JP4637671B2 - Ceramic laminate and gas sensor including the same - Google Patents

Description

  The present invention relates to a ceramic laminate having a groove at a portion opened in an internal hollow portion, and a gas sensor including the ceramic laminate.

In an internal combustion engine such as an automobile, by detecting the oxygen concentration in exhaust gas and controlling the amount of air and fuel supplied to the internal combustion engine based on the detected value, harmful substances such as CO 2 from the internal combustion engine are controlled. A method of reducing HC, NO _x is employed.

  As this detection element, a solid electrolyte type oxygen sensor is used in which a pair of electrode layers are respectively formed on the outer surface and the inner surface of a solid electrolyte substrate mainly composed of zirconia having oxygen ion conductivity.

  A typical example of this oxygen sensor is a hollow plate-like ceramic structure closed at one end. A detection electrode and a reference electrode are provided on the outer surface and the inner surface of the solid electrolyte substrate, respectively. An oxygen sensor in which a ceramic heater in which a heating element made of platinum is embedded is integrated has been proposed (see, for example, Patent Document 1).

  This hollow plate-shaped ceramic structure has a hollow part formed inside, and can be produced by laminating, bonding, degreasing and firing ceramic green sheets. The cross-sectional shape of the produced hollow part is It is a rectangle.

For example, according to FIG. 9, the ceramic laminate 51 is a laminate of a first ceramic body 52, a second ceramic body 53, and a third ceramic body 54, specifically on the first ceramic body 52. A second ceramic body 53 is provided via an adhesive layer 55, and a third ceramic body 54 is provided on the second ceramic body 53 via an adhesive layer 55. A hollow portion 56 is formed inside the ceramic molded body 51.
Japanese Patent Laid-Open No. 9-26409

  However, in the ceramic structure described in Patent Document 1, since the cross-sectional shape of the oxygen sensor is substantially rectangular and the hollow part is also rectangular, cracks CR (for example, see FIG. 9) are generated at the corners of the hollow part. There was a problem to do.

  Therefore, an object of this invention is to provide the ceramic laminated body which can eliminate the crack from the corner | angular part of a hollow part easily, and a gas sensor provided with the same.

  The ceramic laminate of the present invention comprises a first ceramic body provided with a groove on the main surface, a second ceramic body provided with a hollow portion comprising a through hole, and a third ceramic body in this order via an adhesive layer. Each of the grooves is laminated, and at least a part of the groove is open to the hollow portion.

  It is preferable that the groove is formed along the longitudinal direction of the hollow portion, and the groove opens to the hollow portion.

  It is preferable that a plurality of the grooves are provided on the main surface of the first ceramic body.

  It is preferable that the side wall surface of the said hollow part is formed in step shape.

  Preferably, the first ceramic body is composed of a laminate of a plurality of ceramic sheets, and a groove penetrating the ceramic sheet that contacts the second ceramic body among the plurality of ceramic sheets is formed.

  The multilayer ceramic of the present invention is obtained by firing the ceramic multilayer body.

  The gas sensor according to the present invention includes a reference electrode provided on the principal surface of the third ceramic body that constitutes the multilayer ceramic, the reference electrode provided at a position opening in the hollow portion, and the reference electrode. Thus, the detection electrode provided on the opposite main surface opposite to the main surface of the third ceramic body and a heating means for heating the ceramic laminate are provided.

  According to the present invention, cracks are remarkably generated at the corners of the hollow part in the manufacturing process, particularly in the degreasing process. Therefore, if a groove is provided at a position in contact with the hollow part, the shrinkage generated in the manufacturing process, particularly in the drying or degreasing process. Even if the stress caused by this occurs, large strain can be formed on both sides of the groove. As a result, the stress is reduced and the stress concentration on the corner of the hollow part is reduced, and the corner of the hollow part is cracked. Can be suppressed.

  Further, according to the present invention, since the ceramic laminate is used, no cracks are generated at the corners of the hollow portion, and no cracks are generated even when the ceramic laminate is heated. Even if it occurs, since the progress of cracks can be suppressed, a highly reliable gas sensor can be obtained.

