JP4714027B2 - Manufacturing method of gas sensor - Google Patents

Description

  The present invention relates to a method for manufacturing a gas sensor.

  2. Description of the Related Art Conventionally, an oxygen sensor is known as a gas sensor that is installed in an exhaust system of an internal combustion engine and detects oxygen concentration in exhaust gas and is used for combustion control of the internal combustion engine. The oxygen sensor extends in the axial direction, and has a gas sensor element whose tip side is exposed to the gas to be measured, a cylindrical metal shell that surrounds the gas sensor element while projecting the tip side of the gas sensor element from its own tip, A cylindrical protector or the like is attached to the distal end side of the metal shell and covers the distal end portion of the gas sensor element.

  As this gas sensor element, for example, an exploded perspective view shown in FIG. 8 is known. The gas sensor element 300 includes a detection element 100 that detects a gas to be measured. In the detection element 100, a first electrode 101, a first solid electrolyte body 102, a second electrode 103, an insulating layer 104, a third electrode 105, a second solid electrolyte body 106, a fourth electrode 107, and a protective layer 108 are sequentially stacked. ing. In addition, the gas sensor element 300 is integrally provided with a heater element 200 for heating the detection element 100 so that the detection element 100 is activated. In the heater element 200, for example, a first base 201, a heating element 202, and a second base 203 are sequentially stacked.

  For example, the gas sensor element 300 in which the detection element 100 and the heater element 200 are integrated can be manufactured through the following printing process (Patent Documents 1 and 2). First, rectangular green sheets that become the first base 201, the second base 203, the first solid electrolyte body 102, the insulating layer 104, the second solid electrolyte body 106, and the protective layer 108 after firing are prepared. Further, a metal paste is prepared which becomes the heating element 202, the first electrode 101, the second electrode 103, the third electrode 105, and the fourth electrode 107 shown in FIG. In addition, since each green sheet and each metal paste differ in a composition, a shape, etc., in the following, in FIGS. 9-12, the green paste 1 used as the 1st base | substrate 201 after baking, and the metal paste 2 used as the heat generating body 202 after baking. Will be described. A screen 3 on which at least one pattern 3a is formed and a squeegee 4 are prepared.

  Then, the screen 3 is provided on the surface of the green sheet 1, and the squeegee 4 is moved along the metal paste 2 in one direction (direction from the rear end side toward the front end side) D on the screen 3. Thus, the metal paste 2 is screen-printed on the green sheet 1 following the pattern 3a. Hereinafter, the metal paste 2 printed on the green sheet 1 is referred to as a printing layer 5.

  The green sheet 1 having the printing layer 5 is laminated with other green sheets to form a laminate. At this time, as shown in FIG. 8, the external terminals 301 to 305 are interposed so as to be aligned with the printing layer 5 for the heating element 202 and the like. In the laminated body for obtaining the gas sensor element 300 in which the detection element 100 and the heater element 200 are integrated, the laminated body for the detection element 100 and the laminated body for the heater element 200 are integrated.

  And the obtained laminated body is baked. Thus, each green sheet becomes the first base 201, the second base 203, the first solid electrolyte body 102, the insulating layer 104, the second solid electrolyte body 106, and the protective layer 108. In addition, each printed layer 5 becomes a heating element 202, a first electrode 101, a second electrode 103, a third electrode 105, and a fourth electrode 107. Thus, the gas sensor element 300 is obtained. When the laminated body for the detection element 100 and the laminated body for the heater element 200 are separately molded, the gas sensor element is obtained by bonding the individual laminated bodies after firing.

  The gas sensor element thus obtained is assembled into a metal shell or the like to form a gas sensor. The gas sensor is attached to an exhaust system such as an exhaust pipe of an engine, for example, and is used to detect a gas to be measured in the exhaust gas.

JP 2002-202280 A JP 2002-296227 A

  However, in the above conventional method for manufacturing a gas sensor, there is a possibility that the printed layer on the green sheet may become distorted.

  For example, as shown in FIG. 9, the scrape P is likely to occur in the vicinity of the end E on the front end side in the printing layer 5 on the green sheet 1 for obtaining the heater element 200.

