JP6937167B2 - Manufacturing method of gas sensor element - Google Patents

Description

The present invention relates to a method for manufacturing a gas sensor element that is suitably used for detecting the gas concentration of a specific gas contained in combustion gas or exhaust gas of, for example, a combustor or an internal combustion engine.

Conventionally, a gas sensor for detecting the concentration of a specific component (oxygen or the like) in the exhaust gas of an internal combustion engine has been used. This gas sensor has a gas sensor element inside itself. As this gas sensor element, a cell having a sheet of a solid electrolyte body and a pair of electrodes arranged on the solid electrolyte body, an insulating sheet laminated with the cell, and a plate-shaped element having a heater and the like are used. ..
Then, in order to electrically connect the electrodes and heaters inside the plate-shaped element to the external device, through holes are provided in the sheet on which these electrodes and heaters are formed and other sheets laminated on this sheet, and the through holes are provided. It is common practice to print conductor paste on the inner walls of the holes.

By the way, as shown in FIG. 4, at the corner portion 500p of the through hole 500h provided in the sheet 500, the thickness of the conductor paste 600 becomes thin, and there is a risk of disconnection. Therefore, conventionally, the conductor paste 600 has been applied twice. Further, a technique has been developed in which annular convex portions are formed on the front and back surfaces of the sheet 500 surrounding the corner portion 500p so that the conductor paste 600 is thickly placed on the corner portion 500p (see Patent Document 1).

Japanese Unexamined Patent Publication No. 7-183633 (Fig. 1)

However, if the conductor paste is applied twice to the through holes, the productivity and cost are inferior, and the conductor paste is clogged in the through holes, and the corners on the opposite surface to the supply side of the conductor paste are not sufficiently covered with the conductor paste. In some cases.
Further, in the case of the technique described in Patent Document 1, an extra step of forming an annular convex portion on the sheet is required, which leads to a decrease in productivity and an increase in cost.
Therefore, an object of the present invention is to provide a method for manufacturing a gas sensor element capable of forming a through-hole conductor reliably and easily.

In order to solve the above problems, in the method for manufacturing a gas sensor element of the present invention, a through hole is formed in a ceramic green sheet or a laminate of the green sheet and another member, and then a through hole is formed in the inner wall of the through hole. A first method for manufacturing a gas sensor element that forms a conductor, the first is a method of manufacturing a gas sensor element, which is a predetermined conductor portion on both sides of the green sheet or the laminate and forms a pad connected to an external connection terminal on one surface side. A conductor portion forming step of forming the conductor portion and the second conductor portion on the other surface side, a through hole forming step of forming the through hole so as to include the first and second conductor portions, respectively, and the through hole forming step. the conductor paste which is a material of the hole conductor, and the conductor paste supplying step of supplying from the green sheet or the through hole formed in said first conductor portion of one side of the laminate, sandwiching the through hole in said conductor paste opposite by a negative pressure state, the conductor projecting the conductor paste from said second conductor portion of the other surface side of the green sheet or the laminate from the inner wall of the through hole It is characterized by having a supply process.

According to this method of manufacturing a gas sensor element, the thickness of the conductor paste is thin at the corners of the through holes on one surface side, but the conductors are formed in advance at the corners. Therefore, the conductor portion compensates for the thinness of the conductor paste, and the disconnection of the conductor paste at the corner portion and the through-hole conductor can be suppressed to ensure continuity.
On the other hand, at the corners of the through holes on the opposite surface side, the conductor paste is sucked out from the surface of the conductors under negative pressure and protrudes to form the protrusions, so that the thickness of the conductor paste 101s is thin even at the corners. It doesn't become. As a result, it is possible to suppress disconnection of the conductor paste at the corners and, by extension, the through-hole conductor, and ensure continuity.

