CN101566598A - ZrO2 oxygen sensor for solid state reference partial pressure of oxygen and manufacture method thereof - Google Patents

Abstract

The invention relates to a slice type oxygen sensor used for air-fuel delivery ratio control of a vehicle engine and a manufacture method thereof. The manufacture method comprises the following steps: slurry made of yttrium stabilization zirconia powder forms a slice blank through a casting technology; Pt electrodes which have certain gaps are respectively manufactured in silk screens at both sides of the slice blank; a solid state oxygen partial pressure reference slice is prepared on the yttrium stabilization zirconia slice blank through a secondary casting technology; an RuO <2> material heater is printed in a silk screen in the middle of a secondary casting layer, and the thickness of the layer is of 6 to 7 times of a yttrium stabilization zirconia layer; a porous protective layer is formed at the side of an outer electrode on the yttrium stabilization zirconia slice blank in a curtain coating mode; finally, a prefabricated substrate blank is punched into a strip shape according to a required size, an electrode connecting hole is manufactured, and vacuum sintering is carried out in the program temperature rising process with the temperature of as high as 1600 DEG C to manufacture a sensor chip. The method fully utilizes the curtain coating technology of ceramic slice type materials and the silk screen printing technology of slurry electrodes, and has the advantages of less production technology links, high product consistency, high yield and low cost.

Description

ZrO2 lambda sensor of solid state reference partial pressure of oxygen and preparation method thereof

Technical field

The present invention relates to a kind of lambda sensor and manufacture method thereof, particularly disclose a kind of manufacture method of ZrO2 lambda sensor slice structure of solid state reference partial pressure of oxygen, be applied to the air-fuel ratio of motor car engine, reduce the disposal of pollutants of tail gas.

Background technology

Three-element catalytic is the vitals that present motor car engine reduces the tail gas pollution discharging, and its conversion efficiency requires engine operation at theoretical air-fuel ratio (A/F=14.7).For the engine air-fuel ratio control system, the lambda sensor that is used to measure exhaust is crucial parts, the commercial ZrO that mainly contains ₂Concentration cell type and TiO ₂Two kinds of semi-conductor electricity resistance types.Because ZrO ₂Concentration cell is directly exported the electromotive force signal of 0～1V, and theory, the experimental study basis that reaches a century arranged, and has become the mainstream technology of lambda sensor.In order to reduce startup and response time, reduction cost of manufacture, its working method carries out the transition to hot type by hot type not, and structure also develops into chip by traditional tubular type, bar type.About at present existing numerous patents of the lambda sensor of chip and research article, main content comprises the research of yttrium stable zirconium oxide material and the manufacture craft of slice structure, and the cardinal principle of institute's foundation remained 1900, the formula that Nersf (this holder of energy) proposes:

$E=\frac{\mathrm{RT}}{4F}\mathrm{<figure-callout\; id="2"\; label="ln\; P\; O"\; filenames="A20081005064300072.png"\; state="\{\{state\}\}">ln</figure-callout>}\frac{P_{O_{}}^{}}{}\frac{{{}_2}_{\&prime;}^{}}{{\mathrm{<figure-callout\; id="2"\; label="P\; O"\; filenames="A20081005064300072.png"\; state="\{\{state\}\}">P</figure-callout>}}_{O_{}}}$

In the formula: R is gas law constant (8.314J/molK); T is ZrO ₂Electrolyte temperature (K); F is a Faraday constant (9.648 * 10 ⁴C/mol).

The primary structure of chip oxygen sensor is: by a series of technology, with alumina substrate, 2 insulation courses, well heater, reference air duct, internal and external electrode, ZrO ₂Matrix and protect the stacked sheet integral body of making, process procedure is many, requires the control accuracy height.Wherein reference air duct and Pt electrode are crucial links, directly influence the performance of sensor and the yield rate of product.

In recent years, also the someone begins one's study and adopts solid reference material layer to substitute the reference air duct, obtains thermal stability and chemical stability preferably, and representational material has ZrO ₂-CeO ₂-TiO ₂But, do not consider the work simplification design of the global design of sensor, do not see commercial lambda sensor application at present.

Adopt the manufacture method of above-mentioned this chip oxygen sensor that following some deficiency is arranged:

1. each of slice structure layer will be made respectively, is suppressed into one at last, and the bonding of each layer is undesirable during sintering, has the key problem in technology difficult problem of reference air duct sealing.