  When the gas sensor is manufactured from the laminate having the green sheet 1 in which the scrape P is generated in the vicinity of the end portion E of the printed layer 5 in this way, in the heater element 200, the current-carrying area at the front end portion of the heating element 202 becomes small, Sometimes the electrical resistance there is greater than other parts. For this reason, in this gas sensor, only a part of the heating element 202 generates heat to an abnormally high temperature, and other parts hardly generate heat to a predetermined temperature.

  For this reason, in this gas sensor, it may take a long time for the predetermined portion of the detection element 100 to rise to the predetermined temperature, and in this case, the time until the gas to be measured starts to be detected accurately. It will be long. This impairs the operability of the gas sensor.

  In addition, this gas sensor may cause cracks in the first base 201 and the second base 203 due to an abnormal temperature rise in a part of the heating element 202. This impairs the durability of the gas sensor.

  In some cases, the printed layer on the green sheet for obtaining the detection element 100 may be blurred. In this case, the gas sensor is difficult to obtain an accurate electrical signal, and the gas detection accuracy is lowered. There is a risk that.

  The present invention has been made in view of the above-described conventional situation, and it is an object to be solved to provide a method for manufacturing a gas sensor that is less likely to cause scumming in a printed layer that is a metal paste on a green sheet.

  The inventors have intensively researched to solve the above problems, and the end of the printed layer tends to be blurred, and the angle on the front side between the green sheet and the screen at the end point of the corresponding pattern is important. It was discovered that the present invention was completed.

  That is, the gas sensor manufacturing method of the present invention includes a detection element having a plate-like solid electrolyte body extending in the axial direction and a pair of electrodes arranged on the solid electrolyte body, and having a detection unit on the tip side. In the manufacturing method of the gas sensor which has,

  A screen on which at least one pattern is formed is disposed on the surface of the green sheet that becomes the solid electrolyte body after firing, and a metal paste as a material of the electrode is placed on the screen together with a squeegee from the rear end side of the green sheet. Having a printing step of printing the metal paste on the green sheet following the pattern by moving toward the tip side;

In the printing step, at the end of the tip side in the pattern, Ri Do the angle of the front side 0.7 ° or more of between the green sheet and the screen,
The pattern is formed in two or more rows along the axial direction, and the screen is provided with a step for ensuring the angle between the rows .

  The gas sensor manufacturing method of the present invention includes a plate-shaped solid electrolyte body extending in the axial direction and a pair of electrodes disposed on the solid electrolyte body, and a detection element including a detection unit on the distal end side. ,

  A heater element having a plate-shaped substrate and a heating element disposed on the substrate, and laminated on the detection element;

  In the manufacturing method of the gas sensor having

  A screen on which at least one pattern is formed is disposed on the surface of the green sheet to be the base after firing, and a metal paste that is a material of the heating element is placed on the screen together with a squeegee from the rear end side of the green sheet. A printing step of printing the metal paste on the green sheet in accordance with the pattern by moving toward the side,

In the printing step, at the end of the tip side in the pattern, Ri Do the angle of the front side 0.7 ° or more of between the green sheet and the screen,
The pattern is formed in two or more rows along the axial direction, and the screen is provided with a step for ensuring the angle between the rows .

  According to the confirmation of the inventors, the printed layer on the green sheet is likely to be blurred at the end point on the front end side. The cause is presumed as follows.

  As shown in FIGS. 10 to 12, in the printing process, the metal paste 2 on the screen 3 is moved downward by the front surface 4 a of the squeegee 4 and placed on the green sheet 1 through the pattern 3 a of the screen 3. Since portions other than the pattern 3a of the screen 3 are not communicated with each other by the mask 3b, the metal paste 2 is not placed on the green sheet 1 in portions other than the pattern 3a. Thus, the metal paste 2 is screen-printed as the printing layer 5 on the green sheet 1 following the pattern 3a.

  During this time, as shown in FIG. 10, for example, when the squeegee 4 is located at the point A on the rear side of the end point F (the same position as the end E of the printing layer 5) on the leading end side in the pattern 3a, the green sheet 1 The upper printing layer 5a is integrated with the printing layer 5b to be screen-printed thereafter. For this reason, even if the squeegee 4 advances to the tip side from the point A and the squeegee 4 is separated from the screen 3 so that the screen 3 is gradually separated from the green sheet 1 by its own tension, the printed layer 5a on the rear side from the point A Remains on the green sheet 1 due to the viscosity or surface tension with the printing layer 5 b and is not taken away from the green sheet 1 by the screen 3.

