JP2007248123A - Gas sensor element and manufacturing method of gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an electrode in a predetermined shape and thickness and to substantially reduce the use of noble metal, in manufacturing a gas sensor element by forming the electrode by sticking a core to the outer surface of a cylindrical closed-end solid electrolyte and depositing the noble metal around the core as the starting point. <P>SOLUTION: The manufacturing method of the gas sensor element for forming the electrode on the outer surface 1h of the solid electrolyte 1 comprises a core sticking process of sticking the core to the outer surface 1h of the cylindrical closed-end solid electrolyte 1 extending in the axial direction AX, and a plating process of depositing the noble metal in the plating liquid using the plating liquid where the core acts as a catalyst. In the core sticking process, the core is stuck to a first part that includes an electrode planed section 3 planed to form the electrode and is larger than the electrode planed section 3. In the plating process, the noble metal is deposited by masking a second part formed by removing the electrode planed section 3 from the first part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a gas sensor element in which an electrode made of a noble metal is formed on the outer surface of a bottomed cylindrical solid electrolyte body, and a method for manufacturing a gas sensor using the gas sensor element.

  2. Description of the Related Art Conventionally, an oxygen sensor incorporating an oxygen detection element has been used as a means for detecting the oxygen concentration in exhaust gas discharged from an internal combustion engine such as an automobile and controlling the air-fuel ratio of an air-fuel mixture supplied to the internal combustion engine. Yes. Among these, the oxygen detection element has a solid electrolyte body (hereinafter referred to as a base body) in which one end in the axial direction is closed and the other end is opened, and a flange protruding outward in the radial direction is formed at a substantially intermediate portion in the axial direction. And a reference electrode and a detection electrode made of platinum on the inner surface and the outer surface of the substrate.

  Of these, the detection electrode has a detection portion, a lead portion, and a terminal connection portion, and the detection portion generally extends from the distal end portion (closed end portion) to the distal end portion (base portion on the distal end side) of the collar portion. It is formed on the entire outer surface. Further, the lead portion has a thin line shape extending substantially parallel to the axial direction from the detection portion to the vicinity of the rear end portion of the base body beyond the collar portion. Further, the terminal connection portion is connected to the rear end portion of the lead portion and is formed so as to be connected around the circumference of the base. On the other hand, the reference electrode is formed on the entire inner surface of the substrate. (For example, refer to Patent Document 1).

  In such an oxygen detection element, the difference in oxygen partial pressure between the detection gas and the reference gas can be reduced by taking out the electromotive force difference due to the difference in oxygen concentration on both sides (inside and outside) of the solid electrolyte body from the detection electrode and the reference electrode. Used to detect.

Such an oxygen detection element is generally formed as follows. First, a base material (for example, ZrO ₂ ) is press-molded to form a molded body. Next, a precious metal paste containing platinum, palladium, or the like is printed on a portion of the outer surface of the molded body where the lead portion and the terminal connection portion are to be formed, and then the precious metal paste is simultaneously fired. Is fired to obtain a base body (hereinafter referred to as a half element) on which lead portions and terminal connection portions are formed.

  Next, of the outer surface of the half element, a nucleus is attached to a portion (detection portion planned portion) where the detection portion is to be formed (nucleation step), and electroless plating is applied to the attached nucleus. A noble metal is deposited using a method (plating step), and further an aging treatment is performed. (For example, refer to Patent Documents 1 and 2.) After that, the nucleation process and the plating process are performed on the entire inner surface of the half element on which the detection unit is formed in the same manner as described above, and further the aging process is performed, whereby the oxygen detection in which the detection electrode and the reference electrode are formed on the substrate. Get the element.

  Of these, in the nucleation step, for example, the substrate is immersed in a container containing a tetravalent platinum ammine aqueous solution, and a reducing agent having a strong reducing power made of sodium borohydride (SBH) is added to the aqueous solution. A platinum nucleus is attached to the outer surface of the substrate. In this nucleation process, in order to attach the nucleus only to the detection portion planned portion, the other non-detection portion planned portion, that is, the entire portion of the outer surface of the base from the front end portion of the collar portion to the rear end side Masking is performed using a substantially cylindrical mask jig made of a material such as silicon rubber or fluorine rubber.

Further, in the plating process, the half element with the platinum nucleus attached to the outer surface is immersed in a container containing a tetravalent platinum ammine aqueous solution, for example, and the aqueous solution containing hydrazine has a relatively low reducing power. A reducing agent is added (hereinafter, this solution is referred to as a plating solution), and platinum in the plating solution is deposited on the outer surface of the half element starting from the platinum nucleus adhered in the nucleation step. In this plating process, since it is possible to deposit platinum starting from only the nuclei attached in the nucleation process, it is not necessary to perform a mask.
JP 2004-170404 A (Background Art, FIG. 2, etc.) Japanese Examined Patent Publication No. 62-56978 (pages 3-4, etc.)

