JP4579636B2 - Manufacturing method of gas sensor - Google Patents

Description

  The present invention relates to a method of manufacturing a gas sensor, and more specifically, a base sheet mainly composed of an insulating ceramic that becomes a base after firing is laminated on a solid electrolyte sheet mainly composed of zirconia that becomes a solid electrolyte body after firing. The present invention relates to a method for manufacturing a gas sensor having a fired gas sensor element.

  Conventionally, a gas sensor stack type gas sensor element that outputs an electric signal corresponding to the concentration of oxygen or the like in exhaust gas from various internal combustion engines used in automobiles or the like has been known (see, for example, Patent Document 1 and Patent Document 2). ). This laminated gas sensor element includes a first cell portion (first ion introduction portion in Patent Document 2) in which a pair of electrodes are provided on a plate-like first solid electrolyte body mainly composed of zirconia, and zirconia as a main component. A second cell part (second ion introduction part in Patent Document 2) provided with a pair of electrodes on the plate-like second solid electrolyte body is a detection chamber (in Patent Document 2, space, in the claims) It corresponds to the “measuring chamber”).

  And between the 1st cell part and the 2nd cell part, the porous part for rate-limiting introduction | transduction (henceforth a porous part) which has the air permeability of the grade which can rate-control the external measurement gas and can introduce into a detection chamber In addition, an interlayer adjustment layer (also referred to as a substrate) mainly composed of alumina is provided to keep the interlayer between the first cell portion and the second cell portion at the same height as the porous portion. It has been. The detection chamber is formed by a space surrounded by the first cell portion, the second cell portion, the porous portion, and the interlayer adjustment layer. In addition, one of the electrodes of the first cell portion is disposed facing the detection chamber, and one of the electrodes of the second cell portion is disposed facing the detection chamber.

By the way, such a laminated gas sensor element is manufactured as follows. First, a solid electrolyte sheet having a predetermined shape to be a first solid electrolyte body or a second solid electrolyte body after firing is prepared. And the paste for electrodes is printed on each solid electrolyte sheet in a predetermined pattern, and the non-baking electrode used as an electrode after baking is formed. Then, on one solid electrolyte sheet, the porous portion paste and the interlayer adjustment layer paste are printed in a predetermined shape, and the unfired porous portion that becomes the porous portion after firing, and the unfired that becomes the interlayer adjustment layer after firing An interlayer adjustment layer is formed. Moreover, the detection chamber paste having a predetermined shape is printed so that the detection chamber is formed after firing. The detection chamber paste is fired and sublimated after firing. Thereafter, the other solid electrolyte sheet is laminated so as to sandwich the unfired porous portion and the unfired interlayer adjustment layer formed on one solid electrolyte sheet, subjected to pressure-bonding, and then fired.
JP 2003-294697 A JP 2003-294687 A

  By the way, when forming an unbaked interlayer adjustment layer on the solid electrolyte sheet, the thickness of the interlayer adjustment layer needs to be substantially the same as the thickness of the detection chamber and the porous portion (for example, 70 μm to 100 μm). Then, it is difficult to form the thickness by only one screen printing using the interlayer adjustment layer paste, and it is necessary to perform screen printing a plurality of times. Therefore, there is a problem that the process is bulky. Therefore, the present inventors have examined the formation of an unsintered interlayer adjustment layer by using an interlayer adjustment layer sheet mainly composed of alumina, rather than by screen printing. That is, it was considered that the interlayer adjustment layer sheet can be formed on the interlayer adjustment layer having the above thickness by laminating, pressing and firing the interlayer adjustment layer sheet on the first solid electrolyte sheet.

  However, there has been a problem that a crack (crack) occurs in the first solid electrolyte body and further in the second solid electrolyte body in contact with the interlayer adjustment layer. In particular, as a result of studies by the present inventors, it has been found that the occurrence is caused by the first solid electrolyte body and the second solid electrolyte body in contact with the boundary between the interlayer adjustment layer and the detection chamber.

  The present invention has been made in order to solve the above-described problems, and a sensor in which a base mainly composed of an insulating ceramic is in direct contact with a solid electrolyte mainly composed of zirconia that becomes a solid electrolyte body after firing. An element of the present invention is to provide a gas sensor manufacturing method that suppresses the occurrence of cracks in a solid electrolyte body with respect to the boundary between a substrate and an open space.

In order to solve the above-described problem, in the gas sensor manufacturing method according to the first aspect of the present invention, a plate-shaped solid electrolyte body mainly composed of zirconia having oxygen ion conductivity and a pair disposed on the solid electrolyte body. And a plate-like substrate that is mainly composed of an insulating ceramic and laminated so as to be in direct contact with the solid electrolyte body, and an open space is formed in at least a part of the substrate in the lamination direction of the substrate. In the method of manufacturing a gas sensor having a formed gas sensor element, a laminating step of bonding a base sheet that becomes a base after firing to a solid electrolyte sheet that becomes a solid electrolyte body after firing, and the solid electrolyte sheet and the base sheet simultaneously and a firing step of firing at a predetermined firing temperature, prior to said laminating step, to prepare a pre-fired sample sheet consisting of the solid electrolyte sheet, the firing The dimensions before firing the sample sheet A, shrinkage dimension of the dimension at the time of firing is completed by a predetermined firing temperature is B, when fired by the predetermined firing temperature of calcination before the sample sheet is completed, When the dimension A is 1, the ratio of the dimension A to the dimension A is calculated by 1-1 / (A / B), and the ratio of the shrinkage dimension to the dimension A is 0. In the process of firing the pre-firing sample sheet, the ratio of the shrinkage dimension to the dimension A is 1-1 / (A / B) and the firing of the pre-firing sample sheet is 100%. When the ratio of shrinkage dimension with respect to A is changed from 0 to 1-1 / (A / B) and the degree of completion of firing until completion is defined as a percentage, the firing completion rate is defined to, before While calculating | requiring the value of a baking shrinkage rate when the said baking completion rate will be 50% using the sample sheet | seat before baking, the baking shrinkage of the same value as the value of the baking shrinkage rate when the said baking completion rate will be 50% The base sheet is manufactured so that the temperature of the base sheet showing the rate is 35 ° C. or more higher than the temperature of the pre-fired sample sheet when the firing completion rate is 50%. ing.

