JPH11183425A - Oxygen concentration detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten detection accuracy in an oxygen concentration detector with a detecting element covered with an inner cover and an outer cover. SOLUTION: An oxygen concentration detector is provided with an inner cover 31 with a bottom pat 311 opposed to the tip 10a of a detecting element 10 and an outer cover 32 with a bottom part 321 opposed to the bottom part 311 of the inner cover 31. In the outer cover 32, a gas passage hole 23 is provided only for the bottom part 321. The bottom part 311 of the inner cover 31 is formed in the shape of a hemisphere with an inclined surface 311c inclined in a direction distancing from the inner side surface of the outer cover 32, and a gas passage hole 21 is provided at a part of the inclined surface 311c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen concentration detector suitable for detecting oxygen concentration in intake gas or exhaust gas of an engine.

[0002]

2. Description of the Related Art Conventionally, as an oxygen concentration detector for detecting the oxygen concentration in intake gas or exhaust gas of an engine,
The one shown in FIG. 11A has been proposed. The detector 1 includes a detection element 10 and an electric heater 20 for heating the detection element 10 to an activation temperature (for example, 650 ° C.) or higher.
An element cover 3 is arranged to cover the side.

[0003] The element cover 3 comprises an inner cover 31 and an outer cover 32 having a substantially cup shape. These two covers 31 and 32 protect the detection element 10 from water and poisons (lead compounds and the like) mixed in the gas, and also detect the detection element 10 heated by the electric heater 20.
Plays a role in keeping warm. In addition, both covers 3
The gas passing holes 21,
23 is formed, and the side portions 3 of the two covers 31 and 32 are formed.
A plurality (for example, four) of gas passage holes 22 and 24 are provided at equal intervals in the circumferential direction in the holes 12 and 322, and the gas passage holes 22 and 24 are formed in two rows at a predetermined distance in the axial direction. Have been. Bottom portions 311 and 3 of both covers 31 and 32
Reference numeral 21 denotes a planar shape, and the side portions 312 and 322 of the covers 31 and 32 have a cylindrical shape having the same diameter over the entire length in the axial direction.

Since the temperature of the gas is lower than the above-mentioned activation temperature (the temperature of the intake gas is about 80 to 140 ° C. and the temperature of the exhaust gas is about 100 to 500 ° C.), the heat retaining property of the detection element 10 is kept good. As shown in FIG.
3, 24 opening areas are being studied. That is, the gas passage holes 22 and 24 formed in the side portions 312 and 322 are
It has a small diameter of about 1.5 mm and a bottom 31
The gas passage holes 21 and 23 formed in 1,321 are small, having a diameter of about 2.0 mm.

[0005]

By the way, the conventional oxygen concentration detector 1 is usually applied to the engine of a gasoline-powered vehicle. When an attempt was made to apply the detector 1, it was confirmed that the detection accuracy of the oxygen concentration detector 1 was significantly deteriorated in a short period of time.

The following describes what the inventors have experimented, examined, and confirmed as to the cause of the deterioration of the detection accuracy of the oxygen concentration detector 1. First, usually, the detector 1 is arranged with respect to the gas passage so that the gas flows in a direction substantially perpendicular to the axial direction of the oxygen concentration detector 1 (a direction indicated by an arrow B in FIG. 11A). I have. On the other hand, in the above-described conventional technology, a plurality of (four) gas passage holes 24 are formed at equal intervals in the circumferential direction on the side portion 322 of the outer cover 32, and at least one of the gas passage holes 24 is It is arranged so as to face the gas flow. As a result, unburned substances (such as soot composed of carbon fine particles) contained in the gas are deposited around the outer peripheral portion of the gas passage hole 24 facing the gas flow.

Here, since the gas in a diesel engine vehicle contains a much larger amount of unburned substances than the gas in a gasoline engine vehicle, the unburned substance Also becomes very large. As a result, the area of the gas passage hole 24 facing the gas flow is greatly reduced or completely closed, so that it is difficult for the gas to be introduced into the outer cover 32, and the gas reaches the detection element 10. It becomes difficult to do. As a result, the detection accuracy of the oxygen concentration detector 1 decreases in a short period of time.

[0008] Of the unburned substances, those that have passed through the gas passage holes 24 and entered the inside of the outer cover 32 may be deposited on the surface of the inner cover 31 or may be deposited on the inner cover 3.
The intrusion enters the inside of the inner cover 31 through one passage hole 22. And, the low temperature of the inner cover 31 (about 300 ° C. or less)
Sometimes, when the unburned material is deposited on the surface of the inner cover 31, the unburned material is burned when the inner cover 31 becomes high temperature (about 300 ° C. or more). Becomes lower than the actual oxygen concentration. This also deteriorates the detection accuracy of the oxygen concentration detector 1.

Further, the unburned substances that have entered the inside of the inner cover 31 also accumulate on the surface of the detecting element 10, so that the detecting element 10 is deteriorated, which also deteriorates the detection accuracy of the oxygen concentration detector 1. I do. In order to enhance the detection accuracy of the oxygen concentration detector, the present applicant has disclosed that only the bottom portion 321 of the outer cover 32, which is arranged substantially parallel to the gas flow, as shown in FIG. The trial production of forming the passage hole 23 was examined. However, according to such a prototype, the main flow of gas from the gas passage hole 23 is indicated by an arrow X.
As described above, the unburned substance in the gas concentrates on the portion Y of the inner surface of the outer cover 32 that faces the bottom of the inner cover 31 because the unburned material tends to flow between the outer cover 32 and the inner cover 31. It was found to deposit.

