JPS61172054A - Oxygen gas sensor - Google Patents

Abstract

PURPOSE:To prevent the delamination of each layer due to the change in temp., by constituting an oxygen gas sensor by providing a stress release layer comprising Al2O3/ZrO2 in a specific wt. ratio between an Al2O3 support and a ZrO2 solid electrolyte. CONSTITUTION:A support 1 is formed of Al2O3 in a rectangular shape. A stress release layer 3 is sintered on the support, so that the wt. ratio of Al2O3 and stabilized or partially stabilized ZrO2 is set to 0.5-3 and thermal expansion coefficient is set between the thermal expansion coefficient of Al2O3 and that of the ZrO2 solid electrolyte, in a C-shape. Further, a solid electrolyte 4 is provided thereon from ZrO2 in the same size as the support 1. A measuring electrode 5 is provided to the upper surface of the solid electrolyte 4 and a reference electrode 6 is provided to the under surface thereof. All of layers are laminated to constitute an oxygen gas sensor. Because the stress release layer 3 is provided so that the thermal expansion coefficient thereof is set between the thermal expansion coefficient of the support 1 and that of the solid electrolyte 4, the delamination and warpage of the connection part due to the change in temp. at the time of use are prevented and the breakage of the oxygen gas sensor can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oxygen gas sensor used for determining the air-fuel ratio IIJtl of automobiles.

[Prior Art] Conventionally, for example, in combustion equipment such as internal combustion engines, in order to improve fuel efficiency and emissions, the oxygen concentration in the exhaust gas has been detected and the air-fuel mixture combusted in the combustion vessel has been adjusted to near the stoichiometric air-fuel ratio. There is a device that executes so-called feedback v control, in which control is performed to As an oxygen gas sensor used in this type of control device to detect the oxygen concentration in exhaust gas, for example, a porous electrode layer is coated on a ZrO2-based solid electrolyte to form a pair of electrodes, and one electrode is connected to the measuring gas. , which is constructed to introduce a reference gas to the other electrode and is manufactured using lamination technology is disclosed in Japanese Patent Application Laid-open No. 55-1.
25448 and Japanese Patent Application Laid-Open No. 16865/1983.

[Problems to be Solved by the Invention] In the above-mentioned prior art, the oxygen gas sensor using a Zr0z-based solid 'Fi electrolyte uses a Zr0z-based solid electrolyte as a support, or a metal with a In order to improve the strength and reduce the amount of solid interplanetary material used, the support is coated with a solid insulator and disposed on the support.

However, the coefficient of thermal expansion of ZrOz solid electrolyte is about 10
X10, which is quite different from the 8.0X10 of the header 203, and when directly joined, the joined part is likely to separate or the whole will be easily deformed due to this difference in expansion coefficient. In addition, since the thermal expansion coefficient characteristics of the Zr0z solid electrolyte are very similar to those of metals, metals can be used as supports≠valve-1.
There is a problem in that it is difficult to use this as a support structure with sufficient insulation between the metal and the solid electrolyte body, so it is not practical.

Means for Solving Problem E] The present invention employs the following technical means as a configuration of the invention in order to solve the above problems.

That is, the oxygen gas sensor of the present invention includes a support made of A1203, a stress relaxation material having a coefficient of thermal expansion between that of AizOs and a ZrO2-based solid electrolyte, and which can be sintered simultaneously with the AizOs and ZrOz-based solid electrolytes. layer, and a ZrO2-based solid electrolyte body provided with a pair of electrodes and bonded to the stress relaxation layer.

The support is made of commonly used AjLzOs, and may contain a sintering aid in a small amount that does not impair insulation and heat resistance.

As Zr 02-based solid straw disintegrate, ZI"02 and Y2
O1SCa OSMQ O etc. stabilizer 4-15m0
It is possible to use one added with 1%.

As a stress relaxation layer whose coefficient of thermal expansion is between A1201 and Zl'Oz solid electrolyte and which can be sintered simultaneously with AlzOi and Zr0z solid electrolyte, it is possible to use a layer stabilized or partially stabilized with A-ZOS and f= Zr 02 +7)
A single sintered product, a mixed sintered product of AjLzOl and HfO2-based materials, etc. can be used.