  However, with respect to the method of masking in the nucleation step as described above, a slight gap is actually formed between the base and the mask jig, and a solution (hereinafter referred to as a noble metal nucleus) is attached to the gap. , Referred to as a nucleating liquid) flows in, and the nuclei may adhere to the non-detection part scheduled part other than the detection part planned part.

  If nuclei are attached to the non-detection part planned part in this way, since the non-detection part planned part is not masked in the subsequent plating step, the nuclei attached to the non-detection part planned part are the starting points. In some cases, platinum is deposited on the surface, and bleeding or the like is generated in the finally obtained detection portion, so that the desired shape may not be obtained. In addition, since the substrate is immersed in a container in which a predetermined amount of plating solution is placed, a part of the platinum component in the plating solution that should be used only for the detection portion planned portion should also be used for the non-detection portion planned portion. It becomes. Then, the thickness of the detection part finally obtained becomes thin and may not become a desired thickness. Thus, since a detection part cannot obtain desired shape and thickness, when the gas sensor which assembled | attached the gas sensor element is exposed to a high temperature environment, there exists a possibility that durability of a detection part may fall. On the other hand, in such a method, in order to obtain a desired thickness, an amount of plating solution larger than a predetermined amount is used, resulting in an increase in the amount of noble metal used.

  By the way, in recent years, as one method for reducing the amount of noble metal used, it has been studied to reduce the thickness of the lead portion and the terminal connection portion as described above. However, if the thickness of the lead portion and the terminal connection portion is reduced by the printing method using the noble metal paste, there is a possibility that sufficient conduction cannot be obtained. A method of forming through a plating process has been studied.

  However, when trying to form such a thin wire-shaped lead portion through the nucleation step and the plating step at the same time, a conventional cylinder that simply masks the entire rear end side from the front end portion of the collar portion. Instead of the mask jig, a mask jig provided with a slit or the like for forming a lead portion on the side surface portion must be used. As a result, a slight gap is formed between the mask jig and the base in the vicinity of the slit, the nucleating liquid flows into the gap, and bleeding or the like occurs in the lead portion. As a result, a lead portion having a desired shape and thickness cannot be obtained, and there is a problem that the durability of the lead portion is lowered when a gas sensor with a gas sensor element is exposed to a high temperature environment. There is.

  Further, as another method for reducing the amount of noble metal used, a method for reducing the range in which the detection portion is formed has been studied. That is, conventionally, the detection part is formed on the entire outer surface from the tip of the base to the tip of the flange, but the part that actually functions as the oxygen detection element is a heater inserted into the base. Is a relatively narrow portion on the front end side of the base body, so that the detection portion is not provided up to the front end portion of the collar portion but is provided only in the vicinity of the front end portion of the base body to reduce the range.

  However, when the detection unit is to be formed near the tip of the base, the tip of the base must be masked rather than the tip of the collar. By the way, a minute unevenness is conventionally provided on the front end side of the base body in order to increase the adhesion force between the detection portion and a protective layer for protecting the detection portion formed on the detection portion. If a mask is applied to the tip side of the substrate on which such irregularities are formed, the adhesion between the substrate and the mask jig is reduced, and a gap is likely to be generated, and the nucleation liquid flows in as described above. In some cases, bleeding may occur in the detection unit. As a result, a detection part having a desired shape and thickness cannot be obtained, and there is a problem in that the durability of the lead part is lowered when a gas sensor incorporating a gas sensor element is exposed to a high temperature environment. There is.

  The present invention has been made in order to solve the above-described problems. A gas sensor is formed by forming electrodes such as a detection portion, a lead portion, or a terminal connection portion on the outer surface of a substrate through a nucleation step and a plating step. In manufacturing the element, it is possible to make the shape and thickness of the electrode as desired, and to substantially reduce the use of noble metal, and a method for manufacturing a gas sensor element and such a manufacturing method. It aims at providing the manufacturing method of the gas sensor using the gas sensor element obtained.

  The method for producing a gas sensor element of the present invention includes a nucleation step of attaching nuclei to the outer surface of a bottomed cylindrical solid electrolyte body extending in the axial direction, and a plating solution using the nuclei as a catalyst. And a plating step for depositing a noble metal on the outer surface of the solid electrolyte body, and a method for producing a gas sensor element in which an electrode is formed on the outer surface of the solid electrolyte body. An electrode is planned to be formed when an electrode is formed, and the nucleus is attached to a first portion wider than the electrode planned portion, and in the plating step, the electrode predetermined portion is removed from the first portion. The second site is masked to deposit the noble metal.

