JPH0367160A - Manufacture of oxygen sensor - Google Patents

Abstract

PURPOSE:To prevent generation of strain and generation of a crack based thereon by providing a first titania on a first platelike insulated base plate and also forming a recessing part for housing on a second platelike insulated base plate, providing and housing a second titania therein and thereafter laminating a third platelike insulated base plate on the second platelike insulated base plate. CONSTITUTION:A first titania 15 becoming an oxygen detecting element is provided on a first platelike insulated base plate 12 and also a second titania 8 becoming a thermistor element for compensating tem. is provided on a second platelike insulated base plate 9. While laminating a third platelike insulated base plate 11 on the insulated base plate 9 so as to cover this titania 8, a plural ity of platelike insulated base plates incorporating at least the first or third platelike insulated base plate are laminated. An oxygen sensor is formed by calcining them. A recessed part 10 for housing titania 8 is formed on the insulat ed base plate 9. After titania 8 is provided and housed in the recessed part 9, the insulated base plate 11 is laminated on the insulated base plate 9. Thereby generation of strain in titania 8 and the insulated base plates 9, 11 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing an oxygen sensor, and more particularly to a method for manufacturing an oxide semiconductor type oxygen sensor having a thermistor element for temperature compensation.

[Conventional technology]

Generally, in vehicles that use a three-way catalyst as a gas purification device,
In order for the three-way catalyst to function effectively, it is necessary to keep the air-fuel ratio within a certain range around the stoichiometric air-fuel ratio. For this reason, an oxygen sensor (hereinafter referred to as 02 sensor) is provided in the exhaust pipe, and the air-fuel ratio is controlled based on a detection signal from the 02 sensor.

There are various types of 02 sensors used as exhaust gas sensors, and one type of sensor is known as a titania (T!Oz) sensor. The 02 sensor using titania detects oxygen concentration by utilizing the property that titania is oxidized or reduced in response to the surrounding oxygen partial pressure, and its electrical resistance changes accordingly. It is also known that titania's resistance value changes greatly depending on temperature changes, and for this reason, for example,
As shown in Publication No. 62-114355, by arranging titania as a temperature compensation thermistor element in series with titania for oxygen detection, it is possible to accurately detect oxygen concentration without being affected by temperature. 02 sensors configured to allow this are also available.

Furthermore, as a manufacturing method of the 02 sensor having a temperature compensation thermistor element, Japanese Patent Laid-Open No. 58-92946,
Special Publication No. Sho 58-195146, Utility Model Publication No. Sho 62-114
As shown in Publication No. 355, a first titania paste for oxygen detection is placed on a plurality of ceramic green sheets,
It was manufactured by screen printing a second titania paste for temperature compensation, PT electrode paste, etc., laminating and pressing ceramic green sheets printed with this titania paste, etc., and then firing this. .

Particularly, paying attention to titania, which serves as a temperature compensation thermistor element, the temperature compensation thermistor element functions as a reference resistance, so it is necessary to configure it so that the resistance value does not change due to exhaust gas.

For this reason, the temperature compensating thermistor elements t, t are constructed to be embedded within the ceramic base material and isolated from the outside world.

As a conventional method of embedding a thermistor element in a ceramic base material, for example, as shown in FIG. A recess 6 is formed in the ceramic green sheet 5 covering the ceramic green sheet 5, and when each ceramic green sheet 1.5 is laminated,
A method has been used in which the titania 2 is configured to be located in the recess 6 and is fired, thereby embedding the titania 2 in the ceramic base material.

[Problem to be solved by the invention]

However, in the above-described manufacturing method, it is necessary to precisely position titania 2 vertically and arrange it on ceramic green sheet 1 so as to correspond to the arrangement position of recess 6 formed in ceramic green sheet 5. If a positional shift occurs as shown in FIG. 11, the titania 2 will protrude from the recess 6 and will be interposed between the planar portions of the sheets 1 and 5. Therefore, if this is heated and sintered, there is a risk that distortion will occur and cracks will occur in the sensor element and the ceramic base material, and there is also a risk that gaps will be created in the ceramic base material, making it impossible to accurately detect oxygen concentration. There is.

