JP2006032101A - Ceramic heater and gas sensor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater excellent in durability, and a gas sensor using the same. <P>SOLUTION: The ceramic heater is formed by arranging a main heater pattern 2 composed of a main heating part 21, a pair of main electrode parts 22 supplying power to the main heating part 21, and a lead part 23 electrically connecting the main heating part 21 and the main electrode parts 22 on a heater base board. A sub-heater pattern 3 having a sub-heating part 31 for heating the main electrode parts 22 and a pair of sub-electrode parts 32 supplying power to the sub-heating part 31 is arranged on the ceramic heater 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ceramic heater for heating a gas sensor element and the like, and a gas sensor using the same.

For example, an internal combustion engine of an automobile uses a gas sensor that measures an oxygen concentration or the like in exhaust gas in order to perform combustion control. This gas sensor usually has a built-in ceramic heater for heating the gas sensor element in order to prevent variations in measurement values.
The ceramic heater includes a heat generating part for heating the gas sensor element, a pair of electrode parts for supplying electric power to the heat generating part, and a lead part for electrically connecting the heat generating part and the electrode part. A pattern is formed on a heater substrate (see Patent Document 1).

An example of such a ceramic heater is a round bar as shown in FIGS. This ceramic heater 9 is arranged so that a heater substrate 91 (FIG. 26) is wound around the surface of a ceramic mandrel 99. As shown in FIG. 26, the heater substrate 91 is provided with a heat generating portion 93 and a lead portion 94 on one surface 911 and an electrode portion 95 on the other surface 912. The lead portion 94 and the electrode portion 95 are connected via a through hole 913 that penetrates the heater substrate 91.
24 and 25, the heater substrate 91 is wound around the surface of the mandrel 99 so that the electrode portion 95 is on the outside, and a lead wire 96 is joined to the electrode portion 95 by a brazing material 961. ing.

However, moisture contained in outside air or exhaust gas may adhere to the electrode portion 95. This adhesion of moisture may cause corrosion of the electrode portion 95. Further, in a state where moisture is attached, corrosion of the electrode portion 95, the brazing material 961, and the lead wire 96 may progress due to adsorption of a corrosion-causing substance in the exhaust gas.
As a result, there is a possibility that the lead wire 96 joined to the electrode portion 95 may come off, and it may be difficult to ensure the durability of the ceramic heater 9.

  Further, when the ceramic heater 9 is started up, the heat generating portion 93 increases in temperature in a short time, but the electrode portion 95 increases in temperature due to the heat conduction from the heat generating portion 93, so that it takes time to increase the temperature. Therefore, a temperature gradient is generated between the heat generating portion 93 and the electrode portion 95, and a thermal stress is generated on the heater substrate 91 and the heater pattern 930. Further, thermal stress is also generated between the electrode portion 95 and the brazing material 961 and the lead wire 96 joined to the electrode portion 95. As a result, the fracture life at the joint may be shortened.

JP 11-2926649 A

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a ceramic heater excellent in durability and a gas sensor using the same.

1st invention consists of a main heat generating part, a pair of main electrode part for supplying electric power to the main heat generating part, and a lead part which electrically connects the main heat generating part and the main electrode part A main heater pattern is a ceramic heater formed on a heater substrate,
The ceramic heater is provided with a sub-heater pattern having a sub-heat generating portion for heating the main electrode portion and a pair of sub-electrode portions for supplying power to the sub-heat generating portion. It exists in a ceramic heater (Claim 1).

Next, the effects of the present invention will be described.
The ceramic heater is provided with a sub heater pattern having a sub heat generating part for heating the main electrode part. Therefore, the main electrode portion can be heated, and adhesion of moisture to the main electrode portion can be prevented. Even if moisture adheres to the main electrode portion, the main electrode portion can be heated by the sub-heat generating portion to evaporate and remove the moisture. Therefore, by removing moisture that becomes a corrosion factor, corrosion of the main electrode portion can be prevented and the durability of the ceramic heater can be improved.

  In addition, by preheating the main electrode portion, it is possible to suppress the occurrence of thermal stress in the main electrode portion when the ceramic heater is activated. Thereby, durability of the main electrode part can be improved.

  As described above, according to the present invention, a ceramic heater having excellent durability can be provided.

A second invention is a gas sensor having a gas sensor element for detecting a specific gas concentration in a gas to be measured, and a ceramic heater for heating the gas sensor element.
The ceramic heater electrically connects a main heat generating portion for heating the gas sensor element, a pair of main electrode portions for supplying electric power to the main heat generating portion, and the main heat generating portion and the main electrode portion. A main heater pattern consisting of a lead part is formed on the heater substrate,
The ceramic heater includes a sub-heater pattern having a sub-heat generating part for heating the main electrode part and a pair of sub-electrode parts for supplying power to the sub-heat generating part. (10).

Next, the effects of the present invention will be described.
The ceramic heater provided in the gas sensor is provided with a sub heater pattern having a sub heat generating portion for heating the main electrode portion. Therefore, as described above, the durability of the main electrode portion of the ceramic heater can be improved, and as a result, the durability of the gas sensor can be improved.
As described above, according to the present invention, a gas sensor excellent in durability can be provided.

In the first invention (Invention 1) or the second invention (Invention 10), a lead wire may be joined to the main electrode portion.
The pair of sub-electrode portions may be formed separately from the main electrode portion (claims 2 and 11).
In this case, it becomes easy to control the sub heat generating portion independently of the main heat generating portion.