  The electrode in the method for producing a gas sensor element of the present invention has a detection part formed on the entire front end side of the solid electrolyte body, and one or more linear shapes from the detection part toward the rear end side in the axial direction. It is preferable to have at least a lead portion that extends. Further, the solid electrolyte body has a flange portion protruding outward in the radial direction, and the detection portion is formed on the entire circumference of the front end side of the solid electrolyte body with a gap from the flange portion. It is preferable.

  Further, the gas sensor manufacturing method of the present invention is a gas sensor manufacturing method using a gas sensor element in which an electrode having a predetermined shape is formed on the outer surface of a solid electrolyte body, and the gas sensor element manufactures the gas sensor element described above. It is manufactured by the method.

  According to the method for manufacturing a gas sensor element of the present invention, first, in the nucleation step, the electrode includes a planned electrode portion that is expected to be formed on the outer surface of the substrate. In the subsequent plating step, a desired shape is formed on the outer surface of the substrate by masking the second portion of the first portion excluding the planned electrode portion and depositing noble metal in the plating solution. It is possible to form a thick electrode, and the use of noble metals can be substantially reduced.

  Hereinafter, the manufacturing method of the gas sensor element of this invention is demonstrated. Below, the outline | summary of the manufacturing method of the gas sensor element of this invention is demonstrated first, and a specific example is demonstrated after that. The method for producing a gas sensor element of the present invention is to form an electrode on the outer surface of a bottomed cylindrical solid electrolyte body extending in the axial direction, and a nucleation step of attaching a nucleus to the outer surface of the solid electrolyte; And a plating step of depositing a noble metal in the plating solution using a plating solution in which the adhered nuclei act as a catalyst.

  Then, during the nucleation step, the electrode is planned to be formed on the outer surface of the substrate, and the nucleus is attached to the first part wider than the electrode planned part, and the next plating is performed. The process is characterized in that the precious metal in the plating solution is deposited by masking the second part of the first part excluding the planned electrode part.

  That is, even when masking is performed in the plating process, the plating solution may flow into the gap between the base and the mask jig. However, since the gap between the substrate and the mask jig is very narrow, the inflow of new plating solution hardly occurs once the plating solution has flowed. That is, it is difficult for the plating solution to be replaced in the gap between the base and the mask jig.

  For this reason, by masking in the plating process, even if the plating solution flows into the gap between the substrate and the mask jig, the inflow of new plating solution hardly occurs as described above. It is possible to suppress the precipitation of the noble metal starting from the formed nucleus.

  For this reason, in the present invention, in the nucleation step, the nucleus is attached to the first part wider than the planned electrode part, for example, the non-electrode planned part (second part) where the electrode around the planned electrode part is not formed, By masking this second part in the plating process, it is possible to substantially suppress the precipitation of noble metal starting from the nucleus adhering to the second part, and starting from the nucleus adhering to the planned electrode part. It is possible to deposit noble metals only. For this reason, it is possible to obtain a desired shape and thickness without causing bleeding in the finally obtained electrode, and it is possible to suppress unnecessary consumption of the noble metal. Therefore, even if the gas sensor in which the gas sensor element is assembled is exposed to a high temperature environment, it is possible to suppress a decrease in durability.

  Further, the part to which the nucleus is attached in the nucleation step may be the first part wider than the electrode part including the electrode part as described above. For example, the nucleus may be attached to the entire outer surface of the substrate. Is possible. By attaching nuclei to the entire outer surface of the substrate in this way, even if the planned electrode portion varies from one substrate to another, eventually any portion may be used as the planned electrode portion. This is preferable because it facilitates alignment and the like.

  Further, the portion to be masked in the plating step is the second portion of the first portion excluding the planned electrode portion. For example, if the outer surface of the substrate is chucked with a jig or the like during the nucleation step, no nuclei adhere to the outer surface (other than the first portion), and thus no noble metal does not precipitate in the plating step. Therefore, the outer surface other than the first part may or may not be masked in the plating process.

  Further, it is conceivable to mask in the nucleation process as in the prior art, and to mask in the plating process as in the present invention while attaching the nuclei almost only to the planned electrode portion. However, in this method, there is a case where uniform nuclei cannot be attached to the solid electrolyte body near the boundary between the masked part and the unmasked part in the nucleation step, and the electrode obtained finally There is still a possibility that bleeding occurs and the desired shape and thickness are not obtained. In particular, when an attempt is made to simultaneously form a thin wire like a lead portion to be described later through a nucleation step and a plating step, it is particularly susceptible to this influence.