  The present invention will be described with reference to the drawings. In addition, in each figure, the same number is attached | subjected about the same component and duplication of description may be abbreviate | omitted.

  1A and 1B show the structure of a ceramic laminate of the present invention, in which FIG. 1A is a perspective view, FIG. 1B is a cross-sectional view taken along the line AA ′, and FIG. FIG.

  According to FIG. 1, the ceramic laminate 1 is a laminate of a first ceramic body 2, a second ceramic body 3, and a third ceramic body 4, specifically, an adhesive layer on the first ceramic body 2. The second ceramic body 3 is provided via 5, and the third ceramic body 4 is further provided on the second ceramic body 3 via the adhesive layer 5.

  The ceramic molded body 1 has a hollow portion formed therein. For example, as shown in FIG. 1B, the second ceramic body 3 is provided with a groove to be the hollow portion 6 so as to penetrate the second ceramic body 3. The groove to be the hollow portion 6 may extend to the side surface 8 of the ceramic laminate 1, may extend to the opposite side surface opposite to the side surface 8, and further from the side surface 8 to the opposite side surface. You may penetrate to.

  According to the present invention, it is important to provide the first ceramic body 2 with the groove 7 and bring the groove 7 into contact with the hollow portion.

  When the groove 7 is provided at a position where it abuts against the hollow portion 6, for example, when compressive stress is generated at the interface between the first ceramic body 2 and the second ceramic body 3, as shown in FIG. The first ceramic bodies 2 on both sides of the groove are deformed in a direction (arrow direction) in which the width of the groove 7 becomes narrow, and the compressive stress can be relaxed. Even if the stress is a tensile stress, the stress can be relaxed in the same manner if it is deformed in the direction opposite to the arrow in FIG.

  Therefore, by providing the groove 7 in the portion that is open to the hollow portion that is likely to cause stress in this way, the stress is reduced and the stress concentration at the corner portion of the hollow portion 6 is reduced, so that the first ceramic is reduced. It can suppress that a crack generate | occur | produces in the corner | angular part C1, C2 vicinity of the hollow part 6 in the body 2 or the 3rd ceramic body 4. FIG.

  It is to be noted that, by providing a groove (not shown) in a portion that contacts the hollow portion 6 of the third ceramic body 4 similarly to the first ceramic body 2, it is possible to achieve the above-described effects. In particular, when the thickness of the third ceramic body 4 is ½ or more of the thickness of the first ceramic body 2, particularly 2/3 or more, it is preferable to provide a groove in the third ceramic body 4. When the thickness of the third ceramic body 4 is smaller than that of the second ceramic body 2, particularly when it is less than ½, the third ceramic body 4 reduces the stress due to deformation. In addition, it is preferable to form a groove in the third ceramic body 4 in order to more effectively suppress the generation of cracks.

  As the first ceramic body 2, the second ceramic body 3, and the third ceramic body 4, desired ceramics can be used. For example, known engineering ceramic materials such as oxide ceramics such as alumina, zirconia, titania, cordierite, spinel and forsterite, and non-oxide ceramics such as silicon nitride, aluminum nitride and silicon carbide can be used. Among these, alumina is particularly preferable from the viewpoint of inexpensiveness, zirconia is preferable from the viewpoint of high toughness, and silicon nitride is preferable from the viewpoint of high-temperature strength.

  The shape of the ceramic laminate 1 in FIG. 1 is a rectangular shape, but the shape is not limited to a rectangular shape, and a shape such as a disk shape, an elliptical shape, or a trapezoidal shape can also be employed. Moreover, although the cross-sectional shape of the hollow part 6 is also a rectangular shape in FIG. 1, the shape is not limited to a rectangular shape.

  The shape of the groove 7 is not limited as long as the groove can be deformed to relieve stress. Specifically, as shown in FIG. 1, a rectangular shape, a U shape shown in FIG. 2 (a), a V shape shown in FIG. 2 (b), and a reverse taper shape shown in FIG. 2 (c). Can be illustrated.

  The depth of the groove 7 is preferably 1/2 or less, particularly 1/3 or less of the thickness of the first ceramic body.