[0010] The accumulation of unburned substances on the inner side surface Y of the outer cover 32 hinders the flow of gas into the inner side of the inner cover 31, which may deteriorate the detection accuracy of the oxygen concentration detector 1 in a short period of time. Become. The present invention has been made in view of the above points, and in an oxygen concentration detector in which a detection element is covered by an inner cover and an outer cover, a decrease in detection accuracy caused by unburned substances in gas is more accurately performed. The purpose is to be able to control.

[0011]

In order to achieve the above object, according to the first aspect of the present invention, a gas contact portion (11) of a detection element (10) for detecting an oxygen concentration in a gas is covered. An inner cover (31) to be arranged; and an outer cover (32) arranged outside the inner cover (31) and arranged to cover the inner cover (31). A gas passage hole (23) through which gas passes is provided only in a portion facing the bottom (311) of the inner cover (31), and the bottom (3) of the inner cover (31) is provided.
11) has at least a shape having an inclined surface (311c) inclined in a direction away from the inner surface of the outer cover (32), and includes a bottom portion (311) of the inner cover (31).
It is characterized in that a gas passage hole (21) through which gas passes is provided at a portion of the inclined surface (311c).

According to this, the gas passage hole (23) through which the gas passes is provided only in the portion of the outer cover (32) facing the bottom (311) of the inner cover (31), so that the gas passage is achieved. The holes (23) can be arranged parallel to the gas flow, so that the gas passage holes (24) are arranged opposite the gas flow, as in the prior art. There is no such a problem that the amount of unburned substance deposited on the peripheral portion increases in a short period of time, and the opening area of the gas passage hole (24) is significantly reduced or completely closed.

Further, in the inner cover (31), since the gas passage hole (21) is provided on the inclined surface (311c) inclined in a direction away from the inner surface of the outer cover (32), the gas passage hole (21) is provided. The space between the portion and the inner surface of the outer cover (32) is increased. Therefore, the outer cover (3
Even when unburned material is deposited on the inner surface of (2), this unburned material deposited portion and the gas passage holes (2
1) can be kept large. As a result, the open state of the gas passage hole (21) can be more reliably maintained, and a decrease in detection accuracy due to unburned substances in the gas can be accurately suppressed.

According to the second aspect of the present invention, the bottom (31) of the inner cover (31) of the outer cover (32) is provided.
The gas passage hole (2) through which gas passes
3) and a side portion (3) of the outer cover (32).
22), a gas passage hole (24) through which gas passes is provided only in a portion located on the downstream side of the gas flow in the mounted state, and the bottom portion (311) of the inner cover (31) is at least provided with the outer cover ( 32) having a slope (311c) inclined in a direction away from the inner surface of the inner cover (31), and a slope (311c) of the bottom (311) of the inner cover (31).
Is provided with a gas passage hole (21) through which gas passes.

According to this, since the outer cover (32) is provided with the gas passage hole (23) on the bottom side and the gas passage hole (24) on the side part (322), the gas flows into the outer cover (32). The gas flow becomes good. Moreover, the outer cover (3
Since the gas passage hole (24) of the side part (322) of (2) is provided only in the portion located on the downstream side of the gas flow in the mounted state, unburned substances accumulate around the gas passage hole (24). There is very little to do.

The bottom (311) of the inner cover (31)
It can be formed in a tapered shape. More specifically, the tapered shape of the bottom portion (311) of the inner cover (31) can be a hemispherical shape. Further, the tapered shape of the bottom portion (311) of the inner cover (31) may be a polygonal pyramidal shape.

Further, as described in claim 6, the tapered shape of the bottom portion (311) of the inner cover (31) is formed in the inclined surface (311c) inclined in a direction away from the inner surface of the outer cover (32). On the circumferential side, a shape having a sub-inclined surface (311c) inclined in the opposite direction to the inclined surface (311c) is provided, and the sub-inclined surface (311c) is also provided with a gas passage hole (26) through which gas passes. You may do so.

Further, if the gas passage hole (22) through which the gas passes is provided also in the side portion (312) of the inner cover (31) as in the invention of claim 7, the inner cover (31) can be formed. The flow of gas between both sides of the outer cover (32) is improved, and the accumulation of unburned substances on the inner surface (Y portion) of the outer cover (32) can be further reduced. Further, as in the eighth aspect of the present invention, in the second aspect, the side portions (3212) of the outer cover (32) among the side portions (312) of the inner cover (31).
If a gas passage hole (22) through which gas passes is provided also in a portion facing the gas passage hole (24) of 2), the gas flows smoothly through both gas passage holes (24, 22). The flow of gas into (31, 32) can be further improved.

The invention according to claim 9 is characterized in that the concentration of oxygen in intake gas or exhaust gas in a diesel engine is detected by the detection element (10). According to this, the function and effect of the present invention can be particularly effectively exerted in a diesel engine in which a gas containing an extremely large amount of unburned substances is formed.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. (First Embodiment) As shown in FIG. 3, an oxygen concentration detector 1 in the present embodiment is a diesel engine 1 of an automobile.
One of each is mounted on the intake pipe 101 and the exhaust pipe 102 respectively. The detector 1 is disposed so as to be perpendicular to the wall surfaces of the pipes 101 and 102, and so that the tip 1a thereof faces downward in the vertical direction.