  In addition, in the gas sensor manufacturing method of the invention according to claim 2, in addition to the configuration of the invention of claim 1, prior to the laminating step, the firing completion rate is 90% using the sample sheet before firing. The temperature of the base sheet exhibiting the firing shrinkage rate of the same value as the firing shrinkage rate value when the firing completion rate is 90% is calculated while the firing completion rate is determined. The base sheet is produced so as to be higher by 50 ° C. than the temperature of the pre-fired sample sheet at 90%.

  Moreover, in the gas sensor manufacturing method of the invention according to claim 3, in addition to the configuration of the invention of claim 1 or 2, the gas sensor element has a first solid electrolyte body and a second solid electrolyte body, The base is an interlayer adjustment layer sandwiched between the first solid electrolyte body and the second solid electrolyte body, and the open space is the first solid electrolyte body, the second solid electrolyte body, and the interlayer adjustment layer. It is the structure characterized by being a measurement chamber formed by.

  According to the study by the inventors, the shrinkage between the solid electrolyte body and the base body that occurs when the solid electrolyte body mainly composed of zirconia and the base body mainly composed of insulating ceramic are directly bonded and fired simultaneously. It was found that cracks occurred due to the difference. Therefore, it was examined to make the firing behavior of the solid electrolyte body (referring to the firing shrinkage ratio relative to the firing temperature) and the firing behavior of the substrate substantially the same. However, even if the firing behavior of the solid electrolyte body and the firing behavior of the substrate are substantially the same, the generation of cracks in the solid electrolyte body could not be suppressed.

  Therefore, in the gas sensor manufacturing method according to the first aspect of the present invention, when the solid electrolyte sheet that becomes a solid electrolyte body after firing and the base sheet that becomes a base after firing are fired simultaneously, the firing completion rate of the solid electrolyte sheet is The firing of the substrate sheet when the firing shrinkage value at the firing completion rate of 50% of the solid electrolyte sheet is equal to the firing shrinkage value of the substrate sheet than the firing temperature at 50% Bake so that the temperature is higher by 35 ° C. or more. Thereby, generation | occurrence | production of the crack to the solid electrolyte body after baking can be prevented.

  The insulating ceramic is any one of alumina, mullite, spinel, and aluminum nitride. Furthermore, in the present invention, the “main component” means that 50% by mass of the component is contained.

  In addition, in the gas sensor manufacturing method according to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the solid electrolyte sheet has a solid temperature higher than the firing temperature when the firing rate of the solid electrolyte sheet is 90%. Baking is performed so that the firing temperature of the base sheet becomes higher by 50 ° C. or more when the value of the firing shrinkage rate at the firing completion rate of 90% of the electrolyte sheet is equal to the value of the firing shrinkage rate of the base sheet. Thereby, generation | occurrence | production of the crack to the solid electrolyte body after baking can further be prevented.

  In addition, in the gas sensor manufacturing method of the invention according to claim 3, in addition to the effect of the invention of claim 1 or 2, the gas sensor element includes a first solid electrolyte body, a second solid electrolyte body, and a first solid electrolyte. It can be used for a gas sensor having an interlayer adjustment layer sandwiched between a body and a second solid electrolyte body, and a measurement chamber formed by the first solid electrolyte body, the second solid electrolyte body, and the interlayer adjustment layer. The gas sensor using this manufacturing method can suppress cracks generated not only in the first solid electrolyte body but also in the second solid electrolyte body.

  Hereinafter, an embodiment of a gas sensor manufacturing method embodying the present invention will be described with reference to the drawings. First, the structure of the gas sensor 2 in the present embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of the gas sensor 2. The configuration of the gas sensor of the present invention is not particularly limited. As shown in FIG. 1, the gas sensor 2 includes a stacked gas sensor element 1. The gas sensor element 1 includes a holder 211, a buffer material 212 made of talc powder, and a sleeve 213 (a lead frame 25 that electrically connects the gas sensor element 1 and a lead wire 26 described later between the gas sensor element 1 and the sleeve 213). And the like, and the whole is fixed to the metal shell 22. The metal shell 22 has a plurality of holes through which the gas to be measured can be introduced, and the detection part of the gas sensor element 1 (in FIG. 1, the first cell part solid electrolyte body 112 and the second cell part use). A protector 23 that covers the vicinity of one end side including the solid electrolyte body 132 and the like and protects one end side of the gas sensor 2 is disposed, and an outer cylinder that protects the other end side of the gas sensor 2 on the other end side of the metal shell 22. 24 is arranged. Further, from one end side of the outer cylinder 24, water or the like is prevented from entering the separator 27 provided with a through hole through which a lead wire 26 for connecting the gas sensor element 1 to an external circuit is branched and the gas sensor 2. A grommet 28 is provided.

  When the exhaust gas discharged from the internal combustion engine is to be measured using such a gas sensor 2, for example, an exhaust gas in which the exhaust gas flows is provided by providing a screw portion 221 such as a screw shape on the side surface of the metal shell 22. The measurement part of the gas sensor element 1 is attached to the tube so that it protrudes, and the measurement part can be measured by exposing the detection part of the gas sensor element 1 to the gas to be measured.

  Next, the gas sensor element 1 will be described with reference to FIGS. 2 is a schematic perspective view of the gas sensor element 1, FIG. 3 is a schematic exploded perspective view showing a part of the gas sensor element 1, and FIG. 4 is an AA ′ line in FIG. 2. FIG. 5 is a schematic sectional view, and FIG. 5 is a schematic sectional view taken along line BB ′ in FIG. 2. As shown in FIG. 2, the gas sensor element 1 has a narrow, substantially rectangular plate shape. As shown in FIG. 3, the first insulating base 10, the first cell part 11, the second cell part 13, A second insulating base 14 and the like are formed.

  Here, the first insulating base 10 will be described first. The first insulating base 10 is a part that ensures the overall strength of the gas sensor element 1 and has a heater 102 therein. The shape and size of the first insulating base 10 are not particularly limited, but usually the thickness is 0.1 mm or more (preferably 0.2 to 1.5 mm, more preferably 0.5 to 1.0 mm, Usually 2.0 mm or less). However, in order to have the heater 102 inside, the thickness is preferably 0.2 mm or more. If the thickness is less than 0.1 mm, it may be difficult to sufficiently support the first cell unit 111 and ensure the element strength. In particular, it may be difficult to perform a step of laminating another member on the green body that becomes the first insulating base 10 during manufacture. The first insulating base 10 may be a single layer or multiple layers.

