JPH11132993A - Oxygen sensor with heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heating machine characteristics for a detection element without reducing the brazing strength of the lead terminal brazing part of a heater in an oxygen sensor with the heater being provided with a closed-end cylindrical detection element and a ceramic heater being arranged in the internal space. SOLUTION: A ratio Rs/L5 of an internal diameter Rs of a detection element to length L5 from the heat generation pattern part to brazing part of a heater is set to 0.3 or less, and at the same time a ratio L4/L5 of distance L4 from the tip of the heater to the blockade part of a detection element S to length L5 is set to 0.2 or less. Also, a ratio L1/L2 of length L1 of the heat generation pattern part of the heater to entire length L2 of the heater is set to 0.04-0.5, and a ratio L5/L2 of the length L5 to the entire length L2 is set to 0.3-0.9. As a result, the detection element S can be sufficiently heated by heat being generated at the heat generation pattern part, and at the same time heat being transmitted from the heat generation pattern part to the brazing part is suppressed, thus preventing the reduction of brazing strength due to long-term usage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor used for measuring oxygen concentration in exhaust gas of various combustion devices such as an internal combustion engine of an automobile and a boiler, and more particularly, to an oxygen sensor inside a bottomed cylindrical detection element. The present invention relates to an oxygen sensor with a heater in which a ceramic heater for heating is arranged in a space.

[0002]

2. Description of the Related Art Conventionally, an oxygen ion-conducting solid electrolyte such as zirconia has been used in accordance with the principle of an oxygen concentration cell.
As an oxygen sensor for detecting an oxygen concentration in exhaust gas of an internal combustion engine or the like, for example, as shown in FIG.
A detection element main body 3 formed in a bottomed cylindrical shape having one end closed and the other end opened, and a flange 3a formed in the center of the outside.
And a detection element S including a heat-resistant inner electrode 5 and a heat-resistant outer electrode 7 made of, for example, platinum, which are formed on the inner surface and the outer surface of the detection element body 3, respectively. In this type of oxygen sensor, signals are taken out from the inner electrode 5 and the outer electrode 7 on the inner surface side and the outer surface side of the opening of the detection element S, respectively (the clothing is protected).
Lead wires 13 and 14 are connected via connection terminals 9 and 10.

Further, a rod-shaped ceramic heater 17 is housed in the internal space of the detecting element S to heat and activate the detecting element S. The ceramic heater 17 has lead wires 15 and 16 for energizing the heater through a pair of lead terminals 18 respectively brazed to a pair of electrode patterns (brazing portions) formed on the surface thereof.
Is connected.

The detecting element S comprises a ceramic cylindrical holding member 21, 23, talc powder 25, and packing 27.
And so on, are arranged in the metal shell 29 made of heat-resistant metal so as to extend vertically through the metal shell 29 so as to extend in the vertical direction in the figure. And in the lower part of the metal shell 29,
A protective cap 31 having a hole 31a for introducing a gas to be measured is attached so as to cover the tip of the detection element S (the side where one end of the cylinder is closed). An inner cylinder 33 made of, for example, a heat-resistant metal made of stainless steel is attached by caulking via an O-ring 35 so as to cover the periphery of the upper part of the element S and the ceramic heater 17. An outer cylinder 39 made of a heat-resistant metal made of stainless steel is externally fitted.

In a space 41 between the upper part of the inner cylinder 33 and the outer cylinder 39 (ie, a space above the detecting element S), a substantially circular hole having a through hole 43 through which the lead wires 13 to 16 penetrate is formed. Columnar ceramic separator 45 and grommet rubber 47
Are arranged in order from the lower side of the figure, thereby preventing water or the like from entering the inside.

