JPS5830649A - Detector for gas component - Google Patents

Abstract

PURPOSE:To detect exhaust gas of wide-ranged temperature, by mounting a gas detecting element to a substrate and embedding a temperature detecting element in the substrate. CONSTITUTION:Two filmy electrodes 4a and 4b are formed on an alumina green sheet 1a by printing. A filmy heater 5 is formed on a green sheet 1b by printing, an electrode 4c is formed in a position corresponding to the electrode 4a, and a filmy temperature detecting element 3, comprising zirconia added with niobium oxide, is formed by printing on a part where the heater 5 and the electrode 4c are positioned facing and opposite to each other and in a comb shape. The green sheet 1a with an electrode forming surface up is overlapped with the electrode forming surface of the green sheet 1b. The lamination is burned in a furnace at 1,500-1,600 deg.C. Paste of cobalt monocide is printed on the upper and, where the electrodes 4a and 4b are positioned facing and opposite to each other and in a comb shape, then backed to form a gas component detecting element 2.

Description

Detailed Description of the Invention The present invention relates to a gas component detector, particularly a gas component detector for detecting the oxygen concentration in the exhaust gas of an internal combustion engine and measuring the air-fuel ratio. In order to reduce the harmful components of the engine and improve fuel efficiency, the internal combustion engine is operated at an air-fuel ratio that is even thinner than the stoichiometric air-fuel ratio.
A so-called lean burn system has been proposed. This method requires means for accurately detecting the air-fuel ratio in the lean ψ region.

As this type of means, there are detection devices described in Japanese Patent Publication No. 56-6503 and Japanese Patent Application Laid-Open No. 58-88396. In these devices, cobalt monoxide (GoO) or an alloy of cobalt monoxide and magnesium oxide (MgO) is used as an element, m≠, -cobalt oxide is trivalent cobal) (0
osOa ) and for temperature compensation, these elements are kept at a certain temperature, for example 900°C.
It is designed to be used while being heated.

However, it is very difficult to keep the temperature of the element constant in exhaust gas regardless of the exhaust gas temperature or exhaust gas flow rate. When the temperature of the element changes, the electric resistance value changes due to this tM degree change, apart from the oxygen concentration.
The accuracy of oxygen concentration detection decreases and the air-fuel ratio is not accurate)
--You will not be able to do it. Furthermore, if the temperature of the element is to be kept close to constant, the repeater control circuit becomes complicated and expensive.

The object of the present invention is to provide a gas component detector that can accurately detect the concentration of phosphorus regardless of the wide range of temperature changes in exhaust gas and regardless of the oxidation or reduction atmosphere.

The detector of the present invention includes a film-like gas component detection element on a heat-resistant, electrically insulating base, and a film-like temperature detection element whose resistance temperature coefficient is equal to that of the element. It is characterized in that it is embedded in the base so that the change in electrical resistance depends only on temperature without being affected by the atmosphere and FM. The present invention will be explained below with reference to illustrated embodiments.

In the embodiments shown in FIGS. 1 and 1, l is a plate-shaped base body that is different from Al, and includes a gas component detection element 2, a temperature detection element 3, electrodes 4&, 4-40S, Peter S1, lead wires 6& %@bs” with %6d-
Ru. The details of these structures, including the manufacturing method, will be explained with reference to FIGS. 2 to 4.

First, a pair of thin pieces made of arsena green sheet) a
, l'b are prepared. On the alumina green sheet 11, a pair of membrane electrodes made of platinum, platinum-platinum, etc.
, 4k is formed by printing. Green sheet No. 1 has through holes 111 and 112 at the end of the electrode number aS4b.
is provided, and an electrode is also formed inside this which is electrically conductive to the voltages 4 and 4.

Green Sea) Ib is lined with platinum, platinum - rhodium, tungsten, molybdenum -! Form a membranous piece of paper by printing. Furthermore, a similar electrode 40 is formed at a position corresponding to the electrode 4&, and a zirconia (zrO
s) A film-like temperature sensing element S is formed by printing.

Next, the green sheet 11 is stacked with the electrode forming side facing upward (green sheet) ITh electrode formation [FK].

In this case, the lead wire 6 and made of platinum, platinum-rhodium, etc.
, 6b, 6., 6d are attached to green sheets la, l'
Set between the ends of b. The lead wire 6& is connected to the green sheet l via the electrode of the through hole 112 of green sheet 1&.
The lead wire 6b is connected to the electrode 4b of the green sheet 1b through the electrode 40 of the green sheet 1b and the electrode of the through hole 111. 14aKq The lead wires 6d and 6o are positioned so as to be connected to both ends of the heater 5 of the green sheet 11, respectively.

The green sheets 1 & 1b stacked together in this manner are fired in an electric furnace at 1500'=1600° C. for about 5 hours. As a result, the green sea) 1&, lbq are sintered and integrated, the membrane heater 5, the temperature detection element 3, and the electrode 40 are buried inside the base 1, and the membrane electrodes 4m and 4b gradually close to the surface. Lead l[6&, 6b, 6 (1, 6 (1 is Green Sea)) 1&, 1m between the leads is firmly fixed due to shrinkage during sintering Next, paste cobalt monoxide is applied to the electrode 41.4b The L1 gas component detection element 2 is printed on the comb-shaped opposing ends of the L1 gas component detection element 2, and after drying, the L1 gas component detection element 2 is baked in an electric furnace at about WOO° C. for about 2 hours.