2. process procedure is many, and tighter to the alignment precision requirement of electrode via hole, yield rate is restricted.

3. the electrode terminal material adopts the Pt material that one is printed, and cost of manufacture improves relatively.

Summary of the invention

The objective of the invention is provides a kind of technology is simple, with low cost, yield rate is high lambda sensor structure and method for making from the deficiency of structure and the present chip oxygen sensor of corresponding technology solution.

The ZrO2 lambda sensor slice structure of solid state reference partial pressure of oxygen comprises that yttrium stablizes ZrO ₂Layer, solid state reference partial pressure of oxygen layer, sensor chip protective layer, at ZrO ₂The base layer bilateral has the Pt electrode, is provided with RuO in solid state reference partial pressure of oxygen layer inside ₂Well heater.

Its manufacturing process steps comprises: A, casting slurry preparation are about to ZrO ₂The powder of base layer, solid state reference partial pressure of oxygen layer, protective seam adds solvent, spreading agent, bonding agent and plastifier, and ball milling evenly back removes bubble and filtration, makes the suitable slurry of viscosity; B, flow casting molding, the base layer on casting machine that each layer slurry curtain coating one-tenth is even, that certain thickness requirement is arranged; C, the printing of Pt electrode are promptly pressed certain physical dimension at ZrO with high-precision screen process press ₂The base layer bilateral is printed the Pt slurry electrode, and electrode is predrying at a certain temperature after printing; D, well heater are made, and promptly in the intermediate link of secondary curtain coating solid state reference partial pressure of oxygen layer, adopt high-precision silk screen printing technology to print RuO ₂Well heater; E, punching stamp out monolithic by the sensor chip size with the semi-manufacture of sheet; F, electrode connecting hole adopt special-purpose drilling tool, bore the system electrode at bilateral electrode extraction location and connect semi-transparent hole.G, sintering after finishing whole cast layer and serigraphy, place high temperature sintering furnace by certain heating curve sintering the chip blank.The printing of H, external terminal electrode is promptly with the electrode of silk-screen printing technique connector outside the printing of sensor afterbody is suitable for.

Adopt structure of the present invention and process to have following advantage:

1. the technology continuity is good, is feature with ceramic casting technique, and the base film in the process has certain intensity and flexibility, is convenient to the turnover of serigraphy and technology, does not produce fracture and serious deformation.

2. what the present invention adopted is disposable sintering technology, and each laminar flow prolongs the bonding quality that technology and suitable pressure are guaranteed layers of material, chip physical strength height.

3. owing to adopt solid oxygen dividing potential drop reference layer, sensor simple in structure, the technology of the last compacting sintering of impact briquetting stage by stage that the preparation process of sensor chip is more present reduces nearly 8 process procedures, makes the yield rate height, and is with low cost.

Description of drawings:

The structural drawing of Fig. 1 each layer base of the present invention sheet;

The measuring junction sectional view of Fig. 2 chip oxygen sensor of the present invention;

The ZrO2 lambda sensor slice structure manufacture craft flow process of Fig. 3 solid state reference partial pressure of oxygen of the present invention.

Among the figure: 1, sensor chip protective layer; 2, yttrium is stablized ZrO ₂Layer; 3, solid state reference partial pressure of oxygen layer; 4, the external electrode of lambda sensor; 5, the interior electrode of lambda sensor; 6, RuO ₂Well heater

Embodiment:

Further specify particular content of the present invention below in conjunction with accompanying drawing

The present invention adopts the multilayer curtain coating, once sintered technology, and the concrete method of implementing is:

1. the preparation of casting slurry:

At first with yttrium stable zirconium oxide, solid state reference partial pressure of oxygen material, protective materials powder respectively 125 ℃ of vacuum drying 4 hours, add organic solvent and three alkanolamine solution, after fully grinding, adding polyvinyl alcohol (PVA) and lipid plastifier continues to grind 12 hours, after filtering, vacuum condition is removed bubble, finishes the preparation of three kinds of casting slurries.

2. yttrium stable zirconium oxide cast layer preparation:

By the gap of optical grating ruler measurement adjustment casting machine scraper and marble substrate, even for guaranteeing thickness, adopt stationary substrate, the mode that hopper moves.In slurry tank, inject slurry, move, on substrate, form the uniform diaphragm of thickness with certain speed.Under draughty environment, dry 4-6 hour.

3.Pf the preparation of external electrode:

The yttrium stable zirconium oxide base symphysis of flow casting molding is printed the Pt electrode together with the marble substrate on screen process press, dry under cryogenic conditions.