Then, the detector 1 of the intake side pipe 101
The oxygen concentration in the intake gas detected by the above is input to the electric control device 103, and the exhaust gas flow rate of the exhaust gas recirculation pipe 105 is controlled based on the input data. Also,
The oxygen concentration in the exhaust gas detected by the detector 1 in the exhaust pipe 102 is input to the electric control device 103, and the amount of fuel injected from the injection pump 104 to the diesel engine 100 is controlled based on the input data. I do.

The recirculation pipe 105 is connected to the exhaust pipe 1
02 is recirculated to the intake-side pipe 101, and the diaphragm 107 is vertically displaced by the negative pressure circuit switching electromagnetic valve 106, so that the exhaust gas recirculation valve 108 is The exhaust gas flow rate is adjusted by opening and closing. Next, a specific structure of the oxygen concentration detector 1 will be described with reference to FIGS. The oxygen concentration detector 1 is provided with a detection element 10 having an annular section and an elongated cup shape (elongated shape). Inside the detection element 10, the detection element 10 is set to an activation temperature (for example, 650 ° C.). ) An electric heater (heater means) 20 for heating above is provided.

At the base end 10b side of the detecting element 10 (on the side of the cup-shaped opening), the detecting element 10 is connected to the intake side pipe 10
1 or an attachment member 41 for attachment to the exhaust-side pipe 102. The mounting member 41 is a sealing member 416 made of talc in a state where the tip 10a side (the bottom side of the cup shape) of the detection element 10 is exposed to the outside.
Is provided to hold the detection element 10. In addition,
The tip 10a side of the detection element 10 constitutes a gas contact portion 11 that contacts the gas to be detected.

The mounting member 41 is connected to both the pipes 101, 10
2 has a thread 414 that is screwed into the screw holes 101a and 102a, and a flange 415 that positions the detector 1 with respect to the pipes 101 and 102. The attachment member 41 is detachably attached to the pipes 101 and 102 by screw connection. A gasket 462 for sealing is provided between the flange portion 415 of the mounting member 41 and the pipes 101 and 102.

The cover members 442, 44 welded to each other are closer to the base 1b of the detector 1 than the mounting member 41 is.
3 and 446 are provided, and the opening of the mounting member 41 and the cover member 446 are fixed via a metal ring 463. The cover members 442 and 443 are formed with air introduction ports 444 and 445 for introducing air into the cover members 442 and 443, respectively.

Further, a water-repellent ventilation filter (not shown) is provided in the middle of the air introduction passage formed by the air introduction ports 444 and 445. The air introduced from the air inlets 444 and 445 is further guided into the detection element 10 through an air passage (not shown). Detection element 1 of the present embodiment
Numeral 0 is a so-called limiting current type detection element. That is, the detection element 10 includes an elongated substantially cup-shaped element main body 13 made of an oxygen ion-conductive solid electrolyte, and has an inner peripheral surface on the inner peripheral surface of the element main body 13 as shown in FIG. An electrode 14 is formed, and an insulating layer 15, an outer electrode 12, and a diffusion resistance layer 1 are formed all around the outer peripheral surface of the element body 13.
6 are sequentially laminated from the inside to the outside.

The insulating layer 15 is not formed on the band-shaped portion 130 having a predetermined width (for example, 5.0 mm) on the outer peripheral surface of the element body portion 13.
Are provided in contact with each other. Then, a portion of the outer electrode 12 provided in contact with the belt-like portion 130 constitutes a reaction portion 12a of the outer electrode 12. FIG.
2A, the illustration of the insulating layer 15 and the diffusion resistance layer 16 is omitted, and the reaction portion 1 of the outer electrode 12 is omitted.
Only 2a is shown.

As shown in FIG. 1A, the electric heater 20 has a heating part 202 made of tungsten and a lead wire part 203 built in an insulating ceramic body 201. As shown in FIG. 2A, the heat generating portion 202 is provided substantially opposite to the band-shaped portion 130 where the reaction portion 12a is provided. The reaction unit 12
a is intensively heated. The electric heater 20 is connected to the base end 10 b of the detection element 10 via a holder 47.
Held by the side.

The inner electrode 14 and the outer electrode 12 of the detecting element 10 are electrically connected to one end of the output lead-out lines 161, 161. Is electrically connected to one end. The output line 161 and the feed line 162
Cover members 442, 4 via rubber bush 5
43. Then, the output extraction lines 161, 1
The other end of 61 is electrically connected to a data reading unit built in the electric control device 103, and the other end of the power supply line 162 is electrically connected to a heater drive circuit of the electric control device 103. I have.

The gas contact portion 1 is attached to the mounting member 41 described above.
1 is mounted. The element cover 3 includes an inner cover 31 arranged to cover the gas contact portion 11 and an outer cover 32 arranged to cover the inner cover 31. Here, both covers 31, 32 are formed of a metal having excellent corrosion resistance, such as stainless steel (SUS310 or the like).

The element cover 3 serves to prevent water, poisons (lead compounds), and unburned substances (such as soot composed of Cabourne fine particles) from entering the detection element 10. . Since the temperature of the gas (about 80 to 140 ° C. for the intake gas and about 100 to 500 ° C. for the exhaust gas) is lower than the activation temperature (for example, 650 ° C.), the element cover 3 is heated by the heater 20. Also plays a role of keeping the temperature of the detection element 10 warm. The element cover 3 has a double structure of the inner cover 31 and the outer cover 32, so that the above-mentioned role is further fulfilled.

The inner cover 31 is connected to the tip 1 of the detecting element 10.
It is formed in a substantially cup shape having a bottom 311 opposing Oa and a side 312 continuous with the bottom 311. Further, the outer cover 32 is provided at the bottom 3 of the inner cover 31.
11, and is formed in a substantially cup shape having a bottom 321 and a side 322 continuous with the bottom 321.

