JPH1123516A - Ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater that is inexpensive, easy in its manufacture, and excellent in reliability. SOLUTION: A ceramic heater is made up by laminating a plurality of heater base plates 11, 12 comprising exothermic layers 110, 120 and lead layers 111, 121, 151, 152, and 161, 162 for electrifying the exothermic layers 110, 120. The respective lead layers 151, 152 in the respective heater base plates 11, 12 have an exposed part 171 exposed to the outside surface 19 of the ceramic heater 1, and further the respective exposed parts 171 are connected by the connecting/ conducting parts 17 provided to the outside surfaces 19 so that the respective exothermic layers 110, 120 are connected electrically in series.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a ceramic heater provided in an air-fuel ratio sensor or the like used for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, an air-fuel ratio sensor for detecting an air-fuel ratio is installed in an exhaust system of an internal combustion engine such as an automobile engine, and the combustion control of the automobile engine is performed based on the air-fuel ratio detected by the air-fuel ratio sensor. It is carried out. Thus, the purification efficiency of the exhaust gas in the three-way catalytic converter provided in the exhaust system of the automobile engine can be increased. And
As the air-fuel ratio sensor, an oxygen sensor having a built-in oxygen sensor element made of a solid electrolyte having oxygen ion conductivity is used.

The oxygen sensor element has a built-in ceramic heater. By providing the ceramic heater, the oxygen sensor element is quickly heated to the activation temperature, and the time from the start of the internal combustion engine until the oxygen sensor element works effectively to enable combustion control, that is, the activation time is reduced. Can be shortened. As the ceramic heater, a round bar heater having a substantially circular cross section has been widely used.

However, recently, in order to reduce the manufacturing cost of the ceramic heater, a laminated plate type ceramic heater has been proposed in Japanese Patent Publication No. 5-2101, Japanese Patent Laid-Open No. 7-35723, and the like. The laminated plate-type ceramic heater includes, for example, a heater substrate having a heating layer and a lead layer for supplying electricity to the heating layer, and an insulating substrate covering the heater substrate.

[0005] However, such a laminated plate type ceramic heater has a problem that the area of a portion where a heat generating layer can be formed is smaller than that of a conventional round bar heater.
For this reason, when a heat generating layer having a large width that satisfies the durability is provided, it is difficult to design a heat generating layer having a high heater resistance value. In other words, if the length of the heating layer is increased to configure the heating layer so as to correspond to a high heater resistance value, the reliability of the ceramic heater is expected to decrease when the temperature becomes high. Was difficult.

[0006] In order to solve such a problem peculiar to the laminated plate type ceramic heater, Japanese Patent Publication No. 7-503550 has proposed the following structure. That is, as shown in FIG. 7 and FIG.
It has heater substrates 91 and 92 provided with 10, 920 and lead layers 911 and 921, and an insulating substrate 93 sandwiched and arranged between the two heater substrates 91 and 92.

The heater substrate 91 is provided with a heating layer 910, a lead layer 911, and a terminal portion 913 for lead wire wiring provided on the back side of the heater substrate 91. Between the terminal portion 913 and the conductor filling through hole 9 formed through the heater substrate 91.
12 establishes electrical continuity. Similarly, in the heater substrate 92, the heat generating layer 920, the lead layer 921, the conductor filling through hole 922, the terminal portion 923
Is provided. As shown in FIGS. 7 and 8, the heat generating layer 91 and the heat generating layer 92 are electrically connected in series by conductor filled through holes 930 provided in the insulating substrate 93.

Next, a method of manufacturing the ceramic heater 9 will be described. First, two green sheets for a heater substrate are prepared in the same manner as in Embodiment 1 described later.
As shown in FIG. 7, through holes 912 and 922 for connecting between the terminal portions 913 and 923 and the lead layers 912 and 922 are formed on these green sheets. Next, the heat generating layer 91 is formed using a conductive paste.
0,920, lead layers 911, 921, terminal portion 913,
A printing part for 923 is prepared. At this time, the through holes 912 and 922 are also filled with the conductive paste.