  It is important that at least a part of the groove 7 is in contact with the hollow portion 6, thereby relaxing the stress concentration generated in the corner portions C <b> 1 and C <b> 2 of the first ceramic body 2 and suppressing the generation of cracks. Can do. In particular, considering the stress generated when the shape of the groove 7 is long in one direction as shown in FIG. 1A, in order to enhance the effect, the length of the hollow portion 6 It is preferable to provide the groove 7 so as to open into the hollow portion 6 along the direction L, or so that the hollow portion 6 and the groove 7 are continuously formed.

  The number of grooves 7 may be one groove for the hollow portion 6 as shown in FIG. 1 or a plurality of grooves may be provided. For example, FIG. 3 illustrates a ceramic laminate 1a provided with two grooves 7a.

  According to the present invention, the side wall surface 9 in FIG. 3 is constituted by one plane, but as shown in FIG. 4A, the side wall surface of the hollow portion 6 is formed in a stepped shape. preferable. Therefore, the second ceramic body 3 can be formed by laminating a plurality of ceramic sheets 3a having different sizes, and the side wall surface 9b can be stepped.

  By forming the side wall surface 9b into a stepped structure in this way, as shown in FIG. 4B, when compressive stress is generated in the direction of the arrow, the sheet edge portion 10 of the stepped side wall surface 9b. Can be deformed like a wavy line to relieve stress. Therefore, it becomes easier to reduce stress concentration on the corners of the hollow portion 6. The sheet edge portion 10 may be provided with a roundness or a C surface in order to prevent chipping.

  The staircase-like structure has other structures such as a structure with a different direction (not shown) or a structure with a protruding central part (not shown) other than that shown in FIG. 4 unless the size of the hollow part is uniform in the thickness direction. It is also possible to adopt.

  The first ceramic body 2 of the ceramic laminate 1 may be composed of a single ceramic sheet, but may be composed of a plurality of ceramic sheets 2a and 2b as shown in FIG. That is, the ceramic sheet 2b in which the groove 7 is formed is laminated on the ceramic sheet 2a to form the first ceramic body 2, and the second ceramic body 3 and the third ceramic body 4 are stacked thereon in this order, and the hollow portion 6 Form. In this case, it is needless to say that the groove 7 is arranged so as to contact the hollow portion 6.

  Next, the manufacturing method of the ceramic laminated body of this invention is demonstrated.

  First, a first ceramic green sheet, a second ceramic green sheet, and a third ceramic green sheet corresponding to the first ceramic body, the second ceramic body, and the third ceramic body are produced.

  As described above, a desired ceramic can be used as the ceramic, but the case where alumina is used as an example will be described in detail below.

  As an alumina ceramic raw material powder, for example, an organic binder for molding and a solvent are appropriately added to an alumina ceramic raw material powder having an average particle size of 0.2 to 3 μm, a doctor blade method, extrusion molding, hydrostatic pressure, and the like. It can be produced using a known method such as molding (rubber press) or press formation.

  Next, an adhesive slurry is prepared. As the ceramic raw material powder, for example, an organic binder, a solvent, a dispersant and the like are appropriately added to an alumina raw material powder having an average particle size of 0.2 to 3 μm, and for example, a known ball mill, vibration mill, planet A slurry can be obtained by mixing and stirring using a mill or the like. Further, instead of slurry, it is possible to remove the solvent and concentrate it to prepare a paste, which can be used.

  Furthermore, a groove is formed in the first ceramic green sheet. As a method of forming the groove, it can be put into a slit shape by a cutter or the like. Further, it may be formed by laser processing or cutting. In addition, when forming a 1st ceramic body with a some sheet | seat, what is necessary is just to form by punching a groove | channel with the press die etc. in the ceramic green sheet which contact | abuts a hollow part, and laminating | stacking after that.

  Moreover, it is preferable to arrange | position so that a groove | channel forms a groove | channel along the longitudinal direction of a hollow part and a groove | channel and a hollow part continue. In particular, when the hollow portion is elongated, it is preferable that the groove and the hollow portion are arranged in parallel. In addition, if the cross-sectional shape of a hollow part is cylindrical shape, a groove | channel can be formed concentrically.