The conductor paste supply step and the conductor supply step may overlap.
According to this method of manufacturing the gas sensor element, the conductor paste supply process and the conductor supply process overlap, that is, the pressure on the opposite side of the through hole is negative while the conductor paste is being supplied to the through hole. The conductor paste can be reliably sucked out with negative pressure.

Prior to the start of the conductor paste supply step, there may be further a step of putting the side opposite to the conductor portion into a negative pressure state with the through hole interposed therebetween.
According to this method of manufacturing the gas sensor element, the conductor paste can be sucked out more reliably with a negative pressure.

According to the present invention, the through-hole conductor of the gas sensor element can be formed reliably and easily.

It is sectional drawing which shows an example of the gas sensor (oxygen sensor) to which this invention is applied. It is a schematic disassembled perspective view which shows an example of the gas sensor element to which this invention is applied. It is a process drawing which shows the manufacturing method of the gas sensor element which concerns on embodiment of this invention. It is a figure which shows the conductor paste of the corner part of the conventional through hole.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a cross-sectional view taken along the longitudinal direction (axis L direction) showing an example of the gas sensor (oxygen sensor) 1 to which the present invention is applied, and FIG. 2 is a schematic exploded perspective view of the gas sensor element 100.

As shown in FIG. 1, the gas sensor 1 has a main metal fitting 30 that holds the gas sensor element 100, a plate-shaped element 300, and the like inside, a protector 24 that is attached to the tip of the main metal fitting 30, and the like. The gas sensor element 100 is arranged so as to extend in the axis L direction, and is composed of a plate-shaped element 300 and a heater 200 laminated on the plate-shaped element 300.

As shown in FIG. 2, the heater 200 sandwiches the first base 101 and the second base 103 mainly composed of alumina, and the first base 101 and the second base 103, and forms a heating element 102 mainly composed of platinum. Have. The heating element 102 has a heating unit 102a located on the tip side and a pair of heater lead portions 102b extending from the heating unit 102a along the longitudinal direction of the first substrate 101. The terminal of the heater lead portion 102b is electrically connected to the heater side pad 120 via a through hole conductor formed in the heater side through hole 101a provided on the first substrate 101.

The plate-shaped element 300 includes an oxygen concentration detection cell 130 and an oxygen pump cell 140. The oxygen concentration detection cell 130 is formed of a first solid electrolyte body 105 and a first electrode 104 and a second electrode 106 formed on both sides of the first solid electrolyte 105. The first electrode 104 is formed of a first electrode portion 104a and a first lead portion 104b extending from the first electrode portion 104a along the longitudinal direction of the first solid electrolyte body 105. The second electrode 106 is formed of a second electrode portion 106a and a second lead portion 106b extending from the second electrode portion 106a along the longitudinal direction of the first solid electrolyte body 105.

The terminal of the first lead portion 104b is provided in the first through hole 105a provided in the first solid electrolyte body 105, the second through hole 107a provided in the insulating layer 107 described later, and the second solid electrolyte body 109. It is electrically connected to the plate-shaped element side pad 121 via through-hole conductors formed in each of the 4 through-holes 109a and the 6th through-holes 111a provided in the protective layer 111. On the other hand, the terminal of the second lead portion 106b has a third through hole 107b provided in the insulating layer 107 described later, a fifth through hole 109b provided in the second solid electrolyte body 109, and a seventh through hole provided in the protective layer 111. It is electrically connected to the plate-shaped element side pad 121 via a through-hole conductor formed in each of 111b.

On the other hand, the oxygen pump cell 140 is formed of a second solid electrolyte body 109 and a third electrode 108 and a fourth electrode 110 formed on both sides of the second solid electrolyte body 109. The third electrode 108 is formed of a third electrode portion 108a and a third lead portion 108b extending from the third electrode portion 108a along the longitudinal direction of the second solid electrolyte body 109. The fourth electrode 110 is formed of a fourth electrode portion 110a and a fourth lead portion 110b extending from the fourth electrode portion 110a along the longitudinal direction of the second solid electrolyte body 109.

