JPH0617885B2 - Oxygen sensor intermediate assembly - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an intermediate assembly of an oxygen sensor equipped with a gas detector for detecting a gas component or its concentration.

[Prior Art] Conventionally, Sn has been used as a gas detection element as one of gas detectors for detecting the presence or concentration of gas in the atmosphere.
There is a method in which an oxide semiconductor such as O ₂ , ZnO, TiO ₂ , and CoO is used, and the gas is detected by utilizing the characteristic that the electric resistance changes when the gas contacts. In recent years, in this type of gas detector, in order to simplify the structure and improve the productivity, elements such as a gas detection element and its electrode are thick-film printed on a substrate made of an insulating ceramic material. , Hybrid technology is being developed. For example, as an intermediate assembly of an oxygen sensor, a gas detection element whose electric resistance value changes depending on the component of the measurement gas and its concentration, a thermistor element for compensating the temperature dependence of the element, and a conductor connected to both elements. A first insulating ceramic layer provided on the surface thereof, and the first insulating ceramic layer
On the insulative ceramic layer, covering at least the portion of the conductor exposed on the measurement gas side and exposing a part or all of the portion of the gas detection element exposed on the measurement gas side to be laminated. There is a gas detector having two insulating ceramic layers and a spacer fitted to the gas detector.

By the way, when the gas detector is used in an atmosphere in which electrically conductive particles such as carbon are suspended, as in the case of measuring the oxygen concentration in the exhaust gas of an internal combustion engine, the elements and conductors of the gas detector are made of ceramic. Since it is exposed on the surface of the substrate, it is necessary to prevent a short circuit due to the deposition of carbon or the like. Further, in the gas detector, it is necessary to reduce the heat capacity as much as possible on the front side carrying the gas detection element so that the temperature can be easily raised. Further, the gas detector is housed in a housing for holding the detector and fixed with a spacer at a predetermined position. When the spacer is attached so as to abut the ceramic substrate surface, the spacer is The problem of contacting the element and damaging the element must also be solved. Furthermore, temperature compensation using a thermistor should also be suitably performed.

[Object of the Invention] Therefore, in the present invention, in the intermediate assembly of the gas detector having the above-described configuration, the temperature rising property of the portion carrying the gas detection element is well maintained, and the temperature is suitably compensated. It is an object of the present invention to provide an oxygen sensor intermediate assembly having a structure that does not damage the gas detection element when the spacer is assembled.

[Structure of the Invention] A first invention for achieving the above object is to provide a gas detection element whose electric resistance value changes depending on a component of a measurement gas and its concentration, a thermistor element for compensating temperature dependence of the element, and both elements. A first insulative ceramic layer on the surface of which is connected a conductor, and a gas for measuring at least a part of the gas detection element while covering the conductor on the first insulative ceramic layer. An oxygen sensor intermediate assembly comprising: a gas detector having a second insulating ceramic layer that is exposed and laminated on a substrate; and a spacer provided with a hole into which the gas detector fits. An opening through which the gas detection element is exposed is provided in the second insulating ceramic layer, and the thermistor element is exposed through the opening or another opening provided in the same layer, and the second insulating ceramic layer is exposed. By providing a thick step on the base side of the stack layer, the tip side of the gas detector carrying the gas detection element is made thin, and the gas detector is made thick by the step. Is a fitting portion that fits in the hole of the spacer.

A second aspect of the present invention is characterized in that the surface of the gas detection element whose electric resistance value changes depending on the component of the measurement gas and its concentration, the thermistor element for compensating the temperature dependence of the element, and the conductor connected to both elements. A first insulating ceramic layer provided on the first insulating ceramic layer, and a second insulating ceramic layer laminated on the first insulating ceramic layer with the conductor covered and at least a part of the gas detection element exposed to the measurement gas. An insulating ceramic layer, and a spacer provided with a hole into which the gas detector fits, and an oxygen sensor intermediate assembly comprising: An opening through which the gas detection element is exposed is provided, and the thermistor element is exposed through this opening or another opening provided in the same layer, and the second side of the second insulative ceramic layer is directed toward the front side toward the front side. By providing the first and second steps that are thick, the tip side of the gas detector that carries the gas detection element is thin, and the first step is a middle thick gas detector. The oxygen sensor intermediate assembly is characterized in that an intermediate portion of the above is used as a fitting portion that fits into the hole of the spacer, and a step portion of the second step is used as a locking portion of the spacer. .