4.Pf the preparation of interior electrode:

To be printed on the yttrium stable zirconium oxide base film upset of external electrode, adopt the interior electrode of method serigraphy of step 3.

5. solid state reference partial pressure of oxygen layer preparation:

2 method flow casting molding solid state reference partial pressure of oxygen layer set by step, drying at room temperature 4-6 hour.

6. after step 5, by the method for serigraphy, prepare well heater, heater material is RuO ₂Slurry, 3-40 ℃ of drying in printing back 4 hours.

7. solid state reference partial pressure of oxygen layer secondary preparation:

8. on well heater, 5 flow casting molding solid state reference partial pressure of oxygen layers are once more imbedded well heater set by step.

With the base film of completing steps 8 at 85 ℃, 5～10Kg/cm ²Pressure under, rolling 1 hour, afterwards naturally the cooling.Place and carried out the internal stress timeliness in 24 hours.Distortion and cracking during with the minimizing sintering.

10. punching press or be laser-cut into 5 * 7.5 strip-shaped blade.

11. the instrument by special use carries out the half hole processing that electrode connects, and the Pt electrode of imbedding material layer is connected by the screen printing electrode contact with heater electrode, and makes silver-palladium electrode of 45 * 1.5, is used for the adaptive of encapsulating structure electrical insert.

Described integral manufacturing process is: at first, and with ZrO ₂The slurry of base layer material becomes certain thickness thick film sheet by curtain coating, then at ZrO ₂The bilateral printing Pt slurry electrode of matrix diaphragm, protection coating materials is prolonged at an effluent in predrying back; At the solid state reference layer of opposite side curtain coating 1/2 solid state reference partial pressure of oxygen layer thickness, serigraphy RuO ₂Behind the well heater, the solid state reference layer of curtain coating 1/2 solid state reference partial pressure of oxygen layer thickness again; Can suitably pressurize for the physical strength that improves chip, pressure process is finished at a certain temperature because of this, must have simultaneously one slowly temperature-fall period to discharge internal stress; Afterwards, punching press is decomposed into monolithic, adopts special-purpose drilling equipment to make semi-transparent electrode connecting hole; The sintering process of being mentioned is crucial step, is not more than 1 ℃/min at strict control of temperature rise period heating rate, and purpose is to get rid of the adhesive ingredients of layers of material, and sintering is made chip under 1600 ℃ condition at last; For the method for the chip employing serigraphy of doing to make, be used to be electrically connected the electrode of plug-in unit by the connecting hole preparation of boring system.

Claims (2)

1, the ZrO2 lambda sensor of solid state reference partial pressure of oxygen comprises that yttrium stablizes ZrO ₂Layer (2), solid state reference partial pressure of oxygen layer (3), sensor chip protective layer (1) are at ZrO ₂The base layer bilateral has Pt electrode (3), (4), is provided with RuO in solid state reference partial pressure of oxygen layer inside ₂Well heater (6).

2, according to the method for making of the ZrO2 lambda sensor of the said solid state reference partial pressure of oxygen of claim 1:

A, casting slurry preparation are about to ZrO ₂The powder of base layer, solid state reference partial pressure of oxygen layer, protective seam adds solvent, spreading agent, bonding agent and plastifier, and ball milling evenly back removes bubble and filtration, makes the suitable slurry of viscosity;

B, flow casting molding, the base layer on casting machine that each layer slurry curtain coating one-tenth is even, that certain thickness requirement is arranged;

C, the printing of Pt electrode are promptly pressed certain physical dimension at ZrO with high-precision screen process press ₂The base layer bilateral is printed the Pt slurry electrode, and electrode is predrying at a certain temperature after printing;

D, well heater are made, and promptly in the intermediate link of secondary curtain coating solid state reference partial pressure of oxygen layer, adopt high-precision silk screen printing technology to print RuO ₂Well heater;

E, punching stamp out monolithic by the sensor chip size with the semi-manufacture of sheet;

F, electrode connecting hole adopt special-purpose drilling tool, bore the system electrode at bilateral electrode extraction location and connect semi-transparent hole;

G, sintering after finishing whole cast layer and serigraphy, place high temperature sintering furnace by certain heating curve sintering the chip blank;

The printing of H, external terminal electrode is promptly with the electrode of silk-screen printing technique connector outside the printing of sensor afterbody is suitable for.

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