, the thermistor material (comprising well heater) that has different thermal resistivity coefficients by change based on platinum, rhodium and palldium alloy and tungsten, tantalum and molybdenum, and by changing the thickness and/or the width of well heater serpentine 216,220, the temperature distribution history from the center of substrate to periphery can change.

Well heater 212,214 can form in any suitable manner.In certain embodiments, well heater 212,214 is carried out transfer printing by serigraphy, ink jet printing, pattern transfer, patterned foil and/or is made by photoetching method.Well heater 212,214 can be formed on the roasting ceramic substrate, maybe can be co-fired into monolithic body.

Preferably, heater lead 222,224 has lower room temperature resistance value.Heater lead 222,224 can be made by identical or different heater lead material.In a configuration, the temperature-coefficient of electrical resistance (TCR) of heater lead 222,224 value is more much smaller than the value of well heater serpentine 216,220.The TCR value of the serpentine 216 and second serpentine 220 is preferably and differs bigger.

The heater chip resistance value of exemplary heater lead and well heater serpentine and the example of TCR value can comprise:

	The H1 lead-in wire	The H1 serpentine	The H2 lead-in wire	The H2 serpentine
					TCR％/℃	0.05-0.15	0.10-0.20	0.05-0.15	0.50-2.00
The sheet resistance milliohm/square	20-30	50-100	20-30	25-50

Now, show some different instances of a plurality of well heaters on the Different Plane referring to Fig. 5 a and Fig. 5 b.Described a plurality of well heater preferably passes through through hole 300 and electrical links.Well heater can have any suitable configuration, and in illustrated configuration, is placed on two or more Different Plane of associated sensor.In some configurations, can use three or three with upper heater.

Well heater comprises heater lead 310.Heater lead 310 can be connected to one or more well heaters by through hole 309.Also can use other configuration.Ideally, heater lead 310 and electric through-hole 309 and the well heater serpentine that is associated 301,302,303,304,306 are compared with 308 and are had relatively low resistance value and lower temperature-coefficient of electrical resistance (TCR).In some configurations, resistance value (influenced by Pt resistivity of material, well heater printing height and well heater printing width) and TCR value through selecting so that external heater serpentine 302,306 is faster than 304,308 heating of interior heater serpentine.When at first sensor being powered up at low temperatures, electric current passes described two heater resistors (that is, serpentine), and described two heater resistors are according to W=I ²* R=I*V (the R=heater resistance, V=applies voltage for W=heater power, I=electric current) and heating.When local temperature reaches predetermined temperature (it can be high value), because the cause of the relative high electrical resistance that the electric current that making substantially flows passes the respective heater resistor stops, in the described heater resistors group one (for example, 302/304 or 306/308) turn-offed.

In some configurations, can in the single plane of associated sensor, settle a plurality of well heaters.For instance,, two different embodiment are described, wherein settle a plurality of heater resistors 400,402 in the copline mode referring to Fig. 6 (a) and 6 (b).Fig. 6 (c) illustrates another embodiment that settles single heater resistors 500 in associated sensor.A plurality of well heaters can also be placed in the single plane and simultaneously one or more additional heaters be placed in one or more additional planes.Preferably, well heater serpentine 400,402,404 and 500 has different room temperature resistances and TCR value, the feasible heating that can automatically adjust by one or more predetermined heat device resistors (but being less than whole heater resistors) after producing Fast Heating.

Though described the present invention according to certain embodiment, other embodiment that the those skilled in the art understood also belongs in the scope of the present invention.Therefore, can under the situation that does not break away from the spirit and scope of the present invention, make various changes and modification.For instance, can settle various assemblies as required again.In addition, and all described features of nonessential needs, aspect and advantage put into practice the present invention.Therefore, scope of the present invention is set is only defined by appended claims.

Claims (19)

1. flat surface sensor, it comprises:

One oxygen ion conduction main body, it comprises first side and second side;

Sensing electrode of settling along described first side of described main body and the reference electrode of settling along described second side of described main body, described sensing electrode closely contacts described main body with described reference electrode;

Diffusion layer, it extends above described first side of described main body; And

A plurality of through holes, it is formed in the part at least a portion that overlies described sensing electrode of described diffusion layer, the porous ceramics filling material be placed in described a plurality of through holes both or both above in, make describedly to comprise assembly with respect to the more porous of described diffusion layer through filling vias.

2. sensor according to claim 1, wherein said electrode is formed by platinum.

3. sensor according to claim 1, wherein said diffusion layer comprises ceramic main body, and described ceramic main body is mainly made by the material that is selected from the group that is made up of the pottery of aluminium oxide, pure zirconia, partially stabilizedization zirconia, yttria, magnesium oxide, titanium dioxide and rare earth oxide.

4. sensor according to claim 1, wherein said diffusion layer comprise the main body of mainly being made by aluminium oxide-magnesia spinel pottery, glass ceramics and ceramic complexes.

5. sensor according to claim 1, wherein said a plurality of through holes lack noble metal catalyst substantially.

6. sensor according to claim 1, wherein said a plurality of through holes lack the oxygen storage assembly substantially.

7. sensor according to claim 1, wherein said diffusion layer comprises the material that is selected from the group that is made up of the following: the noble heavy metal oxide of platinum, rhodium, palladium, iridium, cadmium, ruthenium, gold, silver, tantalum, molybdenum, niobium, tungsten and alloy, catalysis material and oxide ceramics and metal alloy.

8. sensor according to claim 1, the described through hole that wherein contains described porous ceramics filling material are placed in and directly are adjacent to described sensing electrode place.

9. sensor according to claim 1, the described through hole that wherein contains described porous ceramics filling material be placed in described sensing electrode directly over.

10. sensor according to claim 1, the described through hole that wherein contains described porous ceramics filling material is with respect to described sensing electrode uniformly dispersing substantially.

11. sensor according to claim 1, the described through hole that wherein contains described porous ceramics filling material is with respect to described sensing electrode symmetrical dispersion substantially.

12. sensor according to claim 1, it further comprises the well heater that is placed in described oxygen ion conduction main body below.

13. sensor according to claim 12, wherein said well heater comprises isothermal thick film heater.

14. sensor according to claim 13, wherein said thick film heater comprises a plurality of well heaters.

15. sensor according to claim 14, wherein said a plurality of well heaters comprise primary heater and secondary heater, and described first and second well heaters are placed on the Different Plane.

16. sensor according to claim 14, wherein said a plurality of well heaters comprise primary heater and secondary heater, and described first and second well heaters comprise different serpentine patterns.

17. sensor according to claim 14, wherein said a plurality of well heaters comprise primary heater and secondary heater, and described first and second well heaters comprise different thermistor materials.

18. sensor according to claim 14, wherein said a plurality of well heaters comprise primary heater and secondary heater, and described first and second well heaters comprise different thickness.

19. sensor according to claim 14, wherein said a plurality of well heaters comprise primary heater and secondary heater, and described first and second well heaters comprise different width.

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