The terminal of the third lead portion 108b is a plate via through-hole conductors formed in each of the fifth through-hole 109b provided in the second solid electrolyte body 109 and the seventh through-hole 111b provided in the protective layer 111. It is electrically connected to the pad 121 on the shape element side. On the other hand, the terminal of the fourth lead portion 110b is electrically connected to the plate-shaped element side pad 121 via a through-hole conductor formed in the eighth through-hole 111c provided in the protective layer 111, which will be described later. The second lead portion 106b and the third lead portion 108b have the same potential.

These first solid electrolytes 105 and second solid electrolytes 109 are partially stabilized zirconia sintered bodies obtained by adding _{yttria (Y 2} O ₃ ) or calcia (CaO) as a stabilizer to _{zirconia (ZrO 2).} It is composed of.

The heating element 102, the first electrode 104, the second electrode 106, the third electrode 108, the fourth electrode 110, the heater side pad 120, and the plate-shaped element side pad 121 can be formed of a platinum group element. Examples of suitable platinum group elements forming these include Pt, Rh, Pd and the like, and these may be used alone or in combination of two or more.

An insulating layer 107 is formed between the oxygen pump cell 140 and the oxygen concentration detection cell 130. The insulating layer 107 includes an insulating portion 114 and a diffusion rate controlling portion 115. In the insulating portion 114 of the insulating layer 107, a hollow gas detection chamber 107c is formed at a position corresponding to the second electrode portion 106a and the third electrode portion 108a. The gas detection chamber 107c communicates with the outside in the width direction of the insulating layer 107, and the communication portion communicates with the outside to realize diffusion rate-determining between the outside and the gas detection chamber 107c under a predetermined rate-determining condition. The unit 115 is arranged.
The insulating portion 114 is not particularly limited as long as it is a ceramic sintered body having an insulating property, and examples thereof include oxide-based ceramics such as alumina and mullite.
The diffusion rate-determining portion 115 is a porous body made of alumina. The diffusion rate-determining unit 115 controls the rate when the detected gas flows into the gas detection chamber 107c.

Further, a protective layer 111 is formed on the surface of the second solid electrolyte body 109 so as to sandwich the fourth electrode 110. The protective layer 111 sandwiches the porous electrode protection portion 113a for protecting the fourth electrode portion 110a from poisoning and the fourth lead portion 110b so as to sandwich the fourth electrode portion 110a. It is composed of a reinforcing portion 112 for protecting the second solid electrolyte body 109.
In the gas sensor 100, the direction and magnitude of the current flowing between the electrodes of the oxygen pump cell 140 are set so that the voltage (electromotive force) generated between the electrodes of the oxygen concentration detection cell 130 becomes a predetermined value (for example, 450 mV). It corresponds to an oxygen sensor that is adjusted and linearly detects the oxygen concentration in the gas to be measured according to the current flowing through the oxygen pump cell 140.

Returning to FIG. 1, the main metal fitting 30 is made of SUS430, and has a male screw portion 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 main metal fitting 30 is provided with a metal fitting side step portion 33 projecting inward in the radial direction, and the metal fitting side step portion 33 supports a metal holder 34 for holding the gas sensor element 100. .. A ceramic holder 35 and a talc 36 are arranged in order from the tip side inside the metal holder 34. The talc 36 includes a first talc 37 arranged in the metal holder 34 and a second talc 38 arranged over the rear end of the metal holder 34. The gas sensor element 100 is fixed to the metal holder 34 by compressing and filling the first talc 37 in the metal holder 34. Further, by compressing and filling the second talc 38 in the main metal fitting 30, the sealing property between the outer surface of the gas sensor element 100 and the inner surface of the main metal fitting 30 is ensured.

An alumina sleeve 39 is arranged on the rear end side of the second talc 38. The sleeve 39 is formed in a multi-stage cylindrical shape, a shaft hole 39a is provided along the axis, and the gas sensor element 100 is inserted therein. The crimping portion 30a on the rear end side of the main metal fitting 30 is bent inward, and the sleeve 39 is pressed against the tip end side of the main metal fitting 30 via the stainless steel ring member 40.