  Next, a through hole to be a hollow portion is formed in the second ceramic green sheet. In order to form this through hole, for example, the second ceramic green sheet can be punched into a desired shape with a press die or the like. In the case where the second ceramic body is formed as a laminated body of a plurality of ceramic sheets, the plurality of ceramic sheets each form a through hole that forms a hollow portion having a different size, and the plurality of ceramic sheets A plurality of ceramic sheets are laminated so that the through holes overlap each other and the laminated body of the through holes forms a desired shape, for example, a stepped shape.

  Thereafter, an adhesive slurry is applied to each of the first ceramic green sheet, the second ceramic green sheet, and the third ceramic green sheet, and these are laminated in this order to produce a multilayer ceramic molded body.

  Thereafter, drying, degreasing, and firing are performed under desired conditions to obtain a ceramic laminate in which a hollow portion is formed.

  The ceramic laminate produced in this way has the feature that stress is unlikely to concentrate at the corners of the hollow part, and by firing this, it is possible to produce a laminated ceramic with no cracks at the corners of the hollow part. it can.

  Next, the case of using the gas sensor as an oxygen sensor will be described as an example for the gas sensor of the present invention.

  6A and 6B show the structure of the gas sensor, where FIG. 6A is a transparent perspective view, and FIG. 6B is a cross-sectional view taken along X-X ′.

  According to FIG. 6, the gas sensor of the present invention is a detection provided in the above-mentioned laminated ceramic 21 on the main surface 4 a of the third ceramic body 4 constituting the laminated ceramic 21 at a position opening in the hollow portion. An electrode 22, a reference electrode 23 provided on the opposite main surface 4 b opposite to the main surface 4 a of the third ceramic body 4 so as to face the detection electrode 22, and a heating means 24 for heating the ceramic laminate 1. And are provided.

  The detection electrode 22 provided on the main surface 4a of the third ceramic body 4 is electrically connected to the electrode connection terminal 22P via the electrode lead wire 22L formed on the main surface 4a.

  The reference electrode 23 is also electrically connected to the electrode connection terminal 23 </ b> P like the detection electrode 22, but the electrode lead wire 23 </ b> L connected to the reference electrode 23 is connected to the opposing main surface 4 b of the third ceramic body 4. The electrode lead wire 23L is connected to an electrode connection terminal 23P provided on the main surface 4a via a via conductor. The electrode connection terminals 22P and 23P are connected to a control circuit (not shown), and the electromotive force between the detection electrode and the reference electrode can be measured to know the gas concentration.

  For example, as shown in FIG. 7, the heating means 24 constituting the gas sensor of the present invention includes a heating element 25, a heating element connection terminal connected to an external power source to supply power to the heating element 25, and a heating element. 25 and a heating element lead wire 25L that electrically connects the heating element connection terminal 25P.

It is important that the third ceramic body is a solid electrolyte in order to detect the oxygen concentration. In particular, zirconia ceramics has a feature of high strength and can be suitably used. For example, the solid electrolyte is made of a ceramic containing ZrO ₂ , and Y ₂ O ₃ and Yb ₂ O ₃ , Sc ₂ O ₃ , Sm ₂ O ₃ , Nd ₂ O ₃ , Dy ₂ O _3, etc. are used as stabilizers. 1 to 30 mol% of rare earth oxide in terms of oxide, preferably can be used partially stabilized ZrO ₂ or stabilized ZrO ₂ containing 3 to 15 mol%.

Further, by using ZrO ₂ in which 1 to 20 atomic% of Zr in ZrO ₂ is substituted with Ce, there is an effect that ionic conductivity is increased and responsiveness is further improved. Furthermore, for the purpose of improving the sinterability, Al ₂ O ₃ and SiO ₂ can be added to ZrO ₂ , but if it is contained in a large amount, the creep properties at high temperatures deteriorate, The total amount of Al ₂ O ₃ and SiO ₂ added is preferably 5% by mass or less, particularly 2% by mass or less.

