JPS6367135B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas sensor using an oxygen ion conductive solid electrolyte for measuring the oxygen concentration in the exhaust gas of an internal combustion engine or after the exhaust gas has reached a chemical equilibrium state.

A known exhaust gas sensor of this type is a solid body that has a bottom and has a reference gas side electrode in contact with the atmosphere and a fixed gas side electrode in contact with the exhaust gas attached to the inner and outer surfaces of the bottom side, respectively. an electrolyte tube, a metal housing tube that grips the solid electrolyte tube so that its bottom outer surface is exposed to exhaust gas, and a metal housing tube that extends coaxially from one end of the housing tube to hold the solid electrolyte tube so that the outer surface of the solid electrolyte tube is exposed to exhaust gas. A protection tube device is provided, which includes a tube arranged to surround the bottom side, and the tube is formed with an opening for introducing the exhaust gas flow in a tangential direction. This protection tube device is designed to prevent the porous or porous membrane electrode covered on the bottom outer surface of the solid electrolyte tube from being directly hit by high-temperature exhaust gas shock flow or being bombarded by fine particles in exhaust gas. It is. One such protection tube device includes 1
The side wall of the tube is cut along a line segment that extends long in the axial direction, and the wall portion on one side of the line segment is pushed inward along the line segment to create a structure that is integral with the tube wall. There is a device that has a large number of axially long openings with deflection parts in the circumferential direction, but with this structure, it is inevitable that the electrolyte tube will be exposed from directly above the opening. As a result of experiments, some of the high-speed exhaust gas directly hits the surface of the solid electrolyte tube and tends to damage the thin platinum electrode on the surface, and it is especially useful when gasoline containing lead is used or in engines with a lot of oil leakage. In this case, deposits such as lead oxide mixed in the exhaust gas adhere to porous or porous electrodes, causing catalyst poisoning or clogging, and a large deterioration of the sensor's output performance occurs at a relatively early stage. It turns out that there is a drawback that it can be stored away. Another disadvantage of this structure is that it is difficult to make the opening larger because the axially long wall portion between the openings is likely to be deformed. Another method is to coaxially connect two metal tubes with different diameters with a large number of axial slit holes or round holes on the side wall of the metal protection tube so that the slits or holes of the two tubes do not overlap. However, it has been found that this structure has the drawback that the flow of exhaust gas around the solid electrolyte tube is not smooth, resulting in poor activation performance.

The present invention eliminates the drawbacks of the conventional exhaust gas sensor, and is resistant to damage caused by lead, etc., and has little resistance when exhaust gas flows in and out, allowing smooth flow and increasing the temperature of the main part of the solid electrolyte pipe. The present invention aims to provide a novel exhaust gas sensor that is quick to activate, that is, has excellent activation performance.

That is, the exhaust gas sensor of the present invention has a bottom, and a solid electrolyte having a reference oxygen source side electrode in contact with a reference oxygen source and a measured gas side electrode in contact with exhaust gas are deposited on the inner and outer surfaces of the bottom side, respectively. a metal housing tube that grips the solid electrolyte tube so that its bottom outer surface is exposed to exhaust gas; and a metal housing tube that extends coaxially from one end of the housing tube to the bottom of the solid electrolyte tube. In an exhaust gas sensor for an internal combustion engine, the protection tube device is provided so as to surround the side and has an opening formed in the side wall to deflect and introduce the exhaust gas flow, and the protection tube device is long in the axial direction. A pipe in which a number of holes are bored in the side wall, and a pipe connected to the pipe, extending long inside the pipe along the holes, sloping in the same direction in the width direction of the holes, and also having a width area of the holes. It is characterized by being equipped with a deflection plate that is wide enough to cover a wider area.