  Moreover, the 1st insulating base 10 is comprised with insulating ceramics, and can exhibit sufficient insulation. For example, at a temperature of 800 ° C., the electrical resistance value between the heater 102 and any of the first cell unit electrodes 111 and 113 and the second cell unit electrodes 131 and 133 is 1 MΩ (preferably 10 MΩ) or more. It is preferable that a certain degree of insulation can be exhibited. Examples of the insulating ceramic capable of exhibiting such insulating properties include those containing one or more of alumina, mullite, spinel, steatite and aluminum nitride as a main component. Further, zirconia or the like that can exhibit sufficient insulation at low temperatures but cannot exhibit sufficient insulation at high temperatures of 800 ° C. or higher, for example, is not included in the insulating ceramics. However, it may be contained as a subcomponent within the range in which the above insulating properties are exhibited.

  Among the components constituting these insulating ceramics, alumina is preferable because it is inexpensive and relatively easy to process. When this alumina is used, the first insulating base 10 has 70 mass% or more (more preferably 80 mass%) of alumina with respect to the whole so that sufficient insulation and heat resistance (thermal shock resistance, etc.) are exhibited. (Mass% or more, more preferably 90% by mass). On the other hand, the component which comprises the site | part (for example, 1st cell part solid electrolyte body 112 grade | etc.,) Laminated | stacked in direct contact with the 1st insulating base 10 as a remainder can be contained 1-20 mass%. Thereby, the 1st insulating base 10 can relieve | moderate the thermal expansion difference between the site | parts laminated | stacked in direct contact.

  However, when the first insulating base 10 requires particularly high insulating properties, alumina is 90% by mass or more (more preferably 95% by mass or more, and further preferably 99.99% by mass) with respect to the entire insulating ceramic. It is preferable that the material contains 10000 ppm or less (more preferably 1000 ppm or less, more preferably 50 ppm or less) or does not contain silica (measurement limit or less). By using the first insulating base 10 as described above, current leakage from the heater 102 to any one of the first cell unit electrodes 111 and 113 and the second cell unit electrodes 131 and 133 can be ensured. Can be prevented.

  The heater 102 can include a heat generating portion 102a and a heater lead portion 102b. Among them, the heat generating part 102a is a part that actually raises the temperature by supplying electric power, and the heater lead part 102b is a part that guides electric power from an external circuit to the heat generating part 102a. Although these shapes are not particularly limited, for example, the heat generating portion 102a can be formed narrower than the heater lead portion 102b. Although the material which comprises these heat generating part 102a and heater lead part 102b is not specifically limited, For example, it can comprise with at least 1 sort (s) of noble metals, such as Pt, Pd, Rh, and Ir, molybdenum, and rhenium. Further, the heat generating portion 102a and the heater lead portion 102b may be made of the same material or different materials.

  Next, the first cell unit 11 will be described. The first cell portion 11 is supported by being laminated on the first insulating base portion 10 directly or indirectly via another member. In addition, the first cell unit solid electrolyte body 112 and a pair of first cell unit electrodes 111 and 113 are provided, and predetermined ions or gas are moved from one electrode side to the other electrode side. The part that can be. For example, the first cell unit 11 is a concentration detection cell that can output the concentration of the gas to be measured as a potential difference, or a predetermined ion from one electrode side to the other electrode side by applying a voltage to the pair of electrodes. Or it can function as a pump cell etc. which can move gas etc. The first cell portion 11 may be composed of only the first cell portion solid electrolyte body 112 and the pair of first cell portion electrodes 111 and 113. For example, the first cell portion solid electrolyte may be a first cell portion solid electrolyte. Other parts such as an internal resistance measurement electrode for measuring the internal resistance of the body 112 can be provided. The gas to be measured is a gas constituting the atmosphere to be measured, and is a measurement target gas by the element of the present invention or another element of the present invention, and is composed of one or more components.

  The first cell portion solid electrolyte body 112 is made of a zirconia-based sintered body containing zirconia as a main component and containing a stabilizer such as yttria, and has ionic conductivity. The shape, size, thickness and the like are not particularly limited, but the thickness can be 300 μm or less (preferably 200 μm or less, more preferably 150 μm or less, particularly preferably 50 μm or less, usually 20 μm or more). Even if the first cell part solid electrolyte body 112 is thicker than 300 μm, the function as an element is not lost, but the effect of thinning the first cell part solid electrolyte body 112 is hardly obtained. . On the other hand, when the thickness is less than 20 μm, the production becomes difficult and sufficient ion conductivity tends to be hardly obtained. The first cell portion solid electrolyte body 112 corresponds to the “first solid electrolyte body”.

  The first cell part electrodes 111 and 113 are electrodes formed on the surface of the first cell part solid electrolyte body 112. One of the first cell unit electrodes 111 and 113 is an electrode in contact with a gas to be measured in the measurement chamber 15 described later. The other first cell electrode 111 is disposed opposite to the first cell electrode 113, and is usually in contact with an atmospheric atmosphere or a reference gas. Is a non-contact electrode. The shape, size, thickness, and the like of the first cell portion electrodes 111 and 113 are not particularly limited. For example, the electrode portions 111a and 113a that are formed wide, the electrode lead portions 111b that are formed narrowly, 113b.

  The material constituting the first cell electrode 111, 113 is not particularly limited. For example, at least one of Pt, Au, Ag, Pd, Ir, Ru, and Rh is a main component (usually the entire electrode). In general, it is preferable that Pt is the main component. Moreover, you may contain the main component (zirconia) which comprises the solid electrolyte body 112 for 1st cell parts. The first cell part solid electrolyte body 112 may be made of a different material or the same material.

  Next, the second cell unit 13 will be described. The second cell unit 13 includes a second cell unit solid electrolyte body 132 and a pair of electrodes for the second cell unit 131 and 133, and a predetermined ion or gas is supplied from one electrode side to the other electrode. It is a part that can be moved to the side of Similarly to the first cell unit 11, the second cell unit 13 can also function as a concentration detection cell, a pump cell, or the like. The second cell unit 13 may be composed of only the second cell unit solid electrolyte body 132 and the pair of second cell unit electrodes 131 and 133. For example, the second cell unit solid electrolyte may be used as the second cell unit solid electrolyte. Other portions such as an internal resistance measurement electrode for measuring the internal resistance of the body 132 can be provided.