  However, as shown in FIG. 11, when the squeegee 4 is positioned at the end point F on the leading end side in the pattern 3a, the printing layer 5c on the green sheet 1 does not have any further printing layer integrated with itself. . For this reason, as shown in FIG. 12, when the squeegee 4 advances to the point B on the tip side from the end point F, and the squeegee 4 is separated from the screen 3, the screen 3 is gradually separated from the green sheet 1 by its own tension. The printing layer 5c on the rear side from the end point F is easily separated from the green sheet 1 with the screen 3. Thus, it is considered that the scraping P tends to occur in the end portion E on the front end side in the printing layer 5 on the green sheet 1.

  On the other hand, the inventors have found that blurring can be prevented if the front-side angle between the green sheet and the screen is 0.7 ° or more at the end point on the front end side in the pattern. The cause is presumed as follows.

  As shown in FIG. 11, when the squeegee 4 is positioned at the end point F on the front end side in the pattern 3a and further advances to the front end side, the screen 3 gradually moves away from the green sheet 1 by its own tension. At this time, if the angle θ on the front side between the green sheet 1 and the screen 3 is large, it is considered that the screen 3 tries to quickly leave the green sheet 1 at the contact point e with the green sheet 1 at the end point F. For this reason, it is considered that the printing layer 5c on the green sheet 1 tends to remain on the green sheet 1 due to inertia.

  According to the test results of the inventors, when the angle θ on the front side between the green sheet 1 and the screen 3 is 0.7 ° or more at the end point F on the one direction D side in the pattern 3a, Hard to occur. Thereby, it is considered that the screen 3 tries to quickly leave the green sheet 1 in a direction near the vertical from the contact point e. For this reason, it is considered that moderate inertia acts on the printing layer 5 c on the green sheet 1 and the printing layer 5 tends to remain on the green sheet 1.

  Therefore, according to the method for manufacturing a gas sensor of the present invention, it is difficult for the printed layer, which is a metal paste on the green sheet, to be scummed.

  For this reason, if it is a gas sensor manufactured by this manufacturing method, it will not take a long time to start detecting the gas to be measured accurately, and the operability is high. Moreover, since this gas sensor is hard to produce a crack in the 1st base | substrate etc., durability can also be raised. Furthermore, this gas sensor can easily acquire an accurate electrical signal, and can prevent a decrease in gas detection accuracy.

A green sheet becomes a base | substrate, a solid electrolyte body, an insulating layer, and a protective layer after baking, for example. The green sheet may be made of a material corresponding to these, for example, zirconia (ZrO ₂ ), alumina (Al ₂ O ₃ ), silica (SiO ₂ ), or the like.

  As the metal paste, platinum group elements such as platinum, rhodium, and palladium can be employed. These can be used alone or in combination of two or more. Moreover, it is preferable that a metal paste contains the same component as the component which a green sheet contains. Thereby, the metal paste is easily fixed to the green sheet.

  As the screen, any sheet-like material that can pass the metal paste from the front surface to the back surface can be adopted. For example, a metal mesh, a resin mesh, etc. are employable. On the screen, a mask is formed with a photosensitive resin or the like, and thereby a pattern is formed in a portion where the mask is not formed. A plurality of patterns may be formed on one screen.

  As the squeegee, rubber, resin or the like can be used. The squeegee is preferably softer than the screen. Thereby, since it is hard to degrade a screen, the lifetime of a screen is prolonged.

  According to the test results of the inventors, the angle is preferably 2.8 ° or less. This is because if the angle θ shown in FIG. 11 is too large, the printed layer 5c is smeared. This is because the load is applied in the direction in which the screen 3 is separated from the green sheet 1 at the contact point e, and the adhesion between the screen 3 and the green sheet 1 is considered to decrease. As a result, the printing layer 5c is screen-printed around the position where it should originally be screen-printed, resulting in blurring. For example, if a smear occurs in the printed layer 5c on the green sheet 1 for obtaining a heater element, the heater element may have a large current-carrying area at the site where the smear has occurred, which may make it difficult to generate heat during use.