Here, a gas detection element may be arranged in the opening exposed by the thermistor element. That is, one opening is provided in the second insulating ceramic layer, and this one opening is
You may arrange a thermistor element and a gas detection element.

In addition to the position where the gas detection element is provided, an additional opening may be provided for the thermistor element. That is, two openings may be provided in the second insulating ceramic layer, the thermistor element may be arranged in one opening, and the gas detection element may be arranged in the other opening.

Further, the opening through which the thermistor element is exposed may be covered with a porous filter made of glass or glass and ceramic in a state of communicating with the outside.

As the first insulating ceramic layer, one having a thick film heater in the vicinity of the gas detection element can be adopted.

Alumina can be used as a material for the above-mentioned two insulating ceramic layers.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings by taking as an example the case where the gas detector of the present invention is applied to an oxygen sensor for detecting the oxygen concentration in the exhaust gas of an internal combustion engine.

1 (a) and 1 (b) are partial cutaway views of the oxygen sensor of the first embodiment of the present invention. However, (B) is a partial cutaway view seen from the right direction of (A). In the figure, reference numeral 1 denotes a first insulating ceramic layer 1a as a ceramic substrate, which is provided with an oxygen gas detecting element 2 and a thermistor element 3 as gas detecting elements and covers the parts other than the above-mentioned elements. A gas detector for detecting oxygen concentration, comprising a second insulating ceramic layer 1b, 1c, 1d overlaid on the layer 1a, for holding the gas detector 1 and for mounting the sensor on an internal combustion engine The metal shell 5 formed in a tubular shape is a front end portion 4 of the metal shell 4 on the internal combustion engine side.
A protector attached to a for protecting the gas detector 1, 6 is an inner cylinder for holding the gas detector 1 together with the metal shell 4, and the gas detector 1 is a spacer 7, a filling powder 8 and a glass seal. 9 through the metal shell 4 and the inner cylinder 6
Is being held at. The gas detector 1 fitted in the spacer 7 corresponds to the oxygen sensor intermediate assembly. Further, a threaded portion 4b for mounting the internal combustion engine is engraved on the outer periphery of the metal shell 4, and a gasket 10 is provided at the abutting portion of the internal combustion engine wall surface so that exhaust gas does not leak.

Here, the filling powder 8 is made of a 1: 1 mixed powder of talc and glass for fixing the gas detector 1 in the inner cylinder 6, and the glass seal 9 is made of low melting point glass to prevent leakage of detection gas. This is for preventing and protecting the terminals of the gas detector 1.

Reference numeral 11 is an outer cylinder attached to the metal shell 4 so as to cover the inner cylinder 6, and 12 is a sealing material made of silicon rubber,
Lead wires 13, 14, 15 and terminals 21, 2 from the gas detector 1 protruding from the glass seal 9 shown in FIG.
It serves to insulate and protect the connection portion with 2, 23.
Also, the lead wires 13, 14, 15 and the terminals 21, 22,
As shown in FIG. 3, the seal member 12 and the lead wires 13, 14, 15 are housed in the outer cylinder 11 in advance, and the caulking metal fitting 2 is attached to the tip of each lead wire 13, 14, 15 as shown in FIG.
4, 25, 26 are connected, and then the caulking metal fittings 24, 25,
26 by caulking the terminals 21, 22, 23.

Next, the gas detector 1 of the present embodiment is produced according to the procedure shown in FIGS. 4 to 9. 4 to 9, (a) is a front view in the process of assembling the gas detector 1, and (b) and (c) are cross-sectional views thereof, respectively. Since FIGS. 4 to 9 are for explaining the manufacturing process of the gas detector 1, the dimensions of each part should be made to correspond to those of the gas detector shown in FIG. 1 for easy understanding. The same applies to FIGS. 10 to 18 described later.