The bottom 311 of the inner cover 31 is
2 is formed in a tapered shape (a hemispherical shape in the present embodiment) from the edge to the center tip 311a. The side portion 312 of the inner cover 31 is formed so as to extend in a cylindrical shape from the edge of the bottom portion 311 and have the same diameter in the axial direction. Here, the reason for forming the bottom 311 of the inner cover 31 into a tapered shape is as follows.
In order to form an inclined surface 311c which is inclined in a direction away from the inner surface of the side portion 322 of the outer cover 32. To explain this more specifically, according to the present embodiment, only the hemispherical inclined surface 311c of the bottom 311 of the inner cover 31 is provided with the gas passage hole 21 through which the gas passes.

In the present embodiment, a gas passage hole through which gas passes is provided at a position where the inclination angle α of the detection element 10 with respect to the axial direction T is acute (smaller than 90 °, 60 ° in the present embodiment). 21 are arranged. The inclination angle α is an angle formed between the axial direction T of the detection element 10 and a tangent R to the hemispherical inclined surface 311c. The gas passage holes 21 are circular in shape, and four gas passage holes 21 are provided at equal intervals in the circumferential direction of the hemispherical inclined surface 311c.

On the other hand, the bottom 32 of the outer cover 32
1 is formed in a planar shape, and is disposed substantially perpendicularly to the axial direction T of the detection element 10. The side portion 322 of the outer cover 32 is formed so as to extend in a cylindrical shape from the edge portion 321a of the bottom portion 321 and have the same diameter in the axial direction. And the bottom 3 of the outer cover 32
One circular gas passage hole 23 through which gas passes is formed only at the center of 21.

No gas passage holes are formed in the side portion 312 of the inner cover 31 and the side portion 322 of the outer cover 32. Also, the inclined surface 311 of the bottom 311 of the inner cover 31
c, the gas passage holes 2 in the bottom 321 of the outer cover 32
No gas passage hole is formed in a portion directly facing the central portion of 3 (that is, near the central portion 311a of the bottom portion 311). The total area of the gas passage holes 21 of the inner cover 31 is smaller than the total area of the gas passage holes 23 of the outer cover 32.

The open end 323 of the outer cover 32 is fixed to the mounting member 41 by caulking.
One outer peripheral surface on the opening end 313 side is welded to the inner peripheral surface on the opening end 323 side of the outer cover 32. The inner cover 31 has a stepped portion 31 whose opening end 313 side has a large diameter.
a is formed, and a plurality of (three in this embodiment, only one is shown in FIG. 1A) inwardly recessed portions 32a are arranged in the outer cover 32 so as to be arranged in the circumferential direction. Are formed. The recessed portion 32 a supports the stepped portion 31 a, thereby positioning the inner cover 31 inside the outer cover 32.

That is, the bottom 311 of the inner cover 31
And the bottom portion 321 of the outer cover 32 are positioned and arranged such that the inner cover 31 and the outer cover 32 are separated by a predetermined distance (for example, 4.5 mm or more, preferably about 5.0 mm) in the axial direction. . In addition, the inner cover 31 is arranged such that the side 312 of the inner cover 31 and the side 322 of the outer cover 32 are separated from each other by a predetermined distance (for example, 1.0 mm or more, preferably about 2.0 mm) in the radial direction.
And an outer cover 32.

Here, the water, poison,
In addition, the shape, size, and size of the element cover 3 with respect to the detection element 10 are set so that the response of the detection element 10 can be secured while suppressing intrusion of unburned substances and maintaining the temperature of the detection element 10.
The position, diameter, and the like of each of the passage holes 21, 22, and 23 are determined. Specifically, the outer diameter of the inner cover 31 is 9.0 m.
m, the inner diameter is 8.0 mm, the diameter of the gas passage hole 21 in the bottom 311 of the inner cover 31 is 2.0 mm, the outer diameter of the outer cover 32 is 12.0 mm, the inner diameter is 11.0 mm, and the bottom 321 of the outer cover 32 is formed. The diameter of the gas passage hole 23 is 8.0 mm
It is. The gas passage hole 21 is located at a distance of 30.0 mm from the surface 415a of the flange portion 415 of the mounting member 41 on the element cover 3 side (the lower side in FIG. 1A). And the distance from the surface 415a is 35.0.
mm.

Next, the oxygen concentration detector 1 of the first embodiment
The operation and effect of the present invention will be described. First, the outer cover 32 is provided with the gas passage holes 23 only in the bottom portion 321, and since the gas passage holes 23 are arranged substantially parallel to the gas flow in the mounted state, the pressure of the gas flow accompanying the operation of the engine 100 is reduced. Due to the pulsation, the pressure in the gas passage hole 23 also pulsates.
That is, when the velocity of the gas flow flowing along the bottom portion 321 increases due to the pressure pulsation of the gas flow, the pressure in the gas passage hole 23 decreases, and the gas in the outer cover 32 passes through the gas passage hole 23 to the outside. It is sucked out of the cover 32.

Next, the pressure pulsation of the gas flow causes the bottom 32
When the velocity of the gas flow flowing along 1 decreases, the pressure in the gas passage hole 23 increases, and gas outside the outer cover 32 flows into the outer cover 32 through the gas passage hole 23. In addition, since only the bottom portion 321 of the outer cover 32 which is arranged substantially in parallel with the gas flow in the mounted state has the gas passage hole 23, unburned substances are discharged to the periphery of the gas passage hole 23 of the outer cover 32. Can be suppressed, and the opening area of the passage hole 23 of the outer cover 32 can be reduced and blocked.
The gas can be favorably introduced into the inside.