  Similarly to the first cell part solid electrolyte body 112, the second cell part solid electrolyte body 132 is composed of a zirconia-based sintered body containing zirconia as a main component and a stabilizer such as yttria, and has ionic conductivity. Is. The shape, size, thickness and the like are not particularly limited, but the thickness can be 300 μm or less (preferably 200 μm or less, more preferably 150 μm or less, particularly preferably 50 μm or less, usually 20 μm or more). Even if the second cell portion solid electrolyte body 132 is thicker than 300 μm, the function as an element is not lost, but the effect of thinning the solid electrolyte body is difficult to obtain. On the other hand, when the thickness is less than 20 μm, the production becomes difficult and sufficient ion conductivity tends to be hardly obtained. The second cell part solid electrolyte body 132 corresponds to the “second solid electrolyte body”.

  However, when the second cell part solid electrolyte body 132 contains other members, the resistance measured between the pair of second cell part electrodes 131 and 133 of the second cell part solid electrolyte body 132 is low. The first cell part solid electrolyte body 112 is preferably contained so as not to become larger than the resistance measured between the pair of first cell part electrodes 111, 113. In some cases, a larger current may flow in the second cell unit solid electrolyte body 132 than in the first cell unit solid electrolyte body 112. If the internal resistance of the solid electrolyte body is excessively high, an overvoltage causes the second cell. This is because the solid electrolyte body 132 for parts may be decomposed to cause a phenomenon called blackening.

  The second cell unit electrodes 131 and 133 are electrodes formed on the surface of the second cell unit solid electrolyte body 132. The second cell electrode 133 is an electrode in contact with an external measurement gas. The second cell electrode 131 is an electrode that faces the measurement chamber so as to be in contact with the gas to be measured in the measurement chamber and is opposed to the second cell electrode 133. The shape, size, thickness, and the like of the second cell unit electrodes 131 and 133 are not particularly limited. For example, the electrode units 131a and 133a that are formed wide and the electrode lead units 131b and 131b that are formed narrow are included. 133b. Further, the material constituting the second cell portion electrodes 131 and 133 is not particularly limited, but may be the same as the first cell portion electrodes 111 and 113. The electrodes of the second cell unit electrodes 131 and 133 may be made of different materials or the same material, and constitute the second cell unit solid electrolyte body 132. It may contain a main component (zirconia).

  Next, the second insulating base 14 will be described. The second insulating base portion 14 includes a portion made of insulating ceramics composed of a porous portion 141 and a non-porous portion 142, and the second cell portion 13 is directly or other member (in this embodiment, the second cell). An intermediate layer 134 is provided to maintain a distance between the solid electrolyte body 132 for the part and the second insulating base 14.), And the strength of the entire element is increased by the first insulation. This is a part to be secured together with the sex base 10. Although the shape and size of the second insulating base 14 are not particularly limited, the thickness is usually 0.1 mm or more (preferably 0.2 to 1.5 mm, more preferably 0.5 to 1.0 mm). Usually 2.0 mm or less). If the thickness is less than 0.1 mm, it may be difficult to ensure sufficient element strength. In addition, as in the case of the first insulating base 10, it may be difficult to stack during manufacture. The second insulating base 14 may be a single layer or a multilayer.

  The porous portion 141 and the non-porous portion 142 constituting the second insulating base portion 14 are made of insulating ceramics that can sufficiently exhibit the same insulating properties and heat resistance as the insulating ceramics constituting the first insulating base portion 10. It is preferable that it is formed. However, the insulating ceramic forming the first insulating base 10 and the insulating ceramic forming the second insulating base 14 may have the same composition or different compositions.

  The porous part 141 is a part of the second insulating base part 14 and is a part for bringing the second cell part electrode 133 constituting the second cell part 13 into contact with the external gas to be measured. The porous portion 141 acts to prevent the metal constituting the electrode from being poisoned by phosphorus, lead, silicon, etc., and to be covered at the point of contact with the electrode regardless of the flow velocity of the gas to be measured outside the element. A rate-limiting action or the like that makes the flow rate of the measurement gas substantially constant can be exhibited. The porous portion 141 preferably has a porosity of 5% or more (more preferably 20% or more, still more preferably 40% or more, usually 80% or less) in order to sufficiently exhibit these functions. When the porosity is less than 5%, the responsiveness tends not to be sufficiently improved as compared with an element including the porous portion 141 having a sufficient porosity. The porosity is calculated by dividing the difference obtained by subtracting the mass m1 in the air from the water-containing mass m2 in which water is sufficiently contained in the pores by immersing it in water by the apparent volume (including the pore volume) V. It is calculated by surplusing.

  In the multilayer gas sensor element of the present invention, the porous portion 141 is partially or entirely surrounded by the non-porous portion 142 constituting the second insulating base portion 14. It is preferable that the width of the frame portion surrounding a part or the entire surface of the porous portion 141 is 0.2 mm or more (when the element width is about 2 to 7 mm). When the width of the narrowest portion of the frame portion is less than 0.2 mm, it is difficult to sufficiently obtain durability against a cold cycle or impact during firing or use. In addition, it may be difficult to handle the green body during production.

  The rate limiting introduction porous portion 121 and the interlayer adjustment layer 123 are formed between the first cell portion 11 and the second cell portion 13, and the first cell portion solid electrolyte body 112, the second cell A measurement chamber 15 is formed in an open space surrounded by the solid electrolyte member 132 for part, the porous portion 121 for rate-limiting introduction, and the interlayer adjustment layer 123. Specifically, in the measurement chamber 15, the side wall along the longitudinal direction of the first cell portion solid electrolyte body 112 is formed by the rate limiting introduction porous portion 121, and the side wall along the short side direction is the interlayer adjustment layer. 123. The interlayer adjustment layer 123 corresponds to the “base”.

  The shape and size of the measurement chamber 15 are not particularly limited, but the space between the first cell portion solid electrolyte body 112 and a second cell portion solid electrolyte body 132 described later (usually the first facing the measurement chamber 15). 1 cell portion electrode 113 and second cell portion electrode 131 facing measurement chamber 15 are 1.0 mm or less (more preferably 0.5 mm or less, further preferably 0.1 mm or less, usually 0.02 mm). The above is preferable.