In this type of oxygen sensor, the tip of the detection element S protected by the protective cap 31 projects into the exhaust pipe and is exposed to the exhaust gas as the gas to be measured.
It is attached to an exhaust pipe of an internal combustion engine or the like via a metal shell 29. As a result, between the inner electrode 5 and the outer electrode 7 of the detection element S, the air introduced into the detection element S via the gap between the torsion core wires of the lead wires 13 to 16 is used as a reference of the oxygen concentration. Then, a voltage corresponding to the ratio between the oxygen concentration and the oxygen concentration in the gas to be measured is generated, and the voltage is output to the outside as a detection signal.

[0007]

In this type of oxygen sensor, a ceramic heater 17 used for heating the detecting element S is connected to a pair of lead wires 15 and 16 for energizing the heater. Since the lead terminal 18 is soldered, when the heat generation pattern embedded in the ceramic heater 17 generates heat by energization, the heat is transmitted not only to the detection element S but also to the soldered portion of the lead terminal 18. There is a problem that the heat lowers the brazing strength of the lead terminal 18 at the brazing portion.

In order to increase the brazing strength at the brazing portion, a portion (ie, a heat generation pattern) of the ceramic heater 17 that generates heat when energized is detected by the detecting element S.
Formed only at the tip located on the closed side of the internal space,
It is sufficient that the heat from the heat generating pattern is not easily transmitted to the brazing portion formed on the opposite side to the heat generating pattern. However, if the heat generating pattern is formed only at the tip of the ceramic heater 17, the heat from the ceramic heater 17 is reduced. It becomes difficult to transmit to the entire detection element S, and the warm-up performance for the detection element S is reduced, and the oxygen detection characteristic of the oxygen sensor is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a heater-equipped oxygen sensor having a bottomed cylindrical detection element and a ceramic heater disposed in the internal space thereof. It is an object of the present invention to heat the entire detection element with a ceramic heater without lowering the brazing strength of the attachment portion, so that sufficient oxygen detection characteristics can be obtained even at low temperatures.

[0010]

According to a first aspect of the present invention, there is provided an oxygen ion conductive solid electrolyte formed into a bottomed cylindrical shape having one end closed and the other end open. A detection element formed by forming a porous electrode on the inner and outer surfaces of the solid electrolyte; and a long ceramic sintered body, and a heat generating pattern that generates heat by energization is buried at one longitudinal end of the ceramic sintered body. A conductive pattern for energizing the heat generation pattern is buried from the heat generation pattern toward the other end in the longitudinal direction of the ceramic sintered body,
Furthermore, on the other end surface in the longitudinal direction of the ceramic sintered body, a brazing portion is formed, which is connected to the conductive pattern and to which a lead terminal for supplying power to the conductive pattern from the outside is brazed. And a ceramic heater,
The ceramic heater, in a heater-equipped oxygen sensor arranged in the internal space of the detection element so that one end side on which the heat generation pattern is formed is closer to the closed part of the detection element, an inner diameter Rs of the detection element; A ratio Rs / L5 of a length L5 from the heating pattern along the longitudinal direction of the ceramic heater to the brazing portion is set to 0.3 or less.

The invention described in claim 2 is the first invention.
Similarly to the above, in a heater-equipped oxygen sensor including a detection element and a ceramic heater, a distance L4 from a tip end of the ceramic heater on the heat generation pattern side to an inner wall of a closed portion of the detection element and a longitudinal direction of the ceramic heater Length L5 from the heat generation pattern to the brazing portion
The ratio L4 / L5 is set to 0.2 or less.

Next, according to a third aspect of the present invention, in the oxygen sensor with a heater according to the first or second aspect, a length L1 of the heat generation pattern along a longitudinal direction of the ceramic heater is provided. The ratio L1 / L2 to the total length L2 along the longitudinal direction of the ceramic heater is 0.04 to
According to a fourth aspect of the present invention, in the oxygen sensor with heater according to any one of the first to third aspects, the oxygen sensor is arranged along a longitudinal direction of the ceramic heater. The ratio L5 / L2 of the length L5 from the heat generation pattern to the brazing portion and the total length L2 along the longitudinal direction of the ceramic heater is set in the range of 0.3 to 0.9. It is characterized by the following.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the oxygen sensor with a heater according to the present invention (claims 1 to 4), the heat generated in the heat generation pattern by energizing the ceramic heater is easily transmitted to the detection element side, and the brazing is performed. By stipulating the dimensions (see FIG. 3) of each part of the ceramic heater and the detection element so as to make it difficult to transmit to the part side, the ceramic heater can be used without lowering the brazing strength of the lead terminals in the brazing part. The warm-up characteristic of the detection element can be improved.