The present invention will be described below based on embodiments and with reference to the drawings. Reference numeral 1 denotes an oxygen ion conductive solid electrolyte tube having a flange 1a and a bottom 1b.As the solid electrolyte, a so-called partially stabilized zirconium oxide sintered body containing, for example, itria as a stabilizing oxide is preferably used. 1c is a reference gas side electrode formed of a porous platinum layer deposited on the inner surface of the solid electrolyte tube 1, and 1d is a reference gas side electrode formed of a porous platinum layer deposited on the outer surface of the solid electrolyte tube from the flange 1a to the bottom side. For the measuring gas side electrode, it is preferable to apply, for example, a method of chemically plating platinum, electroplating, and then heat treatment to form a large number of large holes and adhere firmly. In this case, it is preferable that the surface of the portion of the solid electrolyte tube to which the gas-to-be-measured electrode is adhered is made into a strongly uneven surface in advance. Reference numeral 1e designates an electrode protection layer made of a porous ceramic layer, which is made by spraying heat-resistant ceramic powder such as spinel at high temperature over the electrode 1d on the gas side to be measured by flame spraying or the like to firmly adhere to the surface of the solid electrolyte tube. Reference numeral 2 denotes a metal housing tube having a tubular shape as a whole, and has an annular shelf section 2a projecting toward the center on its inner surface, to which the collar section 1a of the solid electrolyte tube is directly or indirectly connected. The device is gripped by employing a known technique in a state where the two are brought into contact with each other. At this time, the housing tube 2 is brought into electrical contact with the gas-to-be-measured electrode 1d at the shelf portion 2a, thereby forming one terminal of the exhaust gas sensor. Reference numeral 2b denotes a screw carved on the outer periphery of the end of the housing tube, which is tightened into a screw hole provided on the side of the exhaust gas tube 3, so that the bottom outer surface of the solid electrolyte tube is exposed to the exhaust gas. 1f is solid electrolyte tube 1
The housing end 2c is integrally joined by crimping the housing end 2c via a filling sealing material 4 such as talc at the upper part of the housing. Reference numeral 5 denotes an external cap that is inserted into the housing tube 2 with gaps and is integrally joined by spot welding 5a at several locations around the circumference, and the reference gas side electrode 1c of the solid electrolyte tube 1 prevents the inflow of water through the gaps. placed in an atmosphere that communicates with the atmosphere in a protected manner. Reference numeral 6 denotes an internal cap which is placed over the upper part 1f of the solid electrolyte tube 1 and has a window 6a communicating with the atmosphere, and is insulatively held by the external cap 5 with a Teflon (registered trademark) material 7 interposed therebetween. Reference numeral 8 denotes a coiled internal lead wire connected to the reference gas side electrode 1c of the solid electrolyte tube 1, the upper part of which is held by the internal cap 6. Reference numeral 9 denotes an insulated external lead wire that is connected to the internal lead wire 8 and is insulatively held by the external cap 5 via silicone rubber 10, and the external lead wire is strengthened by tightening the outer periphery of the external cap. Fixed. 11 is a protection tube device made of heat-resistant metal such as stainless steel for controlling the collision of the exhaust gas flow with the outer surface of the solid electrolyte tube, and is disposed so as to extend coaxially from the end of the housing tube 2. However, here, a tube 11 made of thin stainless steel with a deep pattern and a bottom 11a and a fitting part 11b at the open end is provided, and the fitting part 11b is fitted into the small-diameter end 2d of the housing tube. and fixed by welding etc. as necessary. Reference numeral 12 designates exhaust gas introduction holes formed in the form of a large number of axially long slits bored on the side wall 11c of the pipe 11. This slit is made to be at least 3 to 4 times longer in the axial direction than the width, and
tiers or 2 to 3 tiers arranged at slight intervals;
In this example, the holes are drilled in two stages, and a plurality of rows in this example are arranged equally in eight rows in the circumferential direction. Note that the number of stages in the axial direction is appropriately determined from the viewpoint of the size of the hole and maintaining the strength of the wall surface. To give a specific example of the dimensions of the slit hole, if the protection tube outside diameter is 12.5mm and the inside diameter is 11.5mm,
The slit width is 2 mm, the length is 7.5 mm, and the slit spacing in the axial direction is 2 mm. Reference numeral 13 denotes a deflection plate which is separate from the tube 11 and connected to it, and which extends long inside the tube 11 along the longitudinal direction of the hole 12 and in the width direction of the hole 12, that is, the deflection plate 13. The outer surface of the solid electrolyte tube is tilted in the same direction with respect to the tangential direction of the tube at the portion 12, and extends over a wider area than the width W of the hole 12, that is, when viewed from a distance directly above the hole, the outer surface of the solid electrolyte tube is It should be wide enough so that it cannot be seen. In this embodiment, the deflection plate 13
are two axially aligned slit holes 12,
12, and a plurality of the long plate pieces 13a are connected to a common substantially circular central connecting piece 13d (Fig. 4) on the distal end side of the tube 11. The integrated long plate pieces 13a are bent at a substantially right angle to the central connecting piece 13d, and the integrated long plate pieces 13a are in contact with each other in the bottomed pipe 11. It is housed in the housing and fixed by spot welding at a few places as appropriate. Further, the deflecting plate 13 is provided with an inclined portion 13b and a narrow reinforcing portion 13c bent with respect to the inclined portion 13b. In addition, the widthwise ends of the deflection plate should extend sufficiently so that the outer surface of the solid electrolyte tube cannot be seen from any direction from the hole 12. In other words, the widthwise end of the deflection plate should extend sufficiently so that the outer surface of the solid electrolyte tube cannot be seen from any direction. It is more advantageous for the end to pass through one end of the hole 12 in the width direction and reach the line A (FIG. 3) that is in contact with the outer surface of the solid electrolyte tube in terms of resistance to damage from deposits such as lead. , in this embodiment. In addition, the inclined portion 13b of the deflection plate is aligned in the width direction of the hole, that is, in the tangential direction of the pipe at the hole (third direction).
The larger the angle θ with the direction of the deflection plate, the more advantageous it is for introducing the exhaust gas. However, it is necessary to ensure a flow path for the introduced exhaust gas to flow smoothly around the solid electrolyte tube. The inner end is preferably located approximately midway between the inner surface of the tube 11 and the outer surface of the solid electrolyte tube 1, and is subject to limitations from this point. On the other hand, by making the outer diameter of the solid electrolyte tube smaller, it not only improves the temperature rise of the solid electrolyte tube itself, but also increases the angle θ, which improves the flow of exhaust gas and improves the activation performance of the sensor. It is also advantageous because it can also enhance resistance to damage caused by lead and the like. In this example, the solid electrolyte tube outer diameter is 4.5 mm.
The angle θ is approximately 30°. In addition, the above-mentioned long plate piece assembly (Fig. 4)
is advantageously produced as follows. That is, first, the one shown in FIG. 5, which is the expanded form of the deflection plate, is manufactured. That is, a long plate piece 13a having a predetermined width and a predetermined length, for example, a length slightly shorter than the depth of the tube 11, is attached around a substantially circular central connecting piece 13d (FIG. 5) having a diameter slightly smaller than the inner diameter of the protective tube 11. A number equal to the number of introducing holes arranged in the circumferential direction of the part (Fig. 5) are press-formed in the same plane as the center plane connecting piece part and radially arranged around this, or at the same time or before and after. Then, an inclined portion is press-formed on each long plate piece except for one side edge in the width direction and the end portion in the length direction. 13e is a joint. The product thus produced is placed into a mold with guide grooves for positioning each of the long plate pieces, and the long plate pieces are erected at right angles to the central connecting piece.