  The reference electrode 22 and the detection electrode 23 deposited on the surface of the solid electrolyte substrate are both formed using platinum alone or an alloy of platinum and one kind selected from the group of rhodium, palladium, ruthenium and gold. It is desirable to do. Further, for the purpose of preventing the growth of metal grains in the electrode during the operation of the oxygen sensor and the purpose of increasing the contact at the so-called three-phase interface between platinum particles, solid electrolyte, and gas related to responsiveness, The electrolyte component may be mixed in the electrode at a ratio of 1 to 50% by volume, particularly 10 to 30% by volume.

  The shapes of the reference electrode and the detection electrode are not particularly limited, and may be quadrangular, elliptical, or other shapes. Further, the thickness of the reference electrode and the detection electrode is preferably 3 to 20 μm, particularly 5 to 10 μm, from the viewpoint that the responsiveness is easily stabilized.

  The ceramic laminate made of the first and second ceramics is preferably made of dense ceramics having a relative density of, for example, alumina ceramics of 90% or higher, particularly 95% or higher. By using alumina ceramics, the mechanical strength of the oxygen sensor itself can be increased by having excellent electrical insulation and making the relative density within the above range.

  According to FIG. 6A, the hollow portion 6 is provided in the multilayer ceramic body 21 along the longitudinal direction for introducing the reference atmosphere, and the hollow portion 6 reaches the right side surface in the drawing, Although it is an open end provided with a hollow portion 6 on the side surface, it reaches only the vicinity of the left side surface in the drawing, and is a closed end that is sealed to become a wall surface.

  The hollow portion 6 serves as an air introduction hole at the open end, and air introduced from the open end reaches the reference electrode 22 and becomes a reference value of the oxygen concentration. The gas present around the gas sensor is in contact with the detection electrode 23, and a voltage is applied to the reference electrode 22 and the detection electrode 23, and a current flows through the solid electrolyte sandwiched between the two electrodes. Since it depends on the oxygen concentration difference, it is possible to know the oxygen concentration of the gas around the gas sensor when atmospheric oxygen is used as the reference concentration.

  For example, when measuring the oxygen concentration in the exhaust gas, an electromotive force is generated between the detection electrode 22 and the reference electrode 23. Therefore, the detection electrode 22 and the reference electrode 23 are connected to the electrode lead wires 22L and 23L. By measuring the potential difference between the electrode connection terminals 22P and 23P electrically connected, the function as an oxygen gas sensor can be exhibited by measuring the oxygen concentration in the exhaust gas.

  That is, oxygen molecules become oxygen ions on the surface of the solid electrolyte ceramic on the oxygen concentration side (reference gas side) and move toward the oxygen concentration side (exhaust gas side). In addition, a reaction that changes from oxygen ions to oxygen molecules occurs on the surface of the solid electrolyte ceramics on the side with a low oxygen concentration (exhaust gas side). At this time, electrons are required to become ions on the high concentration side, and conversely, on the low concentration side, the oxygen gas is used, so electrons are unnecessary, and electrons tend to flow from the exhaust gas side toward the reference gas side. Potential is generated. By capturing this potential, it is possible to sense whether there is a difference between the oxygen concentrations on both sides.

  In order to have a sensing function, the temperature is preferably 300 ° C. or higher. For this purpose, the heating element 13 is provided. An air introduction hole is configured to supply the reference air to the reference electrode.

  According to the present invention, as shown in FIG. 7, by forming the ceramic porous layer 26 on the laminated ceramics 21 so as to cover the detection electrode 23, the detection electrode 23 can be protected and the exhaust gas can be exhausted. Corrosion by poisonous substances in the gas can be prevented.

  The ceramic porous layer 26 is preferably formed of a ceramic containing at least one selected from the group consisting of zirconia, alumina, γ-alumina, titania and spinel. As a result, the electrode poisoning substances P, Pb, Si and the like are difficult to reach the electrode, so that the electrode performance is stable and the gas responsiveness can be maintained. Further, the thickness is preferably 10 to 1500 μm, particularly 100 to 500 μm, and the porosity is preferably 10 to 50% from the viewpoint of excellent gas responsiveness.

