JPH0648258B2 - Oxygen concentration detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oxygen concentration detection device used for measuring the amount of oxygen contained in exhaust gas of an internal combustion engine for an automobile, for example.

[Prior Art] In an internal combustion engine, for example, in order to set the fuel injection amount to an appropriate value, the amount of oxygen contained in the exhaust gas is detected and the relationship between the amount of fuel and the amount of air in the combustion chamber of the engine is set to an appropriate value. The air-fuel ratio control set to the value is executed.

In order to execute such air-fuel ratio control, an oxygen concentration sensor is set in the exhaust pipe portion of the internal combustion engine, and the fuel injection amount etc. is corrected and calculated based on the detection signal from this sensor. is there.

As such an oxygen concentration detector, Y ₂ O ₃ , Yb
A detection element made of a solid electrolyte substance made of a ZrO ₂ -based oxygen ion conductor doped with ₂ O ₃ or the like is used. For example, the cup-shaped detection unit is configured by the solid electrolyte material, the electrode layer is formed on the inner surface and the outer surface of the cup-shaped solid electrolyte material, and the atmosphere is the standard in the inner hollow portion. It is designed to be guided as a gas atmosphere. In this case, the solid electrolyte substance portion is heated by the heater so that the oxygen concentration can be effectively detected.

However, in such a configuration, since it is necessary to form the cup-shaped detection portion by the solid electrolyte substance,
The manufacturing process tends to be complicated, and it is difficult to make the mechanical strength sufficient. Then, the structure of the heater portion becomes more complicated.

In consideration of such a point, for example, Japanese Patent Laid-Open No. Sho 55
A detecting element as shown in Japanese Patent No. 125548 has been considered. That is, a heater, electrodes, etc. are laminated and integrated on both sides of a plate-shaped solid electrolyte, and an air inlet is further laminated on the surface portion of this plate-shaped detection element. It is what However, in the case of the detection element configured in a laminated type including the atmosphere introduction port, since the shape thereof is a plate shape, the directionality with respect to the detection gas comes to appear remarkably. Further, since the shape is plate-like, it is difficult to make the assembly structure sufficient. Furthermore, since the heater is laminated on the both sides of the plate-shaped solid electrolyte together with the inner and outer electrodes, it is necessary to laminate a plurality of insulating layers at the same time for their mutual electrical insulation. As a result, the structure of this detection element becomes complicated.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and has a mechanical strength capable of sufficiently withstanding mechanical vibration generated in an internal combustion engine. In addition to being sufficient, the structure is sufficiently simplified to improve the directionality of gas contact, and the assembling property is also good,
For example, it is an object of the present invention to provide an oxygen concentration detecting device that can be effectively used for measuring the oxygen content in the exhaust gas of an automobile internal combustion engine.

[Means for Solving the Problems] That is, in the oxygen concentration detecting device according to the present invention, a cylindrical center shaft whose tip is closed by an insulator is prepared, and a side surface portion close to the tip end of the center shaft is provided. To form an opening. Then, an oxygen detection element made of a plate-shaped solid electrolyte having electrodes formed on both surfaces is fitted and set in the opening portion. A sheet member made of an insulating material is wound around the outer periphery of the center shaft, and an opening is formed in the sheet member so as to correspond to the detection element portion. The sheet member is further connected to the electrode portion of the detection element. The lead wire and the heater wire are formed by printing or the like, and the heater is set in the state where the sheet member is wound around the center shaft, and the lead wire for leading out the detection element is formed.