  The measurement chamber 15 can introduce a specific gas (for example, oxygen or the like) contained in the gas to be measured outside the gas sensor element 1 by the action of the second cell unit 13, and the gas to be measured outside the gas sensor element 1 can be introduced into the gas sensor. This is a space that can be introduced at a substantially constant speed (hereinafter referred to simply as “rate-limiting”) regardless of the flow velocity outside the element 1. In the gas sensor element 1 of the present embodiment, the atmosphere to be measured can be introduced into the gas sensor element 1 by the rate-limiting introduction porous portion 121. Further, the specific gas contained in the atmosphere in the measurement chamber 15 can be led out of the gas sensor element 1 by the action of the second cell unit 13.

  The interlayer adjustment layer 123 is a main part of the present invention, and is provided to form the measurement chamber 15 and to maintain the height of the measurement chamber 15 together with the rate limiting introduction porous portion 121. The material of the interlayer adjustment layer 123 is mainly composed of alumina.

[Example 1]
In such a multilayer gas sensor element 1, firing is performed using the interlayer adjustment layer 123 having a different average particle diameter of alumina material and yttria-stabilized zirconia powder content, and cracks in the solid electrolyte body 112 for the first cell portion are reduced. An evaluation test was conducted to determine whether or not the effect was effective in preventing the occurrence. In the following, for ease of understanding, the symbols of each part are the same before and after firing. In this evaluation test, the number of occurrences of cracks was examined using six types of interlayer adjustment layer sheets 123 (interlayer adjustment layers 123 before firing) of sample numbers A to F. Furthermore, the firing behavior of the solid electrolyte body and each sample was also examined. Table 1 shows the average particle diameter and the zirconia addition amount of the alumina material of Samples A to F, and the number of cracks generated. Furthermore, these Samples A to F and the first cell part solid electrolyte sheet 112 (before firing) The firing shrinkage of the first cell part solid electrolyte body 112) is shown for each predetermined firing temperature.

  For the interlayer adjustment layer sheet 123, alumina powder and yttria-stabilized zirconia powder are put into a pot mill, and a mixed solution of toluene and MEK (methyl ethyl ketone) as an organic solvent, polyvinyl butyral resin as a binder, dibutyphthalate as a plasticizer, pressure bonding Solvent stearyl alcohol is added to form a slurry. Then, this slurry is formed into a sheet having a thickness of 0.1 mm by a doctor blade method. Then, a 3 mm × 50 mm hole is provided to form the measurement chamber 15.

  And the sheet | seat 123 for interlayer adjustment layers is formed on the board | substrate with which the 1st insulating sheet 10 used as the 1st insulating base 10 after baking and the unbaked 1st cell 11 used as the 1st cell part 11 after baking were laminated | stacked. Place it and perform thermocompression bonding. This thermocompression bonding is performed at a temperature of about 60 ° C. for about 60 seconds at a pressure of 50 to 60 MPa. Thereafter, a rate-determining introduction porous paste that becomes the rate-determining introduction porous portion 121 after firing is printed on the short-side end of the hole of the interlayer adjustment layer sheet 123, and further becomes the measurement chamber 15 after firing. A measurement chamber paste made of a sublimation material is printed, and an unfired second cell 13 that becomes the second cell portion 13 after firing and a second insulating sheet 14 that becomes the second insulating base portion 14 after firing are laminated, Crimp.

  Then, after all of the first insulating base 10, the first cell 11, the second cell 13, and the second insulating base 14 are pressure-bonded, the four sides are cut and formed, and the resin is removed and fired at a predetermined temperature. I do. After the firing is completed, the cross section of the gas sensor element 1 is polished and a staining test is performed. That is, a color check solution is applied, and the presence or absence of cracks is visually confirmed at a magnification of 40 times using a stereomicroscope.

  The cracks are generated in the first cell part solid electrolyte sheet 112 and the second cell part solid electrolyte sheet 132 (second cell part solid electrolyte body 132 before firing) during firing. In particular, it occurs at a portion in contact with the end of the interlayer adjustment layer sheet 123. This is because the first cell part solid electrolyte sheet 112, the second cell part solid electrolyte sheet 132, and the interlayer adjustment layer sheet 123 are made of different materials, and the first cell part solid electrolyte sheet 112 and the second cell part. Since the shrinkage that occurs during firing of the solid electrolyte sheet 132 for use and the shrinkage that occurs during firing of the interlayer adjustment layer sheet 123 do not completely match, stress tends to concentrate, and the first cell portion solid electrolyte sheet 112 and the second solid electrolyte It is considered that the sheet 132 is cracked.

  Accordingly, it is considered that the firing of the first cell part solid electrolyte sheet 112 and the second solid electrolyte sheet 132 proceeds to ensure sufficient strength, and then the interlayer adjustment layer sheet 123 is fired. That is, the firing of the interlayer adjustment layer sheet 123 is delayed more than the firing of the first cell part solid electrolyte sheet 112 and the second cell part solid electrolyte sheet 1312. As one method of delaying the firing of the interlayer adjustment layer sheet 123, a sintering inhibitor such as zirconia is added. Another method is to reduce the amount of a firing aid such as a low-melting glass that is added to prevent the firing from proceeding excessively. There is also a method of delaying firing by mixing organic components such as a plasticizer and a binder to reduce the density of alumina grains in the interlayer adjustment layer sheet 123 and by delaying the speed of bonding. In addition, since alumina is usually easily fired as the surface activity is higher, there is a method of delaying the firing by taking a method that does not increase the surface activity. As a method for increasing the surface activity, there are a method of increasing the specific surface area, a method of using alumina with higher purity, and a method of reducing the particle size. Therefore, conversely, by reducing the specific surface area of alumina as much as possible, using alumina having a low purity, or using alumina having a larger particle size, the surface activity is not increased and the firing is delayed.

Therefore, in this test, two kinds of particle diameters of alumina material of 0.3 μm and 0.5 μm were provided, and three kinds of addition amounts of yttria stabilized zirconia were provided of 1 wt%, 3 wt%, and 5 wt%. Yttria-stabilized zirconia is a firing inhibitor, and when this is not added, firing of alumina is completed at about 1300 ° C.