  Next, a method for manufacturing the above-described oxygen sensor will be described with reference to FIG.

  First, a solid electrolyte ceramic green sheet corresponding to the third ceramic body is prepared. This ceramic green sheet is, for example, a zirconia ceramic solid electrolyte powder having oxygen ion conductivity, by appropriately adding an organic binder for molding, doctor blade method, extrusion molding, isostatic pressing (rubber press) Or it can produce by well-known methods, such as press formation.

  The obtained ceramic green sheet is cut into a desired size to produce a ceramic green sheet 101, and both sides thereof are connected to electrode patterns 122 and 123 serving as a detection electrode and a reference electrode, and to the detection electrode and the reference electrode, respectively. A lead wiring pattern 123L, an electrode pad 123P, a via conductor 123V, and the like to be a lead wiring are formed by screen printing, pad printing, roll transfer, for example, using a conductive paste containing platinum, and a sensor unit is manufactured. To do.

  Next, ceramic green sheets 102 to 105 made of an insulating ceramic material corresponding to the first and second ceramic bodies are produced. This ceramic green sheet is produced by, for example, a known method such as a doctor blade method, extrusion molding, isostatic pressing (rubber press) or press formation by appropriately adding a molding organic binder to alumina powder. Is done.

  In addition, the air introduction hole groove 106 is formed in the ceramic green sheet 102 which becomes the second ceramic body. As a method for forming the air introduction hole 106, it can be formed by punching into a desired shape with a press die or the like. Further, when the second ceramic body is formed from a sheet laminate of a plurality of ceramic sheets, the plurality of ceramic sheets are formed by punching hollow portions having different sizes into a desired shape using different press dies or the like. be able to.

  Further, a groove 107 is formed in the ceramic green sheet 103. As a method of forming the groove 107, it can be put into a slit shape by a cutter or the like. Further, it can be formed by laser processing or cutting. Moreover, it can be punched with a press die or the like and then laminated to form a groove.

  Furthermore, the ceramic green sheet 105 is cut to a desired size, and a pattern serving as a heating element 125 and a lead wiring 125L and a connection terminal pattern pad 125P serving as a heating element connection terminal are formed on both sides of the ceramic green sheet 105, respectively. The through hole 125V is formed by screen printing, pad printing, or roll transfer using, for example, a conductive paste containing platinum.

  Next, an adhesive slurry is prepared. As the ceramic raw material powder, for example, when preparing an alumina bonding slurry, an organic binder, a solvent, a dispersant, etc. are appropriately added to the alumina raw material powder having an average particle size of 0.2 to 3 μm, for example, A slurry can be obtained by mixing and stirring using a known ball mill, vibration mill, planetary mill or the like. In some cases, the solvent may be removed and concentrated to form a paste.

  Thereafter, the above-mentioned slurry for adhesion is applied to the ceramic green sheets 101 to 105 and sequentially laminated to produce the ceramic laminate of FIG.

  If desired, for example, a ceramic porous layer 126 containing at least one ceramic selected from the group consisting of alumina, zirconia, and spinel can be formed. Before firing, a dip method using a porous slurry, a printing method, A tape lamination method using a porous sheet can be used. Moreover, if it is after baking, a plasma spraying method etc. can be used.

  Then, well-known drying, degreasing, and baking according to a ceramic raw material, an organic binder, etc. are performed, and the oxygen sensor in which the hollow part (atmosphere introduction hole) was formed can be obtained.

  In addition, as a gas sensor of this invention, it can also be used suitably for gas sensors, such as a NOx sensor and a CO sensor other than an oxygen sensor, for example.

  A ceramic laminate having a hollow shape was produced.

  Alumina powder having a purity of 99.9% and an average particle size of 0.2 μm is mixed with 0.1% by mass of silica, and an acrylic binder and toluene are added thereto to produce a slurry. The doctor blade method Thus, a ceramic green sheet having a thickness of 0.25 mm or 0.08 mm was produced. The ceramic green sheet having a thickness of 0.08 mm was used when the second ceramic body was formed from a plurality of sheets.

