JPH03233351A - Sensor structure - Google Patents

Abstract

PURPOSE:To eliminate directional property and to enable suitable measurement by laminating a detection part and a heating part vertically to the axial direction of a supporting part in the end part thereof and forming these parts and connecting a detection electrode and a heater to a lead part respectively. CONSTITUTION:In a sensor 1, a lead 16 for performing electric conduction is formed in a supporting part 34 formed on a ceramic base plate. Both a heating part 36 equipped with a heater 44 and a detection part 38 equipped with a detection element 2 are laminated vertically to the axial direction of the supporting part 34 in the end part of this axial direction thereof. The heater 44 is connected to the lead 16 by lamination and furthermore a detection electrode 40 is connected to the lead 16. Therefore at a time for measuring the circumferential gas, the detection element 2 is arranged vertically to the axial direction of the sensor 1 in the tip part thereof. After all, the detection element 2 is arranged so that it is always made parallel to the direction of flow of the circumferential gas. Accordingly even when the oxygen sensor 1 is fitted in any direction, the concn. of oxygen is accurately measured without effecting the direction of flow of exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a sensor structure, and specifically relates to a sensor structure including a detection element and a heater formed on a ceramic substrate.

[Prior art] Conventionally, sensors have been used to measure the concentration of surrounding gas (
A variety of sensors using ceramics are known; for example, oxygen sensors have been proposed that include a detection section made of cylindrical ceramics and a detection section formed by laminating ceramic substrates. This oxygen sensor (as shown in FIG. 8, a detection element P made of titania or the like) is laminated on a detection electrode P2, a ceramic substrate P3, and a ceramic substrate P5, on which a heater P4 for heating the detection element P1 is formed. Detection part P6 formed into a columnar shape by laminating
It is equipped with the following.

[Problems to be Solved by the Invention] However, the above-mentioned prior art has the following problems and is still not sufficient.

That is, the detection part P6 of the oxygen sensor is formed on the ceramic substrate P.
Since the detection element P1 is formed on one surface of the sensor 2, the sensor becomes directional, and it is not always possible to accurately measure the concentration of the surrounding gas.In other words, the gas to be measured is formed on the surface of the detection element P1. When the flow is perpendicular to the detection element P1, toward the back side of the detection element P1, or parallel to the detection element P, a problem arises in that the output size and response are different.

In order to avoid this, the shape of the vent holes in the protector has been modified to rotate the gas flow direction so that the gas hits the detection element P1 uniformly.
For this reason, problems arise in that an expensive protector is required and the mounting position of the sensor is limited. The purpose is to provide structure.

[Means for Solving the Problems] The configuration of the present invention for solving such problems includes a sensing portion in which a sensing element and a sensing electrode connected to the sensing element are formed on a ceramic substrate, and a sensing element that heats the sensing element. In the sensor structure, the sensor structure includes a heating part in which a heater is formed on a ceramic substrate, and a support part in which a lead for electrical conduction is formed on the ceramic substrate. The sensor structure is characterized in that the sensing part and the heating part are stacked and formed perpendicularly to the axial direction of the sensor, and the lead is connected to the sensing electrode and the heater, respectively.

Here, it is preferable to adopt a columnar structure in which a number of ceramic substrates are laminated as the support portion, since the leads can be easily formed by thick film printing or the like.

In addition, the ends of the leads are used as electrical input/output parts for taking out output and applying voltage to heaters, but platinum lead wires may be used as this input/output part, It is also possible to adopt a structure (separate type) in which the metal terminals are pressed by a spring member to bring them into contact.

Furthermore, it is desirable that an insulating layer made of, for example, alumina be formed covering the surface of one of the leads exposed on the surface of the sensor structure.

Further, as a detection element, for example, an ionic conductor such as ZrO2 or an electronic conductor such as TiO2 or 5n02 can be used.

[Function] The sensor structure of the present invention (i.e., a lead for electrical conduction is formed in the support part, and a lead is formed at the end of the support part in the axial direction.
A heating section including a heater and a detecting section including a detection element are stacked. This lamination connects the leads to the heater, and further connects the leads to the detection electrode.

Therefore, when measuring ambient gas, the tip of the sensor
The detection element is arranged perpendicularly to the axial direction of the sensor. In other words, since the detection element is always arranged parallel to the direction in which the surrounding gas flows, the directionality of the sensor is improved.