  Furthermore, in the production method of the present invention, the nucleus adhering to the substrate may act as a catalyst for the plating solution later, and examples thereof include platinum, palladium, and rhodium. Further, the noble metal in the plating solution may be any one used as an electrode of a gas sensor, and examples thereof include platinum, palladium, rhodium and the like. The core and the noble metal in the plating solution may be the same material or different materials.

  In addition, according to the manufacturing method of the present invention, at the stage where the plating process is completed, a portion where nuclei are attached to the second portion or a portion where a precious metal is slightly deposited remains, but the thickness of these portions is Since it is very thin and sublimates during the subsequent aging process, there is no particular problem. Note that the portion where the precious metal is slightly deposited refers to the precious metal temporarily attached to the core attached to the masked portion by the plating solution flowing into the gap between the base and the mask jig during the plating process. It is the part deposited in

  Furthermore, the manufacturing method of the present invention includes a detection portion in which the electrode is formed on the entire circumference of the front end side of the solid electrolyte body, and a lead portion extending linearly from the detection portion toward the rear end side in the axial direction. It is effectively used for at least a gas sensor element.

  That is, even if a mask is formed using a cylindrical body having a substantially C-shaped cross section in which a slit for forming a thin lead portion as a mask jig is provided on a side surface portion as a mask jig in the plating process, Even if the plating solution flows into the gap with the mask jig, for the reasons described above, it is possible to suppress the precipitation of the noble metal starting from the nucleus attached to the masked portion. . For this reason, it is possible to obtain a desired shape and thickness even when a thin lead portion is formed. In addition, it is possible to form a thin lead portion or the like, which has been conventionally formed by printing a noble metal paste, through a nucleation process and a plating process, thereby reducing the use of noble metal.

  Furthermore, in the manufacturing method of the present invention, the solid electrolyte body has a flange portion that protrudes radially outward, and the detection portion is formed on the entire periphery of the front end side of the solid electrolyte body with a gap from the flange portion. It is used effectively for the gas sensor element of the form which is made.

  That is, even if a mask is applied to the front end side of a substrate having minute irregularities in the plating process, the plating solution flows into the gap due to such minute irregularities, and for that reason, the mask. It is possible to suppress the precipitation of the noble metal with respect to the nuclei attached to the formed part. For this reason, it becomes possible to obtain a detection part in desired shape and thickness with respect to the front end side of a base | substrate. Moreover, it becomes possible to reduce the area of a detection part, and also to reduce use of a noble metal.

  In addition, the electrode in the manufacturing method of the gas sensor element of the present invention may be any electrode as long as it can be formed on the outer surface of the substrate through the nucleation step and the plating step, such as the detection unit, the lead unit, and the terminal connection unit as described above. Some or all of them may be mentioned, but the present invention is not necessarily limited to such.

  Next, the manufacturing method of the gas sensor element of the present invention will be described with specific examples. In addition, the manufacturing method of the gas sensor element of this invention is not necessarily restricted to such a specific example.

  FIG. 1 is an external view with a part cut away showing an example of a substrate 1 used in the method of manufacturing a gas sensor element of the present invention. The base body 1 has a substantially cylindrical shape extending along the axis AX, and has one end closed and the other end opened. Here, the end on the closed side is the front end 1s, and the end on the opened side is the rear end 1e.

  A flange 2 protruding outward in the radial direction is formed at a substantially intermediate portion in the direction along the axis AX of the base body 1. The flange portion 2 is used for engaging the base body 1 in a metal shell of a gas sensor described later. Of the outer surface 1h, on the entire distal end portion 1s side of the base body 1 from the distal end portion (base portion on the distal end side) 2s of the flange portion 2, although not shown, it is formed on a detection portion described later or on the detection portion. Fine irregularities are provided for enhancing the adhesion of the protective layer and the like.

  In the outer surface 1 h of the base 1, a portion where an electrode is to be formed from now on is a planned electrode portion 3. The electrode planned portion 3 includes, for example, a detection portion planned portion 3g serving as a detection portion, a lead portion planned portion 3s serving as a lead portion, and a terminal connection portion planned portion 3t serving as a terminal connection portion.

  The detection portion planned portion 3g is the entire portion of the outer surface 1h of the base body 1 from the front end portion 1s of the base body 1 to a portion that is spaced a predetermined distance from the front end portion 2s of the flange portion 2 to the front end side. . Here, the reason why the detection portion planned portion 3g is not extended to the tip portion 2s of the flange portion 2 is to reduce the range in which the detection portion is formed to reduce the use of noble metal, and the portion that substantially functions as a gas sensor element. This is because the detection part is intended to be formed only in the vicinity of the front end part 1s of the base body 1.