According to the inventors the test results, the pattern is Ru is formed in two or more rows along the axial direction, blur is likely to occur in one direction side of the end point of the rear side of the pattern between the columns. In this case, it is considered that this is because it is difficult to secure the angle between the front screen between the rows and the green sheet. For this reason, the pattern is formed in two or more rows along the axial direction, and a step is provided on the screen to ensure the angle between the rows . Thus, the angle between the front screen between the rows and the green sheet can be ensured, and the end point on the one-way side of the pattern on the rear side between the rows is less likely to occur.

At this time , the screen preferably has a step formed on the surface of the green sheet. If the step is formed on the surface of the screen on the green sheet side, it is not necessary to prepare a member for forming the step separately from the screen. For this reason, the work is not troublesome, the positional deviation caused by the member forming the step is hardly generated , and the yield is improved, so that the manufacturing cost can be reduced.

  When a step is formed on the surface of the screen on the green sheet side, this step is preferably made of a mask material for forming a pattern. As a result, a step can be formed when the pattern is formed by the mask, and the workability is improved and the manufacturing cost can be further reduced.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below together with test examples with reference to the drawings.

(Example)
As shown in FIG. 1, a gas sensor element 300 obtained by the manufacturing method of the embodiment is an element in which a detection element 100 and a heater element 200 are integrated, and the heater element 200 is connected via heater lead wires 21 and 22. The detection element 100 is activated by generating heat when energized.

  The gas sensor element 300 is a gas sensor in which the metal shell 11, the outer cylinder 15, the protector 17, and the like are assembled. First, this gas sensor will be described.

  In the gas sensor, the gas sensor element 300 is arranged to extend in the axial direction. A support rod 18 is bonded to the rear end side (the upper side in the drawing) of the gas sensor element 300. The support rod 18 is a member that extends in parallel with the axial direction of the gas sensor element 300 and has a substantially U-shaped cross section in a direction orthogonal to the extended axial direction. The concave side of the support rod 18 is bonded toward the side surface of the gas sensor element 300. As the material of the support rod 18, a material close to the thermal expansion coefficient of the glass component constituting the seal member 65, specifically, alumina is used. The support rod 18 is provided to suppress the occurrence of cracks in the gas sensor element 300 due to the difference in thermal expansion between the gas sensor element 300 and the seal member 65.

  The metal shell 11 is made of SUS430, and has a male screw 31 for attaching the gas sensor to the exhaust pipe, and a hexagonal portion 32 to which an attachment tool is applied at the time of attachment. Further, the metal shell 11 is provided with a metal side step portion 33 projecting radially inward, and this metal side step portion 33 is made of alumina for insulation from the gas sensor element 300 via the packing 5. The cylindrical member 16 is supported. Specifically, a protrusion 16 a that protrudes outward in the radial direction of the cylindrical member 16 is supported by the metal-side step 33. On the other hand, a filling member 34 made of talc powder is disposed between the inner surface of the metal shell 11 and the outer surface of the cylindrical member 16 on the rear end side of the protruding portion 16a, and a sleeve on the rear end side of the filling member 34. 35 is arranged in a state of being inserted into the metal shell 11.

  Also, inside the cylindrical member 16, an alumina holder 62 and an adhesive member 63 for fixing the holder 62 and the gas sensor element 300 are disposed in order from the distal end side (lower side in the drawing). Further, a second filling member 64 made of talc powder is filled between the cylindrical member 16 and the gas sensor element 300. The second filling member 64 is obtained by melting and solidifying an active mixed powder containing 12% by mass of a glass component. A seal member 65 made of a glass seal is disposed inside the rear end side of the cylindrical member 16 so as to surround the gas sensor element 300. The seal member 65 is formed by melting and solidifying crystallized glass powder (silica, zinc magnesium borate glass).