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

In this example, a ceramic substrate is applied to an oxygen sensor that detects the oxygen concentration in the exhaust gas of an internal combustion engine as a detection section that detects gas components or their concentration. Fig. 1 shows the detection section of the oxygen sensor. FIG. 2 shows the entire oxygen sensor partially cut away.

In FIG. 2, an oxygen sensor 1 (a detection unit 4 that detects oxygen concentration with a detection element 2 provided on a ceramic substrate), a cylindrical body that grips the detection unit 4 and attaches the oxygen sensor 1 to an internal combustion engine are shown. It includes a metal fitting 6, a protector 8 having a ventilation hole 7 and attached to the tip of the metal shell 6 to protect the detection part 4, and an inner cylinder]O that grips the detection part 4 together with the metal shell 6.

20 An outer cylinder 12 is attached to the metal shell 6 on the outside of the inner cylinder 10, and a sealing material 14 made of silicone rubber is filled inside the upper part of the outer cylinder 12. , the connection portion between the lead wire 16 and the metal terminal 18, which are arranged through the sealing material 14, is insulated and protected.

In addition, the detection part 4 (spacer 20) is held by the metal shell 6 and the inner cylinder 10 via the filling powder 22 and the glass seal 24, and the glass seal 24 (the spacer 20, which prevents the leakage of the detection gas) Lead wire 26 and metal terminal 1
It covers the connection part with 8.

Furthermore, the detection element 2 is formed at the tip of the detection part 4 perpendicularly to the axial direction of the detection part 4.

This detection section 4 (as shown in FIG.
2a and 32b, and a heating section 3 disposed perpendicularly to the axial direction of the support section 34 at the tip of the support section 34.
6, and a detection section 38 laminated on the surface of the heating section 36.

Among these, a pair of detection electrodes 40 are formed on the surface of the detection section 38, and a layer of the detection element 2 made of TiO2 is formed on the surface of the second detection electrode 40. Furthermore, an electrode lead 42 extending from the detection electrode 40 is attached to one side of the detection part 38 (see FIG.
a is formed.

Furthermore, a heater 44 is formed in a meandering manner on the surface of the heating section 36 . A pair of electrode leads 42b are attached to the side surface of the heating section 36.
The heater lead 48b (fifth
Figure (C)) is formed.

Furthermore, the ceramic substrate 30a outside the support part 34
, 30d are formed with an electrode lead 46c and a heater lead 48c, which are connected to the electrode lead 42b and the heater lead 48b, respectively. ni(yo)
A platinum lead wire 26 is attached to each.

Incidentally, upper insulating alumina coat layers 49a, 49b are formed on both side surfaces on the tip side of the detection section 4, covering the electrode leads 42a, 42b, 46c and the heater leads 48b, 48c.

Next, a method for manufacturing the above-mentioned detection section 4 will be explained based on FIGS. 3 to 5.

First, manufacturing of the support part 34, which is the support of the detection part 4, will be explained based on FIG.

As shown in the figure, first to fourth ceramic substrates 3
First to fourth green sheets 5 ranging from 0a to 30d
0a to 50d are AI with an average particle size of 1.5 μm. 0392
Weight%, 5i024% by weight, Ca○2% by weight and Mg0
For 100 parts by weight of mixed powder consisting of 2% by weight, 12 parts by weight of butyral resin and dibutyl phthalate (DBP).
) 6 parts by weight, mixed in an organic solvent to form a slurry, and made into a slurry with a doctor blade to a thickness of 0. Form to 9mm.

Among these, the first and fourth green sheets 50a, 50
Patterns 52, which will become the electrode leads 46C and the heater leads 48c, are formed on the outer surface of d by thick film printing with a platinum paste containing 15% by weight of Al2O3 relative to Pt.

Furthermore, a platinum lead wire 2 is attached to the root end of each pattern 52.
6, the first to fourth green sheets 50a to 50d are laminated, and green sheets 54a and 54b made of Al2O3 and having a thickness of 0.26 mm are laminated and bonded by thermocompression. In addition, this thin film green sheet 5
4a and 54b are insulating sheets 32a and 32b, and windows 56 are formed on both sides thereof.

Then, the support portion 34 is manufactured by cutting the laminate thus formed into a predetermined size shown by the dashed line in the figure.

Next, manufacturing of the detection section 38 and heating section 36 will be explained based on FIG. 4.