That is, in the oxygen sensor with heater according to the first aspect, the ratio Rs / L5 of the inner diameter Rs of the detection element to the length L5 from the heat generation pattern to the brazing portion of the ceramic heater is set to a predetermined value C1 ( = 0.3) or less, and in the oxygen sensor with a heater according to claim 2, the distance L4 from the tip of the heating pattern side of the ceramic heater to the inner wall of the closing portion of the detection element and the heating pattern of the ceramic heater indicate a low value. Ratio L4 / Length to attachment length L5
L5 is set to a predetermined value C2 (= 0.2) or less for the following reason.

First, in order to improve the warm-up characteristic of the detecting element by the ceramic heater without lowering the brazing strength of the lead terminal at the brazing portion,
The heat removal Hr from the heat generation pattern to the brazing portion is suppressed as much as possible, and the heat removal Hs from the ceramic heater to the detection element.
Should be increased as much as possible. Then, based on the minimum required warm-up characteristics and the deterioration characteristics of the brazing strength under the actual use conditions of the oxygen sensor, the relationship between each heat removal Hr and Hs is expressed by the following equation.
(1) Hr / Hs ≦ C (where C is a constant) (1) The above object can be attained by defining as follows and setting the shapes of the ceramic heater and the detecting element to satisfy this condition. .

However, actually, the heat removal Hr and Hs to the brazing portion and the detecting element are measured, and these conditions are set as (1)
It is very difficult to determine such a formula, and even if it is possible, it is also difficult to set the shapes of the ceramic heater and the detecting element based on the result. Therefore, according to the first and second aspects of the present invention, a parameter capable of actually setting the above equation (1) is set from each of the heat drawing Hr, Hs and the actual shape of the oxygen sensor, and the parameter is set. To change
By measuring the warm-up characteristics and the deterioration characteristics of the brazing strength of the oxygen sensor, the parameters are defined so that these characteristics are sufficiently satisfactory when the oxygen sensor is used.

That is, the heat drawing Hr from the heating pattern to the brazing portion increases as the outer diameter Rh of the ceramic heater increases, and increases as the length L5 from the heating pattern to the brazing portion decreases. Pull Hr is “Rh
/ L5 ”. Further, the heat removal Hs from the ceramic heater to the detection element is larger as the outer diameter Rh of the ceramic heater is larger and is larger as the inner diameter Rs of the detection element is smaller.
Rs ”.

For this reason, in the first aspect, the following relational expression (2) is used as a parameter defining a shape for satisfying both the warm-up characteristic of the oxygen sensor and the deterioration characteristic of the brazing strength.
, A length L5 from the heat generation pattern to the brazing portion,
The relationship Rs / L5 between these parameters L5 and Rs, which can set both the inner diameter Rs of the detection element and satisfy both the warm-up characteristics of the oxygen sensor and the deterioration characteristics of the brazing strength, will be described in the following embodiments. He decided experimentally and completed the invention.

Hr / Hs = (Rh / L5) / (Rh / Rs) = Rs / L5 ≦ C1 (2) On the other hand, the heat removal Hr from the heat generation pattern to the brazing portion is:
The smaller the length L5 from the heat generation pattern to the brazing portion, the larger the length, and the larger the heat removal Hs from the ceramic heater to the detection element, the higher the heat generation side of the ceramic heater (that is,
The smaller the distance L4 between the front end of the detection element (closed portion side) and the inner wall of the detection element on the closed portion side, the larger the distance L4 becomes.
Equation (1) can be replaced with the following equation (3) using these parameters.