Further, it is preferable that the main electrode portion and the sub electrode portion are arranged so as to be shifted from each other in the longitudinal direction of the ceramic heater (claims 3 and 12).
In this case, the main electrode portion and the sub electrode portion can be easily formed while ensuring mutual electrical insulation. Further, the main electrode portion and the sub electrode portion can be formed in a sufficient size.

Further, the ceramic heater may have one common electrode in which one of the pair of main electrode portions and one of the pair of sub electrode portions are made common (claims 4 and 13). .
In this case, the main electrode part and the sub electrode part can be easily formed.

The ceramic heater may have a pair of common electrodes in which the pair of main electrode portions and the pair of sub-electrode portions are made common (claims 5 and 16).
That is, one main electrode part and one sub electrode part are made common to form one common electrode, and the other main electrode part and the other sub electrode part are made common to form the other common electrode. Can do.
In this case, it is not necessary to form the sub electrode part in a different part from the main electrode part, and the sub heater pattern can be easily formed.

The sub heat generating portion is preferably configured to heat the main electrode portion before energizing the main heater pattern (claims 6 and 17).
In this case, at the start of energization of the main heater pattern, it becomes easy to raise the temperature of the main electrode portion so that moisture does not exist in the main electrode portion. In addition, when the gas sensor is activated, the causative substance in the exhaust gas leaks and reaches the main electrode, making it easy to keep moisture away from the main electrode, thus eliminating the corrosive environment. Thus, corrosion of the main electrode portion can be prevented more reliably.
In addition, by preheating the main electrode portion before energizing the main heater pattern, it is possible to suppress the occurrence of cold stress in the main electrode portion when the ceramic heater is activated. Thereby, durability of the main electrode part can be improved.

Further, it is preferable that the energization of the sub heater pattern is configured to end at the same time as or before the start of energization of the main heater pattern (claims 7 and 18).
In this case, overheating of the main electrode portion can be prevented and power saving can be achieved.

In addition, the sub-heat generating portion may be configured such that the main electrode portion is energized before the main heater pattern is energized so that the temperature rising rate of the main electrode portion accompanying the temperature increase of the main heat generating portion is 6 ° C./second or less. It is preferable that the temperature is raised (claims 8 and 19).
In this case, the thermal stress generated between the joining member such as the lead wire joined to the main electrode part and the ceramic heater body due to the temperature rise of the main electrode part accompanying the temperature rise of the main heating part is sufficiently suppressed. be able to.
When the temperature increase rate exceeds 6 ° C./second, it may be difficult to sufficiently suppress the cooling stress.
In addition, it is more preferable that the temperature of the main electrode portion is raised in advance so that the temperature rising rate of the main electrode portion is 2 ° C./second or less.

In addition, the sub-heat generating part has a PTC (Positive
(Temperature Coefficient) It is preferable to be composed of a heating element (claims 9 and 20).
In this case, PTC (Positive
Temperature Coefficient) The heating element uses the characteristic that the resistance of the PTC heating element itself increases with the generation of heat and the ultimate temperature is suppressed, so that the sub-heating part can be prevented from overheating and the main electrode part can be prevented from overheating. At the same time, the temperature control system of the sub heater can be simplified.

Next, in the second invention (invention 10), the sub-electrode portion that does not constitute the common electrode is preferably connected to a heater holder for holding the ceramic heater in the gas sensor. (Claim 14).
In this case, since the electric power can be supplied to the sub heater pattern through the heater holder, the structure of the gas sensor can be simplified.

The heater holder is preferably connected to a sensor terminal of the gas sensor element.
In this case, since the sub electrode part and the sensor terminal can be shared, the structure of the gas sensor can be simplified.

The sub-heater pattern is preferably configured not to be energized when the specific gas concentration is detected.
In this case, the leakage current from the sub heater pattern can be prevented from affecting the sensor output. This is particularly effective in the case of a gas sensor that detects a weak current.

Example 1
A ceramic heater and a gas sensor using the same according to an embodiment of the present invention will be described with reference to FIGS.
The ceramic heater 1 of this example is formed by forming a main heater pattern 2 on a heater substrate 11 as shown in FIGS. The main heater pattern 2 electrically connects the main heat generating portion 21, a pair of main electrode portions 22 for supplying power to the main heat generating portion 21, and the main heat generating portion 21 and the main electrode portion 22. And lead part 23 to be used.
The ceramic heater 1 is provided with a sub heater pattern 3 having a sub heat generating portion 31 for heating the main electrode portion 22 and a pair of sub electrode portions 32 for supplying electric power to the sub heat generating portion 31. It becomes.

  The ceramic heater 1 is formed by winding a heater substrate 11 having a main heater pattern 2 and a sub-heater pattern 3 on the surface thereof, as shown in FIGS. 2 and 4, around a cylindrical mandrel 19. . FIG. 3 is a developed view of the heater substrate 11 on which the main heater pattern 2 and the like are formed, and shows a plan view of the outer side surface 111 arranged on the outer side and a plan view of the inner side surface 112 arranged on the inner side. .

  As shown in FIGS. 2 and 3, the pair of sub electrode portions 32 are formed separately from the main electrode portion 22, and the pair of main electrode portions 22 and the pair of sub electrode portions 32 are a heater substrate. 11 is formed on the outer surface 111 at one end portion. The main electrode portions 22 and the sub electrode portions 32 are alternately arranged at the same position in the longitudinal direction of the ceramic heater 1.

