JP2005135793A - Ceramic heater and lamination type gas sensor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater capable of preventing a breakage initiated at a migration pattern when using, and provide a lamination type gas sensor element equipped with such a heater. <P>SOLUTION: The ceramic heater 101 has a center ceramic base plate 105, a heat generating pattern 111 formed on the back surface 105C of the center ceramic base plate 105 and a migration pattern 121 formed on a front surface 105B of the center ceramic base plate 105. Out of those patterns, the migration pattern 121 having a first end part 123 at a base end side, and a second end part 124 between the first end part 123 and a tip part extends from the first end part 123 to the tip side part, returns to the base end part through the tip side part, and connected to the second end part 124. Furthermore, the migration pattern has a bypass reed part 128 connecting the second end part 124 and the migration reed part 129a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ceramic heater and a gas sensor element including the ceramic heater, and more particularly to a ceramic heater in which a heat generation pattern and a migration pattern are formed via a ceramic substrate, and a multilayer gas sensor element including such a ceramic heater. .

  Conventionally, a ceramic heater in which a heat generation pattern and a migration pattern are formed via a ceramic substrate is known. For example, there is a ceramic heater 901 whose configuration is shown in FIG. The ceramic heater 901 has a substantially rectangular plate shape having a heater surface 901B and a heater back surface 901C. The ceramic heater 901 is formed by laminating three layers of ceramic substrates (from the heater surface 901B side to the front surface side ceramic substrate 903, the central ceramic substrate 905, and the back surface side ceramic substrate 907).

  Among them, a heat generation pattern 911 mainly made of Pt is formed on the back surface 905C of the central ceramic substrate 905 (between the central ceramic substrate 905 and the back ceramic substrate 907). The heat generation pattern 911 has a pair of positive electrode portions 913 and negative electrode portions 914 formed on the base end side (right side in the figure) of the central ceramic substrate 905, and from the positive electrode portion 913 to the front end side of the central ceramic substrate 905. It extends in the axial direction toward (left side in the figure), returns to the base end side via the distal end side, has a shape (pattern shape) connected to the negative electrode portion 914, and generates heat when energized. The heat generation pattern 911 includes a meandering heat generation portion 915 disposed on the distal end side and a pair of lead portions 928a and 928b extending from both base ends of the heat generation portion 915 along the axial direction. In order to realize the rapid temperature increase, the line width of the heat generating portion 915 is made smaller than the line width of the lead portions 928a and 928b so that the resistance value per unit length is reduced.

On the other hand, a migration pattern 921 mainly made of Pt is formed on the surface 905B of the central ceramic substrate 905 (between the surface-side ceramic substrate 903 and the central ceramic substrate 905). This migration pattern 921 is also shown in FIG. The migration pattern 921 is formed to face the heat generation pattern 911 approximately. Specifically, the migration pattern 921 includes a first end 923 formed on the base end side of the central ceramic substrate 905 (the right side in FIG. 6 and the lower side in FIG. 7), the front end of the central ceramic substrate 905, and the first end. A second end portion 924 formed between the end portions 923, extends from the first end portion 923 toward the distal end side of the central ceramic substrate 905 in the axial direction, and passes through the distal end side to the proximal end side. Returning, it has a shape connected to the second end 924. As described above, the migration pattern 921 is formed so as to substantially face the heat generation pattern 911, and the miglet tip 925 facing the heat generation part 915 and the lead part 928a, 928b. And a pair of migre lead portions 929a and 929b having a wider line width.
Further, on the surface 905 B of the central ceramic substrate 905, a third end portion 926 formed on the proximal end side of the central ceramic substrate 905 and a lead portion extending from the third end portion 926 to the distal end side of the central ceramic substrate 905. 927 is formed.