As shown in FIG. 1, the base body 1 is housed inside a protective cover 7 made of heat-resistant metal and having a hole 71 for introducing exhaust gas, and a pipe 8 connected thereto. Note that a 7-lunge 9 for fixing to the exhaust pipe is attached to the joint between the protective cover 7 and the pipe 8. Base 1 is pipe B
Inside, it is supported by a holding member 10 made of a sintered body of alumina or the like. In addition, the upper part of the base 1, the lead wire 6
and connected thereto are 11 sub-lead wires made of heat-resistant metal such as stainless steel (fixed in the paper vibrator 8 by an inorganic adhesive 12). Further pipes 13.
14 are connected, and the sub-lead wire 11 is inserted through an insulating tube 15 made of aluminum or the like arranged inside these, a bushing 16 made of fluororubber, etc., and a heat-resistant rubber member 1 made of silicone rubber, etc. The sub-leads all led to the outside are covered with a glossy cover member 18.

Figure 3 shows the detection circuit of the gas component detector having the above configuration, in which the gas component detection element 5 and the temperature detection element 5 are connected in series with 1 these elements ffi, and 3 and Peter S are connected in parallel with the power source 19.
The control circuit 20 is connected to the control circuit 20 and includes a combiator which controls the air-fuel ratio of the air system by the output voltage of the comparator and the fan comparator.
Next, to explain the operation of the above-mentioned detector, when the composition of the exhaust gas, that is, the air-fuel ratio changes, the electrical resistance value g1 of the gas component detection element changes as shown in Fig. 6. becomes smaller as it gets leaner. On the other hand, temperature detection element 3
1F1 Since it is buried in the base 1 and does not substantially come into contact with the exhaust gas, its electrical resistance value tzB is determined only by the temperature without being affected by the air-fuel ratio.
From 1. As the temperature increases, the electrical resistance values of the gas component detection element B and the temperature detection element 3 also decrease accordingly.

However, since the temperature coefficients of resistance of elements it and 3 are almost equal, the air-fuel ratio at which their electrical resistance values of 21.22 intersect does not change even at temperature t1, and at a predetermined air-fuel ratio, the electrical resistance values of 21. The ratio of 2.1+ is constant, and when the fifth fllJ detection circuit is set to #J-, the output of the gas component detector has almost the same value without being affected by temperature.

Figure 7 shows another embodiment, which is a gas component detector for detecting the stoichiometric air-fuel ratio. It's okay. There is no heater branch. Alumina Green Sea) 1aK#f electrodes 4&, 4b and gas component detection element 8 are formed on green sheet 1b, electrodes 4o, +6 and temperature detection element 3 are formed on Green Sea) 11
．． 1b is sintered and integrated with lead wires 6m, 61), and 6(l) set. The gas component detection element 8 supports a catalyst such as platinum, platinum-metal, etc.

In addition to the above-mentioned embodiments, as the gas component detection element 2,
, ZrO dew, S, O, , Zoo can be 4x,
In addition, as the temperature detection element 3, #'1ooo, MidSZr
Omaro and Hou01 can be used.

Further, as a means for embedding the temperature detection element 3 in the base 1, for example, alumina green sea) 1a, lb may be baked and then bonded together with a heat-resistant adhesive. Alternatively, the gas component detection element 2 and the temperature detector ≠4 may be provided on the surface of the same alumina sheet, and the temperature detection element S may be covered with another alumina green sheet, and these may be simultaneously fired and integrated.

As explained above, since the present invention uses a temperature detection element that is not affected by the atmosphere, it is possible to accurately detect the oxygen concentration in the exhaust gas regardless of temperature changes and control the air-fuel ratio to a desired value. I can do it. Furthermore, since the temperature detection element is embedded within the base, it is possible to effectively prevent the influence of the atmosphere on the element. There is also a method of covering the temperature sensor with a glassy material as a means of shielding it from the atmosphere.
In this case, due to the difference in expansion coefficient between the covering member and the base body, the covering member may peel off and gas may enter. In the case of the present invention,?

There is no risk of damage. In addition, in internal combustion engines such as automobiles, the operating temperature range of the detector is extremely wide, from 200 to 900.
Depending on the combination of the gas component detection element and the temperature detection element, it may be difficult to match the resistance temperature coefficients over the entire temperature range.

However, it is easy to match the resistance humidity coefficients within a temperature change range of 100 DEG to '200 DEG C. Therefore, in such a case, it is sufficient to use a pipette, and the temperature should be set to 800, for example.
The temperature may be controlled to ℃±BO@~10.0℃. Such temperature control may involve strict control to a specific temperature, or a simple 011-0? This can be easily done with the F heater control circuit, and under various operating conditions, the output of the paper detection density is changed to P! by the action of the temperature detection element. It can be set to a fixed value.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the overall configuration of an embodiment of the present invention, Fig. 2 is an exploded perspective view of the main constituent parts, Fig. 3 is a side view of an integrated structure of the constituent members shown in Fig. The figure is a cross-sectional view of the Moom in Figure 3, Figure 6 is a diagram showing an example of the detection circuit, Figure 6 is a diagram showing the characteristics of the gas component detection element and the temperature detection element, and Figure 7 is the second embodiment. FIG. 3 is an exploded perspective view of main components in FIG. 1-----Base 1&, 1b...Base component 2...Gas component detection element 3...Temperature detection element 4m, 4b, number o, 4d.・-e・・Electrode 5------
Heater Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 9

Claims (1)

[Claims] A film-like gas component detection element made of a metal oxide that shows an electric signal according to the gas component in the detected gas, an electrode for extracting the electrical signal shown by this element, and a film-like gas component detection element formed on a heat-resistant electrically insulating base, and the film-like gas A component detection element and a film temperature detection element made of a metal oxide having an equal resistance temperature coefficient and an electrode for extracting an electric signal indicated by this element are formed, and the film temperature detection element A gas component detector characterized by being implanted inside the body.