As shown in the figure, green sheets 64 and 66 serve as substrates.
F The above-mentioned first to fourth green sheets 508 to 5
It is manufactured in the same manner as 0d, and the detection electrode 40 and heater 4 are
Patterns 60 and 62 which are number 4 are also formed by thick film printing using platinum paste in the same manner as above. The green sheets 64 and 66 are then laminated and thermocompressed to form a laminate, which is then NC-cut into a predetermined size for the detection section 38 and the heating section 3.
6 is manufactured.

Next 1: The above support part 34. A method for manufacturing the entire detection section 4 using the detection section 38 and the heating section 36 will be explained based on FIG. 5.

First, as shown in FIG. 5(a), a laminate of the detection part 38 and the heating part 36 is placed on the tip of the support part 34, and a green sheet similar to the green sheets 50a to 50d is pasted with butyl calpitol. They are bonded together using the same material, or they are bonded together by thermocompression. At this time, the end electrode lead 46c reaching the side surface of the detection electrode 40 is placed on the same side.

Next, as shown in FIG. 5(b), the electrodes 42a, 4
2b is printed using the platinum paste on the side surface so that the detection electrode 4o and the electrode lead 6c are electrically connected.

Brush painting, etc. (this is how it is formed. Similarly, the 50th (c)
), the heater lead 48b is connected to the one-pole lead 4.
A platinum paste is formed on the opposite side surface of 2a and 42b so as to connect the heater 44 and the heater lead 48c.

Next, as shown in FIG. 5(d), an Al2O3 pole 68 for preventing the detection element 2 from peeling off is attached to the surface of the detection part 3ε.

Furthermore, as shown in FIG. 5(e), the electrode lead 42a,
42b, 42c, 46c (part of (7)) and the printer transfers alumina paste made of the same material as the base so as to cover the heater leads 48b, 48c to form an insulating alumina coat layer 49a.

49b. This alumina coat layer 49a.

49b(7) Thickness (L 10 μm to 100 μm, preferably 20 μm to 70 μm.

After forming the alumina coat layers 49a and 49b, they are left in the atmosphere at 1500° C. for 2 hours and fired. still,
Formation of the alumina coat layers 49a and 49b (↓ may be performed after the above baking and then baked again, or the above balls 6
It may be formed before the deposition of 8, and there is no particular restriction on the timing of its formation as long as insulation can be achieved.

Next, as shown in FIG. 5(f), the detection element 2 will be provided on the surface of the detection section 38. First, 100 mol parts of T i 02 powder with an average particle size of 1.2 μm ( 2 to 1 mole part of platinum black is added, and 3% by weight of ethyl cellulose is added to the total powder, mixed in butylcarpitol (trade name of 2-(2-butoxyethoxy)ethanol), T with viscosity adjusted to 300 poise
Manufacture iO2 paste. And this T i 02
After printing the paste as a thick film on the surface of the detection part 38, 720
Leave it in the air at 0℃ for 1 hour to bake.

The detection unit 4 manufactured in this manner is housed and attached inside the oxygen sensor 1 shown in FIG.
6 between 1: By applying power supply voltage for heating,
The oxygen concentration is detected by heating the heater 44 to activate the detection element 2 and detecting a change in resistance between the electrode leads 46c.

The configuration of this embodiment described above provides the following effects.

In the sensor structure of this embodiment, a detection section 38 is formed at the tip of the detection section 4, and this detection section 38 is arranged perpendicularly to the axial direction of the detection section 4.

Therefore, when the oxygen sensor 1 is attached to an exhaust pipe or the like, the flow of exhaust gas flowing through the exhaust pipe (the surface of the detection part 38,
That is, it becomes parallel to the layer of the detection element 2.

Therefore, no matter what direction the oxygen sensor 1 is attached, the oxygen concentration can be accurately measured without being affected by the direction of the exhaust gas flow. In other words, since the oxygen sensor 1 has no directionality, the oxygen concentration can always be suitably detected.

In addition, in the detection part 4 (the electrode leads 42a, 42b, 42
Since the alumina coat layers 49a and 49b are formed to cover the heater leads 48b and 48c, the insulation of the heater 44 can be improved, thereby suppressing variations in sensor output.

Further 1: Even if unburned gas adheres to the detection part 4, or even if carbon generated by combustion of unburned gas adheres, insulation is ensured by the alumina coat layers 49a and 49b. , accurate sensor output can be obtained for a long period of time.

In the five embodiments (alumina coat layers 49a, 49
b! E. Since it is formed by applying by printing or transferring a paste instead of a sheet, it is possible to suitably prevent short circuits due to adhesion of conductive substances.