Since unburned substances can be prevented from entering the inside of the outer cover 32 through the gas passage holes 23 of the outer cover 32, and accumulation of unburned substances on the surface of the inner cover 31 can be suppressed. The combustion of unburned substances on the surface of the metal can be suppressed. The inner cover 3 passes through the gas passage hole 21 of the inner cover 31.
The intrusion of unburned substances into the inside of the first element 1 can be suppressed, and the accumulation of unburned substances on the surface of the detection element 10 can be suppressed.

Since the poison (lead compound or the like) contained in the gas can be prevented from entering the inside of the outer cover 32 and the poison can be prevented from being deposited on the surface of the detection element 10. Deterioration can be suppressed. By the combination of the above, the detection accuracy of the oxygen concentration detector 1 is higher than that of the related art.

Further, the bottom 311 of the inner cover 31 is
A tapered shape (a hemispherical shape in the present embodiment) is formed from the edge of the side portion 312 to the central front end portion 311a, and the bottom 311 has an inclined surface inclined in a direction away from the inner side surface of the side portion 322 of the outer cover 32. Since the gas passage hole 21 through which the gas passes is provided on the inclined surface 311c, the distance between the portion of the gas passage hole 21 and the inner surface of the side portion 322 of the outer cover 32 is increased.

Therefore, even when the unburned material is deposited on the inner side surface of the side portion 322 (see the portion Y in FIG. 2A), the unburned material deposited portion Y and the gas passage hole 21 on the inclined surface 311c are formed.
Can be kept large, so that the open state of the gas passage hole 21 can be maintained more reliably. Also, the bottom 311 of the inner cover 31 and the bottom 321 of the outer cover 32
Are arranged at a predetermined distance in the axial direction, so that unburned material can be prevented from reaching the inner cover 31, and combustion of unburned material on the surface of the inner cover 31 can be suppressed.
In addition, the deterioration of the detection element 10 is further suppressed. Therefore, the detection accuracy of the oxygen concentration detector 1 can be further improved.

The water and the like mixed in the gas can be prevented from reaching the inner cover 31, the surface of the detection element 10 can be prevented from being wet, and the element crack due to rapid cooling of the detection element 10 can be suppressed. Therefore, it is possible to suppress a decrease in detection accuracy due to element cracks. Further, since the side 312 of the inner cover 31 and the side 322 of the outer cover 32 are arranged at a predetermined distance in the direction perpendicular to the axial direction T, that is, in the radial direction, the side 312 of the inner cover 31 is formed. A gap is formed between the outer cover 32 and the side portion 322 of the outer cover 32, and the heat retention of the detection element 10 heated by the electric heater 20 can be improved.

Further, since the inclined surface 311c of the bottom 311 of the inner cover 31 is formed in a hemispherical shape, the distance between the bottom 311 of the inner cover 31 and the tip 10a of the detecting element 10 can be equalized. The whole can receive heat from the electric heater 20 substantially uniformly. Therefore, bottom 3
Since the entire body 11 is in a high temperature state at substantially the same temperature, unburned substances can always be satisfactorily burned. In addition, it is easier to manufacture as compared to a case of a planar shape.

Further, of the bottom 311 of the inner cover 31, a portion directly facing the center of the opening surface of the gas passage hole 23 of the bottom 321 of the outer cover 32 (that is, the center 31).
Since no gas passage hole is formed in (in the vicinity of 1a), it is possible to prevent water, poisons and the like mixed in the gas from reaching the inner cover 31. Therefore, water and poisoning of the surface of the detection element 10 can be suppressed.

Since the total area of the gas passage holes 21 of the inner cover 31 is smaller than the total area of the gas passage holes 23 of the outer cover 32, the bottom 321 of the outer cover 32 is formed.
The gas tends to stay in the space formed between the inner cover 31 and the bottom 311 of the inner cover 31, and the unburned substances contained in the gas can be captured in this space. Therefore, accumulation of unburned substances on the surface of the inner cover 31 and the surface of the detection element 10 can be more effectively suppressed.

Next, the conventional oxygen concentration detector 1 shown in FIGS. 11A and 11B, the prototype oxygen concentration detector 1 shown in FIG. 11C, and FIGS. An experiment performed by the present inventors to compare the detection accuracy (responsiveness) of the detector 1 with the oxygen concentration detector 1 of the first embodiment, and the results thereof will be described. In the detector 1 of the related art, the diameter and the arrangement position of each of the gas passage holes are as described above. In the detector 1 of FIG. 11C, the diameter of the passage holes 22 of the inner cover 31 is 1.5 mm, and the passage holes 22 are arranged in two rows in the axial direction on the side 311 of the inner cover 31. A total of eight holes are formed so as to be arranged side by side in the circumferential direction. The diameter of the passage hole 21 of the inner cover 31 is 3.5 mm, and one passage hole 21 is formed at the center of the bottom 321. is there. In the detector 1 shown in FIG. 11C, the passage hole 23 of the outer cover 32 has a diameter of 8 mm and is formed at the center of the bottom 321.

Each of the detectors 1 is in an unused state, and the detector 10 is connected to the pipe 10 of the diesel engine 100.
1 and 102, the diesel engine 100
Prepare the one after driving for 00 hours. Then, each of the above detectors 1 is attached to a pipe capable of switching and supplying air having an oxygen concentration of 20% and 15%, respectively.
The time from the moment when switching between the state of supplying 0% air and the state of supplying air with an oxygen concentration of 15% until the above-mentioned detectors 1 detect a change in the oxygen concentration was measured.

