JPS63165752A - Detection element - Google Patents

Abstract

PURPOSE:To avoid the damage of a sensor element part, by filling the piercing hole of an insulating substrate based on alumina with the sensor element part composed of a solid electrolyte. CONSTITUTION:When voltage is applied to the terminal 13 of a heat generator electrode and a sensor element part 5 is heated by a heat generator 15 and a reference electrode 7a is brought into contact with the atmosphere while a measuring electrode 7b is brought into contact with gas to be measured, the electromotive force corresponding to the concn. difference of oxygen gas is generated between the filling part 5a and laminated parts 5b, 5c in a piercing hole 3. This electric signal is outputted between the electrodes 7a, 7b and the concn. of the gas is measured on the basis of said signal. Since a display part 5 is contacted with a substrate only through the filling part 5a and laminated parts 5b, 5c in the piercing hole 3, the contact area thereof is small. Therefore, the damage of the element part 5 accompanied by the difference between the coefficient of thermal expansion of the solid electrolyte of the element part and that of the alumina of the substrate 1 can be avoided. Since the element part 5 is made small, the use amount of expensive zirconia can be reduced and cost reduction becomes possible.

Description

[Detailed description of the invention] [Industrial Application Field J The present invention relates to a detection element such as an oxygen sensor, for example.

[Prior Art and its Problems] In recent years, various sensors have been used for the purposes of pollution prevention, energy conservation, detailed control of processes, and the like.

One such sensor is a plate-shaped oxygen sensor (Japanese Patent Application No. 60-13230). In other words, the plate-shaped oxygen sensor is made of an oxygen ion conductive solid mainly composed of zirconia and yttria solid solution. An insulating substrate made of alumina is placed opposite a detection substrate made of an electrolyte, and a spacer made of a mixture of alumina and zirconia is interposed between the two to form an atmospheric chamber surrounded by the front substrate and the spacer. Then, by introducing the reference atmosphere into this atmospheric chamber, the atmosphere is brought into contact with one side of the solid electrolyte layer, and the gas to be measured is brought into contact with the other side.
．． An electromotive force corresponding to the difference in concentration of the gas to be measured is generated between the solid electrolyte layers, thereby measuring the concentration of the gas to be measured.

By the way, the above spacer is formed by mixing the materials of the insulating substrate and the solid electrolyte layer so as to have a thermal coefficient between those of the solid electrolyte layer. The resulting stress is alleviated to prevent breakage of the detection element.

However, even if such a spacer is used, a detection element used in a high-temperature atmosphere may be damaged by rapid cooling or heating.

In addition, in the oxygen sensor of Han and Kei, a detection substrate made of a solid electrolyte has a similar shape to an insulating substrate and is disposed facing each other to form an atmospheric chamber therebetween. For this reason, the detection substrate becomes large, and if a large amount of high-strength zirconia is used in the solid electrolyte, the cost increases.

On the other hand, as another conventional oxygen sensor, a cylindrical one is known (':X: Publication No. 100658/1983)
This oxygen sensor uses a hollow cylindrical body with a through hole as an insulating substrate, and a solid electrolyte layer having an i4 pole is wrapped around the outer periphery of the hollow cylindrical body, and an air introduction path inside the hollow cylinder is formed from the hollow cylinder. By bringing the atmosphere into contact with one side of the solid electrolyte through the through-hole, and bringing the gas to be measured into contact with the other side, the 4 degrees of the gas to be measured is measured based on the electromotive force between the solid electrolytes. .

However, even such a cylindrical sensor has the same problems as the above-mentioned plate-shaped oxygen sensor, such as damage due to thermal expansion and high cost.

[Means for Solving the Problems] The main components of the detection element of the present invention made to solve the above problems are as follows: 1. An insulating substrate having a through hole formed therein; It is characterized by comprising an element part whose electrical characteristics change according to the environment, and at least pairs of electrodes connected to both ends of the element part and formed respectively on the front and back surfaces of an insulating substrate. .

When applied to an oxygen sensor as a detection element, a material having oxygen ion conductivity, such as Y
2O)-Zl-02, CaOZrO2, etc. can be used. Further, the detection element can be used as a temperature detection element such as a thermistor, a humidity sensor, or the like.

Further, as a preferred embodiment when the detection element is applied to an oxygen sensor, a heating element for activating the element part may be formed on an insulating substrate around the element part.

[Operation] When the element part of the detection element of the present invention is brought into contact with a gas to be measured, an electric signal corresponding to the properties of the gas is output to both end faces of the element part. For example, when the detection element is applied to an oxygen sensor. When one end surface of the element part is brought into contact with the reference gas and the other end face of the element part is brought into contact with the gas to be measured, an electromotive force is generated between the element parts according to the concentration difference of the gas to be measured, By extracting this as an electrical signal using a pair of electrodes, the concentration of the gas to be measured can be measured. Furthermore, when the detection element is used as a temperature detection element, a resistance change proportional to temperature occurs, and this can be extracted as an electrical signal.