Hr / Hs = L4 / L5 ≦ C2 (3) Therefore, in claim 2, as a parameter defining a shape for satisfying both the warm-up characteristic of the oxygen sensor and the deterioration characteristic of the brazing strength, The length L5 from the heat generation pattern to the brazing portion and the distance L4 between the tip of the ceramic heater and the inner wall of the closing portion of the detection element are set, and the relationship L4 /
L5 was experimentally determined so as to satisfy both of the above characteristics practically in an oxygen sensor (see Examples described later), and the invention was completed.

Therefore, according to the oxygen sensor of the first and second aspects, it is possible to realize an oxygen sensor which can sufficiently satisfy the warm-up characteristics and the deterioration characteristics of the brazing strength of the oxygen sensor in practical use. It is possible to provide an oxygen sensor in which the entire detection element is heated by the ceramic heater without lowering the brazing strength of the attachment portion and sufficient oxygen detection characteristics can be obtained even at low temperatures.

Incidentally, the dimensional relationships of the respective parts defined in claim 1 and claim 2 can be applied to one oxygen sensor at the same time. According to the oxygen sensor to which these two inventions are applied, more favorable. Needless to say, excellent characteristics can be obtained. Next, in the oxygen sensor with a heater according to the third aspect, the ratio L1 / L1 of the length L1 of the heat generation pattern along the longitudinal direction of the ceramic heater to the total length L2 along the longitudinal direction of the ceramic heater is further provided. L2 is a predetermined range C3
If the ratio L1 / L2 is smaller than 0.04, the heat generation pattern becomes small, and the detection element cannot be sufficiently heated. If the ratio L1 / L2 exceeds 0.5, on the contrary, if the ratio L1 / L2 exceeds 0.5, the length L5 between the heat generation pattern and the brazing portion of the ceramic heater becomes too short, and heat is drawn to the brazing portion. Is increased, and the brazing strength is reduced.

Further, in the oxygen sensor with a heater according to the fourth aspect, the length L5 from the heat generation pattern along the longitudinal direction of the ceramic heater to the brazing portion, and the total length along the longitudinal direction of the ceramic heater. Ratio L5 with L2
/ L2 is set within the predetermined range C4 (0.3 to 0.9). This is because if the ratio L5 / L2 is smaller than 0.3, the heat extraction to the brazing portion increases. When the ratio L5 / L2 exceeds 0.9, on the contrary, when the ratio L5 / L2 exceeds 0.9, the heat generation pattern becomes small, so that the detection element cannot be sufficiently heated and the activity of the detection element deteriorates.

Therefore, according to the oxygen sensor with a heater according to the third and fourth aspects, the warm-up characteristics and the brazing of the oxygen sensor are different from those of the oxygen sensor with a heater according to the first or second aspect. It is possible to more reliably realize a satisfactory oxygen sensor together with the strength deterioration characteristics.
If all the techniques described in claim 4 are applied, an oxygen sensor with a heater that can obtain better characteristics can be realized.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. The oxygen sensor with heater of this embodiment (hereinafter simply referred to as oxygen sensor) is configured in the same manner as the conventional oxygen sensor shown in FIG. In the oxygen sensor of the present embodiment, the ceramic heater 1 disposed inside the detection element S
As shown in FIG. 2, reference numeral 7 denotes a heat generating pattern portion 52 which generates heat by energization, a pair of conductive pattern portions 54a and 54b extending at both ends of the heat generating pattern portion 52, and a pair of conductive pattern portions 54a and 54b. The heater pattern 50 including the electrode pattern portions 56a and 56b formed at the ends is
A lead terminal sandwiched between two green sheets (a first green sheet 62 and a second green sheet 64) mainly composed of alumina and having conductive pattern portions 54a and 54b formed on the surface of the first green sheet 62. By connecting to the electrode patterns (brazing portions) 66a and 66b for brazing with through holes, a laminate of green sheets is formed. Further, the laminate is placed with the first green sheet 62 facing up. It is produced by winding around a rod-shaped base material (porcelain tube) 68 mainly composed of alumina, followed by firing.