In particular, AlzOs and stabilized or partially stabilized Zr
Zl' 02 (!:(
7) Those with a weight ratio Aiom/Zr0z of 0.5 to 3 are i
I especially like those with a value of 0.7 to 2* L/ &' @
A JL z Os / Z r If O2 is less than 0.5, the electrical insulation at high temperatures will deteriorate.
The difference in thermal expansion coefficient with the OS is too large, and the durability is poor.
If it is larger, the durability of the bonded portion with the Zr0z solid electrolyte will be lost. In addition, a mixed sintered product of AjlzOs and unstabilized ZrO2 has excellent mechanical strength and thermal shock resistance, but it has excellent mechanical strength and thermal shock resistance. ! ! It is not preferable because the elongation is too small.

The materials of the conductors that form the electrodes provided on the solid electrolyte body, the terminals for extracting the output to the outside, and the conductor parts that connect the electrodes and terminals should be heat-resistant and conductive if their main component is gold or platinum metal. It is used because of issues such as gender. In addition, the conductor is made of the same material as the base on which these are provided (for example, 20
(% by weight) is more preferable because the coefficient of thermal expansion becomes close to that of the substrate. It is preferable to provide a porous protective layer such as AizOm on the electrode in rough contact with the measurement gas. Since this protective layer is thin (about 50 am), there is no need to consider thermal stress between the electrode and the electrode.

The support, stress relief layer and solid electrolyte body are stacked to form an oxygen gas sensor. At that time, a passage for introducing outside air is provided in the laminate consisting of the stress relaxation layer and the support.
A reference electrode may be provided on the passage side of the solid electrolyte body, and a measurement electrode may be provided on the side in contact with the measurement gas,
Furthermore, a stress relaxation layer having passages and a support may be laminated on the measurement electrode side. In this way, warping due to a difference in elongation can be completely prevented.

Further, by appropriately configuring the shape of the passageway (particularly the inner height), it is also possible to use the passageway as an oxygen diffusion resistance section to form a power supply type oxygen gas sensor.

Further, it is preferable to provide a heating element on the support because the temperature dependence of the output of the present oxygen gas sensor can be reduced.

The heating element can be provided in the same manner as the conductor section described above. Also, stress consisting of AJlzOi and stabilized or partially stabilized Zr0z! ! 1DII has sufficient insulation, so the conductor that leads the sensor output is in a stressed state 1'0! i
They can be provided in juxtaposition on top.

Oxygen gas sensors such as these include, for example, AizOx,
A stress relaxation layer material such as AizOs and stabilized or partially stabilized ZrOz, and raw material powders such as ZrOz and a stabilizer are mixed with an organic binder, respectively.
Each raw sheet is made into a raw sheet using a blade method, etc., each of the resulting raw sheets is punched or cut into a predetermined shape, and a paste that becomes a conductor or heating element is printed at a predetermined position using a screen method, etc., and a support and stress relaxation are created. It is produced by laminating and pressing the raw sheets of each layer and solid electrolyte body, removing the organic binder, and then firing at 1400 to 1600°C for about 4 hours.

In addition, if necessary, a porous adhesive such as AizOs may be printed on top of the printed paste to serve as a conductor. You may print I.

[Action 1 The coefficient of thermal expansion is AizOs and Zr0z solid 1! If a material that is between W4 quality and can be sintered simultaneously with Humanities 203 and 7rOz solid electrolyte is used as a stress relaxation layer between Humanities 20) and Zr0z solid electrolyte, thermal stress will be relaxed and peeling of the joint will occur. This will no longer occur, and warping caused by differences in expansion rates will also be reduced.

[Example 1 Regarding the embodiment of 'M1 of the present invention, the explanatory view in Figure 1, the perspective view in Figure 2 (A), and the A-AfI in Figure 2 (B)
This will be explained using a FiIII diagram. Note that the scale of these figures has been partially changed for the purpose of explanation.

The oxygen gas sensor of this example has a rectangular plate shape.
Support 1 made of zOs, Al 20 s / Z r
A U-shaped stress relaxation layer that is made of a mixed sintered material of Humanities 203 with an O2 of 1.0 and stabilized or partially stabilized Zr0z, and forms a part of the passage 2 to be described later. 3 and a ZrO2-based solid electrolyte body 4 stabilized or partially stabilized with YzOs and having the same external shape as the support body 1.