  On the other hand, an alumina powder having a purity of 99.9% and an average particle size of 0.2 μm is mixed with 0.1% by mass of silica, and an acrylic binder, terpineol, acetone, and alumina balls are mixed therewith, After mixing with a rotary mill for 20 hours, acetone was vacuum deaerated with an evaporator to prepare an adhesive paste.

  A ceramic green sheet having V-shaped grooves described in FIG. 2B was produced on the obtained ceramic green sheet (thickness: 0.25 mm) using a round blade cutter. The depth of the groove was 100 μm.

  Further, in order to form the second ceramic body, the ceramic green sheet is punched into a size of 1.2 mm in width and 40 mm in length with a press die, and further, one end thereof is an open end and the other end is a closed end. Thus, a ceramic green sheet having a hollow portion with a width of 1.2 mm was produced.

  And said ceramic green sheet was laminated | stacked, the ceramic green sheet corresponded to a 1st, 2nd, 3rd ceramic body was laminated | stacked one by one, and the ceramic laminated body of FIGS. 1-6 was produced.

  When the ceramic laminate shown in FIG. 4 is produced, a ceramic green sheet of 0.08 mm is punched with a press die, and three types of through-holes (widths 1.0, 1.2, 1.4 mm) and laminated to form a hollow portion having a stepped side wall surface.

  Next, the obtained ceramic laminate was dried in air at 100 ° C. for 12 hours, heated to 400 ° C. for 2 hours, held at 400 ° C. for 2 hours, then heated, and finally fired at 1500 ° C. for 2 hours to form a hollow shape A laminated ceramic having the following characteristics was obtained.

  The evaluation was performed by cutting 10 obtained ceramic laminates and observing the corners of the hollow portion with a metal microscope to evaluate the presence or absence of cracks.

The results are shown in Table 1.

  Sample No. of the present invention. As for 1-10, the crack was not recognized by the corner | angular part of a hollow part.

  On the other hand, the sample No. 5 outside the scope of the present invention where no groove was formed. In No. 11, cracks were observed at the corners of the hollow portion.

  An oxygen sensor was produced as an example of a gas sensor.

  In the same manner as in Example 1, a ceramic green sheet having a thickness of 0.25 mm and an adhesive paste were produced.

  In addition, a mixed powder containing 60% by volume of platinum powder having an average particle diameter of 1 μm and 40% by volume of alumina powder having an average particle diameter of 0.5 μm is mixed with three rolls of an acrylic binder and TPO to provide conductivity. A paste was prepared.

  A through hole is formed in a predetermined position of the obtained ceramic green sheet with a press die, and the through hole is filled with a conductive paste using a screen printing method to form a via conductor, and an alumina ceramic green sheet An electrode pattern, a heating element pattern, and a lead wiring pattern were printed on the surface of the substrate by screen printing to produce a ceramic green sheet 101 of FIG. Note that an alumina paste containing 50% by volume of the pore-forming agent having an average particle diameter of 5 μm is applied to the surface of the electrode pattern to be the detection electrode, and a protective layer is formed. The shape of the heating element pattern is measured at room temperature after firing. The resistance value was adjusted to about 8Ω.

  The V-shaped groove shown in FIG. 2B was formed on another ceramic green sheet with a round blade cutter, and the ceramic green sheet 103 of FIG. 8 was produced. The depth of the groove was 100 μm.

  Further, in order to form the second ceramic body, the ceramic green sheet is punched into a size of 1.2 mm in width and 40 mm in length with a press die, and further, one end thereof is an open end and the other end is a closed end. Thus, a hollow portion having a width of 1.2 mm was formed, and the ceramic green sheet 102 of FIG. 8 was produced.

  Furthermore, the ceramic green sheets 101 and 105 were produced by applying an adhesive paste on the surface of the ceramic green sheet.

  And the ceramic green sheets 101-105 were laminated | stacked, the ceramic green sheet corresponded to a 1st, 2nd, 3rd ceramic body was laminated | stacked one by one, and the ceramic laminated body of FIGS. 1-6 was produced.