  Furthermore, the front end side of the inner cylinder 14 made of SUS304 is inserted inside the rear end side of the metal shell 11. The inner cylinder 14 is formed by crimping the rear end portion 11a of the metallic shell 11 in the distal direction inward with the opening end portion 14a having an enlarged diameter on the distal end inserted into the rear end side inside the metallic shell 11. It is fixed to the metal fitting 11. Further, the inner cylinder 14 protects the rear end portion of the cylindrical member 16. Further, the inner cylinder 14 supports the separator 51 disposed on the rear end side from the front end side. The gas sensor has a structure in which the filling member 34 is compressed and filled via a sleeve 35 by caulking the rear end portion 11 a of the metal shell 11.

  The outer cylinder 15 is made of SUS304 formed in a cylindrical shape, and the distal end side is coaxially connected to the inner cylinder 14. The outer cylinder 15 and the inner cylinder 14 are disposed so as to overlap each other, and at least a part of the overlapping portion is caulked toward the inner side in the circumferential direction, thereby being connected to each other. A separator 51 is inserted into the outer cylinder 15. The separator 51 is provided with an insertion hole 51a for inserting the heater lead wires 21 and 22 and the detection lead wires 23 to 25 from the front end side to the rear end side.

  In the insertion hole 51a, the heater lead wires 21 and 22 and the detection lead wires 23 to 25 are connected to the external terminal 301 of the heater element 200 in the gas sensor element 300 and the external terminal 305 of the detection element 100. A connecting member 67 for connecting the terminal 66 is accommodated. These heater lead wires 21 and 22 and detection lead wires 23 to 25 are externally connected to a connector (not shown). Electric signals are input and output between the external devices such as the ECU and the lead wires 21, 22, 23 to 25 through this connector. Further, although not shown in detail, each of the lead wires 21, 22, 23 to 25 has a structure in which the conductive wire is covered with an insulating film made of resin.

  Furthermore, a substantially cylindrical rubber cap 52 for closing the opening on the rear end side of the outer cylinder 15 is disposed on the rear end side of the separator 51. The rubber cap 52 is fixed to the outer cylinder 15 by crimping the outer periphery of the outer cylinder 15 radially inward while being attached to the rear end side of the outer cylinder 15. The rubber cap 52 is also provided with an insertion hole 52a for inserting the heater lead wires 21 and 22 and the detection lead wires 23 to 25 from the front end side to the rear end side.

  On the other hand, a metal protector 17 having a plurality of gas intake holes 17a is attached to the outer periphery on the front end side of the metallic shell 11 by covering the distal end portion of the gas sensor element 300 protruding from the distal end of the metallic shell 11 by welding. . The protector 17 has a double structure, and has a bottomed cylindrical outer protector 71 having a uniform outer diameter on the outer side, and an outer diameter of the rear end portion is larger than an outer diameter of the front end portion on the inner side. The formed bottomed cylindrical inner protector 72 is disposed. The outer surface of the bottom portion of the inner protector 72 is spot welded to the inner surface of the bottom portion of the outer protector 71, and the outer protector 71 and the inner protector 72 are integrated.

  As shown in FIG. 8, in the heater element 200 of the gas sensor element 300, a first base 201, a heating element 202, and a second base 203 are sequentially stacked. The first base 201 has a rectangular shape. The heating element 202 has a W-shaped heating part 202a located on the tip side (left side in the drawing) and a pair of lead parts that are integrated with the heating part 202a and extend rearward in the longitudinal direction (right direction in the drawing) of the first base body 201. 202b and a pair of connecting portions 202c formed integrally with the lead portion 202b on the rear end side (right side of the drawing). The pair of connection portions 202c are electrically connected to the pair of external terminals 301 and 302. The second base 203 is the same as the first base 201.

  The detection element 100 of the gas sensor element 300 includes a first electrode 101, a first solid electrolyte body 102, a second electrode 103, an insulating layer 104, a third electrode 105, a second solid electrolyte body 106, a fourth electrode 107, and a protective layer 108. Are sequentially stacked.

  The first electrode 101 includes an electrode portion 101a formed on the front end side, a lead portion 101b that is integrated with the electrode portion 101a and extends in the longitudinal direction of the first solid electrolyte body 102, which will be described later, and a lead portion 101b. It consists of the connecting part 101c formed on the rear end side. The connection portion 101c is electrically connected to the external terminal 303.

  The first solid electrolyte body 102 has the same size as the first substrate 201.