Here, in each of FIGS. 4 to 9 described above, 30, 3
1, 32 and 33 are Al ₂ O ₃ 92 having an average particle size of 1.5 μm
% By weight, 4% by weight of SiO ₂ , ₂ % by weight of CaO and MgO
12 parts by weight of butyral resin and dibutyl phthalate (DBP) per 100 parts by weight of mixed powder consisting of 2% by weight
6 parts by weight is added and mixed in an organic solvent to form a slurry, which is a green sheet formed by using a doctor plate. Among these, the green sheet 30 is the first insulating ceramic layer 1a. , Green sheet 3
1, 32 and 33 are second insulating ceramic layers 1b,
1c and 1d. The green sheet 30 has a thickness of 1 mm, the green sheet 31 has a thickness of 0.2 mm, and the green sheets 32 and 33 have a thickness of 0.8 mm. Further, 34 to 40 are 7% Al _{2 with} respect to Pt.
It is a pattern formed by thick film printing with a platinum paste to which O ₃ is added and corresponds to a conductor, and 34, 35 and 36 are detection elements 2
Alternatively, an electrode pattern serving as an electrode of the thermistor element 3, 37
Is a heating resistor pattern serving as a heater for heating the detection element 2, and 38, 39 and 40 are heating resistor patterns 3.
7, an electrode terminal pattern for applying a power source to the detection element 2 or the thermistor element 3 or extracting a detection signal.

The gas detector 1 is manufactured by referring to FIG.
As shown in the line end view (b), first, the above 34 to 4 are placed on the green sheet 30 which will be the first insulating ceramic layer 1a.
No. 0 pattern is thick-film printed with platinum paste, and then, as shown in FIG. 5 (a) and its end view along line BB (b), the tip portion of the electrode pattern 36 and the electrode pattern 35 are formed. The pattern 41 for the thermistor element is thick-film printed with a paste of barium titanate or various spinel ceramic materials over the central portion. Further, platinum lead wires 42, 43 and 44 having a diameter of 0.2 mm are arranged on the electrode terminal patterns 38, 39 and 40, respectively.

Next, FIG. 6 (a), the CC line end view (b) and D-
As is apparent from the D line end view (C), the green sheet 31 serving as the second insulating ceramic 1b is punched out so that the tip portions of the electrode patterns 34 and 35 and the thermistor element pattern 41 are exposed. , 46 are formed, and the green sheet 31 is laminated and thermocompression-bonded on the green sheet 30 so as to cover all the patterns except the tips of the electrode patterns 34, 35 and a part of the thermistor element pattern 41.

Subsequently, as shown in FIG. 7A and the end view taken along the line EE of FIG. 7B, the second insulating property having the opening 47 corresponding to the opening 46 is formed on the green sheet 31 of the laminated body prepared above. The green sheet 32 to be the ceramic layer 1c is laminated and thermocompression-bonded, and further the second insulating ceramic layer 1d is formed on the green sheet 32 as shown in FIG. 8 (a) and its end view along line FF (b). The green sheets 33 are laminated and thermocompression-bonded in a stepwise manner.

In this way, a step-shaped laminated plate is formed in which the platinum lead wires 42, 43, 44 are partially projected and the tip portions of the electrode patterns 34, 35 and the thermistor element pattern 41 are exposed. Then, this laminated plate is fired by leaving it in the atmosphere at 1500 ° C. for 2 hours.

After that, as shown in FIG. 9 (a) and the end view of the GG line (b), the gas detecting element 2 is provided in the opening 45 of the fired ceramic substrate. Is TiO ₂ powder 100 having an average particle size of 1.2 μm
1 mol part of platinum black was added to 1 mol part, and further, 3% by weight of ethyl cellulose was added to all powders and mixed in butyl carbitol [trade name of 2- (2-butoxyethoxy) ethanol] 300 A thick film of TiO ₂ paste whose viscosity was adjusted to a poise was formed so as to fill the openings 45 and adhere to the tips of the electrode patterns 34 and 35, and then 1
It is formed by leaving it in the air at 200 ° C. for 1 hour and baking it. The sheet 31 of the gas detecting element 2
The projecting size of the projecting portion from the outer surface is smaller than the thickness of the laminated and sintered green sheet 32.
It is less than mm.