[Operation] In the oxygen concentration detection device configured as described above,
The inner hollow portion of the center shaft is made to communicate with the atmosphere, so that one surface of the detecting element portion made of a solid electrolyte is set in contact with the reference gas atmosphere by the atmosphere, and the other surface is through the opening of the sheet member. And come into contact with the measurement gas atmosphere. Therefore, an electric signal corresponding to the amount of oxygen contained in the measurement gas is derived via the lead wire. Further, the heater for heating the lead wire and the solid electrolyte portion is simply formed on the sheet member by printing or the like, and is easily integrated with the center shaft, so that the structure is sufficiently simple. Not only is it made into a cylinder, but because it is configured in a cylindrical shape,
The directionality against gas contact is lost, and the assembling workability can be improved.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows the structure of the detection mechanism part in the oxygen concentration detection device, which is provided with an inner shaft 11 having a cylindrical tubular shape. This center axis
11 made of a substrate of the detection mechanism, for example, Al ₂ O
₃ and Si ₃ N ₄ etc., it is composed of an electrical insulator, and as shown in FIG. 2 and shown, it has a hollow portion 12 having a base end portion which is an atmospheric air inlet opening, and its front end portion is sealed. It is like this. Further, on the outer peripheral portion of the base end portion of the inner shaft 11, for example, four grooves 131 to 134 which form lead-out portions for lead wires are formed in parallel with the axis.

A hollow portion is provided on the outer periphery of the portion near the tip of the center shaft 11.
An opening 14 is formed so as to penetrate the opening 12, and a holding portion 141 having a step is formed on the outer peripheral edge portion of the opening 14. And the holding portion of this opening 14
The oxygen concentration detecting element 15 is fitted in the 141 to be set.

FIG. 3 is an enlarged view of the oxygen concentration detecting element 15, which is composed of a plate-shaped solid electrolyte 151. The solid electrolyte 151 is, for example, Y ₂ O ₃ or Yb.
_It is made of a ZrO ₂ -based oxygen ion conductor material doped with ₂ O _3, etc., and is fitted into the holding portion 141 of the opening 14 formed in the central shaft 11 so as to be curved along the cylindrical surface of the central shaft 11. It will be set together. The first and second electrodes 152 and 153 are formed on both surfaces of the plate-shaped solid electrolyte 151 by vapor deposition, printing or the like.
, 153 from each one towards the edge 154
And 155 are formed.

Here, each of the electrodes 152 and 153 is formed as a porous electrode made of platinum, and oxygen contained in the gas existing on both surfaces of the electrodes is guided to the solid electrolyte 151. That is, the oxygen concentration detection element 15 is configured as an electrochemical cell that functions as a battery that operates depending on the concentration of oxygen.

A sheet member 16 is wound around the outer periphery of the center shaft 11. FIG. 4 shows the sheet member 16 taken out and shown. The sheet member 161, which is made of the same material as the center rod 11, is used as a base. This sheet 161,
A through hole 162 is formed corresponding to the position of the opening 14 formed in the center shaft 11. The heater is formed of a thin film made of Pt or W so as to surround the through hole 162.
163 is formed. In addition, on the surface of the sheet 161, there is P from the through hole 162 portion toward the base end direction of the center shaft 11.
First and second lead wires 164 and 165 formed by t or W are formed. The lead wires 164 and 165 are adapted to be guided to the grooves 131 and 132 formed in the base end portion of the center shaft 11, respectively.

That is, in a state where the oxygen concentration detecting element 15 is fitted and set in the opening 14 of the inner shaft 11, the sheet member 16 is wound around the outer periphery of the inner shaft 11 with the surface on which the heater 163 and the like are formed as the inner surface. Then, the oxygen concentration detecting element 15 is fixedly held by the holding member 141 of the opening 14 by the sheet member 16. In this case, the oxygen concentration detecting element 15 is set to face the through hole 162 of the sheet member 16, and the second electrode 153 side of the detecting element 16 is exposed to the outside through the through hole 162.

In this state, the first lead wire 164 formed on the sheet 161 has a solid electrolyte 151 as shown in FIG.
Is connected to a lead-out electrode 154 formed so as to fall to the side surface of the second lead wire 16 and
The electrode 5 is connected to the lead electrode 155 by contact.
Then, the electrodes 152 and 153 of the oxygen concentration detecting element 15 are
Are led out from the grooves 131 and 132 of the center shaft 11.

Further, lead wires 166 and 167 from the heater 162 are formed on the seat 161 in parallel with the lead wires 164 and 165, and are guided to the grooves 133 and 134 of the center shaft 11 so as to be led out. There is.