  As shown in FIG. 3, the main heat generating portion 21, the lead portion 23, and the sub heat generating portion 31 are formed on the inner side surface 112 of the heater substrate 11. The main heat generating portion 21 is formed at the end of the heater substrate 11 opposite to the side where the main electrode portion 22 is disposed. Further, the main heat generating portion 21 is formed in a zigzag shape in this example. In addition, the formation pattern of the main heat-emitting part 21 is not restricted to this, It can form in various patterns.

The sub heat generating portion 31 is formed at the end of the heater substrate 11 on the side where the main electrode portion 22 is disposed.
The sub heat generating portion 31 and the sub electrode portion 32 are connected to each other through a through hole 131 that penetrates the heater substrate 11. The main heat generating portion 21 and the main electrode portion 22 are connected via the lead portion 23 and the through hole 132.

As shown in FIGS. 2 and 4, the lead wires 12 are joined to the pair of main electrode portions 22 by a conductive brazing material 121. Similarly, the lead wires 13 are also joined to the pair of sub electrode portions 32.
Further, for example, the main heater pattern 2 and the sub heater pattern 3 have W (tungsten) as a main component, the brazing material 121 has Au (gold) and Cu (copper) as main components, and the lead wires 12, 13 has Ni (nickel) as a main component. In addition, the sub heat generating part 31 can be configured by a PTC (Positive Temperature Coefficient) heat generating element.

  The ceramic heater 1 is used to heat the gas sensor element 45 as shown in FIG. That is, the ceramic heater 1 is incorporated in the gas sensor 4 for detecting a specific gas concentration in the gas to be measured.

Next, the gas sensor 4 of this example will be described in detail.
As shown in FIG. 5, the gas sensor 4 includes a cylindrical housing 40, a cup-type gas sensor element 45 inserted through the housing 40, and an outer cover 411 and an inner cover 412 provided on the front end side of the housing 40. A measurement gas side cover 41 and an atmosphere side cover 42 provided on the base end side of the housing 40 are provided.

The measured gas side cover 41 constitutes a measured gas atmosphere 410, and the gas sensor element 45 performs oxygen concentration measurement based on the exhaust gas introduced therein.
An outer cover 421 is caulked and fixed to the base end side of the atmosphere side cover 42 via a water repellent filter 422. An elastic insulating member 443 is caulked and fixed inside the most proximal end of the atmosphere side cover 42.
The atmosphere side cover 42 constitutes an atmosphere 420, and the atmosphere is introduced into the atmosphere chamber of the gas sensor element 45 described later.

The gas sensor element 45 is inserted into the housing 40, and a powder sealant 431 and an insulating member 432 are disposed between the two to ensure airtightness and liquid tightness.
The base end side of the insulating member 432 is caulked by bending the base end side of the housing 40 inward via a ring-shaped member 434.
An atmosphere side insulator 442 is supported by a disc spring 441 inside the atmosphere side cover 42 and below the elastic insulating member 443.

The gas sensor element 45 is formed by providing an outer electrode and an inner electrode on the outer surface and the inner surface of a bottomed cylindrical solid electrolyte body 49 (not shown).
The interior of the solid electrolyte body 49 is used as an atmosphere chamber 490, and the ceramic heater 1 configured as a separate body is disposed inside the atmosphere chamber 490.

The gas sensor element 45 is provided with contact terminals 471 and 472 that are electrically connected to the outer electrode and the inner electrode, respectively. The contact terminals 471 and 472 are connected to the connection terminals 473 and 474 in the atmosphere-side insulator 442, respectively. To the external lead wires 403 and 404. The contact terminal 472 is provided with a heater holder 46 that holds the ceramic heater 1.
The lead wire 12 connected to the main electrode portion 22 of the ceramic heater 1 is connected to the external lead wire 401 via the connection terminal 451 inside the atmosphere-side insulator 442.

In the gas sensor 4, outside air is introduced into the atmosphere side cover 42 via the water repellent filter 422.
As the engine starts, measurement of the specific gas (oxygen) concentration in the gas to be measured by the gas sensor 4 is started. At this time, exhaust gas from the engine enters the measured gas side cover 41 of the gas sensor 4, and part of the exhaust gas passes through the powder sealing material 431 and the insulating member 432 and reaches the main electrode portion 22 of the ceramic heater 1. is there. This is because the powder sealant 431 and the insulating member 432 ensure airtightness and liquid tightness between the measured gas side and the atmosphere side, but some leakage may occur.

  Therefore, outside air exists around the main electrode portion 22 as shown by a curve A in FIG. 6 before the engine is started (t = 0), and as shown by a curve B, exhaust gas is generated as the engine is started. invade. In addition, the amount of outside air around the main electrode portion 22 is slightly reduced by the amount of intrusion of the exhaust gas (curve A).

In addition, when the engine is started, power is supplied to the main heater pattern 2 of the ceramic heater 1, and the temperature of the gas sensor element 45 is increased by the main heating unit 21. Moreover, the heat of the main heat generating part 21 is also conducted to the main electrode part 22, and the main electrode part 22 is also gradually heated.
On the other hand, by energizing the sub heater pattern 3 as well, the sub heat generating portion 31 promotes the temperature rise of the main electrode portion 22 to be 100 ° C. or higher in a shorter time (curve C1). Thus, when there is no sub heater pattern 3, the sub heater pattern 3 is used in a place where it takes about 2 minutes to raise the temperature of the main electrode portion 22 to 100 ° C. as shown by a curve C0 in FIG. Thus, as shown by a curve C1 in FIG.