  Here, with reference to Table 1, the average particle diameter of the alumina material of samples A to F and the amount of yttria-stabilized zirconia powder added will be described. Sample A has an average particle size of alumina material of 0.3 μm and zirconia added amount of 1 wt%, Sample B has an average particle size of alumina material of 0.3 μm and zirconia added amount of 3 wt%, and Sample C is made of alumina material. The average particle size is 0.3 μm, the zirconia addition amount is 5 wt%, the sample D has an average particle size of the alumina material of 0.5 μm and the zirconia addition amount is 1 wt%, and the sample E has an average particle size of 0. 5 μm, zirconia addition amount is 3 wt%, and sample F has an average particle size of alumina material of 0.5 μm and zirconia addition amount of 5 wt%.

  Next, the number of cracks will be described. In sample A, 10 out of 10 cracks occurred. In sample B, 10 out of 10 cracks occurred. In sample C, 10 out of 10 cracks occurred. In sample D, 1 out of 30 cracks occurred. In the sample E, no crack was generated in 30 samples, and in the sample F, no crack was generated in 30 samples.

  Further, in order to examine the firing behavior of each sample, the first cell part solid electrolyte sheet 112 and the interlayer adjustment layer sheet 123 are cut into 30 mm × 50 mm, and the dimensions before firing (dimension A) are measured. . In the following, the first cell part solid electrolyte sheet 112 and the second cell part solid electrolyte sheet 132 are the same, and only the first cell part solid electrolyte sheet 112 will be described. And after performing the degreasing | defatting of the sample sheet | seat before baking, baking is implemented at the temperature increase rate of 50 degreeC / 1 hour. Here, when the predetermined firing temperature is reached, the temperature is maintained for 1 hour, and the dimension (dimension B) of the subsequent sample sheet is measured. The predetermined temperatures are 1200 ° C., 1300 ° C., 1400 ° C., 1450 ° C., 1475 ° C., 1500 ° C., and 1525 ° C., and the same investigation is performed for each temperature.

  FIG. 6 is a line graph of the firing shrinkage rate in Table 1. The x axis represents the firing temperature and the y axis represents the firing shrinkage rate. The thick solid line indicates the solid electrolyte sheet 112 for the first cell part, the dotted line having a large interval is sample A, the dotted line having a large interval is sample B, the dotted line having a small interval is sample C, and the two-dot chain line having a wide interval is Sample D, a two-dot chain line with a narrow interval indicates sample E, and a dotted line with a small interval indicates sample F. Here, the firing shrinkage ratio is a value obtained by dividing dimension A (dimension before firing) by dimension B (dimension after firing).

  The firing shrinkage rate of the solid electrolyte body at a firing temperature of 1200 ° C. is 1.019, the firing shrinkage rate at a firing temperature of 1300 ° C. is 1.077, the firing shrinkage rate at a firing temperature of 1400 ° C. is 1.147, and the firing temperature is 1450 ° C. The firing shrinkage rate is 1.197, the firing shrinkage rate is 1.210 at a firing temperature of 1475 ° C., the firing shrinkage rate is 1.221 at a firing temperature of 1500 ° C., and the firing shrinkage rate at a firing temperature of 1525 ° C. is 1. 227.

  The firing shrinkage rate of Sample A at a firing temperature of 1200 ° C. is 1.055, the firing shrinkage rate at a firing temperature of 1300 ° C. is 1.087, the firing shrinkage rate at a firing temperature of 1400 ° C. is 1.150, and the firing temperature is 1450 ° C. Has a firing shrinkage of 1.201, a firing shrinkage of 1.214 at a firing temperature of 1475 ° C., a firing shrinkage of 1.221 at a firing temperature of 1500 ° C., and a firing shrinkage of 1.225 at a firing temperature of 1525 ° C. It is. Sample B had a firing shrinkage of 1.040 at a firing temperature of 1200 ° C., a firing shrinkage of 1.079 at a firing temperature of 1300 ° C., a firing shrinkage of 1.146 at a firing temperature of 1400 ° C., and a firing temperature of 1450 ° C. The firing shrinkage ratio is 1.199, the firing shrinkage ratio is 1.216 at a firing temperature of 1475 ° C., the firing shrinkage ratio is 1.221 at a firing temperature of 1500 ° C., and the firing shrinkage ratio is 1.225 at a firing temperature of 1525 ° C. It is. Sample C had a firing shrinkage of 1.028 at a firing temperature of 1200 ° C., a firing shrinkage of 1.054 at a firing temperature of 1300 ° C., a firing shrinkage of 1.134 at a firing temperature of 1400 ° C., and a firing temperature of 1450 ° C. Has a firing shrinkage ratio of 1.194, a firing shrinkage ratio of 1.215 at a firing temperature of 1475 ° C., a firing shrinkage ratio of 1.220 at a firing temperature of 1500 ° C., and a firing shrinkage ratio of 1.224 at a firing temperature of 1525 ° C. It is.

  Sample D had a firing shrinkage of 1.044 at a firing temperature of 1200 ° C., a firing shrinkage of 1.072 at a firing temperature of 1300 ° C., a firing shrinkage of 1.113 at a firing temperature of 1400 ° C., and a firing temperature of 1450 ° C. Has a firing shrinkage of 1.156, a firing shrinkage of 1.168 at a firing temperature of 1475 ° C., a firing shrinkage of 1.185 at a firing temperature of 1500 ° C., and a firing shrinkage of 1.196 at a firing temperature of 1525 ° C. It is. Sample E had a firing shrinkage of 1.029 at a firing temperature of 1200 ° C., a firing shrinkage of 1.046 at a firing temperature of 1300 ° C., a firing shrinkage of 1.094 at a firing temperature of 1400 ° C., and a firing temperature of 1450 ° C. Has a firing shrinkage of 1.159, a firing shrinkage of 1.173 at a firing temperature of 1475 ° C., a firing shrinkage of 1.188 at a firing temperature of 1500 ° C., and a firing shrinkage of 1.202 at a firing temperature of 1525 ° C. It is. Sample F had a firing shrinkage of 1.025 at a firing temperature of 1200 ° C, a firing shrinkage of 1.047 at a firing temperature of 1300 ° C, a firing shrinkage of 1.090 at a firing temperature of 1400 ° C, and a firing temperature of 1450 ° C. Has a firing shrinkage of 1.151, a firing shrinkage of 1.167 at a firing temperature of 1475 ° C., a firing shrinkage of 1.180 at a firing temperature of 1500 ° C., and a firing shrinkage of 1.188 at a firing temperature of 1525 ° C. It is.