Furthermore, since the thickness of the alumina coat layers 49a and 49bl can be reduced by applying the paste, the power consumption of the heater 44 can be reduced, and furthermore, the power consumption of the heater 44 can be reduced.
The heat transfer balance is good and the temperature characteristics of the sensor do not deteriorate.

Next, another embodiment will be described based on FIGS. 6 and 7.

As shown in FIG. 6(a) 1: The detection section 72 and heating section 74 of the detection section 70 of this embodiment are the same as those of the above embodiment, but
The support portion 76 and the electrical input/output portions at the ends of the support portion 76 are different. That is, the support part 76 is made up of six ceramic substrates 78a to 78f, and electrode leads 80 and heater leads 82 are formed on the inner surfaces of the ceramic substrates 78a and 78f on both sides. and,
At the tip of the support part 76, an electrode lead 80 and a heater node 82 are bent outward at right angles and are connected to a detection electrode 84 and a heater 86.
), at the base of the detection unit 70 (covering each end of the upper electrode lead 80 and heater lead 82,
Metallized layer 88 for electrical connection using platinum paste
is formed.

Note that an insulating alumina coat layer 89 is provided on the side surface where the electrode lead 80 and heater lead 82 at the tip of the detection unit 70 are exposed (upper electrode lead 80 and heater lead 82 are covered).
a and 89b are formed.

The detecting section 70 of this embodiment (as shown in FIG. 7, is used in a separate type oxygen sensor 90. That is, a metal terminal connected to a lead wire 92 is attached to the metallized layer 88 at the end of the detecting section 70. 94 are pressed into contact with each other by a spring member 96. Note that the size of the metallized layer 88 is smaller than that of the metal terminal 94.
It is set as appropriate depending on the situation.

The above-described configuration has the advantage that the electrode lead 80 and the like are arranged closer to the inside of the sensor, so that insulation can be suitably performed. Further, since the input/output portion of the detection section 70 is the metallized layer 88 instead of the platinum lead wire 26, there is an advantage that the overall structure of the sensor is simplified and manufacturing is facilitated.

Although each embodiment of the present invention has been described above, the present invention is not limited to these embodiments in any way, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention.

For example, the (i) detection element and the heater may be formed on separate ceramic substrates, or may be formed on the front and back sides of two ceramic substrates.

[Effects of the Invention] As described above, according to the present invention, a sensing portion including a sensing element and a detection electrode and a heating portion including a heater are provided at the tip of the supporting portion perpendicularly to the axial direction of the supporting portion. Because of the stacked structure, the detection elements are not arranged perpendicularly to the flow of the measurement gas as in the conventional case, but are arranged parallel to the flow direction of the measurement gas. Therefore, since the influence of the directionality of the detection element is reduced, the state of the measurement gas can be detected accurately. Therefore, when installing the sensor, work such as adjusting the direction of the sensor is not required, and work efficiency is improved. Furthermore, there is an advantage that there is no need to use an expensive protector and that the mounting location and direction can be freely selected.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing a partially broken main part of an embodiment of the present invention, FIG. 2(a) is a partially broken front view showing an oxygen sensor, and FIG. A-A sectional view, Figure 3 is an explanatory diagram showing a method of manufacturing the support part of the oxygen sensor, Figure 4 is an explanatory diagram showing a method of manufacturing the detection part and heating part of the oxygen sensor, and Figure 5 is an explanation of the manufacturing method of the detection part. Perspective view showing the method, Figure 6 (a
) is an exploded perspective view showing a partially broken detection section of another embodiment, FIG. 6(b) is an end view thereof, FIG. 7 is a sectional view of the oxygen sensor of another embodiment, and FIG. FIG. 2 is an exploded perspective view showing a detection section of a conventional oxygen sensor. ], 90...Oxygen sensor 2...Detection element 4.70...Detection section 34.76...Support section 36.74...Heating section 38.72...Detection section 40.84. ...Detection electrode 44.86...Heater

Claims (1)

[Claims] 1. A sensing part in which a sensing element and a sensing electrode connected to the sensing element are formed on a ceramic substrate; a heating part in which a heater for heating the sensing element is formed on a ceramic substrate; A sensor structure comprising a supporting part in which conductive leads are formed on a ceramic substrate, wherein the detecting part and the heating part are stacked on an end of the supporting part perpendicularly to the axial direction of the supporting part. A sensor structure characterized in that the lead, the detection electrode, and the heater are connected to each other.