Then, the rate of change of the detection time was calculated by using the detection time of the detector 1 in the unused state as the initial detection time and the detection time of the detector 1 after 100 hours of use as the detection time after the endurance. . The rate of change is obtained by dividing the detection time after the endurance by the initial detection time. As a result, the change rate of the detection time of the conventional detector 1 is about 20,
The rate of change of the detection time of the detector 1 in FIG. 11C is 4, and the rate of change of the detection time of the detector 1 of the present embodiment is 1.
As described above, since the detector 1 of FIG. 11C and the detector 1 of the present embodiment have a significantly smaller rate of change than the conventional detector 1, the detection accuracy can be favorably maintained for a long time. Further, the detector 1 of the present embodiment has a smaller change rate than the detector 1 of FIG.
It was confirmed that the detection accuracy could be maintained over a long period of time better than that of the detector 1.

(Second Embodiment) A second embodiment is a modification of the first embodiment, and as shown in FIG.
A circular gas passage hole 22 is also provided in the side portion 312 of the inner cover 31. The gas passage holes 22 have a circular shape, and are formed in the side portion 311 such that, for example, only one row is arranged in the axial direction and, for example, four rows are arranged in the circumferential direction. These gas passage holes 22 are formed in portions of the side portion 312 other than the portion facing the reaction portion 12a, and in the illustrated example of FIG. 4, the gas passage holes 22 are closer to the detection element base end 10b than the reaction portion 12a. The gas passage hole 22 is arranged at the position.

According to the second embodiment, the inner cover 31
By additionally providing the gas passage holes 22 also at the side portions 312 of the inner cover 31, gas can flow into the inside of the inner cover 31 through the gas passage holes 22. The gas flow between the side portion 322 and the side portion 322 becomes good, so that the amount of unburned substances deposited on the Y portion can be reduced. Therefore, the open state of the gas passage hole 21 can be more reliably maintained.

The gas passage hole 22 is formed in a portion of the side portion 312 of the inner cover 31 other than the portion facing the reaction portion 12a (see FIG. 4). The path of the gas reaching the portion 12a has a maze structure, so that the gas can be suppressed from entering the vicinity of the surface of the reaction portion 12a of the detection element 10. Therefore, the reaction part 12a and the reaction part 12
It is possible to improve the heat retention of a portion near a (hereinafter, referred to as an output portion of the detection element 10), and to satisfactorily maintain the output portion of the detection element 10 at or above the activation temperature.

The accumulation of unburned substances contained in the gas on the surface of the reaction section 12a can be suppressed.
Degradation can be suppressed. (Third Embodiment) A third embodiment is a modification of the first embodiment, and as shown in FIG.
Both the side portion 312 and the side portion 322 of the outer cover 32 are provided with circular gas passage holes 22 and 24. The gas passage holes 22 and 24 are portions of the side portions 312 and 322 that are located on the downstream side of the gas flow in the mounted state.
In addition, only one of the side portions 312 and 322 is formed at a portion other than the portion facing the reaction portion 12a.

According to the third embodiment, the gas passage holes 2
In addition to gas flowing into and out of both covers 31, 32 through 3, 21 as well as through gas passage holes 22, 24,
Since gas flows into and out of both covers 31, 32, gas permeability can be further improved. The reaction unit 12
a (see FIG. 2), the gas passage holes 22 and 24 are formed in portions other than the portion facing the gas passage hole 2 (see FIG. 2).
The path of the gas from 2, 24 to the reaction part 12a has a maze structure, and it is possible to suppress the gas from entering the vicinity of the surface of the reaction part 12a of the detection element 10.

(Fourth Embodiment) A fourth embodiment is a modification of the first embodiment, and as shown in FIGS. 6A and 6B, the bottom 311 of the inner cover 31 is tapered. As the shape, a polygonal pyramid shape (a quadrangular pyramid shape in the fourth embodiment) is formed instead of the above-mentioned hemispherical shape.

Accordingly, a plurality (4 in this embodiment) inclined toward the tip 10a of the detection element 10 (upward in FIG. 6A).
) Into a shape having a flat inclined surface 311c.
Are formed. In addition, the inclination angle α of the plane inclined surface 311c with respect to the axial direction T of the detection element 10 is, for example, 45 °. Even in this case, the same effect as in the first embodiment can be obtained.

(Fifth Embodiment) In the present embodiment, the first
This is a modification of the embodiment. As shown in FIGS. 7A and 7B, the bottom 311 of the inner cover 31 is
The central portion 311a is provided with a circular flat portion G perpendicular to the axial direction of the detection element 10, and from the circular flat portion G to the edge of the side portion 312, the tip 10a side of the detection element 10 (upper side in FIG. 7A). The bottom 311 is formed in a shape having a plurality (four in the present embodiment) of inclined planes 311c inclined toward the bottom. In addition, the inclination angle α of the plane inclined surface 311c with respect to the axial direction of the detection element 10 is, for example, 45 °. Even in this case, the same effect as in the first embodiment can be obtained.

(Sixth Embodiment) A sixth embodiment is a modification of the first embodiment, and as shown in FIG.
The side 312 of the inner cover 31 is formed so as to extend from the edge of the hemispherical inclined surface 311c of the bottom 311 into a cylindrical shape whose diameter gradually increases. The detection element 10
The inclination angle β of the side portion 312 of the inner cover 31 with respect to the axial direction is, for example, 3 °.