  In addition, the lead portion planned portion 3s extends from the rear end portion of the detection portion planned portion 3g to the portion slightly beyond the front end side from the rear end portion 1e of the base body 1 beyond the flange portion 2 in the outer surface 1h of the base body 1. This is a thin line portion along the axis AX. Further, the terminal connection portion planned portion 3t is a rear end portion of the lead portion planned portion 3s in the outer surface 1h of the base body 1 and is a thin line-shaped portion that goes around the base body 1 in the circumferential direction.

  In addition, on the outer surface 1 h of the substrate 1, a portion other than the planned electrode portion 3 is a non-electrode planned portion 4. In this figure, the non-electrode scheduled portion 4 includes an intermediate non-electrode scheduled portion 4s that is a portion excluding the lead portion planned portion 3s among the portions surrounded by the detection portion planned portion 3g and the terminal connection portion planned portion 3t. The terminal connection portion planned portion 3t includes a rear end non-electrode planned portion 4e which is a portion on the rear end side. In the present embodiment, the intermediate non-electrode scheduled part 4s corresponds to the second part of the claims, and the intermediate non-electrode scheduled part 4s and the electrode planned part 3 correspond to the first part of the claims. To do.

  As such a base | substrate 1, what was manufactured by the well-known manufacturing method can be used, for example, the solid electrolyte body which has a zirconia as a main component and a bottomed cylindrical molded object using a well-known press molding method, Then, it can be used which is baked for about 2 hours in an atmosphere of 1500 ° C.

  And on such a base | substrate 1, an electrode is formed in the outer surface 1h through a nucleation process and a plating process as mentioned above. In addition, it is preferable to perform the pre-processing process which etches the outer surface 1h of the base | substrate 1 before a nucleation process.

  FIG. 2 shows an example of the nucleation process. In this nucleation step, for example, the rear end portion 1e of the base 1 (which will later become the rear end non-electrode scheduled portion 4e) is fitted into the hole 5a of the base fixing jig 5, and further this base fixing jig. 5 is fixed by being fitted into the hole 6a of the fixing jig fixing plate 6.

The base 1 fixed by the fixing jig fixing plate 6 in this manner is immersed in an aqueous platinum complex salt solution (for example, a tetravalent platinum ammine aqueous solution or a divalent platinum ammine aqueous solution) 8a (platinum concentration: 45 g / m ³ ). Further, the platinum complex aqueous solution 8a in which the substrate 1 is immersed is heated to 60 ° C., and the aqueous solution 8b of sodium borohydride is added. Then, the substrate 1 is allowed to stand for 10 minutes in the nucleating solution 8 as a mixed solution, and platinum nuclei are deposited on the outer surface 1 h of the substrate 1.

  In this example of the nucleation step, not only the platinum nucleus is attached to the planned electrode portion 3, but also the intermediate non-electrode scheduled portion 4s, which is the other portion, is attached with the platinum nucleus, Platinum nuclei are attached to a first portion wider than the planned electrode portion 3 including the planned portion 3.

  In this example of the nucleation step, platinum nuclei are not attached to the rear end non-electrode scheduled portion 4e fitted into the hole 5a of the substrate fixing jig 5 in the outer surface 1h of the substrate 1.

  FIG. 3 shows how the substrate 1 is prepared prior to the plating process. First, a mask jig 10 used for masking the outer surface 1h is attached to the base body 1 to which the platinum nucleus is attached, and the base body 1 to which the mask jig 10 is attached is attached to a mask jig fixing plate 11. The base 1 and the mask jig 10 are integrally fixed by the mask jig fixing plate 11 as shown in FIG.

  Here, the mask jig 10 has a cylindrical shape having a substantially C-shaped cross section with a slit (cut) 10a in the side surface portion. The mask jig 10 is shaped so as to mask only the intermediate non-electrode planned portion 4s in the outer surface 1h of the base 1 shown in FIG. 1, so that the slit 10a coincides with the lead portion planned portion 3s. It is a simple shape.

  For this reason, the mask jig 10 is mounted in alignment on the intermediate non-electrode scheduled portion 4 s of the base 1. However, when platinum nuclei are attached to the entire outer surface 1h excluding the rear end non-electrode planned portion 4e in the nucleation step as in this example, the alignment along the axis AX of the substrate 1 is as follows. Although it is necessary to accurately carry out the relationship with the detection portion planned portion 3g and the terminal connection portion planned portion 3t, the alignment in the circumferential direction is particularly effective because any portion can be used as the lead portion planned portion 3s. do not have to. In other words, the final planned electrode portion 3, particularly the lead portion planned portion 3 s, is determined when the mask jig 10 is mounted.