  Here, the graph of FIG. 6 is read and the firing behavior of the solid electrolyte sheet 112 for the first cell part is compared with the firing behavior of each sample. The firing behaviors of Sample A and Sample B almost coincide with the firing behavior of the solid electrolyte sheet 112 for the first cell portion, although firing is slightly advanced around 1200 ° C to 1300 ° C. Moreover, although the firing behavior of Sample C is higher than that of the first cell part solid electrolyte sheet 112 at the stage of 1200 ° C., the firing is somewhat suppressed at 1300 ° C. to 1400 ° C., and 1450 ° C. to 1525 ° C. The temperature coincides with the firing behavior of the solid electrolyte sheet 112 for the first cell part at ° C. The firing behavior of Sample D is higher than that of the first cell part solid electrolyte sheet 112 at a stage of 1200 ° C., but at 1300 ° C. or higher, the firing is suppressed more than that of the first cell part solid electrolyte sheet 112. Yes. In the sample E, firing is proceeding more than the first cell portion solid electrolyte sheet 112 at the stage of 1200 ° C., but firing is further suppressed than the sample D at 1300 ° C. or higher. In the sample F, firing is proceeding more than the first cell part solid electrolyte sheet 112 at the stage of 1200 ° C., but firing is further suppressed than the sample E at 1300 ° C. or higher.

  Here, the number of cracks generated and firing behavior are compared. From the graph of FIG. 6, the firing behavior of sample B substantially matches the firing behavior of the solid electrolyte sheet 112 for the first cell part, but cracks occurred in 10 out of 10. Therefore, it can be seen that the firing behavior consistent with the firing behavior of the solid electrolyte sheet 112 for the first cell part is not desirable. Also, Sample A and Sample C, which almost coincide with the firing behavior of the first cell part solid electrolyte sheet 112 on the high temperature side in the graph, are cracked in 10 out of 10 samples, which is an undesirable firing behavior. I know that there is. That is, the firing behavior that substantially coincides with the first cell part solid electrolyte sheet 112 at a high temperature of 1450 ° C. or higher is not desirable. Conversely, it can be seen that Samples D, E, and F are free of cracks and have a desirable firing behavior. That is, it is desirable that the firing behavior be suppressed more than the firing temperature of the first cell part solid electrolyte sheet 112 at a high temperature of 1450 ° C. or higher. At this time, in the state where the firing is hardly progressed as in the stage of 1200 ° C., there is no problem even if the firing shrinkage is advanced as compared with the solid electrolyte sheet 112 for the first cell part.

  Here, the firing behavior of the solid electrolyte sheet 112 for the first cell part and the firing behavior of the sample are compared based on the firing shrinkage during the firing. Specifically, when the firing of the first cell part solid electrolyte sheet 112 is completed, the firing completion rate is 100%. From the graph shown in FIG. 6, the firing completion rate of the first cell part solid electrolyte sheet 112 is 90%. The firing shrinkage rate at the time of% and the time of 50% is determined. Then, based on the firing shrinkage rate, the temperature at which the first cell part solid electrolyte sheet 112 and each sample have the firing shrinkage rate is obtained and compared from the graph shown in FIG.

From Table 1, the firing shrinkage rate (ie, A / B) at the time when firing of the solid electrolyte sheet 112 for the first cell part is completed is 1.227. Therefore, with respect to the dimension B (dimension after firing) given by A / (A / B), if the dimension A (dimension before firing) is 1, the ratio of the dimension B (dimension after firing) to the dimension A is 1 / ( A / B) = 1 / 1.227. That is, the first cell part solid electrolyte sheet 112 contracted by “1- (1 / 1.227) ≈0.185” at a ratio to the dimension A.

Here, considering the shrinkage dimension at the time when 50% firing is completed, the ratio to the dimension A is “0.185 × 0.5 = 0.0925”. Therefore, the dimension of the solid electrolyte sheet 112 for the first cell part at this time is “1−0.0925 = 0.0.975” as a ratio to the dimension A. Therefore, the firing shrinkage rate when the firing completion rate is 50% is “1 / 0.9075≈1.102”. The firing temperature at which the firing shrinkage rate is 1.102 is between 1300 ° C. and 1400 ° C. from the graph. Therefore, from Table 2, the firing shrinkage rate at 1300 ° C. is 1.077, and the firing shrinkage rate at 1400 ° C. is 1.147, and therefore passes through two points (1300, 1.077) and (1400, 1.147). From the straight line, x at which the value of y is 1.102 is obtained, and the firing temperature at which the firing shrinkage rate is 1.102 is obtained. Then, since the equation of the straight line is “y = 0.007x + 0.167”, the firing temperature is about 1336 ° C.

Next, as in the case of 50%, the shrinkage at the time when 90% firing is completed is considered. The dimension in the case of 90% firing completion rate is “1-0.185 × 0.9≈0.834” in proportion to the dimension A , and the firing shrinkage ratio is “1 / 0.834 in proportion to the dimension A. ≒ 1.199 ". The firing temperature at this time is between 1450 ° C. and 1475 ° C. When calculated from the graph of FIG. 6 as in the case of 50%, it is about 1454 ° C.

  Next, for the samples D, E, and F in which no cracks occurred, the firing temperatures at which the firing shrinkage rates are “1.102” and “1.199” are obtained. In Sample D, the firing shrinkage ratio is “1.102” between 1300 ° C. and 1400 ° C. Therefore, when the firing temperature is calculated from the graph, it is about 1373 ° C. Moreover, it is 1525 degreeC or more that a baking shrinkage rate will be "1.119." Therefore, when the firing temperature is calculated from the graph by extending the 1500 ° C. to 1525 ° C. straight line, it is about 1532 ° C. In Sample E, the firing shrinkage ratio is “1.102” between 1400 ° C. and 1450 ° C. Therefore, when the firing temperature is calculated from the graph, it is about 1406 ° C. Moreover, it is between 1500 degreeC-1525 degreeC that a baking shrinkage rate will be "1.119." Therefore, when the firing temperature is calculated from the graph, it is about 1520 ° C. In sample F, the firing shrinkage ratio is “1.102” between 1400 ° C. and 1450 ° C. Therefore, when the firing temperature is calculated from the graph, it is about 1410 ° C. Moreover, it is 1525 degreeC or more that a baking shrinkage rate will be "1.119." Therefore, when the firing temperature is calculated from the graph by extending the straight line of 1500 ° C. to 1525 ° C., it is about 1559 ° C.