A measuring electrode 5 is provided on the upper surface of the solid electrolyte body 4, and a standard electrode 6 is provided on the lower surface thereof. It is connected to the outside air through 2. The measuring electrode 5 and the standard electrode 6 are also connected via a conductor track 7.8 provided on the solid electrolyte body 4 to a measuring terminal 9.10. Further, a heating element 11 is provided on the surface of the two passages of the support 1, and the sensor can be heated by connecting 'R11II to the heating element terminal 12.13.

A porous AjLzOl protective layer 14 is provided so as to roughly cover the measurement electrode 5 .

The manufacturing of this example can be carried out, for example, as follows.

(2) Zr0z powder, an appropriate amount of YiOx powder, and a binder are kneaded, and a green sheet with a thickness of 0.6 mm is formed by a known method.

■AjLzOs is also made into a raw sheet with a thickness of 1.0 mm in the same manner as in ■.

■ A1zOs/Zr Oz is llI ratio t'1.0t'
5mo 1 of YzOs to a certain AJLzOm and ZrO2
The mixture with % stabilized ZrO2 is made into a green sheet having a thickness Q of 5 mm in the same manner as in (2).

0 The green sheets produced in steps ①, ② and ① are cut into a predetermined shape. Additionally, provide through holes where necessary.

AjLz Os raw sheet is 7x64 to serve as a support.
The rectangular raw sheet made of Alzos and stabilized Zr0z has an outer diameter of 7X to form a stress relaxation layer.
A green sheet made of Y2O1 and Zr0z is cut into a rectangular shape of 7x64mm to form a solid electrolyte body into a U-shape of 64mm and a concave part of 4x62mm.

(2) A conductor is formed on each formed cut-out raw sheet by screen printing using a Pt paste containing 20% of the same material as each raw sheet.

A paste is printed as a heating element on the side facing the solid electrolyte on the raw sheet corresponding to the support, and electrodes 5.6, conductor paths 7.8 and measurement terminals 9 are printed on both sides of the raw sheet corresponding to the solid electrolyte body. Print the paste as .10 and then
A which becomes the protective layer 14 on s! Print L2ol to a thickness of approximately 50 μm.

(2) Cut raw sheets corresponding to the support, stress relaxation layer, and solid N disintegration body are laminated and pressure-bonded.

■ The laminate formed by
C. for about 4 hours to obtain the oxygen gas sensor of this example.

In the oxygen gas sensor manufactured in the above-described manner for the critical Wii example, the bonded portion did not peel off due to thermal expansion, and there was little warping.

Regarding the second embodiment of the present invention, the explanatory diagram of FIG.
This will be explained with reference to the perspective view in Figure (A) and the B-8 sectional view in Figure 4 (B). Note that the scale of these figures has been partially changed for illustrative purposes.

The oxygen gas sensor of this example has a rectangular plate shape A!
Support 31. manufactured by Lzoi. AJLzO*/Zroz is 1
．． The relaxation layer A33 is U-shaped and is made of a mixed sintered material of AjlzOi, which is 0, and stabilized or partially stabilized ZrO2, and forms a part of the passage 32, which will be described later. A relaxation layer B34 provided with a part of a passage 32, which will be described later, and a ZrOz-based solid electrolyte body 3 stabilized or partially stabilized by Y2O3.
It consists of 5. In addition, on the upper surface of the solid electrolyte body 35,
and is connected to the outside air via a passage 32 formed by the support body 31. In addition, the measurement electrode 36 and the standard type ei
37 is a conductor path 38 and 39 provided on the relaxation 11B34
It is connected to measurement terminals 40, 41 via. Furthermore, a heating element 42 is provided on the surface of the support body 31 on the passage 32 side, and the sensor can be heated by connecting a power source to heating element terminals 43 and 44. A porous human body 20B protection 145 is provided so as to roughly cover the measurement electrode 36.

This embodiment can be manufactured in substantially the same manner as the first embodiment.

However, since the A jL z Os raw sheet is used as a support, it is rectangular with a G diameter of 64 mm, and the raw sheet made of A1201 and stabilized ZrO2 has an outer diameter of 7 x 64 mm and a concave part in order to make the stress m sum jlA and B. is 4x5
In order to make a solid electrolyte body, a green sheet made of Y2O3 and ZrO2 is used. 7X18mm
Cut and shape each into rectangles.