FIG. 5 shows an example of the plating process. In the plating step, a mask jig fixing plate 11 on which the substrate 1 and the mask jig 10 are integrally fixed is attached to a platinum complex aqueous solution (for example, a tetravalent platinum ammine aqueous solution or a divalent platinum ammine aqueous solution) 12a (platinum concentration: 600 g / m). ³ ) Immerse in and heat. Then, a hydrazine aqueous solution 12b (concentration: 85% by mass) having a reducing power to such an extent that platinum does not precipitate is added to the platinum complex aqueous solution 12a in which the substrate 1 is immersed, except for the portion where the nucleus is attached. The substrate 1 is left in a certain plating solution 12 while swinging for about 2 hours, and platinum is deposited on the nuclei attached to the outer surface 1 h of the substrate 1.

  In this plating process, platinum is formed in the electrode surface portion 3 on which the mask jig 10 is not mounted, that is, the detection portion planned portion 3g, the lead portion planned portion 3s, and the terminal connection portion planned portion 3t, of the outer surface 1 of the substrate 1. Precipitate.

  On the other hand, the intermediate non-electrode scheduled portion 4s on which the mask jig 10 is mounted is basically not in contact with the plating solution 12 because the mask jig 10 is mounted, and platinum nuclei are attached. However, platinum in the plating solution does not precipitate. Further, even if the plating solution 12 flows into the gap between the substrate 1 and the mask jig 10, platinum is not substantially deposited because the substitution of the plating solution in the gap between the substrate and the mask jig hardly occurs. Further, since no platinum nucleus is attached to the rear end non-electrode scheduled portion 4e in the nucleation step, platinum does not precipitate even when the plating solution 12 comes into contact.

  In this way, by mounting the mask jig 10 on the outer surface 1h of the substrate 1 in the plating step, platinum can be deposited only on the detection portion planned portion 3g, the lead portion planned portion 3s, and the terminal connection portion planned portion 3t. And can have a desired shape.

  Further, in particular, on the outer surface 1h on the distal end side of the distal end portion 2s of the flange portion 2 of the base body 1, minute irregularities are provided in order to increase the fixing force of the detection portion and the protective layer formed thereon. However, with respect to the detection portion planned portion 3g and the lead portion planned portion 3s in the portion having such minute irregularities, platinum can be deposited only on the planned portion, and a desired shape can be obtained.

  When the plating process is completed in this manner, the base 1 to which the mask jig 10 is mounted is removed from the mask jig fixing plate 11 and the mask jig 10 is further removed from the base 1 as shown in FIG. Thereafter, the outer surface 1h of the substrate 1 is washed with water and dried.

  Then, an aging process is performed on the portion of the outer surface 1h of the substrate 1 where the platinum nucleus has grown. Specifically, heat treatment is performed at 1200 ° C. for about 1 hour. At this time, the nuclei attached to the non-electrode planned portion 4, particularly the intermediate non-electrode planned portion 4 s of the outer surface 1 h of the substrate 1, or the noble metal deposited on such nuclei is sublimated to the electrode planned portion 3. Only the deposited platinum remains. And after performing such heat processing, in order to protect the surface of a detection part, a spinel powder is sprayed by a plasma spraying method, and an electrode protective layer is formed.

  Next, an electrode is also formed on the inner surface 1 n of the substrate 1. For forming the electrode on the inner surface 1n, a method of performing the conventional nucleation process and plating process can be employed. In addition, it is preferable to perform the pre-processing process which etches the inner surface 1n of the base | substrate 1 before a nucleation process.

  In the nucleation step, a chloroplatinic acid aqueous solution (platinum concentration: 0.5 g / L) is injected into the substrate 1 and heated, and then the chloroplatinic acid aqueous solution is discharged, and platinum chloride is applied to the inner surface 1n of the substrate 1. A coating film of an acid aqueous solution is formed. Then, an aqueous solution of hydrazine (concentration: 5 mass%) is injected into the internal space of the substrate 1, heated to 75 ° C. and allowed to stand for 30 minutes to precipitate platinum nuclei on the inner surface 1 n of the substrate 1.

  Further, in the plating step, a plating solution prepared by mixing a platinum complex aqueous solution (platinum concentration: 15 g / L) and an aqueous solution of hydrazine (concentration: 85% by mass) is injected into the substrate 1 and heated. Then, the platinum in the plating solution is deposited.