When alumina is used as an insulating substrate, there is a difference in thermal expansion.
As a countermeasure, the element part of this detection element having the above-mentioned properties contacts the insulating substrate within the through hole, and the contact area is small, so if the thermal expansion of the material of the insulating substrate and the element part Even if the difference in coefficients is large, the stress generated between the two is small, and damage to the element portion etc. due to heat stress can be avoided.

In addition, when ZrO2 is used for the element part, if AQzo3-MgO (magnesia alumina spinel), which has almost the same thermal expansion as ZrO2, is used for the insulating substrate, the stress caused by the temperature rise during this time will be reduced. , damage to the element portion etc. can be further avoided. In this case, AQeOs and Mg
The ratio of O is effective in the range of Mg020 to 80 mol%, preferably in the range of 40 to 60 mol%.

Furthermore, since the material of the element portion only needs to be filled in at least the inside of the through hole, the amount of material used can be reduced, and the amount of expensive material such as zirconia can be reduced.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

The first [M] shows a detection substrate having an element part made of zirconia, and this detection substrate constitutes an oxygen sensor together with a substrate (not shown) which is disposed facing each other across a gap that serves as a gas introduction part. It is something to do. Figure 2 is II-II
It is a sectional view along the line.

In these figures, ■ has AQ20z as its main component, has a length of 5 Q mm, a width of 4 nt m, and an yl width of 0. 5m
m, and the end of this insulating substrate 1 has a diameter of 0.
．． A plurality of through holes 3 of about 5 mm are formed. A sensor element portion 5 made of an oxygen ion conductive solid electrolyte is formed on the front and back surfaces of the insulating substrate 1 in and around these through holes 3. The sensor element section 5 is formed of a filling section 5a filled in the through hole 3 and laminated sections 5b and 5C laminated on the insulating substrate 1. The sensor element section 5 is made of Y2O3-Z
It is formed by printing a paste containing rO2 as a main component mixed with a commonly used organic binder on an insulating substrate. Further, on the laminated parts 5b and 5C of the sensor element part 5, Zr
A porous electrode 7 containing platinum as a main component is formed, one of which is a reference electrode 7a, and the other is a measurement electrode 71). The reference electrode 7a is connected to the reference electrode terminal 11a through a portion 9εt of the conductor 1 formed on the back surface of the insulating substrate 1 and the through pole 8 (see FIG. 3), while the measuring electrode 7b is The measurement electrode terminal 11b is connected to the measurement electrode terminal 11b via a conductive portion 9b formed on the surface of the electrode 1. Furthermore, a heating element 15 connected to a heating element electrode terminal 3 is formed on the insulating substrate 1]- around the laminated portion 5b of the sensor element section 5.

In order to manufacture the detection board for the 2-2 acid accumulation sensor, first, a green sheet containing alumina as a main component is formed, and this green sheet is cut into a predetermined shape and the through holes 3 are cut into a predetermined shape.
．． 8 to form 9 Next, paste Y2O3-ZrO
A commonly used organic binder is mixed with the solid solution raw material powder, and the sensor element portion 5 is formed on the green sheet using thick film printing.

Further, a reference electrode 7a, a conductive part 9a, and a reference electrode terminal 11a are formed on the m-layer part 5 and the front and back surfaces of the green sheet by thick film printing with platinum paste to a thickness of about 10 μm, and then the measurement electrode 7b and the conductive 91) and the measuring electrode terminal 11b are formed in the same manner, and then the heating element electrode terminal 1
3 and a heating element 15 are formed on a green sheet. Subsequently, as shown in FIG. 3, after laminating other green sheets 17 and 19 to form an atmospheric chamber 16, the green sheets 17 and 19 are fired at 1400° C. to 1500° C. to complete the detection element. Incidentally, FIG. 4 shows the state of the green sheet 1a with the element portion, electrodes, etc. omitted.

Then, the oxygen sensor is completed by storing and holding the fired product shown in FIG. 3 in a case (not shown).

Next, the use of the oxygen sensor having the above configuration will be explained.

Now, while applying voltage to the heating element electrode terminal 13 and heating the sensor element part 5 by the heating element 15, the reference electrode 7a side facing the atmospheric chamber 16 is brought into contact with the atmosphere, and the measurement electrode 7bll is connected to the gas to be measured. When brought into contact with the electrode, an electromotive force corresponding to the difference in oxygen gas concentration is generated in the filling part 5a and the laminated parts 5b and 5cffi in the through hole 3, and this electric signal is output between the reference electrode 7a and the measurement electrode 7b. The gas concentration is measured based on

The configuration and operation of the oxygen sensor have the following effects.

■ The sensor element part 5 is formed in contact with the insulating substrate 1 only by the filling part 5a in the through hole 3 and the laminated parts 5b and 5c, and the contact area is the same as that of the plate facing the same shape as described in the conventional technique. Since it is smaller than the disposed insulator, damage due to the difference in thermal expansion coefficient between the solid electrolyte of the sensor element section 5 and the alumina of the insulating substrate 1 can be avoided.

(2) Since the sensor element portion 5 can be made smaller, the amount of expensive zirconia used can be reduced, and costs can be reduced.