Hereinafter, this manufacturing procedure will be described. Procedure 1: Mixing of raw material powder Alumina powder having an average particle size of 1.5 μm and a purity of 99.9%, and an average particle size of 2 μm and a purity of 99.9 as a sintering accelerator
% Silica powder, magnesia powder having an average particle diameter of 2 μm and a purity of 99.9%, and calcia powder having an average particle diameter of 2 μm and a purity of 99.9%, respectively, at 93.5: 5.0: 1.0. :
After mixing at a ratio of 1.5 and wet mixing with a ball mill for 20 to 60 hours, the mixture is dehydrated and dried. In addition, N in alumina powder
The amount a is preferably 0.1% or less from the viewpoint of durability. The particle size of the alumina powder is 0.8 to 0.8 in terms of sheet formability.
The thickness is preferably 3.5 μm, more preferably 1 to 2.5 μm. Step 2: Preparation of a base material (insulator tube) 68 The mixed powder obtained in the above step 1 was mixed with 1% methylcellulose,
15% of Maxelon (trade name) and 10% of water are added and kneaded. Then, it is formed into a cylindrical shape by an extrusion molding method, cut into a predetermined size, and calcined at 1200 ° C. to produce a base material 68 having an outer diameter of about 2.3 mm. Step 3: Preparation of First Green Sheet 62, Second Green Sheet 64, and Heater Pattern 50 Polyvinyl butyral 8 was added to the compounded powder obtained in Step 1 above.
%, DBP4%, methyl ethyl ketone, toluene 70%
Is added and mixed with a ball mill to form a slurry. After defoaming under reduced pressure, the first green sheet 62 having a thickness of 0.2 to 0.4 mm is formed by a doctor blade method.
Is prepared.

Next, a paste adjusted with tungsten, an organic binder (ethocell) and butyl carbidol was applied to the surface of the sheet 12 by a thick film printing method for 10 to 30 μm.
m, and the heat generating pattern portion 52, the conductive pattern portions 54a and 54b, and the electrode pattern portion 56
A heater pattern 50 composed of a and 56b is formed.

Further, a thickness of 0.05 formed on the printing surface by the same method as that of the first green sheet 62.
mm second green sheet 64 is pressed to form a laminate of the green sheets. In addition, the first green sheet 6
On the surface (front surface) opposite to the second heater pattern 50, the conductive pattern portions 54 a and 54
b, the brazing parts 66a, 6
6b and a through-hole (not shown) penetrating through the back surface side on which the heater pattern 50 is laminated by conducting with each of the brazing portions 66a and 66b is filled or printed with the above-mentioned paste (tungsten or tungsten as a main component). Metallized ink). Procedure 4: Integration of base material 68 and laminate of green sheets The second green sheet 64 of the laminate obtained in Procedure 3 above
A paste formed by adding 25% of polyvinyl butyral, 8% of DBP, and 30% of butyl carbidol to the blended powder obtained in Procedure 1 is applied to the side surface. Then, the laminated body is wound around the base material 68 so as to be bonded to the base material 68 so as to be used for bonding the coated surface to the base material 68. At this time, it is desirable that the base material 68 protrude 0.3 to 3 mm above and below the sheet so that the end face of the sheet does not break.

Then, after the resin is removed at 250 ° C., it is fired at 1500 to 1600 ° C. in a hydrogen furnace atmosphere to obtain the ceramic heater 17 of the present embodiment in which the above-described parts are integrally sintered. However, at this time, the calcination temperature of the base material 68 is adjusted so that the difference in shrinkage between the sheet and the base material 68 becomes 0.01 to 0.1.