Further, on the outer periphery on the tip end side of the main metal fitting 30, a metal protector 24 having a plurality of gas intake holes 24a is attached by welding while covering the tip portion of the gas sensor element 100 protruding from the tip of the main metal fitting 30. .. This protector 24 has a double structure, and has a bottomed cylindrical outer protector 41 having a uniform outer diameter on the outer side, and the outer diameter of the rear end portion 42a on the inner side is larger than the outer diameter of the tip portion 42b. A large bottomed cylindrical inner protector 42 is arranged.

On the other hand, the tip end side of the outer cylinder 25 made of SUS430 is inserted into the rear end side of the main metal fitting 30. The outer cylinder 25 has an enlarged tip portion 25a on the tip side fixed to the main metal fitting 30 by laser welding or the like. A separator 50 is arranged inside the rear end side of the outer cylinder 25, and a holding member 51 is interposed in the gap between the separator 50 and the outer cylinder 25. The holding member 51 is engaged with the protruding portion 50a of the separator 50, which will be described later, and is fixed by the outer cylinder 25 and the separator 50 by crimping the outer cylinder 25.

Further, the separator 50 is provided with an insertion hole 50b for inserting the lead wires 11 to 15 for the plate-shaped element 300 and the heater 200 from the front end side to the rear end side (note that the lead wires 14 and 15). Is not shown). In the insertion hole 50b, a connection terminal 16 for connecting the lead wires 11 to 15 and the plate-shaped element side pad 121 of the plate-shaped element 300 and the heater side pad 120 of the heater 200 is housed. The lead wires 11 to 15 are externally connected to a connector (not shown), and an electric signal is input / output between the external device such as an ECU and the lead wires 11 to 15 via the connector.

Further, on the rear end side of the separator 50, a substantially columnar rubber cap 52 for closing the opening 25b on the rear end side of the outer cylinder 25 is arranged. The rubber cap 52 is fixed to the outer cylinder 25 by crimping the outer circumference of the outer cylinder 25 inward in the radial direction while being mounted inside the rear end of the outer cylinder 25. The rubber cap 52 is also provided with insertion holes 52a for inserting the lead wires 11 to 15, respectively, from the front end side to the rear end side.

Next, a method of manufacturing the gas sensor element according to the embodiment of the present invention will be described.
In the example of FIG. 2, the present invention applies to the heater 200. Hereinafter, each step of the method for manufacturing the gas sensor element according to the embodiment of the present invention will be described with reference to FIG.
First, the unfired heating element 102x is paste-printed on one side of the unfired first substrate 101x. Next, the unfired first substrate 101x is turned over, and the unfired heater side pad 120x is paste-printed on the opposite surface (FIGS. 3A and 3B: conductor portion forming step).
Next, a through hole 101a is formed so as to include the unfired heater side pad 120x and the unfired heating element 102x in the stacking direction (FIG. 3 (c): through hole forming step).

Further, the conductor paste 101s, which is a material for the through-hole conductor, is supplied (filled) from the through-hole 101a on the unfired heater side pad 120x side (upper side in FIG. 3) (FIG. 3 (d): conductor paste supply step).
Then, under a state where the unfired heating element 102x side opposite to the unfired heater side pad 120x sandwiching the through hole 101a has a negative pressure NP, the conductor paste 101s supplied to the through hole 101a is transferred from the through hole 101a to the unfired heater side. It is projected from the surface of the unfired heating element 102x on the side opposite to the pad 120x (lower side in FIG. 3) (FIG. 3 (d): conductor supply step).