The negative electrode portion 914 of the heat generation pattern 911 and the first end portion 923 of the migration pattern 921 are electrically connected via a first through-hole conductor 931 formed through the central ceramic substrate 905. Therefore, the migration pattern 921 has the same potential as the negative electrode portion 914 of the heat generation pattern 911 when energized.
Further, the positive electrode portion 913 and the third end portion 926 of the heat generation pattern 911 are also electrically connected via a second through-hole conductor 932 formed through the central ceramic substrate 905. Therefore, the third end portion 926 and the lead portion 927 are at the same potential as the positive electrode portion 913 of the heat generation pattern 911 when energized.

  As shown in FIG. 6, a negative electrode that is electrically connected to the first end 923 of the migration pattern 921 and extends outward from the base end of the ceramic heater 901 is interposed between the front-side ceramic substrate 903 and the central ceramic substrate 905. A positive electrode external terminal 942 that is electrically connected to the external terminal 941 and the third end 926 and extends to the outside from the base end of the ceramic heater 901 is provided.

By the way, in general, when the ceramic heater 901 is energized, a component that is easily ionized in the heat generation pattern 911 moves to a low potential direction due to a direct current electric field and high heat to locally become a high concentration, and the ionized component that has moved is low. It becomes difficult to move in the low temperature part on the potential side, and it tends to accumulate as an oxide or carbide. As a result, the heat generation pattern 911 may be disconnected.
However, in the ceramic heater 901, the migration pattern 921 having substantially the same shape is formed on the opposite surface (surface 905B) of the central ceramic substrate 905 on which the heat generation pattern 911 is formed. The movement of the existing easily ionized component to the low potential side is suppressed, and the disconnection of the heat generation pattern 911 can be effectively prevented.
As a document related to the technology of such a migration pattern 921, for example, Patent Document 1 is cited.

Japanese Patent Publication No. 5-36915

  The heat generation pattern 911 and the migration pattern 921 are formed by, for example, simultaneous firing with the ceramic substrates 903, 905, and 907, and thus have a porous structure. For this reason, moisture may enter the migration pattern 921 itself from the end of the ceramic heater 901. Such moisture is heated in the vicinity of the tip when the heater is energized, and part of the moisture becomes water vapor. Then, the moisture in the migration pattern 921 is pushed out to the base end side of the ceramic heater 901 by the pressure. At this time, while being connected to one of both base ends of the migre tip end portion 925, in the migre lead portion 929a connected to the first end portion 923, moisture pushed out from the migre tip end portion 925 is discharged from the first end portion 923 to the outside. Will be.

  However, in the migre lead portion 929b that is connected to the other of the base ends of the migre tip end portion 925 and is connected to the second end portion 924, the water pushed out from the migre tip end portion 925 causes the second end portion 924 to become the lead portion 927. Is not connected to the outside and cannot escape to the outside, and accumulates in the vicinity of the second end 924. When such moisture is heated to become water vapor, the pressure in the vicinity of the second end portion 924 is increased, the vicinity of the second end portion 924 is ruptured, and as a result, the ceramic heater 901 is cracked (broken).

  The present invention has been made in view of the current situation, and an object of the present invention is to provide a ceramic heater capable of suppressing breakage starting from a migration pattern at the time of use, and a multilayer gas sensor element including such a ceramic heater. To do.

  The solution includes a plate-like first ceramic substrate having a first main surface and a second main surface and extending in the axial direction from the front end to the base end, and the base end formed on the first main surface. A heating pattern having a positive electrode portion and a negative electrode portion on the side, extending from the positive electrode portion to the distal end side, returning to the proximal end side via the distal end side, and connecting to the negative electrode portion And a first end on the base end side, a second end between the first end and the tip of the first end, and the first end to the first end A migration pattern that extends to the distal end side, returns to the proximal end side through the distal end side, and is connected to the second end portion, and has a negative potential rather than the positive electrode portion when energized. And a plate-like second ceramic laminated on the second main surface and covering the migration pattern. And a bypass lead portion that connects the second end portion and a portion extending in the axial direction from the first end portion toward the tip end side. It is the ceramic heater characterized by the above-mentioned.