The platinum lead wires 42, 43, 44 and the terminals 21, 22, 22 projected outside the gas detector 1 thus produced
As shown in FIG. 10, the terminals 23, 22 and 23 integrally formed by etching on a nickel plate having a thickness of 0.3 mm are connected to the platinum lead wires 42, 43, 44 as shown in FIG.
And welding them. still,
The nickel plate integrally formed with the terminals 21, 22, and 23 has the gas detector 1 fixed to the metal shell 4, and then a part of the substrate of the gas detector 1 and the platinum lead wires 42, 43, and 44.
Glass seal 9
Protected by, fixed in the inner cylinder 6, and then cut into a predetermined length. Further, (a) in FIG. 10 shows a front view of the present gas detector 1, and (b) shows a right side view thereof.

As described above, in this embodiment, the electrode patterns 34, 35, 36, which are conductors, and the electrode terminal pattern 4 are used.
Since 0, 38, 39 and the heater are all covered with the insulative ceramic layer 31 containing Al ₂ O ₃ as a main component, the gas detection element 2 and the thermistor element 3, carbon adheres to the surface of the detector. However, it does not cause a short circuit or abnormal detection.
In addition, the thermistor element 3 (41) is completely
Are separated from each other by Al ₂ O _3, so that when the Pt-containing liquid is permeated into the gas detection element 2 to improve its sensitivity by the catalytic effect, the Pt thermistor element 3
Is prevented. Therefore, it is possible to prevent the characteristics of the thermistor element 3 from being influenced by Pt. Further, the thermistor element 3 has the openings 46 and 47,
It is possible to adjust the resistance value by trimming after firing the gas detector. Also, after trimming, the openings 46 and 47 are formed.
May be sealed with a porous filter made of glass or glass and ceramic. When the detection element 2 side substrate surface of the gas detector 1 is formed in a stepped shape, the green sheet 32 is baked when the spacer 7 is attached to the gas detector 1 as shown in FIG. Positioning can be reliably performed at the step portion between the insulating ceramic layer 1c and the second insulating ceramic layer 1d on which the green sheet 33 is fired. When the gas detector 1 and the spacer 7 are fitted to each other to form the oxygen sensor intermediate assembly, the spacer 7 is provided from the tip side of the gas detector 1 to the back side of the first insulating ceramic layer 1a. Then, the inner surface of the hole of the spacer 7 is slid toward the original side of the gas detector 1 while abutting the inner surface of the spacer 7 and moved to the fitting portion for fitting. Since the hole portion) has a width dimension equal to or larger than the thickness of the detection element 2 portion, the detection element 2
Can be installed without damaging.
Therefore, the work efficiency of attaching the metal shell 4 of the gas detector 1 is improved, and damage to the detection element 2 can be prevented.

Since the oxygen sensor prepared above corresponds to the circuit shown in FIG.
The heating resistor pattern 37 is heated by applying a heating power supply between the five terminals to activate the detection element 2, and the resistance value Rt between the lead wires 14 and 15 and the lead wires 13 and 14 are activated.
By detecting the resistance value Rg between them, obtaining the resistance values of the gas detection element 2 and the thermistor element 3 respectively from Rt and Rg, and correcting the resistance value of the gas detection element 2 with the resistance value of the thermistor element 3. The temperature-compensated oxygen concentration can be detected. FIG. 12B shows a graph in which the resistance values of the gas detection element 2 and the thermistor element 3 depending on the air-fuel ratio are detected by changing the temperature. The sloped curve at each temperature t1 to t3 is the resistance value of the gas detection element 2, and the horizontal straight line is the resistance value of the thermistor element 3. As can be seen from the above, even if the temperature changes, the relative relationship between the two resistance values is almost the same, and if the resistance value of the thermistor element 3 is used for correction, temperature compensation is possible.

Next, a second embodiment of the present invention will be described. The present embodiment is the same as the first embodiment except for the gas detector. The gas detector 51 in this embodiment will be described by its assembling procedure.

The gas detector 51 is produced according to the procedure shown in FIGS. 13 to 18. 13 to 18, (a) is a front view in the process of assembling the gas detector 51, and (b) and (c) are sectional views thereof.

In each of FIGS. 13 to 18, the green sheets 80 to 83 have the same composition and the same thickness as the green sheets 30 to 33 of the first embodiment. . Among these, the green sheet 80 serves as the first insulating ceramic layer 80a, and the green sheets 81, 82 and 83 serve as the second insulating ceramic layers 81a, 82a and 83a, respectively. Further, the patterns 84 to 90 are also the patterns 3 of the first embodiment.
4 to 40 are formed by the same process with the same composition.