Next, a green body for the insulating substrate 93 is formed by laminating green sheets. Then, a through-hole 93 is provided in the molded body, and the through-hole 93 is filled with a conductive paste. Thereafter, the two green sheets and the molded body are laminated and pressed together so that the through hole 93 overlaps the portions A and B, which are the ends of the heat generating layers 910 and 920, to form a laminate. Further, the laminate is cut into an intermediate. Finally, the intermediate body is fired, and a lead wire (not shown) is joined to the terminal portions 913 and 923 to form a ceramic heater.

[0010]

However, the ceramic heater using the through-hole in the above-mentioned prior art,
Various problems may occur in actual manufacturing. First, the ceramic heater requires more through-holes because of the provision of through holes. For this reason, the manufacturing cost may be increased.

In addition, due to misalignment of the green sheet serving as a heater substrate at the time of manufacturing, insufficient filling of conductors in through holes, etc.
Connection failures that did not lead to disconnection were likely to occur.

The amount of increase in the resistance value of the through hole due to the poor connection is very small as compared with the combined resistance value of the two heater substrates, and therefore, it is difficult to find out in the resistance value inspection. Therefore,
This connection failure is very likely to be overlooked at the time of product manufacture, and this connection failure is detected by local heat generation in the through-hole during actual use and disconnection of the through-hole.

Furthermore, since the thermal expansion difference between the ceramic material forming the heater substrate and the conductor filled in the through hole is large, cracks are generated in the through hole due to thermal shock during actual use, leading to oxidative disconnection. I also have.

The present invention has been made in view of the above-mentioned problems, and is intended to provide a ceramic heater which is inexpensive, easy to manufacture, and excellent in reliability.

[0015]

According to a first aspect of the present invention, there is provided a ceramic heater in which a plurality of heater substrates each having a heating layer and a lead layer for supplying a current to the heating layer are stacked. Each lead layer has an exposed portion exposed on the outer side surface of the ceramic heater, and each exposed portion has a connecting conductor provided on the outer side surface so that the heat generating layers are electrically connected in series. The ceramic heater is connected by a portion.

The operation of the present invention will be described below. In the ceramic heater according to the present invention, each lead layer is electrically connected in series by a connection conductor provided on the outer side surface. As a result, without using through holes,
Each lead layer and each heat generating layer can be electrically connected in series through the lead layer.

Here, in the ceramic heater according to the present invention, the connection conductor has a thickness of 0.010 to 0.020 m.
If m, each lead layer can be sufficiently connected.
On the other hand, the ceramic heater according to the prior art is required to have a diameter of 0.3 to 0.5 mm and a large number of installations in order to avoid local heat generation in the through hole. Was. In general, disconnection due to thermal shock is less likely to occur as the thickness of the conductor is smaller. Therefore, the connection conductor according to the present invention is hardly cracked,
Hard to break.

In addition, the number of steps in the step of providing a connecting conductor is smaller than that in the step of forming a through hole, and the work is easy. Furthermore, when connecting the stacked lead layers, there is no need for precise alignment, and defects due to misalignment hardly occur. For this reason, the ceramic heater according to the present invention is easy to manufacture, and in this respect the manufacturing cost is low.

As described above, according to the present invention, a ceramic heater which is inexpensive, easy to manufacture, and excellent in reliability can be provided.

Next, as in the second aspect of the present invention, it is preferable that the exposed portion is formed in a concave portion provided on an outer side surface of the heater substrate. In the present invention, since the connecting conductor is not convex from the surface of the main body of the ceramic heater, damage to the connecting conductor by a component (commonly called a holder) for fixing the ceramic heater in the oxygen sensor element can be prevented. In addition, since the surface area of the connection conductor can be made large, the adhesive force between the connection conductor and the exposed portion on the lead can be improved, and the joining reliability between the two can be increased.

Next, it is preferable that an insulating substrate is provided between each of the heater substrates. As a result, the heat generating layers can be reliably insulated from each other, and a short circuit between them can be reliably prevented.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 A ceramic heater and a method of manufacturing the same according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the ceramic heater 1 of the present embodiment has a heating layer 11
0 and a lead layer 111 for energizing the heating layer 100,
Heater substrate 1 formed with 121, 151, 152
It is formed by laminating two sheets 1 and 12.