Furthermore, if the B product of the recess 6 is large with respect to the length of the titania 2, as shown in FIG. 12, the titania 2 and the recess i! fl
Since a gap is created between the ceramic green sheet 1 and the titania 2, the titania 2 is not held on the inner wall of the recess 6, but is held only by the bonding force at the contact area between the ceramic green sheet 1 and the titania 2 (the area indicated by the arrow in the figure). It will be done.

Therefore, the holding force of the thermistor element by the ceramic base material is small, and there has been a problem that the thermistor element is easily weakened.

The present invention was created in view of the above points, and provides a method for manufacturing an oxygen sensor that can manufacture a highly reliable oxygen sensor by preventing the occurrence of distortion and the occurrence of separation due to this. The purpose is to

[Means to solve the problem]

In order to solve the above problems, in the present invention, a first titania serving as an oxygen detection element is disposed on a first flat insulating substrate, and a temperature compensating thermistor element is disposed on a second flat insulating substrate. a third flat insulating substrate is stacked on the second flat insulating substrate so as to cover the second titania, and at least the first to third flat insulating substrates are laminated on the second flat insulating substrate so as to cover the second titania. A method for manufacturing an oxygen sensor in which a plurality of flat insulating substrates including insulating substrates are laminated and fired to form an oxygen sensor, the second flat insulating substrate having a storage recess for storing a second titania. After forming the second titania and arranging and storing the second titania in the storage recess, the third flat insulating substrate is laminated on the second flat insulating substrate.

[Effect]

According to the above manufacturing method, as shown in FIGS. 1 and 2, the second titania 8 is disposed and stored in the storage recess 10 formed in the second flat insulating substrate 9. The second titania 8 does not protrude above the upper surface 9a of the second flat insulating substrate 9. As a result, the second titania 8. It is possible to prevent the occurrence of distortion in the second and third flat 18-edge substrates 9 and 11, and to ensure that the second flat insulating substrate 9 and the third flat insulating substrate 11 are firmly bonded during lamination. There is a gap f
There's nothing wrong with that. The second Titania 8 in history has a storage concave FAIO
It is in wide contact with the inner wall surface of the By increasing the contact area in this way, the titania 8 of the cylinder 2 after firing is placed in the storage recess 10.
Since the second titania 8 is strongly held, peeling of the second titania 8 can be prevented.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. Third
The figure shows 70 disassembly of an oxygen sensor (02 sensor) manufactured by the manufacturing method that is an embodiment of the present invention! This is a perspective view. The 02 sensor 7 shown in the figure has flat insulating substrates 9, 11, and 11 made of approximately t4 ceramic green sheets.
12.13 (hereinafter simply referred to as an insulating substrate). The structure of each substrate and its manufacturing method will be described below. Note that the state shown in the figure is a state in which the firing process has not yet been performed.

The first insulating substrate 12 has an electrode 14a on its upper surface.

14b and a first titania 15 are provided.

IJil 4a, 14b has platinum (Pt) as the pole,
Each of them is electrically connected to the first titania 15, and the first titania 15 serves as an m-prefecture detection element. To form the electrodes 14a, 14b and the first titania 15 on the first insulating substrate 12, first the electrodes 14a, 14b and the first titania 15 are formed on the first insulating substrate 12.
, 14b using screen printing or the like, and then using screen printing or the like (the first titania 1
5 is printed and formed. At this time, the first titania 15 is placed so as to partially overlap the tops of the @poles 14a and 14b that have already been placed. Therefore, after firing, which will be described later, each electrode 1
4a, 14b and the first titania 15 are electrically connected, and an oxygen detection signal is taken out from the electrodes 14a, 14b.