As a result, the bottom 311 of the inner cover 31
The radial distance between the outer cover 32 and the side portion 322 is
Side 312 of inner cover 31 and side 3 of outer cover 32
22 is even longer than the radial distance. Therefore, the open state of the gas passage hole 21 formed in the bottom 311 is more favorably maintained. (Seventh Embodiment) A seventh embodiment is a modification of the first embodiment, and as shown in FIG.
An intermediate cover 33 is provided between the first cover 1 and the outer cover 32. The intermediate cover 33 is provided on the bottom 31 of the inner cover 31.
1 is formed in a substantially cup shape having a bottom portion 331 opposed to the first portion. This bottom part 331 is formed in a planar shape,
It is arranged substantially perpendicular to the axial direction of the detection element 10,
One circular gas passage hole 25 is formed.

A gas passage hole 23 is formed in the outer cover 32 so as to open the bottom 321 entirely. The bottom 331 of the intermediate cover 33 and the bottom 31 of the outer cover 32
2 are arranged at the same position in the axial direction of the detection element 10. The inner peripheral portion of the outer cover 32 on the opening end 323 side is welded and fixed to the mounting bracket 41, and the outer peripheral portion of the intermediate cover 33 on the opening end 333 side is welded and fixed to the inner peripheral portion of the outer cover 32 on the opening end portion 323. Open end 313 of inner cover 31
The side inner peripheral portion is fixed to the mounting bracket 41 by welding.

According to the seventh embodiment, since the element cover 3 has a triple structure, the heat retaining property of the detection element 10 can be further improved. (Eighth Embodiment) The eighth embodiment is a modification of the third embodiment shown in FIG. 5, and as shown in FIG.
On the inner peripheral side of the inclined surface 311c inclined away from the inner surface of the second side 322, a sub-inclined surface 311d inclined in a direction opposite to the inclined surface 311c is formed.

The sub-inclined surface 311d is also provided with a gas passage hole 26 through which gas passes. The bottom 31 where the sub-slope surface 311d and the gas passage hole 26 are provided is provided.
Needless to say, the tapered shape 1 can be adopted in the first embodiment of FIG. 2, the second embodiment of FIG. 4, and the like. (Other Embodiments) In the first embodiment, the gas passage hole 21 is formed at a position where the inclination angle α is 60 °, but the gas passage hole 21 is formed at a position where the inclination angle α is smaller than 60 °. The hole 21 may be formed, or the inclination angle α is 6
The gas passage hole 21 may be formed at a position larger than 0 ° and smaller than 90 °.

Further, in the fourth and fifth embodiments, the gas passage hole 21 is formed at the portion where the inclination angle α is 45 °, but the gas passage hole 21 is formed at the portion where the inclination angle α is smaller than 45 °. The hole 21 may be formed, or the gas passage hole 21 may be formed at a position where the inclination angle α is larger than 45 ° and smaller than 90 °. In the fourth and fifth embodiments, the tapered shape of the bottom 311 of the inner cover 31 is a polygonal pyramid having four flat inclined portions 311c. However, the number of the flat inclined portions 311c is five or more. It may have a shape having three or three or less.

In the sixth embodiment, the inclination angle β is set to 3 °, but may be smaller than 3 °.
It may be larger than 3 °. In each of the above embodiments,
Although four gas passage holes 21 are formed in the inclined surface 311c of the bottom 311 of the inner cover 31, the number may be less than four or more than four.

In each of the above embodiments, the outer cover 3
The bottom 321 of the second has a flat shape, but may have a curved shape. Further, the bottom portion 321 may have a shape that is entirely open. Further, in each of the above embodiments, each of the gas passage holes 21, 22, 23, 24, and 25 is circular.
It may be square or any other shape.

In each of the above embodiments, the outer cover 3
Although one gas passage hole 23 is formed in the bottom portion 321 of the second, a plurality of gas passage holes 23 may be formed. In each of the above embodiments,
Although the oxygen concentration detector 1 is mounted on both the intake pipe 101 and the exhaust pipe 102, it may be mounted on only one of them.

In each of the above embodiments, the piping 10
The detector 1 is mounted vertically on the wall surfaces of the detectors 1 and 102, and the intake gas and the exhaust gas pass through the tip side of the detector 1 substantially vertically. Perpendicular to the wall surfaces of the pipes 101 and 102 (90
The angle may be slightly shifted back and forth from (°). In particular, the detector 1 is arranged so that the gas flows from the upstream side to the downstream side while being inclined downward in the axial direction of the detector 1.
Is arranged, the bottom surface passing hole 2 of the outer cover 32 is formed.
The accumulation of unburned substances in the peripheral portion of No. 3 and the passage of unburned substances in the bottom passage holes 23 can be further reduced.

Further, in each of the above embodiments, the oxygen concentration detector 1 is applied to the diesel engine 100. However, in addition to the above, the element cover 3 is provided in the gas such as an exhaust gas system of a power generating engine using natural gas. The present invention may be applied to a substance containing a large amount of a substance which easily deposits. In each of the above embodiments, the limiting current type detection element 10 is used. Alternatively, a pump current type (concentration cell type) detection element having no insulating diffusion layer 16 may be used. Alternatively, a semiconductor type detection element or the like may be used.

[Brief description of the drawings]

FIG. 1A is a vertical cross-sectional view of an oxygen concentration detector according to a first embodiment, and FIG. 1B is an enlarged vertical cross-sectional view of a tip end side of a detection element.

