JPH0778487B2 - Method of manufacturing oxygen sensor for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an oxygen sensor for an internal combustion engine, and more particularly to a close relationship with an air-fuel ratio of an air-fuel mixture that is attached to an exhaust pipe of an internal combustion engine and supplied to the engine. Measure the oxygen concentration in the exhaust gas at
The present invention relates to a method for manufacturing an oxygen sensor used for providing a feedback signal in air-fuel ratio feedback control.

<Prior Art> Conventionally, as this type of oxygen sensor, there is a sensor that can measure a wide range from a high oxygen concentration region (air-fuel ratio lean region) to a low oxygen concentration region (air-heat ratio rich region) (SAE paper 85
0378, JP-A-60-36949, etc.).

As shown in FIG. 3 and FIG. 4, a heater 3 coated with an insulating material 2 such as alumina is laminated on a substrate 1 made of zirconia, and a planar substantially U-shaped zirconia whose front end is closed is formed. The flat plate 4 is laminated on the substrate 1 so as to sandwich the heater 3 to form an atmosphere chamber 5 into which the atmosphere is introduced, and an oxygen concentration detection unit 6 is provided on the flat plate 4. The oxygen concentration detection unit 6 is configured by providing detection electrodes 8 and 9 made of platinum on both surfaces of a zirconia sheet 7 which is an oxygen ion conductive solid electrolyte.
Since the detection electrode 9 on the side is exposed to exhaust gas as described later, its outer surface is covered with a protective layer 10 made of alumina or the like.

Further, on the protective layer 10 covering the detection electrode 9, a high-temperature pyrolyzable substance (polyvinyl, which decomposes when the oxygen concentration detection unit 6 and the oxygen pump unit 11 are laminated and fired to form a space of the measurement chamber 12). Polyethylene, theobromine, etc.) 13 are provided so as to occupy the space of the measurement chamber 12. The oxygen pump unit 11 is
Zirconia sheet 14 which is an oxygen ion conductive solid electrolyte
It is configured by providing pump electrodes 15 and 16 made of platinum on both sides of each of them, and since the pump electrodes 15 and 16 are exposed to engine exhaust gas on both sides, their outer surfaces are covered with protective layers 17 and 18 made of alumina or the like. is there.

The zirconia sheet 14 is provided with an introduction hole 19 for introducing the engine exhaust into the measurement chamber 12, and the detection electrode 8 and the pump electrode 15 exposed to the atmosphere in the measurement chamber 12 and further exposed to the exhaust pipe. The pump electrode 16 to be formed has a protective layer 1 as described above.
It is covered with 0,17,18 for protection.

In such a structure, the substrate 1, the flat plate 4, and the zirconia sheets 7 and 14 are laminated with a predetermined pressure on each other in the state where the electrodes and the like are laminated, and then baked to form an oxygen sensor. Since the high-temperature decomposition substance 13 is burned down by the heat of this lamination firing, the measurement chamber 12 is formed between the oxygen concentration detection unit 6 and the oxygen pump unit 11 as shown in FIG.

The oxygen concentration detection unit 6 generates a voltage between the detection electrodes 8 and 9 according to the ratio between the oxygen concentration in the atmosphere introduced into the atmosphere chamber 5 and the oxygen concentration in the engine exhaust introduced into the measurement chamber 12. By doing so, the oxygen concentration in the exhaust gas (atmosphere in the measurement chamber 12) is detected. In addition, the oxygen pump unit 11 includes the pump electrode 1
By reversing the polarities of 5 and 16, oxygen (oxygen ions O ^2- ) is pumped out of the measurement chamber 12 through the zirconia sheet 14 which is an oxygen ion conductive solid electrolyte, or from the outside (inside the exhaust pipe) of the measurement chamber. Pump oxygen into the inside.

Therefore, in order to make the atmosphere in the measurement chamber 12 constant (theoretical air-fuel ratio), the oxygen action is adjusted by the pump action of the oxygen pump unit 11, and at that time, the value of the current flowing between the pump electrodes 15 and 16 is measured to measure the exhaust gas. Detects the oxygen concentration of.

For example, an air-fuel ratio lean region where the oxygen concentration in the exhaust gas is high (lean / rich of the air-fuel ratio is detected by the oxygen concentration detection unit 6).
When detecting the air-fuel ratio, a voltage is applied with the outer pump electrode 16 as the anode and the pump electrode 15 on the measurement chamber 12 side as the cathode. Then, oxygen (oxygen ion O ^2- ) proportional to the electric current
Are pumped out of the measurement chamber 12. Then, when the applied voltage exceeds a predetermined value, the flowing current reaches a limit value, and this limit current value is proportional to the oxygen concentration in the exhaust gas.By measuring this limit current value, the oxygen concentration in the exhaust gas, in other words, Then, the air-fuel ratio of the engine intake air-fuel mixture can be detected. On the contrary, using the pump electrode 16 as the cathode and the pump electrode 15 as the anode, the measuring chamber 12
If oxygen is pumped into the inside, detection can be performed in the air-fuel ratio rich region where the oxygen concentration in the exhaust gas is low.

In this way, the oxygen sensor for an internal combustion engine can measure in a wide range of oxygen concentration.

<Problems to be Solved by the Invention> However, according to such a conventional oxygen sensor, the substrate
1, the flat plate 4 and the zirconia sheets 7, 14 are stacked on top of each other with the electrodes etc. stacked on the stacking surface and the surfaces are uneven, so the stacking pressure is not constant and uneven Therefore, there is a possibility that problems such as peeling of the laminated surface due to insufficient pressure and crushing of the measurement chamber 12 space due to excessive pressure may occur.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent the occurrence of peeling of the stacking surface and crushing of the measurement chamber space by making the stacking pressure of the oxygen sensor uniform.