  Further, the sub-heat generating portion 31 can also heat the main electrode portion 22 before energizing the main heater pattern 2 (for example, about 20 seconds before) as shown by a curve C2 in FIG. That is, it is possible to energize the sub-heater pattern 3 and start up the temperature of the main electrode portion 22 before starting the engine.

  In FIG. 6, a curve A represents a change over time in the amount of outside air introduced to the vicinity of the main electrode portion 22, and a curve B represents a change over time in the amount of exhaust gas entering the periphery of the main electrode portion 22. A curve C0 represents a time change of the temperature of the main electrode part 22 when the sub heat generating part 31 is not used, and a curve C1 represents a time change of the temperature of the main electrode part 22 when the sub heat generating part 31 is energized when the engine is started. A curve C2 represents a change over time in the temperature of the main electrode portion 22 when energization of the sub heat generating portion 31 is started prior to engine startup.

Next, the function and effect of this example will be described.
As shown in FIGS. 1 and 3, the ceramic heater 1 is provided with a sub heater pattern 3 having a sub heat generating portion 31 for heating the main electrode portion 22. Therefore, the main electrode part 22 can be heated, and adhesion of moisture to the main electrode part 22 can be prevented. Even if moisture adheres to the main electrode portion 22, the main electrode portion 22 can be heated by the sub heat generating portion 31 to evaporate and remove the moisture. Therefore, it is possible to eliminate the corrosive environment by removing moisture that becomes a corrosive factor, thereby preventing the main electrode portion 22 from being corroded and improving the durability of the ceramic heater 1.
That is, for example, corrosion at the interface between the main electrode portion 22 and the brazing material 121 or at the interface between the brazing material 121 and the lead wire 12 can be prevented, and the detachment of the lead wire 12 can be prevented.

  Further, as shown by the curves C1 and C2 in FIG. 6, since the temperature of the main electrode portion 22 can be raised to 100 ° C. or more in a short time after the engine is started, the main electrode portion 22 The time of exposure to the exhaust gas can be greatly shortened or eliminated. Thereby, the corrosive environment in the main electrode part 22 can be excluded.

In other words, if there is no sub-heating unit 31, it takes about 2 minutes from the start of the engine until the temperature of the main electrode unit 22 reaches 100 ° C., as shown by the curve C0 in FIG. . During this time, moisture may remain in the main electrode portion 22. Then, as shown in FIG. 6, the exhaust gas leaks into the gas sensor 4 and reaches the vicinity of the main electrode portion 22. If it does so, there exists a possibility that the corrosive environment may be formed by the corrosion cause substance in exhaust gas adhering to the main electrode part 22 to which the moisture adhered.
On the other hand, according to this example, as described above, the corrosive environment in the main electrode portion 22 can be eliminated.

In addition, by heating the main electrode portion 22 in advance, when the ceramic heater 1 is started, the temperature rapidly rises due to heat generated by the main heat generating portion 21 and heat conduction from the heat generating portion. The occurrence of thermal stress in other parts including the balanced main electrode part 22 can be mitigated and suppressed. Thereby, durability of the ceramic heater 1 can be improved.
Further, since the pair of sub-electrode portions 32 are formed separately from the main electrode portion 22, the sub-heat generating portion 31 can be easily controlled independently from the main heat generating portion 21.

  The sub heat generating portion 31 can also heat the main electrode portion 22 before energizing the main heater pattern 2. Thereby, at the time of starting energization to the main heater pattern 2, the temperature of the main electrode portion 22 can be increased to such an extent that moisture (water environment) does not exist. Therefore, when the corrosion-causing substance in the exhaust gas reaches the main electrode portion 22 when the gas sensor 31 is started, it becomes easy to make the moisture not exist in the main electrode portion 22. As a result, it is possible to eliminate the corrosive environment by removing moisture that becomes a corrosive factor, and more reliably prevent the main electrode portion 22 from being corroded.

  In addition, by heating the main electrode portion 22 in advance before energizing the main heater pattern 2, it is possible to mitigate and suppress the occurrence of the thermal stress of the ceramic heater 1 as described above, thereby improving the durability. be able to.

  Further, when a PTC heating element is used as the sub heat generating portion 31, overheating of the sub heat generating portion 31 can be prevented and overheating of the main electrode portion 22 can be prevented. That is, the temperature of the sub heat generating portion 31 can be controlled so as not to be higher than about 200 ° C. (see curves C1 and C2 in FIG. 6). In addition, since the PTC (Positive Temperature Coefficient) heating element has a characteristic that the resistance of the PTC heating element itself increases with the generation of heat and the temperature reached by itself is suppressed, the temperature control system of the sub-heater can be simplified.

  As described above, according to this example, a ceramic heater excellent in durability and a gas sensor using the same can be provided.

(Example 2)
This example is an example of the ceramic heater 1 in which the sub heat generating portion 31 is formed on the sub heater substrate 110 different from the heater substrate 11 on which the main heater pattern 2 is formed, as shown in FIG.
The sub heater substrate 110 is bonded to the inner side surface 112 of the heater substrate 11. The sub-heater substrate 110 and the heater substrate 11 are wound around the mandrel 19 (see FIG. 2).

The sub heat generating portion 31 is formed on the inner surface of the sub heater substrate 110, that is, the surface opposite to the contact surface with the heater substrate 11. Further, the sub heat generating portion 31 is disposed on the back side portion in the vicinity of the position where the main electrode portion 22 is disposed. The sub heat generating portion 31 is electrically connected to the sub electrode portion 32 through the sub heater substrate 110 and the through hole 131 that penetrates the heater substrate 11.
Others are the same as in the first embodiment.