As shown in FIG. 2, each of the lead layers 151 and 152 on each of the heater substrates 11 and 12 has an exposed portion 17 exposed on the outer side surface 19 of the ceramic heater 1.
1,172. Further, each of the exposed portions 171,
172 is connected by a connection conductor 17 provided on the outer side surface 19 so that the heat generating layers 110 and 120 are electrically connected in series.

The details will be described below. As shown in FIG. 1, the ceramic heater 1 is provided on both sides of an insulating substrate 13.
The heater substrates 11 and 12 are formed by stacking the surfaces on which the heat generating layers 110 and 120 are provided toward the insulating substrate 13. The heater substrates 11 and 12 have heat generating layers 110 and 120 and lead layers 111 and 15 on their surfaces.
1, 161, 121, 152 and 162 are provided. Here, the two heating layers 110 and 120 are electrically connected in series by the lead layers 151 and 152 and the connection conductor 17.

The lead layers 161 and 162 also have exposed portions 181 and 182 exposed on the outer side surface 19 of the ceramic heater 1.
A lead wire connecting conductor 18 is provided so as to cover 1 and 182. Then, a lead wire 19 for supplying power to the heating layers 110 and 120 is connected to the lead wire connecting conductor 18.
0 is connected.

Next, a method of manufacturing the ceramic heater 1 according to this embodiment will be described. First, Al ₂ O ₃ 92wt
%, SiO ₂ and MgO 8 wt% to prepare a slurry. The slurry was formed into a sheet having a thickness of 0.35 mm by a doctor blade method. The above sheet was subjected to a punching press to produce eight square green sheets of 120 mm × 120 mm. In the production of the green sheet, another manufacturing method such as extrusion molding can be used.

Next, W / Re is defined as a weight ratio of W / Re.
= A powder mixed at a ratio of 80/20 is prepared. A binder and a plasticizer were added to the powder and kneaded with a three-roll mill. Thus, a conductive paste was obtained. The conductive paste is screen-printed to form a plurality of heater patterns for the one green sheet, as shown in FIG.
A print was formed in the shape shown in FIG. Note that pad printing can also be used to form the heater pattern. Two green sheets having such a heater pattern are prepared and used as a green sheet for a heater substrate.

Here, the heater pattern indicates a heating layer and a lead layer for one ceramic heater. In the manufacturing method according to the present example, a heater pattern for a plurality of ceramic heaters is manufactured on a green sheet in order to manufacture a plurality of ceramic heaters at one time.

Next, six green sheets are laminated and
This was pressed to obtain a molded body for the insulating substrate 13. In addition, this molded body can also be manufactured by using extrusion molding or the like. Next, a green sheet for a heater substrate was laminated on the molded body for an insulating substrate so that the surface on which the heater pattern was provided was in contact with the molded body, and was bonded by pressure bonding to form a laminated body.
Thereafter, the laminate was dried.

Next, the above-mentioned laminated body is connected to FIG.
As shown in FIG. 3B, an intermediate was prepared. Here, printed portions for the lead layers 151 and 152 are exposed on the outer side surface of the intermediate body, and exposed portions 171 and 172 are formed. Similarly, the printed portions for the lead layers 161, 162 are exposed, and the exposed portions 1
81 and 182 are formed.

Then, as shown in FIG.
A printed part is formed using a conductive paste so as to cover 71 and 172. In addition, a printed portion that covers the exposed portions 181 and 182, respectively, is similarly manufactured.

Next, the above intermediate was replaced with nitrogen /
It was fired at a temperature of 1580 ° C. in a hydrogen atmosphere. In this example, since W was used for the heat generating layer and the lead layer, the firing was performed in a reducing atmosphere. However, when Pt or the like is used for the same material, the firing can be performed in a normal atmosphere.