In addition to the heat generation pattern, the ceramic heater of the present invention has a migration pattern for preventing disconnection of the heat generation pattern. Among these, the migration pattern has a first end portion, a second end portion, and a portion connecting them, similarly to those exemplified in the prior art, but besides these, the second end portion and the first end portion And a bypass lead portion connecting the portion extending in the axial direction from the tip end side to the tip end side.
In the migration pattern of the prior art, as described above, the second end is covered with the ceramic substrate and positioned so as to be interrupted in the middle of the second main surface, so that the portion extending from the tip side to the second end is formed. The extruded water cannot escape to the outside, and it is heated to become water vapor, and the vicinity of the second end is ruptured, leading to cracking (breaking) of the ceramic heater.
However, in the present invention, as a part of the migration pattern, a bypass lead portion that connects the second end portion and the portion connecting the first end portion and the tip end side is formed, so that moisture has entered the migration pattern. However, the moisture that has entered the portion extending from the distal end side to the second end portion returns from the second end portion to the portion connecting the first end portion and the distal end side through the bypass lead portion, and further from the first end portion to the outside. Released. Therefore, all moisture that has entered the migration pattern is released. For this reason, it is possible to prevent rupture near the second end portion during use due to moisture that has entered the migration pattern, and to prevent destruction of the ceramic heater.

  Furthermore, in the ceramic heater described above, the second end portion and the bypass lead portion are both formed on the tip side from the center of the first ceramic substrate. good.

  According to the present invention, the second end portion and the bypass lead portion that allows the moisture that has moved from the tip end side to the second end portion to escape to the first end portion side are formed on the tip side from the center of the ceramic substrate. . By providing the second end portion and the bypass lead portion on the tip side of the ceramic substrate in this manner, even when the bypass lead portion is used, the amount of electrode material used to form the migration pattern can be reduced, and it is inexpensive. A highly reliable ceramic heater can be obtained.

  Furthermore, in the ceramic heater according to any one of the above, the bypass lead portion extends from the second end portion toward the proximal end side, and is an axis line from the first end portion toward the distal end side. The ceramic heater is preferably connected to a portion extending in the direction.

  The ceramic heater has a shape in which the heat generation pattern extends from the positive electrode part to the tip side and is connected to the negative electrode part via the tip side, so the tip side is easily heated, and moisture that has penetrated into the migration pattern is also on the tip side. Tends to be water vapor. Therefore, moisture that has entered the migration pattern moves from the distal end side toward the proximal end side. Based on such a phenomenon, in the present invention, since the bypass lead portion is formed from the second end portion toward the proximal end side, moisture that has entered the migration pattern passes through the bypass lead portion from the second end portion. Easy to escape to the first end. Therefore, rupture near the second end can be more effectively prevented.

  Furthermore, the ceramic heater according to any one of the above, wherein the negative electrode portion of the heat generation pattern and the first end portion of the migration pattern are electrically connected. .

  According to the present invention, the negative electrode portion of the heat generation pattern and the first end portion of the migration pattern are electrically connected. By connecting the two in this way, the migration pattern can be easily set to a negative potential as compared with the positive electrode portion of the heat generation pattern.

  According to another aspect of the invention, there is provided a ceramic heater according to any one of the above, and a gas detection element including at least a solid electrolyte layer in which a pair of electrode layers is formed and stacked on the ceramic heater. This is a feature of a stacked gas sensor element.