In the case of this example, since the sub heat generating portion 31 can be wired regardless of the wiring position of the main heater pattern 2, it can be easily and sufficiently wired at the corresponding position of the main electrode portion 22. Thereby, the temperature rise of the main electrode part 22 can be performed efficiently.
In addition, the same effects as those of the first embodiment are obtained.

Example 3
In this example, as shown in FIGS. 8 and 9, the main electrode portion 22 and the sub electrode portion 32 are arranged so as to be shifted from each other in the longitudinal direction of the ceramic heater 1.
That is, the sub electrode part 32 is offset at a position shifted from the main electrode part 22 toward the front end side of the ceramic heater 1.
Others are the same as in the first embodiment.

In the case of this example, the main electrode part 22 and the sub electrode part 32 can be easily formed while ensuring mutual electrical insulation. Further, the main electrode portion 22 and the sub electrode portion 32 can be formed in a sufficient size.
In addition, the same effects as those of the first embodiment are obtained.

Example 4
In this example, as shown in FIG. 10, the main electrode portion 22 and the sub electrode portion 32 are arranged so as to be shifted from each other in the longitudinal direction of the ceramic heater 1 and the heater substrate 11 on which the main heater pattern 2 is formed. This is an example of the ceramic heater 1 in which a sub heat generating portion 31 is formed on a separate sub heater substrate 110.
That is, the sub-heater substrate 110 is used in the ceramic heater 1 in which the main heater pattern 2 and the sub electrode portion 32 similar to those in the third embodiment are formed, as in the second embodiment.
In the case of this example, the same effects as those of Example 2 and Example 3 are obtained.

(Example 5)
This example is an example of the ceramic heater 1 having one common electrode 14 in which one of the pair of main electrode portions 22 and one of the pair of sub electrode portions 32 are shared as shown in FIGS. 11 and 12. .
The sub electrode portion 32 that does not constitute the common electrode 14 is disposed at a substantially central portion in the longitudinal direction of the ceramic heater 1. The sub electrode portion 32 is connected to a heater holder (see reference numeral 46 in FIG. 5) for holding the ceramic heater 1 in the gas sensor.
The heater holder is also connected to a sensor terminal of a gas sensor element (see reference numeral 45 in FIG. 5).

Further, the sub heat generating portion 32 is connected to the lead portion 23 of the main heater pattern 2 as shown in FIG. Thereby, the main electrode portion 22 also functions as the sub electrode portion 32 and becomes the common electrode 14.
Others are the same as in the first embodiment.

In the case of this example, since the number of electrodes to be formed can be substantially reduced, the main electrode portion 22 and the sub electrode portion 32 can be easily formed. Moreover, since electric power can be supplied to the sub-heater pattern 3 through the heater holder, the structure of the gas sensor can be simplified.
Moreover, since the sub electrode part 32 and the sensor terminal can be shared, the structure of the gas sensor can be further simplified.
In addition, the same effects as those of the first embodiment are obtained.

(Example 6)
As shown in FIG. 13, this example has one common electrode 14 in which one of the pair of main electrode portions 22 and one of the pair of sub-electrode portions 32 are shared, and the main heater pattern 2 is formed. This is an example of the ceramic heater 1 in which a sub heat generating portion 31 is formed on a sub heater substrate 110 that is separate from the heater substrate 11.
That is, the sub-heater substrate 110 is used in the ceramic heater 1 in which the main heater pattern 2 and the sub electrode portion 32 similar to those in the fifth embodiment are formed, as in the second embodiment.
Others are the same as in the first embodiment.
In the case of this example, the same effects as those of Example 5 and Example 3 are obtained.

(Example 7)
This example is an example of the ceramic heater 1 having a pair of common electrodes 140 in which a pair of main electrode portions 22 and a pair of sub-electrode portions 32 are made common, as shown in FIGS.
Further, the sub heat generating portion 32 is connected to the lead portion 23 of the main heater pattern 2 as shown in FIG. Thereby, the main electrode portion 22 also functions as the sub electrode portion 32 and becomes the common electrode 140.
Others are the same as in the first embodiment.

In the case of this example, it is not necessary to form the sub electrode part 32 in a part different from the main electrode part 22, and the sub heater pattern 3 can be easily formed.
In addition, the same effects as those of the first embodiment are obtained.

(Example 8)
As shown in FIG. 16, this example includes a pair of common electrodes 140 in which a pair of main electrode portions 22 and a pair of sub electrode portions 32 are shared, and a heater substrate 11 on which the main heater pattern 2 is formed. These are examples of the ceramic heater 1 in which the sub heat generating portion 31 is formed on the separate sub heater substrate 110.
That is, the sub-heater substrate 110 is used in the ceramic heater 1 in which the main heater pattern 2 and the sub-electrode portion 32 similar to those in the seventh embodiment are formed, as in the second embodiment.
Others are the same as in the first embodiment.
In the case of this example, the same effects as those of Example 7 and Example 3 are obtained.

Example 9
In this example, as shown in FIG. 17, the ceramic heater 10 of the present invention is applied to the laminated gas sensor element 5. FIG. 17 is an exploded perspective view illustrating a state in which the gas sensor 5 is separated into each component. The same applies to FIGS. 18 and 19 described later.
In the ceramic heater 10 in this example, the main heat generating portion 21 and the lead portion 23 of the main heater pattern 2 are formed on one surface 114 of the flat heater substrate 11, and the sub heat generating of the sub heater pattern 3 is formed on the other surface 115. A portion 31 is formed.