In the detection mechanism section configured as described above, first, the inner shaft 11 is molded by a predetermined material, and the oxygen concentration detection element 15 is formed by the solid electrolyte 151 on which the inner shaft 11 is a substrate and electrodes and the like are formed by screen printing or the like. Similarly, by screen printing etc., heater 163, lead wires 164 to 16
The sheet material 16 on which 7 is formed is aligned with each other, set around the center shaft 11 and set, and integrally fired. After that, it becomes a protective layer such as an electrode by plasma spraying or the like. Al ₂ O ₃ or Mg O.Al
A porous protective layer 17 formed by a ceramic coating layer made of ₂ O ₃ spinel is formed.

The ceramic coating layer that constitutes the protective layer 17 is
The porosity can be adjusted as appropriate, and the porosity enables selective use as a potentiometric or polarometric graphic sensor.

FIG. 5 shows the configuration of a detection device configured using the oxygen concentration detection mechanism configured as described above.
The cylindrical detection mechanism configured with 11 as a base is set in a hollow portion formed in the central shaft portion of the support housing 20. This cylindrical detection mechanism consists of rings 21, 22 and talc 2
3, and the packing 24 holds and sets it in the hollow portion of the housing 20, and particularly the packing 24 allows the front end portion and the base end portion of the detection mechanism of the housing 20 to be separated in an airtight state.

The tip of the detection mechanism in which the oxygen concentration detecting element 15 is set is set so as to project from the housing 20, and the housing 20 surrounds the tip of the detection mechanism. A cover element 25 is provided. The cover element 25 is formed with a large number of through holes, and the surrounding gas penetrates through the through holes to the vicinity of the tip detection portion of the detection mechanism, and passes through the protective layer 17 of the detection mechanism. The gas is brought into contact with the detection element 15.

On the opposite side of the housing 20 from the cover element 25,
The tubular cover protection 26 is attached and set by brazing or the like. And this cover protection 26
The central axis 11 of the detection mechanism is set in the central axis part of the. A holder 27 is appropriately interposed between the center shaft 11 and the cover protection 26 so that the holder 27 holds and sets the detection mechanism.

The lead connection 28 is the above-mentioned cover protection 26.
It is formed inside an insulator 29 that is set coaxially with the holder 27, and the position of this insulator 29 is fixed by a rubber bush 30. In this case, the insulator 29 and the rubber bush 30 are configured to have air permeability, and the atmosphere prevents the rubber bush 30 and the insulator 29 from reaching the atmosphere.
Through, is guided to the base end opening of the center axis 11 of the oxygen concentration detection mechanism, on the inner surface portion of the oxygen concentration detection element 15 of this center axis 11,
The reference gas atmosphere by the atmosphere is set.

A lead wire 32 is connected to the lead connection 28. The lead wire 32 is a groove 131 to 134 formed in the base end portion of the center shaft 11, and the lead wire from the detection element 15 and a heater. Connected to the lead wire from. The lead connection 28 is led out to the outside through a wire lead 33 that is set to penetrate the rubber bush 30.

A flange 34 is integrally attached to the holding housing 20. The flange 34 is not shown in the figure, and is used for mounting the detecting device on an exhaust pipe of an internal combustion engine, for example. . And housing 20
The cover element 25 part of is set in the above exhaust pipe,
The oxygen concentration detection element 15 part at the tip of the oxygen concentration detection mechanism,
The position is set in the exhaust gas.

That is, in the oxygen concentration detecting device configured as described above, the oxygen concentration detecting element 15 portion of the oxygen concentration detecting mechanism is set in the exhaust gas in a state where the oxygen concentration detecting device is attached and set to the exhaust pipe of the internal combustion engine. As a result, the outer surface of the detection element 15 comes into contact with the gas to be measured, that is, the exhaust gas, via the protective surface 17 and the electrode 152.
Then, the inner surface of the detection element 15 comes into contact with the reference gas set in the hollow portion of the center shaft 11 via the electrode 153. Therefore, an electric signal corresponding to the amount of oxygen contained in the exhaust gas can be obtained between the electrodes 152 and 153 formed on both surfaces of the oxygen concentration detecting element 15. In this case, the heater 163 is set to heat the detecting element 15 portion, and the oxygen concentration measuring operation with high accuracy can be executed.