Table 1 shows the results of an evaluation test conducted using an actual device for the sensor according to the embodiment of the present invention. The sensors used in this test are shown in Table 1, and are No. 1 (product A of the present invention).
No. 2 is the sensor of the above embodiment, in which the outer surface of the solid electrolyte tube is not exposed at all through the hole, and No. 2 (product B of the present invention) is a deflection plate with a wide width exceeding the width of the hole, but the outer surface of the solid electrolyte tube is not exposed through the hole. No. 3 (outside the range) differs only from the previous two in that the width of the deflection plate does not reach the width of the hole. The activation evaluation test in the table was conducted until the sensor output reached 700 mV when the sensor was attached to the exhaust pipe and the exhaust gas with the solid electrolyte tube tip temperature of sensor No. 1 above was 400°C and the air overload factor λ = 0.9. This is the value measured using a 1MΩ recorder.
The lead toxicity evaluation test used gasoline with a lead content of 1.5 mg/gallon, and the temperature at the tip of sensor No. 1 was 500°C.
This is the value obtained by measuring the responsiveness of the sensor after 30 hours of lead-encrusted operation under these conditions. Responsiveness is determined by sensor No.
It is shown as the time it takes for the sensor output to go from 600 mV to 300 mV when the sensor is placed in a gas at 600°C with a tip temperature of 1 and changed stepwise from λ = 0.9 to λ = 1.1. If a lead compound adheres to the porous electrode and causes clogging, the output response to changes in λ deteriorates. Although No. 1 and No. 2, which are products of the present invention, have almost no difference in activation performance compared to No. 3, their resistance to lead damage is significantly superior. This shows that there was no change in responsiveness before and after the lead deposition operation, indicating that the test was excellent. Although the conventional product No. 4 has good lead damage resistance, it has been shown that the activation performance is significantly inferior.