Thereafter, electroless Ni plating was applied to the fired connection conductor 17 and lead wire connection conductor 18.
Then, the lead wire 190 is connected to the lead wire connecting conductor 18.
Were connected using a Cu low. Thereafter, the lead wire connecting conductor 18 was again subjected to electroless Ni plating. Thus, the ceramic heater 1 according to this example was obtained.

Next, the operation and effect of this embodiment will be described. The ceramic heater 1 according to this embodiment has an outer side surface 19.
Of the lead layers 151 and 15
2 are electrically connected in series. Thereby, each lead layer 151, 1 can be used without using a through hole.
52 and the heat generating layers 110 and 120 can be electrically connected in series.

The ceramic heater 1 according to the present embodiment
Means that the thickness of the connection conductor 17 is 0.010 to 0.02
It is as thin as 0 mm. In general, disconnection due to thermal shock is less likely to occur as the thickness of the conductor is smaller. Therefore, the connecting conductor portion 17 according to this example has a structure in which cracks are less likely to occur and disconnection is less likely. For this reason, the ceramic heater 1 according to the present example has high reliability.

In addition, the number of steps involved in manufacturing the connection conductor portion 17 according to the present embodiment is small, and it can be performed by an easy operation of printing. Furthermore, the wide conductor connection portion 17
Is used to connect the lead layers 151 and 152, so that when the heater substrates 11 and 12 are laminated, there is no need to perform precise alignment, and defects due to misalignment hardly occur. As described above, the ceramic heater 1 according to the present embodiment is easy to manufacture, and in this respect, the manufacturing cost is low. Further, in this example, since a plurality of ceramic heaters 1 are manufactured at one time, the manufacturing cost is low in this respect as well.

Although the ceramic heater according to the present embodiment has a structure in which two heater substrates are stacked, three or more heater substrates can be stacked. In addition, when laminating the heater substrates, an adhesive may be applied and laminated.

Embodiment 2 As shown in FIG. 3, this embodiment is a ceramic heater comprising two heater substrates and a covering substrate for covering the same.
As shown in FIG. 3C, the ceramic heater 1 according to the present embodiment is configured by laminating a heater substrate 12 on a heater substrate 11 and further laminating a covering substrate 14 thereon.

A method for manufacturing the ceramic heater 1 according to this embodiment will be described. Similarly to the first embodiment, green sheets 211 and 212 for heater substrates 11 and 12 are provided.
A green sheet 22 for the covering substrate 14 is prepared. Then, the green sheets 21 for the heater substrates 11 and 12 are formed.
In the same manner as in the first embodiment, five heater patterns 201 and 202 were formed on one green sheet 211 and 212 by printing in the shape shown in FIG.

Thereafter, as shown in FIG. 3A, two green sheets 211 and 212 were laminated, and a green sheet 22 for the covering substrate 14 was further laminated thereon to form a laminate 23. Next, the laminate 23 is cut along the dashed line shown in FIG. As a result, FIG.
As a result, an intermediate 24 was obtained. Here, the intermediate 2
A part of the n portion, which is a printed portion for the lead layer, is exposed on the outer side surface of No. 4 to form an exposed portion. Similarly, a part of the m portion is exposed to form an exposed portion.

Then, as shown in FIG. 3B, printing sections 283, 284 and 285 are provided for the above-mentioned exposed sections, respectively. Thereafter, the intermediate body 24 is fired, and the printing unit 28 is fired.
Bake 3,284,285. Thereby, the connection conductor 17 and the lead wire connection conductor 18 are obtained. Then, as shown in FIG. 3C, a lead wire 190 was attached to the lead wire connecting conductor 17 to obtain the ceramic heater 1. Other configurations are the same as those of the first embodiment. In addition, the ceramic heater of this embodiment also has the same operation and effect as the first embodiment.

Embodiment 3 In this embodiment, as shown in FIGS. 4 to 6, a ceramic heater 1 having exposed portions 171 and 172 formed in a concave portion 16 provided on an outer side surface 19 and a method of manufacturing the ceramic heater 1 will be described. is there. That is, as shown in FIGS. 4 and 5, the ceramic heater 1 according to the present embodiment has the same structure as that of the first embodiment.
It is composed of a plurality of heater substrates 11 and 12 and an insulating substrate 13 sandwiched therebetween.