■ Since the surface area of the laminated parts 5b and 5C of the sensor element part 5 is small, the heating element 1 is placed on the insulating substrate 1 around the laminated part 5L+.
5 can be directly formed, so it is possible to form the heating element on top of it with another insulating layer interposed, as is commonly used in the past, or to place the heating element in a laminated part facing each other with a gap between them. Since there is no need to provide a heating element on the printed circuit board, the configuration becomes simple.

■ Since the sensor element part 5 is provided with a plurality of filling parts 5a and is in contact with the atmosphere and the gas to be measured, stable output 18 is achieved.
You can get the number.

FIG. 5 shows a detection board that is a modification of the one shown in FIG. 2, in which a buffer part 21 is interposed between the through hole 3 formed in the insulating board 1 and the filling part 5a of the sensor element part 5. This II
The neighboring part 21 is made of a mixture of alumina and zirconia, and has an intermediate coefficient of thermal expansion with respect to the alumina of the insulating substrate 1 and the solid electrolyte of the filling part 5a. With this detection board!
This is more effective than the part 1 of the IIIf part 21 in preventing damage to the insulating substrate 1 and the filling part 5a due to thermal expansion.

Next, as a preferred embodiment, the present invention can also be applied to an oxygen sensor in which a detection substrate is wrapped around the outer periphery of a hollow cylindrical body shown between FIGS. 6 and 71. In FIG. 9, 31 is an insulating substrate. It is a hollow cylindrical body, and its outer diameter is 3. 2mm,
The inner diameter is 1.5 mm. This hollow cylindrical body 3
1 is made of alumina and has a through hole 33 at its end.
Two are formed. And, one end of the hollow cylindrical body 31 is In'a! The other end is opened by R35, and the other end is an opening 37, and the inside is hollow, forming a reference gas introduction path 39 (71'2).

-1- A detection substrate having substantially the same structure as the detection substrate described in the embodiment of FIG. 1 is wound around the outer periphery of the hollow cylindrical portion 31. That is, as shown in the exploded perspective view of FIG. 7, the detection substrate 4 includes an insulating substrate 43 having a plurality of through holes 42 formed at its end, and a plurality of through holes 42 laminated on both sides of this insulating substrate 43. A sensor element part 45 made of a solid electrolyte filled therein, a reference electrode 51 and a measurement electrode 53 formed on the sensor element part 45 and having terminal parts 47 and 49, and a porous ceramic layer covering the measurement electrode 53. an insulation 1f 455 consisting of an insulation 1f 455, five heating elements laminated on the insulation substrate 43 around the sensor element part 45 and having a terminal part 57, and a heating element having an opening 60 that covers the heating element 53 and exposes the insulation 155. It is made up of a protective ceramic 161.

In this embodiment, air from the atmosphere introduction path 39 in the hollow cylinder 31 contacts one end surface of the sensor element section 45 via the through hole 33 → the porous reference electrode 51, while the gas to be measured contacts the porous reference electrode 51. The sensor element section 4 is
5 and detects the concentration of the gas to be measured based on the electromotive force between the two end surfaces.

In this embodiment, the member wound around the hollow cylindrical body is not formed of solid electrolyte as described in the conventional technique, but the sensor element portion 45 of solid electrolyte is formed only in the through hole 42 and its surroundings. Therefore, similar to the embodiment shown in FIG. 1, the contact area between the sensor element portion 45 filled in the through pole 42 and the insulating substrate 43 can be reduced, which has the effect of preventing damage due to the difference in thermal Q coefficient. etc.

Note that in the embodiments shown in FIGS. 6 and 7, the heating element 59 is formed on the outer peripheral side of the insulating substrate 43;
It goes without saying that the same effect can be obtained even if it is formed on the inner peripheral side of the hollow cylinder 31, that is, between the hollow cylindrical body 31 and the insulating substrate 43.

[Effects of the Invention] As described above, according to the present invention, it is possible to avoid the stress of the element due to the difference in thermal VJj tensile coefficient between the insulating substrate and the element portion. In addition, since it is possible to reduce the amount of material used in the element portion, it is possible to reduce the cost compared to those in which an expensive material such as zirconia is used for the element portion.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of the main parts of an oxygen sensor according to an embodiment of the present invention, and FIG. 3 is a sectional view of an oxygen sensor with an air introduction path provided on opposing substrates, FIG. 4 is a perspective view illustrating the configuration of the oxygen sensor, and FIG. 5 is a modification of FIG. 2. A sectional view showing an example; FIG. 6 is a perspective view showing an oxygen sensor according to another embodiment;
FIG. 7 is an exploded perspective view of the embodiment shown in FIG.
Sensor element part 5a...Filled part 5L+, 5c...Laminated part 7...Electrode 7a, 51...Reference electrode 7b, 53.
...Measuring electrode 15...Heating element

Claims (1)

[Scope of Claims] An insulating substrate with a through hole formed therein, an element portion filled in the through hole and whose electrical characteristics change depending on the surrounding environment, and an insulating substrate connected to both ends of the element portion. and at least one pair of electrodes formed on the front and back surfaces of the detection element.