6 and 7 show another embodiment,
In this embodiment, as shown in FIG. 6 (A), the oxygen concentration detecting element 15 is composed of a solid electrolyte 41 formed so as to wind around a half circumference of the outer peripheral portion of the center shaft 11. And the opening of the central shaft 11 in this solid electrolyte 41.
The first electrode 42 is formed on the portion corresponding to 14, and the second electrode 43 is formed on the opposite surface. Then, from these electrodes 42 and 43, the solid electrolyte
The lead wires 44 and 45 are formed by printing toward the base end portion of the center shaft 11 of 41.

Further, as shown in FIG. 6 (B), a sheet 51 made of the same material as that of the center shaft 11 which surrounds the remaining half circumference of the center shaft 11 is used.
The heater 52 and the lead wires 53 and 54 are formed by printing on the surface.

Then, as shown in FIG. 7, the solid electrolyte 41 and the sheet 51 shown in FIGS.
Around the outer circumference of each of the above, one half turn is wound and the whole is baked.

[Effects of the Invention] As described above, in the oxygen concentration detecting device according to the present invention, the center shaft made of an insulating material is used as the base body, and the center shaft is mounted and wound around the center shaft. The member forming the solid electrolyte and the electrode attached to the solid electrolyte.
Therefore, the assembly structure is very simple because there is no laminated structure or the like, and the mechanical strength can be sufficient. Further, since the shape is basically based on the cylindrical shape, its directionality is not particularly limited.

[Brief description of drawings]

FIG. 1 shows a detection mechanism portion of an oxygen concentration detection device according to an embodiment of the present invention. (A) is a sectional view, (B) is a side view, and FIG. (A) is a partial cross-sectional side view, (B) is a cross-sectional view taken along the line bb of (A), and FIG. 3 is a similar oxygen concentration detection element. A plan view, (B) is a back view, (C) is a cross-sectional view, FIG. 4 is a view showing the same sheet member, and FIG. 5 is a cross-sectional configuration diagram for explaining an oxygen concentration detection device using the above detection mechanism. 6A and 6B show another embodiment of the present invention. FIG. 6A is a diagram showing a detection element portion, FIG. 6B is a diagram showing a sheet member portion, and FIGS. 7A and 7B are diagrams showing this embodiment. It is a figure explaining the structure of a detection mechanism part. 11 …… Center shaft, 12 …… Hollow part, 131-134 …… Groove, 14 ……
Aperture, 15 …… Oxygen concentration detection element, 151 …… Solid electrolyte,
152, 153 ... electrodes, 16 ... sheet member, 161 ... sheet, 162 ... through hole, 163 ... heater, 164, 165 ...
Lead wire, 17 ... Protective layer.

Claims (2)

[Claims] 1. A center rod made of an insulating material, which is formed in a hollow cylindrical shape with a closed tip, and an opening formed in a peripheral portion of the center rod near the tip portion so as to communicate with the hollow portion. An oxygen concentration detection element formed of a plate-shaped solid electrolyte substance having electrodes formed on both surfaces corresponding to the hollow portion and the outer portion of the center rod, respectively, which are formed so as to be fitted and set in the opening, A sheet member in which an electrode lead wire including a heater wiring made of a metal thin film is formed on an insulator sheet which is wound around the outer periphery of the center shaft and has an opening corresponding to the oxygen concentration detecting element portion, and the sheet member A protective layer made of an insulating material having a vent hole formed to cover the outer peripheral portion of the tip of the center rod including the opening, and the center shaft and the sheet member are integrally fired, and the oxygen Degrees both surfaces respectively having electrodes for detection member, the reference gas atmosphere of the hollow portion of the center pole, and the oxygen concentration detecting device is characterized in that so as to be contacted respectively to the measurement gas atmosphere via the protective layer. 2. The sheet member is divided and set into a first and a second sheet member along a line along the axis of the center shaft, and the first sheet member has the oxygen concentration detecting element portion. Along with the corresponding openings, first and second lead wires are formed so as to be connected to the electrodes on both sides of the oxygen concentration detecting element set in the openings, respectively, and a heater and this heater are formed on the second sheet member. The oxygen concentration detection device according to claim 1, wherein each lead wire led out from the heater is formed.