Next, in the oxygen gas sensor of this example, which was manufactured in the same manner as the first example, the bonded portion did not peel off due to thermal expansion, and there was little warping. Relatively expensive Zr0z is used only for the part that detects
Since it is sufficient to use a system solid electrolyte, it also has the effect of lowering costs.

5 and 6 regarding the third embodiment of the present invention.
This will be explained using a perspective view of the figure. Note that the scale of these figures has been partially changed for illustrative purposes.

The oxygen gas sensor of this example has a rectangular plate shape.
A support A51 made of zOs, a U-shaped support 853 made of Al2OS that forms a part of a passage 52 to be described later, and a support 853 made of Al2OS that has the same external shape as the support A51 and a part of a passage 52 to be described later are provided. AjLzos support C54 and A
Aiz whose n z Os / Z ro2 is 1.0
Zr stabilized by Os and 5mol1% Y2O1
A stress relaxation layer 56 which is made of a mixed sintered material with ZrO2 and has the same external shape as a solid electrolyte body 55 described later and is provided with a part of a passage 52 described later, and a ZrO2-based solid stabilized by Y2O3. @ Consists of decomposition body 55.

A measuring electrode 57 is provided on the upper surface of the solid electrolyte body 55, and an 81 semi-straw TF158 is provided on the lower surface thereof, and the standard electrode 58 is provided with supports A51.853, C54 and stress relaxation I
! It is connected to the outside air via a passage 52 formed by 56 . The measuring electrode 57 and the standard electrode 58 are also connected to a measuring terminal 61.62 via a conductor track 59.60 provided on the support C54. Furthermore, support A51
A heating element @3 is provided on the side surface of the passage 52, and the heating element terminal 54
．． By connecting a power source to 55, the sensor can be heated. Further, a porous AjLzOs layer 11161 is provided to cover the measurement electrode 57.

The oxygen gas sensor of this example, which was manufactured in the same manner as the second example, has the advantages of the second example, in addition to the fact that the joint of materials with different coefficients of thermal expansion is a part of the longitudinal direction. Since there are few areas subject to thermal stress, there is almost no warping.

Furthermore, since the conductor paths 59 and 60 are provided on AjLzOs, the insulation between the conductor paths is improved, allowing for more accurate measurements.

[Effects of the Invention] The oxygen gas sensor of the present invention is provided with a stress relaxation layer between the support and the solid electrolyte, so that the oxygen gas sensor is free from delamination and warping of the joint due to temperature changes during use. damage can be prevented. Therefore, the oxygen gas sensor can be used stably over a long period of time.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the first embodiment of the present invention, Figure 2 (a)
is its perspective view, Figure 2 (b) is its A-A end view, and Figure 3 is its perspective view.
The figure is an explanatory diagram of the second embodiment of the present invention, FIG. 4 (A) is a perspective view thereof, FIG. 4 (B) is an 8-8 end view thereof, and FIG. An explanatory diagram of an example, FIG. 6 is a perspective view thereof. 1.31.51.53.54...Support 3.33.3
4.56-...Stress relaxation layer 4.35.55...Solid electrolyte body 5.6.36.37.57.58...I! pole 11.4
2, i3... heating element

Claims (1)

[Scope of Claims] 1 A support made of Al_2O_3; a stress relaxation layer having a coefficient of thermal expansion between that of Al_2O_3 and a ZrO_2 solid electrolyte and capable of being sintered simultaneously with the Al_2O_3 and ZrO_2 solid electrolytes; An oxygen gas sensor comprising: a ZrO_2 solid electrolyte body provided with an electrode and bonded to the stress relaxation layer. 2 The stress relaxation layer is made of Zr stabilized or partially stabilized with Al_2O_3
2. The oxygen gas sensor according to claim 1, wherein the oxygen gas sensor comprises Al_O_3/ZrO_2 in a weight ratio of 0.5 to 3. 3. A patent claim in which the solid electrolyte body is used only for the part that detects oxygen gas, and at least one electrode provided on the solid electrolyte body is connected to the outside through a passage formed by the stress relaxation layer and the support body. The oxygen gas sensor according to the range 1 or 2. 4. The oxygen gas sensor according to any one of claims 1 to 3, wherein the stress relaxation layer is provided only in a portion of the solid electrolyte body to be joined. 5. The oxygen gas sensor according to any one of claims 1 to 4, wherein a heating element is provided on the support.