  The second electrode 103 is formed integrally with the electrode portion 103a formed on the distal end side, a lead portion 103b that is integrated with the electrode portion 103a and extends rearward in the longitudinal direction of the first solid electrolyte body 102, and the lead portion 103b. The connecting portion 103c is formed on the rear end side. The connection portion 103c is electrically connected to the external terminal 304.

  The insulating layer 104 has the same size as the first solid electrolyte body 102. The insulating layer 104 is provided with a gas detection chamber 104a on the front end side, and the gas detection chamber 104a communicates with the outside on both sides in the width direction of the gas sensor element via a pair of diffusion rate limiting bodies 104b. The diffusion control body 104b is porous. The diffusion rate-limiting body 104b performs rate-limiting when the detection gas flows into the gas detection chamber 104a.

  The third electrode 105 is integrally formed with the electrode portion 105a formed on the front end side, a lead portion 105b that is integrated with the electrode portion 105a and extends in the rearward direction of the second solid electrolyte body 106, which will be described later, and the lead portion 105b. The first connection portion 105c formed on the rear end side and the second connection portion 105d formed in parallel with the first connection portion 105c. The first connection part 105 c is also electrically connected to the external terminal 304. The second connection portion 105d is electrically connected to the external terminal 305.

  The second solid electrolyte body 106 is the same as the first solid electrolyte body 102. The second solid electrolyte body 106 has an insertion hole 106a penetrating in the thickness direction on the rear end side.

  The fourth electrode 107 is formed on the rear end side integrally with the electrode portion 107a formed on the front end side, the lead portion 107b extending integrally with the electrode portion 107a and extending rearward in the longitudinal direction, and the lead portion 107b. It consists of the connection part 107c. The connecting portion 107 c is electrically connected to the second connecting portion 105 d of the third electrode 105 through the insertion hole 106 a of the second solid electrolyte body 106.

  The protective layer 108 includes a porous body 108a and a main body portion 108b. The protective layer 108 includes the porous body 108a at the same position in the height direction as the gas detection chamber 104a. The porous body 108a is for protecting the fourth electrode 107 from poisoning.

  Hereinafter, a method for manufacturing the gas sensor element 300 will be described. First, as a printing process, green sheets to be the first base 201, the second base 203, the first solid electrolyte body 102, the insulating layer 104, the second solid electrolyte body 106, and the protective layer 108 after firing were prepared. In addition, metal pastes that become the heating element 202, the first electrode 101, the second electrode 103, the third electrode 105, and the fourth electrode 107 after firing were also prepared.

  Here, the case where the printing process is performed with the metal paste 2 on the green sheet 1 to be the first base 201 after firing will be described in detail. In the following, the case where the heater element 200 is obtained by the green sheet 1 that becomes the first base 201 after firing and the metal paste 2 that becomes the heating element 202 after firing will be described, but the same applies to the case where the detection element 100 is obtained. .

  The green sheet 1 is obtained as follows. First, a slurry composed of 97 wt% alumina and 3 wt% in total of silica, calcia (CaO) and magnesia (MgO) was prepared. And this slurry was made into the sheet-like thing of thickness 0.5mm by the doctor blade method, and it cut | disconnected to 150 mm x 300 mm continuously. Thus, a green sheet 1 was obtained.

  The metal paste 2 is composed of 85 to 95 parts by mass of platinum, 5 to 15 parts by mass of alumina, and appropriate amounts of an organic binder and a solvent.

  And as shown in FIG. 2, the screen 6 for the heat generating body 202 was also prepared. The screen 6 is made of a stainless steel mesh, and a stainless steel frame 6c is provided at the periphery. A plurality of patterns 6a shown in FIG. 3 are formed on the screen 6 in plan view by a mask 6b (see FIG. 7) made of a photosensitive resin.

  Each pattern 6a has a W-shaped heat generating part forming portion 61a located on the tip side (lower side in the drawing) and an axial direction integrally with the heat generating part forming portion 61a, as in the case where the heat generating elements 202 are viewed in the stacking direction. And a pair of connecting portion forming portions 61c formed on the rear end side integrally with the lead portion forming portion 61b.