Since the multilayer gas sensor element of the present invention includes the ceramic heater described above, it is possible to prevent the vicinity of the second end caused by moisture that has entered the migration pattern, and to prevent the ceramic heater from being destroyed. Therefore, a highly reliable stacked gas sensor element can be obtained.
The laminated gas sensor element may be of any type as long as it satisfies the above requirements, and examples thereof include an oxygen sensor element, a full-range air-fuel ratio sensor element, and a NOx sensor element. Moreover, even if the multilayer ceramic element was obtained by firing and integrating a ceramic heater and a gas detection element, it was obtained by pasting the fired ceramic heater and gas detection element through a bonding layer (for example, cement). It may be a thing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A perspective view of the ceramic heater 101 of this embodiment is shown in FIG. 1, and a configuration of the ceramic heater 101 is shown in FIG. The ceramic heater 101 extending in the axial direction is used for a stacked NOx sensor element. The ceramic heater 101 has a substantially rectangular plate shape of about 45 mm (length in the axial direction) × about 3.6 mm (width) × about 1.2 mm (thickness) having the heater front surface 101B and the heater back surface 101C. The ceramic heater 101 includes three layers of ceramic substrates, that is, from the heater surface 101B side, a front surface side ceramic substrate 103 (second ceramic substrate), a central ceramic substrate 105 (first ceramic substrate), and a back surface side ceramic substrate 107. Are stacked. These ceramic substrates 103, 105, and 107 are mainly made of alumina.

  Among these, a porous heat generation pattern 111 mainly composed of Pt is formed on the back surface 105C (first main surface) of the central ceramic substrate 105, that is, between the central ceramic substrate 105 and the back-side ceramic substrate 107. The heat generation pattern 111 has a pair of positive electrode portion 113 and negative electrode portion 114 formed on the proximal end side (right side in FIG. 2) of the central ceramic substrate 105, and from the positive electrode portion 113 to the distal end of the central ceramic substrate 105. It extends in the axial direction toward the side (left side in FIG. 2), returns to the base end side via the distal end side, has a shape (pattern shape) connected to the negative electrode portion 114, and generates heat when energized. The heat generating pattern 111 includes a meandering heat generating portion 115 disposed on the distal end side, and a pair of lead portions 116a and 116b extending from both base ends of the heat generating portion 115 along the axial direction. In order to increase the temperature rapidly, the line width of the heat generating portion 115 is made smaller than the line width of the lead portions 116a and 116b so that the resistance value per unit length is reduced.

  On the other hand, a porous migration pattern 121 mainly made of Pt is formed between the surface 105B (second main surface) of the central ceramic substrate 105, that is, between the surface side ceramic substrate 103 and the central ceramic substrate 105. This migration pattern 121 is also shown in FIG. The migration pattern 121 is formed to face the heat generation pattern 111 approximately. Specifically, the migration pattern 121 includes a first end 123 formed on the base end side (the right side in FIG. 2 and the lower side in FIG. 3) of the central ceramic substrate 105, the front end of the central ceramic substrate 105, and the first end. And a second end portion 124 formed between the end portion 123 (specifically, a position on the tip side from the center in the axial direction), and the axis line extending from the first end portion 123 to the tip side of the central ceramic substrate 105. It extends in the direction, returns to the base end side via the distal end side, and is connected to the second end portion 124. As described above, the migration pattern 121 is formed so as to substantially face the heat generation pattern 111, and the miglet tip part 125 facing the heat generation part 115 and the lead parts 116 a and 116 b. And a pair of migre lead portions 129a and 129b having a wider line width.

By the way, in this embodiment, it has the bypass lead part 128 extended from the 2nd end part 124, and connected to the migre lead part 129a extended from the 1st end part 124 to the front end side. The bypass lead portion 128 is formed on the distal end side from the center in the axial direction of the central ceramic substrate 105 and extends from the second end portion 124 toward the proximal end side.
Further, on the surface 105B of the central ceramic substrate 105, a third end 126 formed on the base end side of the central ceramic substrate 105 and leads extending from the third end 126 toward the front end side of the central ceramic substrate 105. A portion 127 is formed. The lead portion 127 and the second end portion 124 described above are formed in an electrically unconnected state.

The negative electrode portion 114 of the heat generation pattern 111 and the first end portion 123 of the migration pattern 121 are electrically connected via a first through-hole conductor 131 formed through the central ceramic substrate 105. Therefore, the migration pattern 121 including the bypass lead portion 128 has the same potential as the negative electrode portion 114 of the heat generation pattern 111 when energized.
Further, the positive electrode portion 113 and the third end portion 126 of the heat generation pattern 111 are also electrically connected via a second through-hole conductor 132 formed so as to penetrate the central ceramic substrate 105. Accordingly, the third end portion 126 and the lead portion 127 have the same potential as the positive electrode portion 113 of the heat generation pattern 111 when energized.