The ceramic heater 1 manufactured as described above
7, the brazing portion 66 formed on the surface
A lead terminal 18 for connecting a lead wire is soldered to a and 66b, and when the heater pattern 50 is energized through the lead terminal 18, the heat generating pattern portion 52 generates heat. Therefore, for example, as shown in FIG. 1, a heater holding portion 9a is formed at the connection terminal 9 which is fitted through the opening of the detection element S and is connected to the inner electrode 5, and a ceramic heater is provided via the heater holding portion 9a. By arranging 17 in the internal space of the detection element S, the detection element S can be heated and activated.

However, every time the oxygen sensor is operated, the brazing portion 66
a, 66b may be heated to a high temperature.
The brazing strength of the lead terminals 18 at 6a and 66b is reduced in a short time, and the life of the oxygen sensor is shortened. Further, if the size of the heat generating pattern portion 52 is reduced in order to suppress the heat transmitted from the heat generating pattern portion 52 to the brazing portions 66a and 66b, the warm-up characteristic of the ceramic heater 17 with respect to the detecting element S is reduced, and the detecting element S is sufficiently provided. It can no longer be heated.

Therefore, the inventors of the present application set the brazing portion 66
In order to ensure the warm-up characteristic of the detection element S by the ceramic heater 17 without lowering the brazing strength of the lead terminals 18 at a and 66b, the shape of the ceramic heater 17 and the detection element S must be adjusted. Were examined in various ways, and the dimensional relationship between the ceramic heater 17 and each part of the detection element S was determined by the following Experiments 1 to 3.

Hereinafter, the experiment and the experimental result will be described. In this experiment, the brazing portions 66a and 66b of the ceramic heater 17 manufactured as described above were plated with Ni, and a Ni-based metal (Fe) was formed using a brazing material (eutectic brazing).
A lead terminal 18 made of a base metal (although the base terminal may be a Ni base metal in this embodiment) was joined, and Ni plating was further applied thereon. In addition, the Ni plating thickness of the brazed portions 66a and 66b and the Ni plating after brazing is preferably 0.5 to 10 μm in order to prevent oxidation of the brazing material. The Ni plating thickness was set in this range.

The size of the brazing portions 66a, 66b is the length a1 along the longitudinal direction of the ceramic heater 17.
Is 4 mm, the length a2 in the width direction orthogonal to this is 2 mm,
From the outer end of the ceramic heater 17 to the brazing portion 66
The length L3 between a and 66b is 0.2 mm, and the diameter Rh of the ceramic heater 17 is 2.8 mm.

In the following Experiments 1 to 3, FIG.
, The inner diameter Rs of the detecting element S and the brazing portions 66a, 66b of the heat generating pattern portion 52 in the ceramic heater 17.
Length L5 from side tip to brazing parts 66a, 66b
(Length along the longitudinal direction of the ceramic heater 17) Rs / L5, a distance L4 from the tip of the ceramic heater 17 on the side of the heating pattern portion 52 to the inner wall of the closed portion of the detection element S, and heat generation in the ceramic heater 17 Ratio L4 / L to length L5 from pattern portion 52 to brazing portions 66a and 66b
5. The ratio L1 / L2 of the length L1 of the heat generating pattern portion 52 along the longitudinal direction of the ceramic heater 17 to the total length L2 along the longitudinal direction of the ceramic heater 17, and the heat generating pattern portion 52 of the ceramic heater 17
L5 from the length L5 to the brazing portions 66a and 66b and the total length L2 along the longitudinal direction of the ceramic heater 17
In order to obtain the optimal ranges C1, C2, C3 and C4 of 5 / L2, respectively,
The ratio Rs / L5, L4 / L5, L1 / L2 of these parts
A number of oxygen sensors having different L5 / L2 (the structure is the same as that shown in FIG. 1) were manufactured, and the light-off time and the brazing strength of each oxygen sensor were measured. However, the total length L0 (length along the longitudinal direction of the ceramic heater 17) of the internal space of the detection element S is 40 mm.