In the above embodiment, the end of the deflection plate 13 of the protective tube device on the inner surface side of the tube was assembled in contact with the inner surface of the tube, but a small gap may be formed between them. There is no difference in the effects of the present invention,
Further, in the above embodiment, the deflection plate is provided as an assembly (see FIG. 4), but this has the advantage that the protective tube device can be manufactured easily and accurately, but is not limited to this. The strip-shaped deflection plate 131 shown in FIG. 6 includes an inclined portion 131b,
It is also possible to manufacture the reinforcing portion 131c and the joining portions 131d and 131e by individually press-forming plate materials and joining them individually to the inner surface of the tube. In any case, since the deflection plate is provided inside the tube separately from the tube, the opening of the tube can be effectively utilized for introducing exhaust gas, and a sensor with good activation performance can be obtained. Furthermore, the inclined surface of the deflection plate may have a slight curvature as long as it does not interfere with the introduction of exhaust gas and the circulating flow.

As detailed above, in the exhaust gas sensor for an internal combustion engine of the present invention, a deflection plate for circulating exhaust gas in a constant circumferential direction, which is separate from the pipe in which the exhaust gas introduction hole of the protection tube device is formed, is provided from the width area of the introduction hole. Since they are arranged over a wide area, the resistance to the inflow and outflow of exhaust gas is reduced, and the initial activation performance of the sensor is excellent. This has the great effect of significantly suppressing catalyst poisoning or clogging and significantly improving the durability of the output performance of the sensor.

[Brief explanation of drawings]

FIG. 1 is a half-cut side view of an exhaust gas sensor according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line A--A in FIG.
The figure is an enlarged view of the deflection plate part, Figure 4 is a view showing the deflection plate inserted into the protection tube, A is an enlarged side view, B is a plan view, Figure 5 is a developed view of Figure 4, and Figure 6 is a diagram showing the deflection plate inserted into the protection tube. In the diagrams showing other embodiments of the deflection plate, A is an enlarged side view and B is B of A.
- This is a cross-sectional view taken along line B. 1...Solid electrolyte tube, 2...Housing tube, 11...
Protection tube, 12... introduction hole, 13... deflection plate, 13a...
Long plate piece, 13b, 131b...slanted part, 13c, 1
31c...Reinforcement part, 13d...Center connecting piece.

Claims (1)

[Scope of Claims] 1. A solid electrolyte tube having a bottom and having a reference oxygen source side electrode in contact with a reference oxygen source and a measured gas side electrode in contact with exhaust gas attached to the inner and outer surfaces of the bottom side, respectively. , a metal housing tube that grips the solid electrolyte tube so that its bottom outer surface is exposed to exhaust gas; and a metal housing tube that extends coaxially from one end of the housing tube to hold the bottom side of the solid electrolyte tube. In an exhaust gas sensor for an internal combustion engine, the protection tube device is equipped with a protection tube device that is provided so as to surround the device and has an opening formed in a side wall to deflect and introduce the exhaust gas flow. A pipe having a large number of holes bored in the side wall, and a pipe connected to the pipe, extending long inside the pipe along the hole, sloping in the same direction in the width direction of the hole, and also being larger than the width of the hole. An exhaust gas separator for an internal combustion engine, characterized in that it is equipped with a deflection plate that is wide enough to cover a wide area. 2. The exhaust gas sensor according to claim 1, wherein the outer surface of the solid electrolyte tube is blocked by a deflection plate and cannot be seen when looking inside from the hole in the tube. 3. The exhaust gas sensor for an internal combustion engine according to claim 1 or 2, wherein the free end of the deflection plate is located at a position approximately halfway between the inner diameter of the tube and the outer diameter of the solid electrolyte tube. 4. The exhaust gas sensor for an internal combustion engine according to claim 1 or 2, wherein the outer diameter of the portion of the solid electrolyte tube surrounded by the tube is 1/2 or less of the inner diameter of the tube. 5. The holes are one or more slit-shaped holes extending in a line in the axial direction, and are arranged in multiple rows in the circumferential direction of the tube, and the deflection plate has one or more slit-like holes extending in a line in the axial direction. It is formed of long plate pieces that extend one by one, and each of the long plate pieces is continuously integrated with a common central connecting piece on the distal end side of the tube, and is bent approximately at right angles to the central connecting piece. The exhaust gas sensor for an internal combustion engine according to claim 1 or 2, wherein the exhaust gas sensor is curved.