  FIG. 4 shows the back side of the screen 6. As shown in the figure, the screen 6 is formed with two rows of patterns 6 a along the direction D. Each pattern 6a of each set is aligned in the axial direction in the direction D in a state where the heat generating portion forming portions 61a are positioned in front of the direction D. Thereby, the end points on the direction D side in the pattern 6a are F1 and F2, as shown in FIG.

  Further, as shown in FIGS. 6 and 7, a step 6 d is formed on the screen 6 between the rows in the direction D on the rear surface of the green sheet 1 side. The step 6d is aligned in a direction orthogonal to the direction D. As a result, as shown in FIG. 7, the angle θ on the front side between the green sheet 1 and the screen 6 is 0.7 ° or more at the first end point F1 on the one direction D side in the pattern 6a. The angle was set to 8 ° or less. Similarly, at the second end point F2, the angle θ is 0.7 ° or more and 2.8 ° or less. Each angle θ is determined by setting a distance between the green sheet 1 and the screen 6 to a predetermined distance.

  The step 6d is made of the same photosensitive resin as the mask 6b. For this reason, when the pattern 6a is formed by the mask 6b, the step 6d can also be formed, so that the workability can be improved and the manufacturing cost can be further reduced.

  A rubber squeegee 4 shown in FIG. 5 was also prepared.

  Thereafter, the green sheet 1 was placed on the printing stand 20, and the screen 6 was placed above the green sheet 1. Further, the metal paste 2 and the squeegee 4 were disposed on the screen 6. Subsequently, the squeegee 4 was moved in the direction D on the screen 6 together with the metal paste 2. At this time, the squeegee 4 was moved away from the screen 6 when the squeegee 4 was moved forward from the second end point F2. Thus, by the first screen printing, the metal paste 2 was screen-printed on the green sheet 1 following the pattern 6a.

  In succession to the first screen printing, the metal paste 2 and the squeegee 4 were placed on the screen 6, and the squeegee 4 was moved in the one direction D on the screen 6 together with the metal paste 2. Also at this time, the squeegee 4 was moved away from the screen 6 when the squeegee 4 was moved forward from the second end point F2. Thus, the metal paste 2 was screen-printed on the green sheet 1 following the pattern 6a also by the second screen printing. In addition, the printing layer 5 can be formed correctly by performing screen printing twice.

  During these screen printings, as shown in FIG. 6, the metal paste 2 on the screen 6 is moved downward by the front surface 4a of the squeegee 4 and placed on the green sheet 1 through the pattern 6a of the screen 6. Since portions other than the pattern 6a of the screen 6 are not communicated with each other by the mask 6b, the metal paste 2 is not placed on the green sheet 1 in portions other than the pattern 6a. Thus, the metal paste 2 is screen-printed as the printing layer 5 on the green sheet 1 following the pattern 3a.

  Meanwhile, in this embodiment, the screen 6 in which the step 6d is formed at a specific position on the back surface is used. For this reason, it is difficult for the printed layer 5 which is the metal paste 2 on the green sheet 1 to be dull.

  Similar screen printing is performed on the other green sheets, and a predetermined number of laminates are obtained by cutting along each pattern. And each laminated body is baked and the gas sensor element 300 is obtained.

  The gas sensor having the above configuration is attached to an exhaust system such as an exhaust pipe of an engine, for example, and is used for detecting a gas to be measured in the exhaust gas.

  Since this gas sensor employs the gas sensor element 300, it does not take a long time to accurately detect the gas to be measured, and has high operability. In addition, this gas sensor also exhibits high durability because cracks are unlikely to occur in the first base 201 and the like. Furthermore, this gas sensor can easily acquire an accurate electrical signal, and can prevent a decrease in gas detection accuracy.

  In manufacturing the gas sensor element 300, since the step 6d is formed on the surface of the screen 6 on the green sheet 1 side, high workability and yield are exhibited, and the manufacturing cost can be reduced.

(Test example)
In the printing process, the height of the step 6d is changed, and the angle θ on the front side between the green sheet 1 and the screen 6 at the first end point F1 on the one direction D side in the pattern 6a is 0.6 °. 8 °, 1.1 °, 1.7 °, 2.3 °, or 2.9 °. The green sheets 1 after printing obtained by these were designated as test products 1-6.