  Then, after the plating step is completed, water is sprayed on the inner surface 1n side of the substrate 1 for cleaning, and then the substrate 1 is accommodated in a dryer and sufficiently dried, and further subjected to an aging treatment.

  FIG. 7 is an external view in which a part of the gas sensor element 20 manufactured as described above is cut out. In the gas sensor element 20, an electrode 21 including a detection portion (detection electrode) 21g, a lead portion 21s, and a terminal connection portion 21t is formed on the outer surface 1h of the base 1, and an electrode (reference electrode) 22 is also formed on the inner surface 1n. ing.

  FIG. 8 shows the base 1 on the tip side of the tip 2 s of the flange 2 and the lead 21 s formed on the outer surface 1 h in the gas sensor element 20 actually manufactured using the manufacturing method of the present invention. Is. In the drawing, the vertical direction is the direction along the axis AX of the base 1. In the drawing, the white portion is the base 1 and the portion sandwiched between them is the lead portion 21s.

  As can be seen from FIG. 8, according to the manufacturing method of the present invention, the occurrence of bleeding can be suppressed and the lead portion 21s can be formed in a desired shape. In particular, a minute unevenness is provided on the distal end side of the distal end portion 2s of the collar portion 2, but the occurrence of bleeding can also be suppressed in such a portion, and the lead portion 21s can be formed in a desired shape. It turns out that it is possible.

  On the other hand, FIG. 9 shows the same part of the gas sensor element actually manufactured by the manufacturing method in which the mask jig is mounted only in the conventional nucleation process. In this conventional manufacturing method, the conditions were the same as those of the manufacturing method of the present invention as described above, except that the mask jig was mounted only in the nucleation step.

  As shown in FIG. 9, according to the conventional manufacturing method, a portion where the bleeding is completely generated is seen in the lower right portion of the lead portion 21 s, and it is difficult to form the lead portion 21 s in a desired shape. Recognize. Moreover, according to the conventional manufacturing method, although it is not as much as the above-mentioned part, it turns out that a blur generate | occur | produces as a whole.

  The gas sensor element 20 manufactured by such a manufacturing method of the present invention can be used for manufacturing a gas sensor in the same manner as a conventional one. FIG. 10 shows an example of a gas sensor 30 using the gas sensor element 20 manufactured by the manufacturing method of the present invention.

  The gas sensor 30 includes a gas sensor element 20 and a cylindrical metallic shell 31 that surrounds the gas sensor element 20 in an annular shape. Further, the gas sensor 30 includes an inner terminal member 32 that is partially inserted and held in the gas sensor element 20, and a heater 33 that is disposed in the gas sensor element 20 and whose posture is held by the inner terminal member 32. Have

  The metal shell 31 engages and holds the flange portion 2 of the gas sensor element 20 (base 1) by interposing metal packings 34, 35, 36, insulators 37, 38 and ceramic powder 39 inside the hollow cylinder. . Thereby, the gas sensor element 20 is airtightly held in the metal shell 31.

  Furthermore, a protector 40 is attached to the metal shell 31 so as to cover the tip of the gas sensor element 20 protruding from the opening on the tip side of the metal shell 31. The protector 40 has a double structure of an outer protector 40a and an inner protector 40b. The outer protector 40a and the inner protector 40b are formed with a plurality of gas permeation ports through which exhaust gas is transmitted. For this reason, the electrode 21 formed on the outer surface 1 h of the gas sensor element 20, particularly the detection part 21 g, can come into contact with the exhaust gas through the gas transmission port of the protector 40.

  On the other hand, in the metal shell 31, the tip end portion of the cylindrical metal outer tube 41 is fixed to the connection portion 31c on the rear end side of the hexagonal portion 31h from the outside by all-around laser welding. Further, the rear end side opening of the metal outer cylinder 41 is swaged and sealed by fitting a grommet 42 made of fluoro rubber. A separator 43 made of insulating alumina ceramic is provided on the tip end side of the grommet 42. The sensor output lead wires 44 and 45 and the heater lead wires 46 and 47 are disposed through the grommet 42 and the separator 43.

  A through hole is formed in the center of the grommet 42 along the axis AX, and a metal pipe 49 in a state where a sheet-like filter 48 having water repellency and air permeability is covered is fitted into the through hole. . As a result, the atmosphere outside the gas sensor 30 is introduced into the metal outer cylinder 41 via the filter 48 and eventually into the gas sensor element 20.