<Means for Solving Problems> Therefore, in the manufacturing method according to the present invention, the sheet-shaped high-temperature decomposable substance occupying the measurement chamber space is sandwiched between the oxygen concentration detection unit and the oxygen pump unit, and the oxygen concentration detection is performed. At least two electrodes between the oxygen ion conductive solid electrolyte forming the part and the oxygen ion conductive solid electrolyte forming the oxygen pump, and a sheet having the same thickness as each of the laminates containing the high temperature decomposition material. It was laminated on the periphery, and the high temperature decomposition substance was burned down by the heat during firing after the lamination to form the measurement chamber space.

<Operation> According to the oxygen sensor, since the measurement chamber is formed by burning away the high-temperature decomposed substance by the heat during the multilayer firing,
It is not necessary to form a space such as a concave portion that becomes a measurement chamber space on the laminated surface. Then, while the sheet-shaped member having the same thickness as the thickness of the high-temperature decomposing substance laminated on the detection electrode of the oxygen concentration detecting unit is laminated so as to surround the high-temperature decomposing substance to make the laminated surface flush,
If sheet-like members with the same thickness as the electrodes facing the measurement chamber space are stacked to make them flush, and the stacking surfaces that are flush are stacked, the stacking pressure will be applied uniformly and the pressure will be insufficient. There is no overpressure.

<Example> An example of the present invention will be described below with reference to FIGS. 1 and 2. The same elements as those of the conventional example shown in FIGS. 3 and 4 are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 1, substrate 1, flat plate 4, zirconia sheet 7,
Before the layers 14 are laminated and fired with each other, sheets 20 to 26 made of zirconia are arranged so that their respective laminated surfaces are flush with each other.

That is, since the heater 3 covered with the insulating material 2 such as alumina is laminated on the substrate 1, the sheets 20 and 21 are laminated on the substrate 1 so as to surround the insulating material 2 in order to eliminate the unevenness caused by this. is there.

In addition, a zirconia sheet 7 that constitutes the oxygen concentration detection unit 6
First, the detection electrode 8 and a sheet 22 having the same thickness as the detection electrode 8 and surrounding the detection electrode 8 are laminated on the measurement chamber 12 side, and the detection electrode 8 is placed on the sheet 22.
Protective layer 10 for protecting the and a sheet 23 that surrounds the protective layer 10 with the same thickness as that, and further decomposes the high temperature decomposing substance 13 that occupies the space of the measurement chamber 12 and the high temperature decomposing material with the same thickness. Substance 13
The sheets 24 surrounding the sheet are laminated so that the laminated surface of the zirconia sheet 7 on the measurement chamber 12 side is flush.

On the other hand, the laminated surface of the zirconia sheet 14 constituting the oxygen pump section 11 on the measurement chamber 12 side is flush with the laminated surfaces of the zirconia sheet 7 by the sheets 25 and 26.

By laminating and firing the substrate 1, the flat plate 4, and the zirconia sheets 7 and 14 with the respective laminating surfaces being flush with each other at a predetermined pressure, the laminating pressure becomes uniform, so that after firing, No peeling occurs between the laminated surfaces, and the space in the measurement chamber 12 is not collapsed by the laminating pressure. The space of the measurement chamber 12 is formed by burning the high-temperature decomposable substance 13 by the heat of lamination firing as shown in FIG.

In this example, since the substrate 1, the flat plate 4, and the zirconia sheets 7 and 14 are all formed of zirconia,
The sheets 20 to 26 for making the laminating surfaces flush with each other were made of zirconia so that the laminating could be performed well.

<Effects of the Invention> As described above, according to the present invention, the stacking pressure is uniformly applied during stacking of the oxygen sensor, and peeling of the stacking surface and collapse of the measurement chamber space can be prevented in advance. Has the effect of becoming.

[Brief description of drawings]

FIG. 1 is an exploded cross-sectional view of an oxygen sensor according to an embodiment of the present invention before stacking, FIG. 2 is a cross-sectional view of the oxygen sensor according to the above embodiment, and FIG. FIG. 4 is a sectional exploded view of the oxygen sensor in the conventional example. 6 ... Oxygen concentration detector, 7,14 ... Zirconia sheet, 8,
9 …… Detection electrode, 11 …… Oxygen pump part, 12 …… Measuring room, 1
3 …… High temperature decomposition material, 15,16 …… Pump electrode, 20〜26 ……
Sheet

Claims (1)

[Claims] 1. Oxygen formed by providing a pair of detection electrodes on both sides of an oxygen ion conductive fixed electrolyte to form an oxygen concentration detection section, and by providing a pair of pump electrodes on both sides of an oxygen ion conductive solid electrolyte. An oxygen sensor for an internal combustion engine in which a pump section is stacked above the oxygen concentration detecting section through a measurement chamber space into which engine exhaust gas is introduced, and the non-measuring chamber side of the oxygen concentration detecting section is brought into contact with the atmosphere. A method for manufacturing an oxygen ion conductive solid which forms a sheet-shaped high-temperature decomposing substance that occupies the measurement chamber space between the oxygen concentration detection unit and the oxygen pump unit, and forms the oxygen concentration detection unit. At least two electrodes between an electrolyte and an oxygen ion-conducting solid electrolyte forming the oxygen pump, and a sheet having the same thickness as each of the laminates containing the high-temperature decomposable substance are provided around each of them. Layers, and a manufacturing method for an internal combustion engine oxygen sensor forming the measurement chamber space by burning out the pyrolysis material by heat during baking after lamination.