  Table 1 shows the angles θ and the printing states of the test products 1 to 6. The printed state is obtained by visually checking whether the printed layer 5 is dull or blurred. In Table 1, ◯ indicates that no blurring or blurring has occurred, x indicates that blurring has occurred, and Δ indicates that blurring has occurred.

  From Table 1, it can be seen that blurring occurs when the angle θ is 0.6 °, and no blurring occurs when the angle θ is larger than this. It can also be seen that blurring occurs when the angle θ is 2.9 °, and no blurring occurs when the angle θ is smaller than this.

  Therefore, according to the manufacturing method of the test products 2-5, it turns out that it is hard to produce a blur and a blur in the printing layer 5 which is the metal paste 2 on the green sheet 1. FIG.

  In the above, the present invention has been described with reference to examples and test examples. However, the present invention is not limited to the examples and the like, and it is needless to say that the present invention can be appropriately modified and applied without departing from the scope of the present invention. Absent.

  The present invention can be used for a gas sensor.

It is sectional drawing of the gas sensor which concerns on an Example. It is a top view of the screen for a heat generating body concerning an Example. It is an enlarged plan view which shows the pattern for the heat generating bodies formed in the screen according to the Example. It is a top view which concerns on the Example and shows the back surface of a screen. It is sectional drawing which shows the condition before performing screen printing in a printing process according to an Example. It is sectional drawing which shows the condition which concerns on an Example and is performing screen printing in a printing process. FIG. 6 is an enlarged cross-sectional view illustrating a situation where screen printing is performed at an end point on one direction side of a pattern according to an example. It is a model disassembled perspective view of an Example and the conventional gas sensor element. It is a principal part expanded sectional view of the gas sensor element | device which shows the conventional shading. It is a schematic cross section which shows the condition which is performing screen printing in the back side from the end point of the one direction side of a pattern. It is a schematic cross section which shows the condition which is performing screen printing in the end point of the one direction side of a pattern. It is a schematic cross section which shows the condition which is performing screen printing in the front side from the end point of the one direction side of a pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Green sheet 2 ... Metal paste 6a ... Pattern 6 ... Screen 4 ... Squeegee D ... One direction F1, F2 ... End point θ ... Angle 6d ... Step

Claims (5)

In a gas sensor manufacturing method having a plate-like solid electrolyte body extending in the axial direction and a pair of electrodes arranged on the solid electrolyte body, and having a detection element provided with a detection part on the tip side,
A screen on which at least one pattern is formed is disposed on the surface of the green sheet that becomes the solid electrolyte body after firing, and a metal paste as a material of the electrode is placed on the screen together with a squeegee from the rear end side of the green sheet. Having a printing step of printing the metal paste on the green sheet following the pattern by moving toward the tip side;
In the printing step, at the end of the tip side in the pattern, Ri Do the angle of the front side 0.7 ° or more of between the green sheet and the screen,
The gas sensor manufacturing method, wherein the pattern is formed in two or more rows along the axial direction, and the screen is provided with a step for ensuring the angle between the rows . A detection element having a plate-like solid electrolyte body extending in the axial direction and a pair of electrodes disposed on the solid electrolyte body, and having a detection unit on the tip side;
A heater element having a plate-shaped substrate and a heating element disposed on the substrate, and laminated on the detection element;
In the manufacturing method of the gas sensor having
A screen on which at least one pattern is formed is disposed on the surface of the green sheet to be the base after firing, and a metal paste that is a material of the heating element is placed on the screen together with a squeegee from the rear end side of the green sheet. A printing step of printing the metal paste on the green sheet in accordance with the pattern by moving toward the side,
In the printing step, at the end of the tip side in the pattern, Ri Do the angle of the front side 0.7 ° or more of between the green sheet and the screen,
The gas sensor manufacturing method, wherein the pattern is formed in two or more rows along the axial direction, and the screen is provided with a step for ensuring the angle between the rows .   The method of manufacturing a gas sensor according to claim 1 or 2, wherein the angle is 2.8 ° or less. The gas sensor manufacturing method according to any one of claims 1 to 3 , wherein the step is formed on a surface of the green sheet side of the screen. The method of manufacturing a gas sensor according to claim 4 , wherein the step is made of a mask material for forming the pattern.

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