  A first cover substrate 15 that covers the main heater pattern 2 is laminated on one surface 114 of the heater substrate 11, and a second cover that covers the sub heater pattern 2 is formed on the other surface 115 of the heater substrate 11. A substrate 16 is laminated. The second coated substrate 16 has a pair of main electrode portions 22 and a pair of sub electrode portions 32 formed on the surface opposite to the heater substrate 11.

The main heat generating portion 21 and the lead portion 23 are electrically connected to the main electrode portion 22 through a through hole 132 that penetrates the heater substrate 11 and the second cover substrate 16. Further, the sub-heat generating portion 31 is electrically connected to the sub-electrode portion 32 through a through hole 131 that penetrates the second coated substrate 16.
The sub heat generating portion 31 is disposed on the back side of the second coated substrate 16 near the position where the main electrode portion 22 is disposed, and is configured to heat the main electrode portion 22.

  The gas sensor element 5 includes a solid electrolyte plate 51, a measurement gas side electrode 55 that is provided on the surface of the solid electrolyte plate 51 and is exposed to the measurement gas, and a reference gas side electrode 56 that is exposed to the reference gas. 50. And the ceramic heater 10 is laminated | stacked integrally.

As shown in FIG. 17, the solid electrolyte plate 51 is laminated on the first coated substrate 15 of the ceramic heater 10 via a spacer 52 for forming a reference gas chamber.
Further, an electrode protective film 57 is laminated so as to cover the measured gas side electrode 55 provided on the solid electrolyte plate 51.
A reference gas side electrode 56 is provided on the other surface of the solid electrolyte plate 51, and the reference gas side electrode 56 faces the reference gas chamber.

The measurement gas side electrode 55 and the reference gas side electrode 56 are provided with output lead portions 551 and 561 and terminals 552 and 562, respectively.
The spacer 52 is configured in a U shape, and the reference gas chamber is configured by the spacer 52 and the first coated substrate 15 in the ceramic heater 10.
Others are the same as those of the first embodiment and have the same effects as the first embodiment.

(Example 10)
In this example, as shown in FIG. 18, a laminated type gas sensor using a ceramic heater 10 having one common electrode 14 in which one of a pair of main electrode portions 22 and one of a pair of sub-electrode portions 32 are made common. This is an example of the element 5.
Others are the same as in the ninth embodiment.
In the case of this example, since the number of electrodes to be formed can be substantially reduced, the main electrode portion 22 and the sub electrode portion 32 can be easily formed.
In addition, the same effects as those of the first embodiment are obtained.

(Example 11)
As shown in FIG. 19, this example is an example of a stacked gas sensor element 5 using a ceramic heater 10 in which a main heat generating portion 21 and a sub heat generating portion 31 are both formed on one surface 114 of the heater substrate 11.
The main heat generating portion 21 and the sub heat generating portion 31 are wired in a state where electrical insulation can be ensured so as not to short-circuit each other.

Further, the ceramic heater 10 of this example does not have the second coated substrate 16 (see FIGS. 17 and 18) shown in the ninth and tenth embodiments. The main electrode part 22, the sub electrode part 32, and the common electrode 14 are formed on the other surface 115 of the heater substrate 11. The common electrode 14 functions as the main electrode portion 22 and the sub electrode portion 32.
Others are the same as in the first embodiment.

In the case of this example, since it is not necessary to provide the second coated substrate 16 (see FIGS. 17 and 18) shown in Examples 9 and 10, the material cost of the ceramic heater 10 is reduced and the productivity is improved. be able to.
Further, as in the case of the tenth embodiment, the number of electrodes to be formed can be substantially reduced, so that the main electrode portion 22 and the sub electrode portion 32 can be easily formed.
In addition, the same effects as those of the first embodiment are obtained.

(Example 12)
In this example, as shown in FIG. 20, the sub-heat generating portion heats the main electrode portion before energization to the main heater pattern, and the energization to the sub-heater pattern is terminated before energization to the main heater pattern is started. This is an example of the configuration.
That is, the sub heater control circuit connected to the sub heater pattern and the main heater control circuit connected to the main heater pattern control energization to each pattern as follows, for example.

First, as shown in FIG. 20, when the driver opens the door of the automobile when getting in (t0), the opening of the door is detected and energization of the sub heater pattern is started (curve D). As a result, the main electrode portion is raised to 100 ° C. or higher to remove the water environment (curve F).
When a preset energization time, input power amount, or the like is detected (t1), energization to the sub heater pattern is terminated (curve D).
Next, energization of the main heater pattern is started simultaneously with the engine start (t2) (curve E). At this time, detection of the specific gas concentration by the gas sensor is started.

After the energization of the sub-heater pattern is finished (t1) and until the energization of the main heater pattern is started (t2), the temperature of the main electrode part slightly decreases, but the state of 100 ° C. or higher is maintained (curve F). .
Further, due to energization of the main heater pattern, the temperature of the main heat generating portion rises and saturates in a state where it reaches, for example, 600 to 900 ° C. (curve G).
On the other hand, the temperature of the main electrode portion also gradually rises again due to heat transfer from the main heat generating portion, and saturates when reaching 200 to 400 ° C., for example (curve F).
In FIG. 20, T1 and T2 are saturation temperatures of the main heat generating portion and the main electrode portion, respectively. The same applies to FIGS. 21 to 23 described later.
Others are the same as in the first embodiment.