  In Sample D, the temperature difference when the firing shrinkage rate is “1.102” is 37 ° C., and the temperature difference when the firing shrinkage rate is “1.119” is 78 ° C. In sample E, the temperature difference when the firing shrinkage rate is “1.102” is 70 ° C., and the temperature difference when the firing shrinkage rate is “1.119” is 66 ° C. In Sample F, the temperature difference when the firing shrinkage rate is “1.102” is 74 ° C., and the temperature difference when the firing shrinkage rate is “1.119” is 105 ° C.

  Therefore, in the samples D, E, and F in which no cracks occur, the interlayer adjustment layer is increased after the firing temperature of 1336 ° C. when the firing complete rate of the first cell part solid electrolyte sheet 112 is 50% is increased by 35 ° C. or more. The firing shrinkage rate of the sheet 123 for firing is the firing shrinkage rate “1.102” when the firing completion rate of the solid electrolyte sheet 112 for the first cell part is 50%. Furthermore, after the firing completion rate of the solid electrolyte sheet 112 for the first cell part becomes 90%, the firing shrinkage ratio of the sheet 123 for the interlayer adjustment layer increases after the firing temperature of 1454 ° C. exceeds the first cell part. The firing shrinkage rate when the firing completion rate of the solid electrolyte sheet 112 for use is 90% is “1.119”.

  The upper limit of the amount of stearyl alcohol added as a pressure-bonding solvent is 20% of the slurry. This is because when the amount of stearyl alcohol is large, the interlayer adjustment layer 123 is not baked densely. If precise firing is not performed, the interlayer adjustment layer 123 absorbs moisture, and bursts due to rapid cooling or rapid heating, or current leaks and an accurate measured value cannot be obtained. Therefore, when the amount of stearyl alcohol added was 0%, 2%, 4%, 6%, 10%, 15%, 20% and 30%, respectively, and the dyeing test was performed, 0% to 20% were obtained. % Sample did not show color check solution stain, but 30% sample showed stain. That is, if the amount of stearyl alcohol is 20% or less, it is calcined densely, but if it is 30%, it is not calcined densely.

  The gas sensor of the present invention is suitable for a gas sensor having a gas sensor element having an open space in the stacking direction by laminating a base sheet mainly composed of an insulating ceramic on a solid electrolyte sheet that becomes a solid electrolyte body after firing. Is possible.

2 is a schematic cross-sectional view of a gas sensor 2. FIG. 1 is a schematic perspective view of a gas sensor element 1. FIG. 1 is a schematic exploded perspective view showing a part of a gas sensor element 1. FIG. It is typical sectional drawing of the AA 'line in FIG. It is typical sectional drawing of the BB 'line | wire in FIG. It is a line graph which shows the baking shrinkage rate of sample A-F and the solid electrolyte sheet 112 for 1st cell parts.

DESCRIPTION OF SYMBOLS 1 Gas sensor element 2 Gas sensor 10 1st insulating sheet 10 1st insulating base 11 Unbaked 1st cell 11 1st cell part 13 Unbaked 2nd cell 13 2nd cell part 14 2nd insulating base sheet 14 2nd insulation Sex base 15 measurement chamber 112 solid electrolyte body 123 for first cell part interlayer adjustment layer 123 sheet for interlayer adjustment layer

Claims (3)

A plate-like solid electrolyte body mainly composed of zirconia having oxygen ion conductivity;
A pair of electrodes disposed on the solid electrolyte body;
It has a plate-like base material mainly composed of an insulating ceramic and laminated so as to be in direct contact with the solid electrolyte body,
In a gas sensor manufacturing method having a gas sensor element having an open space formed in at least a part of the base body in the stacking direction of the base body,
A laminating step of bonding a base sheet that becomes a base after firing to a solid electrolyte sheet that becomes a solid electrolyte body after firing;
A firing step of firing the solid electrolyte sheet and the base sheet simultaneously at a predetermined firing temperature,
Prior to the lamination step,
Prepare a pre-firing sample sheet consisting of the solid electrolyte sheet,
The dimension before firing of the sample sheet before firing is A, and the dimension when firing at the predetermined firing temperature is completed is B,
The shrinkage dimension when the firing at the predetermined firing temperature of the sample sheet before firing is completed is obtained by 1-1 / (A / B) as a ratio to the dimension A when the dimension A is 1.
The pre-firing sample sheet whose ratio of shrinkage dimension to dimension A is 0 is set to 0%, and the ratio of shrinkage dimension to dimension A is 1-1 / (A / B). When the firing of the sheet is completed as 100%, in the process of firing the sample sheet before firing, the ratio of the shrinkage dimension to the dimension A is changed from 0 to be completed as 1-1 / (A / B). The value of the firing shrinkage rate when the firing completion rate is 50% using the sample sheet before firing , when the percentage of the degree of completion of firing up to is defined as the firing completion rate While seeking
The temperature of the base sheet exhibiting the firing shrinkage rate of the same value as the firing shrinkage rate when the firing completion rate is 50% is higher than the temperature of the sample sheet before firing when the firing completion rate is 50%. The method for producing a gas sensor is characterized in that the base sheet is produced so that the temperature is 35 ° C. or higher. Prior to the lamination step,
While obtaining the value of the firing shrinkage rate when the firing completion rate is 90% using the sample sheet before firing,
The temperature of the base sheet exhibiting the firing shrinkage rate of the same value as the firing shrinkage rate when the firing completion rate is 90% is higher than the temperature of the sample sheet before firing when the firing completion rate is 90%. The method for producing a gas sensor according to claim 1, wherein the base sheet is produced so that the temperature of the substrate is higher by 50 ° C. or more.   The gas sensor element includes a first solid electrolyte body and a second solid electrolyte body, and the base is an interlayer adjustment layer sandwiched between the first solid electrolyte body and the second solid electrolyte body, The gas sensor manufacturing method according to claim 1, wherein the space is a measurement chamber formed by the first solid electrolyte body, the second solid electrolyte body, and the interlayer adjustment layer.

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