The light-off time represents the time from the energization of the ceramic heater 17 to the activation of the oxygen sensor. In this experiment, the various oxygen sensors manufactured as described above were used in an oxygen-rich atmosphere containing little oxygen. And the ceramic heater 17 was energized, and the time until the output of the oxygen sensor reached 450 mV was measured to measure the light-off time.

In order to measure the brazing strength, various oxygen sensors prepared as described above were attached to a pipe through which a model gas at 500 ° C. was flowed, and a heater was energized for 5 minutes.
The endurance test of the oxygen sensor is performed by repeating the energization / non-energization cycle for 10,000 cycles in such a procedure that the energization is stopped (non-energization) for 5 minutes. Was taken out and the bonding strength of the lead terminal 18 brazed to the ceramic heater 17 was measured by a tensile test, and the result of the tensile test (tensile strength) was taken as the brazing strength. [Experiment 1] First, the above ratios Rs / L5, L4 / L
In order to define the optimum ranges C1 and C2, the length L1 of the heating pattern portion 52 is set to 10 mm,
Is 70 mm, the inner diameter Rs of the detecting element S, the length L5 from the heating pattern portion 52 to the brazing portions 66a and 66b, and the distance L4 from the tip of the ceramic heater 17 to the inner wall of the closing portion of the detecting element S. Were set to different values, respectively, and the light-off time and the brazing strength were measured. Table 1 shows an example of this measurement result.
Shown in

[0038]

[Table 1]

As can be seen from Table 1, the light-off time is shortened (for example, 40 sec. Or less),
In addition, in order to obtain a large brazing strength (for example, 5 kg · f or more), the ratios Rs / L5 and L4 / L5 should be as small as possible. From the pattern section 52 to the brazing section 66a,
Optimum range C1 of ratio Rs / L5 to length L5 up to 66b
Is set to 0.3 or less (C1 ≦ 0.3), the distance L4 from the tip of the ceramic heater 17 to the inner wall of the closed portion of the detection element S, and the distance from the heating pattern portion 52 to the brazing portion 66 are set.
It can be seen that the optimum range C2 of the ratio L4 / L5 to the length L5 up to a and 66b may be set to 0.2 or less (C2 ≦ 0.2). [Experiment 2] Next, the optimum range C3 of the above ratio L1 / L2
In order to define the inner diameter Rs of the detection element S to 3.8 m
m, from the heating pattern portion 52 to the brazing portions 66a, 66b
The distance L4 from the tip of the ceramic heater 17 to the inner wall of the closed portion of the detection element S is 5 mm.
An oxygen sensor was prepared in which the length L1 of the heat generating pattern portion 52 and the total length L2 of the ceramic heater 17 were set to different values, respectively, and the light-off time and the brazing strength were measured. Table 2 shows an example of the measurement results.

[0040]

[Table 2]

From Table 2, it can be seen that if the ratio L1 / L2 is too small, the write-off time is prolonged. Conversely, if the ratio L1 / L2 is too large, the brazing strength is reduced. Shorten the time (for example, 40se
c.) and to obtain a large brazing strength (for example, 5 kg · f or more), the optimum range C3 of the ratio L1 / L2 is set within the range of 0.04 to 0.5 ( In other words, it can be seen that it is sufficient to set 0.04 ≦ C3 ≦ 0.5). [Experiment 3] Next, in order to define the optimum range C4 of the ratio L5 / L2, the inner diameter Rs of the detection element S was set to 3.8.
mm, the length L1 of the heating pattern portion 52 is 5 mm, the distance L4 from the tip of the ceramic heater 17 to the inner wall of the closed portion of the detection element S is 5 mm, and the length L5 from the heating pattern portion 52 to the brazing portions 66a, 66b is L5. An oxygen sensor in which the total length L2 of the ceramic heater 17 was set to different values was manufactured, and the light-off time and the brazing strength were measured. Table 3 shows an example of the measurement results.