At this time, in the corner portion 101p1 of the through hole 101a on the unfired heater side pad 120x side (upper side in FIG. 3), the thickness of the conductor paste 101s is thin, but the unfired heater side pad 120x is previously formed in the corner portion 101p1. It is formed. Therefore, the thin portion of the conductor paste 101s can be supplemented by the unfired heater side pad 120x, the disconnection of the conductor paste 101s at the corner 101p1 can be suppressed, and the continuity can be ensured.
On the other hand, at the corner 101 p2 of the through hole 101a on the unfired heating element 102x side (lower side in FIG. 3) opposite to the unfired heater side pad 120x, the conductor paste 101s is formed on the surface of the unfired heating element 102x due to the negative pressure NP. The conductor paste 101s does not become thin even at the corners 101 p2 because the conductor paste 101e is sucked out by the negative pressure NP and protrudes to form the protrusion 101e. As a result, disconnection of the conductor paste 101s at the corner portion 101 p2 can be suppressed, and continuity can be ensured.

Further, the unfired second substrate 103 (not shown) is laminated on the unfired heating element 102x side, and the whole is fired to complete the heater 200, and the conductor paste 101s becomes a through-hole conductor.
As described above, according to the present embodiment, it is not necessary to apply the conductor paste twice to the through hole or to form the annular convex portion on the sheet, and the through hole conductor can be formed reliably and easily, and the productivity can be improved. It is also excellent in cost.
The unfired first substrate 101x corresponds to the "green sheet" in the claims. Further, the unfired heating element 102x and the unfired heater side pad 120x correspond to the "conductor portion" in the claims.

Here, in the above embodiment, after the conductor paste 101s is supplied (filled) to the through hole 101a, the unfired heating element 102x side of the through hole 101a is exhausted to obtain a negative pressure NP. The unfired heating element 102x side of the through hole 101a may be set to a negative pressure NP while overlapping with the supply process, that is, while the conductor paste 101s is being supplied to the through hole 101a. In this case, the conductor paste 101s can be reliably sucked out by the negative pressure NP.
Further, the unfired heating element 102x side of the through hole 101a may be put into a negative pressure NP state before the start of the conductor paste supply step. In this case, the conductor paste 101s can be more reliably sucked out by the negative pressure NP.

The present invention is not limited to the above embodiment, and can be applied to any plate-shaped gas sensor element that forms a through-hole conductor by firing a green sheet and supplying a conductor paste to the through-hole. Needless to say, it extends to various deformations and equivalents contained in. For example, the present invention may be applied to a NOx sensor (NOx sensor element) that detects the NOx concentration in the gas to be measured, an HC sensor (HC sensor element) that detects the HC concentration, and the like.

100 Gas sensor element 101a Through hole 101s Conductor paste 101x Green sheet 102x, 120x Conductor part NP Negative pressure

Claims (3)

A method for manufacturing a gas sensor element in which a through hole is formed in a ceramic green sheet or a laminate of the green sheet and another member, and then a through hole conductor is formed in the inner wall of the through hole.
A first conductor portion that is a predetermined conductor portion on both sides of the green sheet or the laminate and forms a pad connected to an external connection terminal on one surface side, and a second conductor portion on the other surface side. And the process of forming the conductor part that forms
A through-hole forming step of forming the through-hole so as to include the first and second conductor portions, respectively.
The conductor paste which is a material of the through-hole conductor, and the conductor paste supplying step of supplying from the green sheet or the through hole formed in said first conductor portion of one side of the laminate,
Wherein the opposite side of the conductive paste across the through holes By a negative pressure state, the other surface side of the second conductor of the conductor paste wherein the inner wall of the through-hole green sheet or the laminate The conductor supply process that projects from the part and
A method for manufacturing a gas sensor element. The method for manufacturing a gas sensor element according to claim 1, wherein the conductor paste supply step and the conductor supply step overlap. The method for manufacturing a gas sensor element according to claim 2, further comprising a step of putting the side opposite to the conductor portion into a negative pressure state with the through hole interposed therebetween before the start of the conductor paste supply step. ..

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