  Next, the obtained ceramic laminate was dried in the atmosphere at 100 ° C. for 12 hours, heated to 400 ° C. for 2 hours, held at 400 ° C. for 2 hours, then heated, and finally fired at 1500 ° C. for 2 hours. The oxygen sensor described in 1 was produced.

  The oxygen sensor was subjected to a temperature cycle of 100,000 times between 25 ° C. and 1100 ° C. in an air atmosphere, and the oxygen concentration was measured. Even when the temperature cycle was applied, the oxygen sensor showed a constant oxygen concentration and operated normally.

  On the other hand, as a comparative example, an oxygen sensor in which the groove 7 was not formed was manufactured in the same manner, and the oxygen concentration was measured under a temperature cycle. However, the measured value of the oxygen concentration was changed after the temperature cycle was 100,000 times. Therefore, when a portion corresponding to the X-X ′ cross section of FIG. 7 was cut, cracks were observed at the corners.

The structure of the ceramic laminated body of this invention is shown, (a) is a perspective view, (b) is sectional drawing of AA 'in (a), (c) is the elements on larger scale near the groove | channel in (b). It is. It is sectional drawing which shows the structure of the groove | channel provided in the ceramic laminated body of this invention. It is sectional drawing which shows the other structure of the ceramic laminated body of this invention. FIG. 4 shows still another structure of the ceramic laminate of the present invention, in which (a) is a cross-sectional view and (b) is a partially enlarged view of (a). It is sectional drawing which shows other structure of the ceramic laminated body of this invention. The structure of the gas sensor of this invention is shown, (a) is a permeation | transmission perspective view, (b) is sectional drawing in X-X '. The other structure of the gas sensor of this invention is shown, (a) is a permeation | transmission perspective view, (b) is sectional drawing of X-X 'in (a). It is a lamination | stacking exploded view of the oxygen sensor which is an example of the gas sensor of this invention. It is sectional drawing of the conventional ceramic laminated body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a ... Ceramic laminated body 2 ... 1st ceramic body 2a, 2b ... Ceramic sheet 3, 3b ... 2nd ceramic body 4 ... 3rd ceramic body 4a ... 3rd ceramic Main surface 4b of the body: Opposing main surface 5 of the third ceramic body 5 ... Adhesive layer 6 ... Hollow portion 7, 7a ... Groove 8 ... Side surface 9, 9b ... Side wall surface 10 ..Sheet edge portion 21 ... Laminated ceramic 22 ... Detection electrode 23 ... Reference electrode 23L ... Electrode lead wire 23P ... Electrode connection terminal 24 ... Heating means 25 ... Heat generation Body 25L ... Heating element lead wire 25P ... Heating element connection terminal 26 ... Ceramic porous layer

Claims (7)

A first ceramic body provided with a groove on the main surface, a second ceramic body provided with a hollow portion formed of a through hole, and a third ceramic body are laminated in this order via an adhesive layer, and the groove At least a part of the ceramic laminate is opened in the hollow portion. The ceramic laminate according to claim 1, wherein the groove is formed along a longitudinal direction of the hollow portion, and the groove is open to the hollow portion. The ceramic laminate according to claim 1 or 2, wherein a plurality of the grooves are provided on a main surface of the first ceramic body. The ceramic laminate according to any one of claims 1 to 3, wherein a side wall surface of the hollow portion is formed in a stepped shape. The said 1st ceramic body consists of a laminated body of a some ceramic sheet | seat, and the groove | channel penetrated in the ceramic sheet | seat contact | abutted with the said 2nd ceramic body among these ceramic sheet | seats is formed. The ceramic laminated body in any one of -4. A multilayer ceramics obtained by firing the ceramic laminate according to claim 1. The multilayer ceramics according to claim 6, wherein a reference electrode provided on a main surface of the third ceramic body constituting the multilayer ceramic is provided at a position opening in the hollow portion, and the reference electrode is opposed to the reference ceramic electrode. A gas sensor comprising: a detection electrode provided on an opposing main surface opposite to the main surface of a third ceramic body; and a heating means for heating the ceramic laminate.

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