[0042]

[Table 3]

It can be seen from Table 3 that if the ratio L5 / L2 is too small, the brazing strength will be small, and if the ratio L5 / L2 is too large, the light-off time will be long. Shorten the time (for example, 40 sec.
In order to obtain a large brazing strength (for example, 5 kg · f or more), the optimum range C4 of the ratio L5 / L2 is set within the range of 0.3 to 0.9 (in other words, If
0.3 ≦ C4 ≦ 0.9).

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.
Various embodiments can be adopted. For example, in the above-described embodiment, the ceramic heater 17 is formed by forming the base green sheet laminate into a cylindrical shape by extrusion molding.
Although the ceramic heater 17 has been described as being manufactured by winding around the periphery of the base material 8, the ceramic heater 17 may be formed into a prism shape by winding around a base material formed into a prism shape, for example.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of an oxygen sensor according to a related art and an example.

FIG. 2 is an explanatory diagram illustrating a configuration and a manufacturing procedure of a ceramic heater.

FIG. 3 is an explanatory diagram illustrating dimensions of each part of a ceramic heater and a detection element.

[Explanation of symbols]

S: detecting element 17: ceramic heater 18: lead terminal 50: heater pattern 52: heating pattern 54a, 54b: conductive pattern 56a, 56b ...
Electrode pattern portion 62 first green sheet 64 second green sheet 66a, 66b brazing portion 68 base material

Claims (4)

[Claims] 1. A detection element in which an oxygen ion conductive solid electrolyte is formed in a closed-end cylindrical shape having one end closed and the other end opened, and a porous electrode formed on inner and outer surfaces of the solid electrolyte. A heat generating pattern that generates heat by energization is embedded at one longitudinal end of the ceramic sintered body, and extends from the heat generating pattern toward the other longitudinal end of the ceramic sintered body. A conductive pattern for energizing the heat generation pattern is buried, and further, a lead terminal connected to the conductive pattern on the other end surface in the longitudinal direction of the ceramic sintered body to supply power to the conductive pattern from outside. And a ceramic heater having a brazing portion to which the heat generating pattern is formed. ,
An oxygen sensor with a heater disposed in an internal space of the detection element, wherein a ratio of an inner diameter Rs of the detection element to a length L5 from the heating pattern to the brazing portion along a longitudinal direction of the ceramic heater. An oxygen sensor with a heater, wherein Rs / L5 is set to 0.3 or less. 2. A detection element in which an oxygen ion conductive solid electrolyte is formed in a closed-end cylindrical shape having one end closed and the other end opened, and a porous electrode formed on inner and outer surfaces of the solid electrolyte. A heat generating pattern that generates heat by energization is embedded at one longitudinal end of the ceramic sintered body, and extends from the heat generating pattern toward the other longitudinal end of the ceramic sintered body. A conductive pattern for energizing the heat generation pattern is buried, and further, a lead terminal connected to the conductive pattern on the other end surface in the longitudinal direction of the ceramic sintered body to supply power to the conductive pattern from outside. And a ceramic heater having a brazing portion to which the heat generating pattern is formed. ,
In the oxygen sensor with a heater disposed in the internal space of the detection element, a distance L4 from a tip end of the ceramic heater on the heat generation pattern side to an inner wall of the closed part of the detection element and a lengthwise direction of the ceramic heater. The ratio L4 / L5 to the length L5 from the heat generation pattern to the brazing portion is:
An oxygen sensor with a heater, which is set to 0.2 or less. 3. The oxygen sensor with a heater according to claim 1, wherein a length L1 of the heat generation pattern along a longitudinal direction of the ceramic heater and a total length L2 of the ceramic heater along the longitudinal direction. Ratio L1 / L2 with
Is set in the range of 0.04 to 0.5. 4. The oxygen sensor with a heater according to claim 1, wherein a length L5 from the heat generation pattern along the longitudinal direction of the ceramic heater to the brazing portion, and a length of the ceramic heater. An oxygen sensor with a heater, wherein a ratio L5 / L2 with respect to an overall length L2 along a longitudinal direction is set in a range of 0.3 to 0.9.