A concave portion 16 is provided on the outer side surface 19 of the ceramic heater 1, and exposed portions 171 and 172 are formed so as to face the concave portion 16. And
As shown in FIG. 5, the connection conductor 160 according to the present embodiment is formed in the recess 16. The recess 16 is configured so that its cross section is semi-elliptical.

A method for manufacturing the ceramic heater 1 according to this embodiment will be described. First, green sheets 211 and 212 provided with heater patterns for the heater substrates 11 and 12 were prepared in the same manner as in the first embodiment. Also, a green body 213 for the insulating substrate 13 was prepared by laminating six green sheets. The molded body 213 can also be manufactured by using extrusion molding or the like. Next, the molded body 21
Green sheets 211 and 212 were laminated on 3 so that the surface on which the heater pattern was provided was in contact with the molded body 213, and were bonded by pressure bonding to form a laminated body 23.

Next, as shown in FIG. 6A, a through hole 269 for the concave portion 16 having a desired shape was formed in the laminate 23 by a punching machine. Next, the laminate 23 was cut along a dashed line shown in FIG. 6A to produce an intermediate 24 shown in FIG. 6B.

Next, as shown in FIG. 6C, a printed portion 260 for the connection conductor 160 was provided in the recess 16 formed on the side surface of the intermediate body 24 by using a pad printing method. Thereafter, as in the case of the first embodiment, the intermediate body 24 was fired and the lead wires 190 were connected to obtain the ceramic heater 1 according to the present example. Other configurations are the same as those of the first embodiment.

In the ceramic heater 1 of this embodiment, since the connecting conductor 160 is not convex from the surface of the main body of the ceramic heater 1, the ceramic heater 1 is provided in the oxygen sensor element.
Connecting part 16 by a component (commonly known holder) for fixing
0 can be prevented. Further, since the surface area of the connection conductor 160 can be made large, the adhesive force between the connection conductor 160 and the exposed portions 171 and 172 on the lead portions can be improved, and the joint reliability between them can be increased. . Others have the same operation and effects as the first embodiment.

[Brief description of the drawings]

FIG. 1 is a perspective developed view of a ceramic heater according to a first embodiment.

FIG. 2 is a perspective view of a ceramic heater according to the first embodiment.

FIG. 3 is an explanatory view showing a manufacturing process of the ceramic heater according to the second embodiment.

FIG. 4 is a perspective view showing a concave portion provided on an outer side surface of a ceramic heater according to a third embodiment.

FIG. 5 is a perspective view of a ceramic heater according to a third embodiment.

FIG. 6 is an explanatory view showing a manufacturing process of the ceramic heater according to the third embodiment.

FIG. 7 is a perspective development view of a ceramic heater according to a conventional example.

FIG. 8 is an explanatory diagram showing a positional relationship among a heating layer, a lead portion, and a conductor-filled through hole of a ceramic heater according to a conventional example.

[Explanation of symbols]

1. . . Ceramic heater, 11,12. . . Heater substrate, 110,120. . . Heat generation layer, 111, 121, 151, 152, 161, 16
2. . . 12. Lead layer, . . 15. insulating substrate; . . Recess, 17. . . Connecting conductor part, 171, 172. . . Exposed part, 19. . . External aspect,

Claims (3)

[Claims] 1. A ceramic heater in which a plurality of heater substrates each having a heat generating layer and a lead layer for supplying a current to the heat generating layer are stacked, wherein each lead layer of each of the heater substrates is provided outside the ceramic heater. It has an exposed portion exposed on the side surface, and further, each of the exposed portions is connected by a connection conductor provided on the outer side surface so that the heat generating layers are electrically connected in series. Characteristic ceramic heater. 2. The ceramic heater according to claim 1, wherein said exposed portion is formed in a concave portion provided on an outer side surface of said heater substrate. 3. The ceramic heater according to claim 1, wherein an insulating substrate is provided between the heater substrates.