In the case of this example, overheating of the main electrode portion can be prevented, and deterioration of the brazed joint portion between the main electrode portion and the lead wire can be prevented. Further, since unnecessary power is not supplied to the sub-heater pattern, power saving can be achieved.
In addition, the same effects as those of the first embodiment are obtained.

(Example 13)
In this example, as shown in FIG. 21, a ceramic heater configured to end energization of the sub heater pattern simultaneously with the start of energization of the main heater pattern.
That is, energization to the main heater pattern is started simultaneously with engine start (t2), and energization to the sub heater pattern is ended (curves E and D).
Others are the same as in Example 12.

In the case of this example, since the energization start to the main heater pattern and the energization to the sub heater pattern can be ended by detecting the engine start signal, the control can be simplified.
Moreover, temperature control can be easily performed in a gas sensor in which the sensor terminal of the gas sensor element and the sub-electrode portion are shared as shown in the fifth embodiment (FIGS. 11 and 12). That is, before the engine is started, electric power is supplied from the sub electrode portion to the sub heater pattern, and after the engine is started, the sub electrode portion functions as a sensor terminal of the gas sensor element, and the sensor output can be taken out.
In addition, the same effects as those of the twelfth embodiment are obtained.

(Example 14)
In this example, as shown in FIG. 22, the sub heat generating unit maintains the main electrode unit at a set temperature of 100 ° C. or more before starting the engine, and ends energization to the sub heater pattern simultaneously with starting the engine. It is.
That is, before starting the engine, after energizing the sub-heater pattern and causing the main electrode portion to reach a predetermined temperature of 100 ° C. or higher (for example, 150 ° C.) as indicated by the curve F (after t3), as in the twelfth embodiment. ) The energization of the sub heater pattern is controlled so as to maintain this predetermined temperature (area D1).
Simultaneously with the engine start (t2), energization to the main heater pattern is started and energization to the sub heater pattern is ended (curves E and D).
Others are the same as in Example 13.

In the case of this example, overheating of the main electrode part can be prevented more reliably and the water environment can be reliably eliminated.
In addition, the same effects as those of the thirteenth embodiment are obtained.

(Example 15)
In this example, as shown in FIG. 23, the main heating pattern is energized before the main heater pattern so that the heating rate of the main electrode portion is 6 ° C./second or less by the sub heating portion. This is an example in which the temperature of the electrode part is raised.

First, similarly to Example 12, the temperature of the main electrode part is raised by the sub heat generating part (curve F) before the engine is started (t2). Thereafter, the temperature rise is continued (curve F) until the time point (t4) at which the temperature rise rate of the main electrode portion accompanying the temperature rise of the main heating portion becomes 6 ° C./second or less. Note that the temperature may continue after the engine is started, or may continue after the start of energization to the main heater pattern (t2).
Others are the same as in Example 12.

In the case of this example, a joining member (lead wire 12, brazing material 121, etc. (see FIG. 4)) joined to the main electrode portion by the temperature rise of the main electrode portion accompanying the temperature rise of the main heat generating portion and the ceramic heater body Can be sufficiently suppressed.
That is, as the main heat generating part generates heat, the temperature of the main electrode part is increased by heat transfer. At this time, stress is generated due to a difference in thermal expansion between the ceramic material of the heater substrate on which the main electrode portion is disposed and the brazing material and the metal material of the lead wire. Since the generated stress is proportional to the rate of temperature rise, it can be controlled by changing the rate of temperature rise of the main electrode portion.
Therefore, as described above, the temperature of the main electrode portion is increased by the temperature of the main heat generating portion by increasing the temperature of the main electrode portion in advance by the sub heat generating portion before energizing the main heater pattern. Thus, the generated stress can be reduced.

For example, when the maximum temperature of the main heat generating portion is 900 ° C., the maximum temperature of the main electrode portion is 345 ° C. When the time to reach the maximum temperature is 40 seconds, the rate of temperature increase accompanying the heat generation of the main heat generating portion is assumed to be when the preheating by the sub-heater is not performed (the temperature is increased from RT 25 ° C. according to the temperature increase of the main heat generating portion. In the case).
On the other hand, if the temperature of the main electrode part is raised to 150 ° C. in advance using a sub-heater, the rate of temperature rise accompanying the heat generation of the main heating part can be moderated to about 4.9 ° C./second. it can. And in this case, the thermal stress which generate | occur | produces between the joining member and ceramic heater main body which were fully joined to the main electrode part can be suppressed.
In addition, the same effects as those of the twelfth embodiment are obtained.