FIG. 2A is a vertical cross-sectional view of a tip side of an oxygen concentration detector according to the first embodiment, and FIG. 2B is a horizontal cross-sectional view along AA in FIG.

FIG. 3 is an explanatory diagram showing a mounting location of the oxygen concentration detector according to the first embodiment.

FIG. 4 is a vertical cross-sectional view on the distal end side of an oxygen concentration detector according to a second embodiment.

FIG. 5 is a vertical cross-sectional view on the distal end side of an oxygen concentration detector according to a third embodiment.

FIG. 6A is a vertical sectional view on the tip side of an oxygen concentration detector according to a fourth embodiment, and FIG. 6B is a view taken in the direction of arrow C in FIG.

FIG. 7A is a vertical cross-sectional view of a tip side of an oxygen concentration detector according to a fifth embodiment, and FIG. 7B is a view taken in the direction of arrow C in FIG.

FIG. 8 is a vertical cross-sectional view on the distal end side of an oxygen concentration detector according to a sixth embodiment.

FIG. 9 is a vertical cross-sectional view of a tip side of an oxygen concentration detector according to a seventh embodiment.

FIG. 10 is a vertical cross-sectional view of a tip side of an oxygen concentration detector according to an eighth embodiment.

11 (a) is a vertical sectional view of a tip side of an oxygen concentration detector according to a conventional technique, FIG. 11 (b) is a transverse sectional view taken along line AA of FIG. 11 (a), and FIG. It is a front end side sectional view of the oxygen concentration detector concerning a prototype.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Detection element, 10a ... Tip of a detection element, 11 ... Gas contact part, 12a ... Reaction part, 20 ... Electric heater, 31 ... Inner cover, 311 ... Bottom part of inner cover, 312 ... Side part of inner cover, 32 ... Outer cover, 321, bottom of outer cover, 322 side of outer cover, 21, 22, 23,
24, 25 ... gas passage holes.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masato Sahashi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Fumihiko 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (9)

[Claims] A gas contact portion (1) in contact with a gas to be detected.
1) is formed in a long shape having a tip (10a) side,
A detection element (10) for detecting the oxygen concentration in the gas; a heater means (20) provided near the detection element (10) for heating the detection element (10); and the detection element (10). An inner cover (31) formed in a substantially cup shape having a bottom (311) facing the tip (10a), and arranged to cover the gas contact portion (11) of the detection element (10); An outer cover (3) disposed outside the inner cover (31) and disposed to cover the inner cover (31).
2), and the inner cover (3) of the outer cover (32) is provided.
A gas passage hole (23) through which the gas passes is provided only at a portion facing the bottom portion (311) of 1), and the bottom portion (311) of the inner cover (31) is at least the outer cover. (32) is formed in a shape having an inclined surface (311c) inclined in a direction away from the inner side surface of the inner cover (31), and a portion of the bottom surface (311) of the inner cover (31) on the inclined surface (311c), An oxygen concentration detector, wherein a gas passage hole (21) through which the gas passes is provided. 2. A gas contact portion (1) in contact with a gas to be detected.
1) is formed in a long shape having a tip (10a) side,
A detection element (10) for detecting the oxygen concentration in the gas; a heater means (20) provided near the detection element (10) for heating the detection element (10); and the detection element (10). The gas contact portion (11) of the detection element (10) is formed in a substantially cup shape having a bottom (311) facing the tip (10a) and a side (312) continuous with the bottom (311). An inner cover (31) arranged so as to cover the inner cover (31), and an outer cover (3) arranged outside the inner cover (31) and arranged so as to cover the inner cover (31).
2), and the inner cover (3) of the outer cover (32) is provided.
A gas passage hole (23) through which the gas passes is provided at a portion facing the bottom portion (311) of 1), and a side portion (322) of the outer cover (32) is provided.
A gas passage hole (24) through which the gas passes is provided only in a portion located on the downstream side of the gas flow in the attached state, and a bottom portion (311) of the inner cover (31) is at least the outer cover. (32) is formed in a shape having an inclined surface (311c) inclined in a direction away from the inner side surface of the inner cover (31), and a portion of the bottom surface (311) of the inner cover (31) on the inclined surface (311c), An oxygen concentration detector, wherein a gas passage hole (21) through which the gas passes is provided. 3. The bottom (31) of said inner cover (31).
The oxygen concentration detector according to claim 1 or 2, wherein 1) is formed in a tapered shape. 4. The bottom (31) of the inner cover (31).
The oxygen concentration detector according to claim 3, wherein the tapered shape of (1) is a hemispherical shape. 5. A bottom (31) of the inner cover (31).
The oxygen concentration detector according to claim 3, wherein the tapered shape of (1) is a polygonal pyramid shape. 6. A bottom (31) of the inner cover (31).
The tapered shape of 1) is a shape having a sub-inclined surface (311d) inclined in the opposite direction to the inclined surface (311c) on the inner peripheral side of the inclined surface (311c). 4. The oxygen concentration detector according to claim 3, wherein a gas passage hole (26) through which the gas passes is provided also in (1). 7. A side portion (31) of the inner cover (31).
The oxygen concentration detector according to any one of claims 1 to 6, wherein a gas passage hole (22) through which the gas passes is provided also in (2). 8. A side portion (31) of the inner cover (31).
2) a side portion (322) of the outer cover (32);
The oxygen concentration detector according to claim 2, wherein a gas passage hole (22) through which the gas passes is provided also at a portion facing the gas passage hole (24). 9. An oxygen concentration detector according to claim 1, wherein said detection element detects an oxygen concentration in an intake gas or an exhaust gas in a diesel engine. .