This gas detector 51 is manufactured by referring to FIG.
As shown in the end view (-B) of the line H, first, the above 84 is placed on the green sheet 80 to be the first insulating ceramic layer 80a.
Each pattern of Nos. 90 to 90 is started by thick film printing with a platinum paste, and then FIG.
As shown in the I line end view (b), a thick film printing of the thermistor element pattern 91 is performed between the tip portion of the electrode pattern 86 and the central portion of the electrode pattern 85 with a paste of barium titanate or various spinel ceramic materials. To do.
Further, a diameter of 0.2 is formed on the electrode terminal patterns 88, 89, 90.
mm platinum lead wires 92, 93, 94 are provided respectively.

Next, FIG. 15 (a), the end view along the line JJ (b) and K.
As is apparent from the -K line end view (c), the green sheet 81 which becomes the second insulating ceramic layer 81a is punched out so that both the tip portions of the electrode patterns 84 and 85 and the thermistor element pattern 91 are exposed. By 95
Is formed on the green sheet 80 so as to cover all the patterns except the tips of the electrode patterns 84 and 85 and a part of the thermistor element pattern 91.
Are laminated and thermocompression bonded.

Subsequently, as shown in FIG. 16 (a) and the end view of the line L-L (b), the green sheet 81 of the laminated body produced as described above.
A green sheet 82 to be the second insulating ceramic layer 82a is laminated and thermocompression-bonded thereon, and further, as shown in FIG. 17 (a) and an end view of the MM line (b), the green sheet 82 is formed.
A green sheet 83, which will be the second insulating ceramic layer 83a, is laminated and thermocompression-bonded thereon in a stepwise manner.

In this way, a step-shaped laminated plate is formed in which the platinum lead wires 92, 93, 94 are partially projected and the tip portions of the electrode patterns 84, 85 and the thermistor element pattern 91 are exposed. Then, this laminated plate is fired by leaving it in the atmosphere at 1500 ° C. for 2 hours.

After that, as shown in FIG. 18A and the end view of the NN line (B), the gas detecting element 97 is provided on the entire surface of the opening 95 and the exposed green sheet 81 of the fired ceramic substrate. Become. This gas detection element 97 is the first
A paste having the same composition as that of the embodiment is used to fill the openings 95 and adhere to the tips of the electrode patterns 84 and 85 and a part of the thermistor element pattern 91 to be the thermistor element 98 after firing, and further expose the green sheet 81. After printing thick film so that it adheres to the exposed area,
It is formed by leaving it for a while and baking it. still,
The thickness of the gas detecting element 97 rising from the outer surface of the sheet 81 is smaller than the thickness of the laminated and sintered green sheet 82, and is 0.3 mm or less.

The platinum lead wires 92, 93, 94 and the terminals 21, 2 projected to the outside of the gas detector 51 thus produced
The connection with 2, 23 is made in the same way as in the first embodiment. The oxygen sensor of this embodiment has the same effect as that of the first embodiment except for the effect of Pt permeation prevention and trimming after firing, and in addition, it has one opening 95, and the filling process is simple. The effect of being converted also occurs.

In both of the above-mentioned embodiments, the second insulating ceramic layer is composed of three layers, but even if only one layer is provided, it is sufficiently effective in preventing a short circuit due to adhesion of carbon or the like and detection abnormality.

Further, the temperature raising property of the gas detection element carrying portion of the oxygen sensor intermediate assembly can be maintained well, and the gas detection element is not damaged when the spacer is assembled.
Further, the temperature compensation by the thermistor is excellent, and the thermistor can be trimmed at the opening.

[Effects of the Invention] As described in detail above, in the oxygen sensor intermediate assembly of the first invention and the second invention, the temperature rising property of the carrying portion of the gas detection element is improved. Further, the temperature compensation by the thermistor is excellent, and trimming can be easily performed at the opening. Further, there is a remarkable advantage that the gas detecting element is not damaged when the spacer is assembled.