1 is a schematic diagram of a ceramic heater in Example 1. FIG. 1 is a front view of a ceramic heater in Embodiment 1. FIG. FIG. 3 is a development view of a ceramic heater in the first embodiment. FIG. 3 is a cross-sectional view of a vicinity of a joint portion between a main electrode portion and a lead wire in Embodiment 1. 1 is a longitudinal sectional view of a gas sensor in Embodiment 1. FIG. The diagram showing the change of the temperature of the main electrode part in Example 1, the amount of introduction of outside air, and the amount of introduction of exhaust gas. FIG. 6 is a development view of a ceramic heater in Example 2. The front view of the ceramic heater in Example 3. FIG. FIG. 6 is a development view of a ceramic heater in Example 3. FIG. 6 is a development view of a ceramic heater in Example 4. The front view of the ceramic heater in Example 5. FIG. FIG. 6 is a development view of a ceramic heater in Example 5. The expanded view of the ceramic heater in Example 6. FIG. The front view of the ceramic heater in Example 7. FIG. The expanded view of the ceramic heater in Example 7. FIG. The expanded view of the ceramic heater in Example 8. FIG. FIG. 10 is a developed perspective view of a gas sensor element in Example 9. The expanded perspective view of the gas sensor element in Example 10. FIG. The expanded perspective view of the gas sensor element in Example 11. FIG. FIG. 14 is a diagram illustrating control of energization to a sub heater pattern and a main heater pattern and a temperature change of a main heat generating part and a main electrode part in Example 12. FIG. 14 is a diagram illustrating control of energization to a sub heater pattern and a main heater pattern and a temperature change of a main heat generating part and a main electrode part in Example 13. FIG. 16 is a diagram showing control of energization to the sub heater pattern and the main heater pattern and temperature changes of the main heat generating part and the main electrode part in Example 14. FIG. 16 is a diagram showing control of energization to the sub heater pattern and the main heater pattern and temperature changes of the main heat generating part and the main electrode part in Example 15. The front view of the ceramic heater in a prior art example. Sectional drawing of the junction part vicinity of an electrode part and a lead wire in a prior art example. The development view of a ceramic heater in a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10 Ceramic heater 11 Heater board 2 Main heater pattern 21 Main heating part 22 Main electrode part 23 Lead part 3 Sub heater pattern 31 Sub heating part 32 Sub electrode part 4 Gas sensor 45, 5 Gas sensor element

Claims (21)

A main heater pattern comprising a main heat generating portion, a pair of main electrode portions for supplying electric power to the main heat generating portion, and a lead portion for electrically connecting the main heat generating portion and the main electrode portion, a heater A ceramic heater formed on a substrate,
The ceramic heater is provided with a sub-heater pattern having a sub-heat generating part for heating the main electrode part and a pair of sub-electrode parts for supplying electric power to the sub-heat generating part. Ceramic heater.   2. The ceramic heater according to claim 1, wherein the pair of sub electrode portions are formed separately from the main electrode portion.   3. The ceramic heater according to claim 2, wherein the main electrode portion and the sub electrode portion are arranged so as to be shifted from each other in the longitudinal direction of the ceramic heater.   2. The ceramic heater according to claim 1, wherein the ceramic heater has one common electrode in which one of the pair of main electrode portions and one of the pair of sub electrode portions are shared.   2. The ceramic heater according to claim 1, wherein the ceramic heater has a pair of common electrodes in which the pair of main electrode portions and the pair of sub-electrode portions are respectively shared.   6. The ceramic heater according to claim 1, wherein the sub heat generating portion is configured to heat the main electrode portion before energizing the main heater pattern.   7. The ceramic heater according to claim 6, wherein energization of the sub heater pattern is completed at the same time as or before the start of energization of the main heater pattern.   8. The sub heat generating portion according to claim 6 or 7, wherein the sub heat generating portion is energized before the main heater pattern is energized so that a temperature rising rate of the main electrode portion is 6 ° C./second or less. A ceramic heater characterized in that the temperature of the main electrode portion is raised.   9. The ceramic heater according to claim 1, wherein the sub heat generating portion is formed of a PTC heat generating element. In a gas sensor having a gas sensor element for detecting a specific gas concentration in a gas to be measured and a ceramic heater for heating the gas sensor element,
The ceramic heater electrically connects a main heat generating portion for heating the gas sensor element, a pair of main electrode portions for supplying electric power to the main heat generating portion, and the main heat generating portion and the main electrode portion. A main heater pattern consisting of a lead part is formed on the heater substrate,
The ceramic heater includes a sub-heater pattern having a sub-heat generating part for heating the main electrode part and a pair of sub-electrode parts for supplying power to the sub-heat generating part. Gas sensor.   11. The gas sensor according to claim 10, wherein the pair of sub electrode portions are formed separately from the main electrode portion.   12. The gas sensor according to claim 11, wherein the main electrode portion and the sub electrode portion are arranged to be shifted from each other in the longitudinal direction of the ceramic heater.   11. The gas sensor according to claim 10, wherein the ceramic heater has one common electrode in which one of the pair of main electrode portions and one of the pair of sub electrode portions are made common.   14. The gas sensor according to claim 13, wherein the sub electrode portion that does not constitute the common electrode is connected to a heater holder for holding the ceramic heater in the gas sensor.   The gas sensor according to claim 14, wherein the heater holder is also connected to a sensor terminal of the gas sensor element.   11. The gas sensor according to claim 10, wherein the ceramic heater has a pair of common electrodes in which the pair of main electrode portions and the pair of sub electrode portions are made common.   17. The gas sensor according to claim 10, wherein the sub heat generating portion is configured to heat the main electrode portion before energizing the main heater pattern.   18. The gas sensor according to claim 17, wherein energization of the sub heater pattern is configured to end simultaneously with or before energization of the main heater pattern.   19. The sub-heat generating unit according to claim 17 or 18, before energization of the main heater pattern, so that a temperature rising rate of the main electrode unit accompanying a temperature increase of the main heat generating unit is 6 ° C./second or less. A gas sensor characterized in that the temperature of the main electrode part is raised.   The gas sensor according to any one of claims 10 to 19, wherein the sub heat generating portion is formed of a PTC heat generating element.   21. The gas sensor according to claim 10, wherein the sub heater pattern is configured not to be energized when the specific gas concentration is detected.

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