  In addition, between the surface side ceramic substrate 103 and the central ceramic substrate 105, as shown in FIGS. 1 and 2, it is electrically connected to the first end 123 of the migration pattern 121, and from the base end of the ceramic heater 101. A negative electrode external terminal 141 extending to the outside and a positive electrode external terminal 142 electrically connected to the third end portion 126 and extending to the outside from the base end of the ceramic heater 101 are provided.

  Such a ceramic heater 101 has a bypass lead portion 128 connecting the migration pattern 121 with the second end portion 124 and the migre lead portion 129a extending from the first end portion 123 toward the front end side. When the heater tip is heated by applying a voltage between the negative electrode external terminals 142, the moisture that has entered the porous migration pattern 121 itself through the first end 123 is transferred from the miglet tip 125. It returns to the migre lead portion 129a through the migre lead portion 129b, the second end portion 124, and the bypass lead portion 128, and is further discharged to the outside from the first end portion 123. Therefore, it is possible to prevent the vicinity of the second end portion 124 caused by the moisture that has entered the migration pattern 121 and to prevent the ceramic heater 101 from being destroyed.

In the present embodiment, since the bypass lead portion 128 is formed from the second end portion 124 toward the base end side, moisture that has entered the migration pattern 121 flows from the second end portion 124 to the bypass lead portion 128. It is easy to escape to the migreid lead part 129a and the first end part 123 through. Therefore, the rupture near the second end portion 124 can be more effectively prevented.
In the present embodiment, since the negative electrode portion 114 of the heat generation pattern 111 and the first end portion 123 of the migration pattern 121 are electrically connected, the migration pattern 121 is more than the positive electrode portion 113 of the heat generation pattern 111. It can be easily set to a negative potential.
The ceramic heater 101 can be manufactured based on a known method for manufacturing a ceramic heater.

  Next, the NOx sensor element 201 having the ceramic heater 101 will be described. FIG. 4 shows a schematic perspective view of the NOx gas sensor element 201 of the present embodiment, and FIG. 5 shows a partially enlarged sectional view of the vicinity of the tip of the NOx gas sensor element 201. The NOx gas sensor element 201 is a stacked sensor element and has a substantially rectangular parallelepiped shape. The NOx gas sensor element 201 includes the ceramic heater 101 described above and a plate-shaped gas detection element 211 joined to the heater back surface 101C.

Among these, the gas detection element 211 is formed by laminating a plurality of zirconia solid electrolyte layers, and has a conventionally known structure and measurement principle disclosed in JP 2000-258388 A. NOx) concentration is detected.
That is, as shown in FIG. 5, the gas detection element 211 is configured such that the exhaust gas of the automobile as the gas to be measured passes through the first diffusion passage 213, the first chamber 215, and the second diffusion passage 217 in order. The zirconia sheets 221, 223, and 225 and the alumina insulating layers 227 and 229 are alternately stacked so as to reach the chamber 219. In order to heat and activate the gas detection element 211, the above-described ceramic heater 101 is disposed at a position adjacent to the gas detection element 211 constituted by these layers (upper side in the drawing).

  Porous electrodes 231a and 231b are provided on both surfaces of the upper zirconia sheet 221 arranged closest to the ceramic heater 101 to form the first oxygen ion pump cell 231 on the zirconia sheet 221. Yes. A second diffusion passage 217 is formed in the center zirconia sheet 223 laminated on the upper zirconia sheet 221 across the first diffusion passage 213, the first chamber 215, and the alumina insulating layer 227, and the second diffusion passage 217 is formed. Porous electrodes 233a and 233b are provided on both surfaces of the zirconia sheet 223 in the vicinity of the two diffusion passages 217 in order to form an oxygen concentration measurement cell 233. Furthermore, the lower zirconia sheet 225 laminated in the middle of the figure across the second chamber 219 and the alumina insulating layer 229 has a surface facing the second chamber 219 and the alumina insulating layer 229. Porous electrodes 235a and 235b are provided on the opposite surface to form the second oxygen ion pump cell 235. The first diffusion passage 213 and the second diffusion passage 217 mean diffusion resistance portions having diffusion resistance.