The second insulating substrate 9 is a substrate that is a feature of the present invention. This second insulating substrate 9 stores l! A second titania 8 serving as a temperature compensating thermistor element is housed in this housing recess 1o.

First, a method of forming the four storage parts 10 will be described.

The second insulating substrate 9 is obtained by laminating two substrate halves 16a and 16b and pre-sintering them, as shown in FIG. A rectangular through hole 17 is formed in the substrate half 16a, and the other substrate half 16b has a flat plate shape ε. Therefore, both board halves 16a.

The storage recess 10 is formed by stacking the substrates 16b, pre-firing and bonding them to form the second rounded substrate 9. The formation position of this storage recess 10 is based on the first insulating substrate 12 described above.
The first titania 15 is located at a position opposite to the position where the first titania 15 is disposed.

The second titania 8 is applied within the storage recess 10 recessed from the upper surface 9a of the substrate. This second application of titania 8 is a work of simply applying titania 8 into the pre-formed storage recess 10, and unlike the conventional method where titania is disposed on a flat substrate, titania is Since there is no need to pay attention to the arrangement position, the work becomes easier and there is no possibility of misalignment of the arrangement position.

Further, since the second titania 8 is disposed in the storage recess 10 recessed from the upper surface 9a of the substrate, the titania 8 of the cylinder 2 after the arrangement is
G, t does not protrude from the upper surface 9a of the substrate, and the second titania 8 does not protrude from the storage recess 10.

Further, paying attention to the contact area between the second titania 8 and the storage recess 10, in the disposed state, the second titania 8 is in contact with all of the inner wall 5 of the storage recess 10 except for the upper opening. Therefore, after firing, the second titania 8 is bonded to the five inner walls of the storage opening tS10 with which it comes in contact, so that the second titania 8 is firmly held in the storage recess 10. This prevents the titania 8 from moving out of the storage recess 10 after firing, and the reliability of the 02 sensor 7 can be improved.

The third insulating substrate 11 is a substrate disposed between the first I8 edge M plate 12 and the second insulating substrate 9.

A heater 18 made of platinum or the like is provided on the surface of the M3 insulating substrate 11 facing the first insulating substrate 12.
Further, on the surface facing the second insulating substrate 9, electrodes 19a, 1
9b is provided. This heater 18 and electrode 19a
, 19b are both printed by a screen printer or the like. Further, the pattern shape of the heater 18 is selected so that the facing area is wide in the portion facing the first titania 15 and the second titania 8. Furthermore, an electrode 19a.

19b&i are formed so as to extend to a position facing the second titania 8. Therefore, when the third insulating substrate 11 is laminated on the second MAR substrate 9, the electrodes 19a, 1
9bLt is configured to contact and be electrically connected to the second titania 8. Further, the thickness H+ of the third insulating substrate 11 is configured to be approximately equal to the thickness H2 of the first insulating substrate 11 (H+ = Hz).

Although no structure is particularly provided on the fourth insulating substrate 13, its length in the longitudinal direction is equal to that of the other insulating substrates 9.11.12.
It is shorter than . Thereby, when the fourth insulating substrate 12 is laminated on the first insulating substrate 12, the first titania 15 is exposed to the outside.

Note that the manufacturing order of the insulating substrates 9, 11, 12, and 13 described above does not mean that one must be manufactured first, but any insulating substrate may be manufactured starting from any one.
Furthermore, each of the insulating substrates 9.11.degree. 12.13 may be manufactured simultaneously by parallel processing. In addition, each insulating substrate 9.11,1
Since 2.13 has a flat plate shape, its manufacture is easy.