[Brief description of drawings]

1 to 12 show a gas detector of the present invention applied to an oxygen sensor for detecting the oxygen concentration in the exhaust gas of an internal combustion engine.
Fig. 1 shows an embodiment, Fig. 1 (a) is a front partial cutaway view of the entire structure of the oxygen sensor, (b) is a right side partial cutaway view, and Fig. 2 is a gas detection fixed in the inner cylinder. 3 is a partial cutaway view of the terminal portion of the vessel, FIG. 3 is a partial cutaway view of the outer cylinder mounting structure of the lead wire connected to the terminal, and FIGS. 4 to 9 show the procedure for assembling the gas detector 1. In the figure, each (a)
Is a front view, (b) and (c) are end views, FIG. 10 shows the connection of the terminals of the gas detector 1, (a) is a front view, and (b).
Is a right side view, FIG. 11 is a perspective view in which the spacer 7 is attached to the gas detector 1, and FIG. 12 (a) is a circuit diagram of this embodiment.
(B) is a graph showing temperature compensation by the thermistor element 3, and FIGS. 13 to 18 are second embodiments in which the gas detector of the present invention is applied to an oxygen sensor for detecting the oxygen concentration in the exhaust gas of an internal combustion engine. Showing the assembling procedure of the gas detector 51 of
In each drawing, (a) is a front view, and (b) and (c) are end views. 2, 97 ... Gas detection element 3, 98 ... Thermistor element 1a, 80a ... First insulating ceramic layer 30, 80 ... Green sheet 1b, 1c, which becomes the first insulating ceramic layer after sintering 1d, 81a, 82a, 83a ... 2nd insulating ceramic layer 31, 32, 33, 81, 82, 83 ... Green sheet 34, 35, 36, 84 which becomes a 2nd insulating ceramic layer after sintering , 85, 86 ... Electrode pattern 38, 39, 40, 88, 89, 90 ... Electrode terminal pattern 37, 87 ... Heater

Claims (4)

[Claims] 1. A surface is provided with a gas detection element whose electric resistance value changes depending on the component of the measurement gas and its concentration, a thermistor element for compensating the temperature dependence of the element, and a conductor connected to both elements. A first insulating ceramic layer, and a second insulating layer laminated on the first insulating ceramic layer by covering the conductor and exposing at least a part of the gas detection element to the measurement gas. A ceramic layer,
An oxygen sensor intermediate assembly comprising: a gas detector including a gas detector; and a spacer provided with a hole into which the gas detector fits, an opening through which the gas detecting element is exposed in the second insulating ceramic layer. And the above thermistor element is exposed through the opening or another opening provided in the same layer, and a step having a large thickness is provided on the original side portion of the second insulating ceramic layer, whereby the gas detection Oxygen sensor characterized in that the front end side of the gas detector carrying the gas detection element is thin, and the original side of the gas detector thickened by the step is a fitting portion for fitting with the hole of the spacer. Intermediate assembly. 2. A surface is provided with a gas detection element whose electric resistance value changes depending on the component of the measurement gas and its concentration, a thermistor element for compensating the temperature dependence of the element, and a conductor connected to both elements. A first insulating ceramic layer, and a second insulating layer laminated on the first insulating ceramic layer by covering the conductor and exposing at least a part of the gas detection element to the measurement gas. A ceramic layer,
An oxygen sensor intermediate assembly comprising: a gas detector including a gas detector; and a spacer provided with a hole into which the gas detector fits, an opening through which the gas detecting element is exposed in the second insulating ceramic layer. And the above thermistor element is exposed through the opening or another opening provided in the same layer, and the first and second layers are gradually thickened toward the original side of the second insulating ceramic layer. By providing the second step, the tip side of the gas detector that carries the gas detection element is made thin, and the intermediate portion of the gas detector, which is made the intermediate thick portion by the first step, is the spacer. The oxygen sensor intermediate assembly, wherein the oxygen sensor intermediate assembly is a fitting portion that fits into the hole of the second step, and the step portion of the second step is a locking portion of the spacer. 3. The oxygen sensor intermediate assembly according to claim 1, wherein the opening is provided in a thick portion of the second insulating ceramic layer. 4. The oxygen sensor intermediate assembly according to claim 2, wherein the opening is provided in an intermediate thick portion of the second insulating ceramic layer.