  The NOx gas sensor element 201 can also be manufactured based on a known manufacturing method of the gas sensor element. In the present embodiment, the ceramic heater 101 and the gas detection element 211 are separately manufactured (fired) and then bonded together via a bonding layer (cement).

  Since such a NOx gas sensor element 201 includes the ceramic heater 101 described above, it prevents rupture of the vicinity of the second end portion 124 caused by moisture that has entered the migration pattern 121, thereby preventing destruction of the ceramic heater 101. it can. Therefore, the gas sensor element 201 with high reliability can be obtained.

In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof. .
For example, in the NOx gas sensor element 201 of the above embodiment, the ceramic heater 101 and the gas detection element 211 are separately manufactured (fired) and then joined together. However, by firing the ceramic heater 101 and the gas detection element 211 at the same time, It may be manufactured.

It is a perspective view of the ceramic heater which concerns on embodiment. It is explanatory drawing which shows the structure of the ceramic heater which concerns on embodiment. It is explanatory drawing which shows a migration pattern among the ceramic heaters concerning embodiment. It is a perspective view of the NOx gas sensor element concerning an embodiment. It is a partial expanded sectional view near the tip of the NOx gas sensor element concerning an embodiment. It is explanatory drawing which shows the structure of the ceramic heater which concerns on a prior art. It is explanatory drawing which shows a migration pattern among the ceramic heaters based on a prior art.

Explanation of symbols

101 Ceramic heater 103 Front side ceramic substrate (second ceramic substrate)
105 Central ceramic substrate (first ceramic substrate)
105B (center ceramic substrate) surface (second main surface)
105C (center ceramic substrate) back surface (first main surface)
107 Back side ceramic substrate 111 Heat generation pattern 113 Positive electrode portion 114 (of heat generation pattern) Negative electrode portion 121 (of heat generation pattern) First end portion 124 (of migration pattern) Second end portion 128 (of migration pattern) Bypass lead part 201 (of migration pattern) Gas sensor element 211 Gas detection element

Claims (5)

A plate-like first ceramic substrate having a first main surface and a second main surface and extending in the axial direction from the front end toward the base end;
Formed on the first main surface, having a positive electrode portion and a negative electrode portion on the proximal end side, extending from the positive electrode portion to the distal end side, and returning to the proximal end side via the distal end side A heat generation pattern having a shape connected to the negative electrode portion;
Formed on the second main surface, having a first end on the base end side, a second end between the first end and the tip of the first end, and from the first end to the tip side A migration pattern having a shape connected to the second end portion via the distal end side and connected to the second end portion, wherein the migration pattern has a negative potential than the positive electrode portion when energized,
A plate-like second ceramic substrate laminated on the second main surface and covering the migration pattern;
A ceramic heater comprising:
The ceramic heater, wherein the migration pattern includes a bypass lead portion connecting the second end portion and a portion extending in the axial direction from the first end portion toward the tip end side. The ceramic heater according to claim 1,
The ceramic heater according to claim 2, wherein both the second end portion and the bypass lead portion are formed on the tip side from the center of the first ceramic substrate. The ceramic heater according to claim 1 or 2,
The ceramic wherein the bypass lead portion extends from the second end portion toward the proximal end side and is connected to a portion extending in the axial direction from the first end portion toward the distal end side. heater. The ceramic heater according to any one of claims 1 to 3,
The ceramic heater, wherein the negative electrode portion of the heat generation pattern and the first end portion of the migration pattern are electrically connected. The ceramic heater according to any one of claims 1 to 4,
A gas detection element comprising at least a solid electrolyte layer formed with a pair of electrode layers, and laminated on the ceramic heater;
A laminated gas sensor element comprising:

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