After each insulating substrate 9, 11, 12, 13 is manufactured, the insulating substrates 9, 11, 12, 13 are then stacked on top of each other in the order shown in FIG. Each insulation board 9.11.12.1
3, especially the second and third insulating substrates 9 and 11.
Focusing on the second titania 8Lt as mentioned above, the second titania 8Lt
The housing (!1) formed on the insulating substrate 9 does not protrude above the top surface 9a of the substrate because it is disposed within the part 10. Therefore, the third insulating substrate 11 is stacked on the second insulating substrate 9. Even when the second titania 8 and the insulating substrates 9 and 11 are subjected to some kind of shock during firing or after firing, the second titania 8 and the insulating substrates 9 and 11 will not be strained. No cracks occur in the 02 sensor 7, and the reliability of the 02 sensor 7 can be improved.

Same again! For this reason, when stacking, each insulating substrate 9,
11 is laminated in close contact with both substrates 9 and 10, and 1! ! There will be no gaps. Therefore, after firing, the thermistor element (the fired second titania 8 is hereinafter referred to as such) is connected to the outside. a is not formed, and the thermistor element F is reliably isolated from the outside. This prevents the thermistor element from being affected by exhaust gas, making it possible to accurately detect oxygen concentration.

The laminated insulating substrates 9.11, 12.13 are heated while being pressurized in an electric furnace, and the insulating substrates 9.11, 12.13.
13 is sintered and integrated to form a ceramic base material 20. Next, the fired first titania 15 is touched and melted with gold (or a mixture of platinum and D-dium, etc.). The oxygen sensor element 21 is formed by being supported by dropping or the like. In this way, 02 Sensa is completed.

Note that the electrodes 14a and 19blJ are electrically connected after firing by placing platinum paste in advance in the small holes 22 and 23 formed in the first and third insulating substrates 11 and 12. Moreover, each electrode 14a, 14h.

19a, 19b and each end of the heater 18 have l! A terminal pin is connected, and each electrode 14a, 14b, 19a, 19b and heater 18 are connected to 02 by this terminal pin.
It is drawn out to the outside of the sensor 7.

5 and 6 show the 02 sensor 7 manufactured by the above manufacturing method. Here, the arrangement position a of the thermistor element 8 and the oxygen sensor element F21 with respect to the heater 18 is
We will focus on the rm section and explain it below. As shown in each figure, the heater 18 is interposed between the cables 8 and 21, and as explained using FIG. The thickness dimension H of the insulating substrate 11 of
It is considered to be the same as 2. The distance from the heater 18 to the thermistor element 8 corresponds to the thickness dimension H+ of the third insulating substrate 11, and the distance from the heater 18 to the oxygen sensor 21 corresponds to the thickness dimension H2 of the first insulating substrate 12. Therefore, the distances from the heater 18 to each element 8° 21 are approximately the same distance.

With this configuration, the heat generated by the heater 18 is applied substantially equally to each element 8, 21, so that each element 8, 21 can always be operated at the same temperature.

This eliminates the need to take into account resistance changes due to temperature differences, so the ridge resistance (electrical resistance value when oxygen concentration is low) and lean resistance (electrical resistance value when oxygen concentration is high at 21 degrees Celsius) of the oxygen sensor element 21 is eliminated. The resistance level of the thermistor element 8 can be easily set to an intermediate value. The resistance value of the thermistor element 8 serves as a reference resistance value, and by easily setting this reference resistance value to an appropriate value, the sensitivity characteristics can be improved.

Also, the distance from the heater 18 to each element 8.21 is the first
This can be easily set by changing the thickness dimensions of the second insulating substrates 11 and 12. Therefore, by adjusting the thickness of each insulating substrate 11, 12, it is possible to adjust the degree to which heat from the heater 18 is applied to each element 8.
The resistance value can be adjusted.

Furthermore, it is known that in the thermistor element 8 and the SL cable sensor element 21 made of titania, the main operating region is the portion near the Li electrode. Therefore, the portion to be heated by the heater 18 is also the portion near the electrode. This is shown in this example. 2 sensor 7 has each element 8, as shown in FIG.
21, d5 and electrodes 14a, 14b, 19a, 1
9bG;it: Since the heater 18 is disposed close to the heater 18, the heat of the heater 18 can be effectively applied to a position that directly contributes to the operation of each element 8.21.