  The outer terminal member 50 made of a stainless steel plate includes an outer fitting portion 50p having a substantially C-shaped cross section in the direction perpendicular to the axis AX, and a separator insertion portion extending from the vicinity of the center of the rear end side of the outer fitting portion 50p to the rear end side. 50s and a connector portion 50c positioned on the rear end side. Among these, the connector part 50c grips the core wire of the sensor output lead wire 45 by caulking, and electrically connects the outer terminal member 50 and the sensor output lead wire 45.

  Further, the separator insertion portion 50s is inserted into the separator 43, and the separator contact portion 50d that branches and protrudes from the separator insertion portion 50s elastically contacts the holding hole 43d. 50 itself is held in the separator 43.

  Further, the inner terminal member 32 made of a stainless copper plate includes a base body insertion portion 32k having a substantially horseshoe-shaped cross section in the direction orthogonal to the axis AX, and a separator insertion portion 32s extending from the vicinity of the rear end side center of the base body insertion portion 32k to the rear end side. And a connector portion 32c located on the rear end side. Among these, the connector part 32 c grips the core wire of the sensor output lead wire 44 by caulking, and electrically connects the inner terminal member 32 and the sensor output lead wire 44. The separator insertion portion 32 s is inserted into the separator 43, and a separator contact portion 32 d that branches and protrudes from the separator insertion portion 32 s elastically contacts the holding hole 43 d, and the inner terminal member 32. It holds itself in the separator 43.

  Although the gas sensor 30 according to the present invention has been described above, the gas sensor 30 is manufactured using the conventional gas sensor except that the gas sensor element 20 obtained by the gas sensor element manufacturing method of the present invention is used as the gas sensor element 20. It can be manufactured in the same manner. According to such a gas sensor manufacturing method of the present invention, since a gas sensor element that uses less precious metal is used, the gas sensor can be manufactured at a lower cost than the conventional gas sensor manufacturing method.

The partially cutout external view which showed an example of the base | substrate used for the manufacturing method of the gas sensor element of this invention. The figure which showed an example of the nucleation process typically. The figure which showed typically mounting | wearing of the mask to a base | substrate. The figure which showed typically the base | substrate with which the mask etc. were mounted | worn. The figure which showed typically an example of the plating process. The figure which showed typically the mode of removal of the mask etc. from a base | substrate. The partially cutout external view which showed the gas sensor element obtained by the manufacturing method of the gas sensor element of this invention. The photograph which expanded and showed the lead part of the gas sensor element obtained by the manufacturing method of the gas sensor element of the present invention. The photograph which expanded and showed the lead part of the gas sensor element obtained by the manufacturing method of the conventional gas sensor element. Sectional drawing which showed the gas sensor which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base | substrate (1s ... front-end | tip part, 1e ... rear-end part, 1h ... outer surface, 1n ... inner surface), 2 ... collar part (2s ... front-end | tip part, 2e ... rear-end part), 3 ... scheduled electrode part (3g) Detecting part scheduled part, 3s ... Lead part scheduled part, 3t ... Terminal connection part scheduled part), 4 ... Non-electrode scheduled part (4s ... Intermediate part non-electrode scheduled part, 4e ... Rear end non-electrode scheduled part), 10 ... Mask jig (10a ... Slit), 20 ... Gas sensor element, 21 ... Electrode (21g ... Detection part, 21s ... Lead part, 21t ... Terminal connection part), 22 ... Electrode, 30 ... Gas sensor

Claims (4)

A nucleation step of attaching nuclei to the outer surface of a bottomed cylindrical solid electrolyte body extending in the axial direction; and a plating solution in which the nuclei act as a catalyst to remove noble metal in the plating solution from the solid electrolyte body. Through a plating process for depositing on the surface, a method for producing a gas sensor element in which an electrode is formed on the outer surface of the solid electrolyte body,
In the nucleation step, the electrode includes a planned electrode portion that is scheduled when the electrode is formed, and the nucleus is attached to a first portion wider than the electrode planned portion,
In the plating step, the noble metal is deposited by masking a second portion of the first portion excluding the planned electrode portion.   The electrode has at least a detection part formed on the entire front end side of the solid electrolyte body, and a lead part extending linearly from the detection part toward the rear end side in the axial direction. The method of manufacturing a gas sensor element according to claim 1. The solid electrolyte body has a flange that protrudes radially outward,
3. The method of manufacturing a gas sensor element according to claim 2, wherein the detection unit is formed on the entire circumference of the solid electrolyte body with a gap from the flange.   A method for manufacturing a gas sensor using a gas sensor element in which an electrode having a predetermined shape is formed on an outer surface of a solid electrolyte body, wherein the gas sensor element is a method for manufacturing a gas sensor element according to any one of claims 1 to 3. A method of manufacturing a gas sensor, characterized by being manufactured by the method described above.