In the above example, the oxygen sensor element 21 was formed by calcining the first titania 15 and then adding a catalyst solution dropwise thereto, but the invention is not limited to this. A configuration may be adopted in which titania is provided as the first titania.

Further, in this embodiment, electrodes 19a and 19b connected to the second titania 8 are formed on the back surface of the third insulating substrate 11,
The second insulating substrate 9 and the third insulating substrate 11! Although the configuration is such that each electrode 19a, 19b and the second titania 8 are connected when forming the a layer, the present invention is not limited to this. For example, as shown in FIG. 7, when forming the second insulating substrate 9, electrodes 22a and 22b are formed in advance on the substrate half 16b, and a through hole 17 is formed at a position facing the electrodes 22a and 22b. The second titania 8 may be applied to the second insulating substrate 9, which has a structure in which the formed substrate half 16a and the substrate half 16b are temporarily sintered.

With this configuration, each electrode 22a.

22b and the second titania 8 can be electrically connected more reliably.

Further, in this embodiment, the shape of the storage recess 10 is a rectangular recess having a predetermined depth, but the shape is not limited to this.
As shown in Figure 8, the circular storage [! It is also possible to have a configuration in which one portion 23t is used to widen the contact surface, and as shown in FIG. 9, the storage 1' is provided with a taper in the depth direction! ! It may be set as 1 part 24.

〔Effect of the invention〕

As described above, according to the present invention, the second titania is stored in the storage recess and does not protrude above the second insulating substrate. It is possible to improve the reliability of the sensor without causing distortion in the substrate, and without causing cracks in the thermistor element or ceramic ball material due to distortion during firing and after firing. In addition, since the second titania is in contact with the storage recess over a wide area, the force with which the storage recess holds the thermistor element F after firing is large, and it is possible to prevent the thermistor element from peeling off. Since the thermistor element is completely isolated from the exhaust gas, the thermistor element is not affected by the exhaust gas, and highly accurate oxygen concentration measurement can be performed. It has characteristics.

[Brief explanation of drawings]

Fig. 1 is a perspective view for explaining the second titania arrangement method which is a feature of the present invention, Fig. 2 is a sectional view taken along the line 3-3 in Fig. 1, and Fig. 3 Is the disassembly angle of the 02 sensor manufactured using the manufacturing method that is an embodiment of the present invention? R
Figure 4 is an exploded perspective view for explaining the manufacturing method of the second insulating substrate, Figure 5 is a vertical cross-sectional view of the completed 02 sensor, and Figure 6 is taken along the line ■-■ in Figure 5. Cross section, 7th
The figure is an exploded perspective view showing the second insulating substrate on which electrodes to be connected to the second titania are predetermined, FIGS. 8 and 9 are diagrams for explaining modified examples of the storage recess, and FIGS. 1st
FIG. 2 is a diagram for explaining a conventional 02 sensor manufacturing method and its drawbacks. 7...02 sensor, 8... second titania (thermistor element), 9... second flat insulating substrate, 10°2
3.24--Storage recess, 11...Third flat insulating substrate, 12...-First flat insulating substrate, 15...
First titania, 16a, 16b...Substrate half-closed, 18
... Heater, 20... Ceramic base material, 21-...
Oxygen sensor element.

Claims (1)

[Claims] A first titania serving as an oxygen detection element is disposed on a first flat insulating substrate, and a second titania serving as a temperature compensation thermistor element is disposed on a second flat insulating substrate. a third flat insulating substrate is laminated on the second flat insulating substrate so as to cover the second titania; A method for manufacturing an oxygen sensor in which an oxygen sensor is formed by laminating flat insulating substrates and firing the same, comprising: forming a storage recess in the second flat insulating substrate to store the second titania; A method of manufacturing an oxygen sensor, comprising: laminating the third flat insulating substrate on the second flat insulating substrate after arranging and storing the second titania in the recess.