JP3257431B2 - Oxygen sensor cover - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cover for an oxygen sensor used in an internal combustion engine or the like, and more particularly to a cover for an oxygen sensor having an introduction hole through which a gas to be measured flows.

[0002]

2. Description of the Related Art An oxygen sensor generally comprises an element formed of a solid electrolyte (such as zirconia) and a pair of electrodes provided on the element. A cover for protecting the element is provided on the outer periphery of the element, and the cover is provided with a plurality of introduction holes for introducing gas therein (for example, Japanese Patent Publication No. 2-2).
No. 536, an oxygen sensor cover).

When the oxygen sensor is disposed in the atmosphere of the detection gas to be detected, the detection gas passes through the introduction hole of the cover and comes into contact with the element. Each electrode outputs a detection signal corresponding to the oxygen concentration of the detection gas.

In the air-fuel ratio control of an internal combustion engine using the oxygen sensor as described above, as shown in FIG.
The oxygen concentration of the exhaust gas is detected by an oxygen sensor (exhaust-side oxygen sensor) 102 provided in the exhaust passage 101 at 00, and the actual air-fuel ratio is calculated based on the oxygen concentration. Then, feedback control is performed so that the air-fuel ratio becomes a target air-fuel ratio (normally, a stoichiometric air-fuel ratio).

In the internal combustion engine 100, an exhaust gas recirculation device (EGR device) for reducing NOx (nitrogen oxide) in the exhaust gas or an exhaust gas leaked into a crankcase (not shown) of the engine 100 is used. In some cases, a blow-by gas reducing device (PCV device) for discharging an air-fuel mixture or the like (blow-by gas) is used.

[0006] As shown in FIG.
At 0, the exhaust passage 101 and the intake passage 103 are communicated by the EGR passage 201, and the amount (EGR amount) of EGR gas (exhaust gas) returned from the exhaust passage 101 to the intake passage 103 through the passage 201 is controlled by the flow regulating valve 202. Adjusted.

In the PCV device 300, the internal combustion engine 1
00 cylinder head cover (not shown) and the intake passage 1
03, a portion upstream of the throttle valve 104 is communicated with the pressure passage 301 and the engine 1
The inside of a crankcase (not shown) of No. 00 and the downstream side of the throttle valve 104 in the intake passage 103 are communicated by a PCV passage 302. A flow control valve 303 is provided in the middle of the PCV passage 302, and regulates the amount of blow-by gas (PCV amount) introduced into the intake passage 103 from inside the crankcase by the valve 303.

As described above, the EGR device 200 or the PCV
In the internal combustion engine 100 provided with the device 300, E
The oxygen concentration of the intake air differs depending on the change in the GR amount and the PCV amount. As a result, it may be difficult to control the actual air-fuel ratio by accurately following the change in the target air-fuel ratio.

Therefore, conventionally, as shown in FIG. 17, in addition to the exhaust-side oxygen sensor 102 described above,
3 is provided with another oxygen sensor (intake-side oxygen sensor) 105, and a method of detecting the oxygen concentration of intake air including the influence of EGR gas or blow-by gas by the intake-side oxygen sensor 105 is also taken. In this way, the control accuracy in the air-fuel ratio control described above can be improved by also referring to the oxygen concentration of the intake air.

[0010]

The internal combustion engine 1
Each of the oxygen sensors 102 and 105 provided in the exhaust passage 101 or the intake passage 103 is always exposed to exhaust gas or intake air containing EGR gas and blow-by gas when the internal combustion engine is in an operating state. However, the following problems cannot be ignored.

That is, the intake and exhaust contain a mixture of carbon and engine oil (hereinafter referred to as "soot").
Then, this soot is covered by the cover 1 of the oxygen sensors 102 and 105.
However, there is a problem in that it adheres to the cover 106 and 107 and clogs an introduction hole (not shown) formed in the covers 106 and 107. In the portions of the covers 106 and 107 corresponding to the inner peripheral wall of the introduction hole, since minute irregularities such as burrs are formed at the time of machining the hole, soot grows using the convex portion as a nucleus. This is because clogging of the introduction hole is facilitated. If such clogging of the introduction hole occurs, a difference occurs in the oxygen concentration between the inside and outside of the covers 106 and 107, and the oxygen sensors 102, 1
In this case, the detection accuracy, particularly the responsiveness, of the detection signal 05 deteriorates.

In particular, in the intake-side oxygen sensor 105, since the temperature of the intake air (including the EGR gas or the blow-by gas) passing through the intake passage 103 is lower than the exhaust temperature, the soot has high adhesiveness and the cover has a high stickiness. Since it tends to adhere to the inlet 107, clogging of the introduction hole is more likely to occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the introduction hole formed in the cover for an oxygen sensor from being clogged by soot.

[0014]

In order to achieve the above object, the present invention is directed to a metal material which covers an element of an oxygen sensor for measuring the oxygen concentration of a gas and has an introduction hole through which the gas flows. The purpose of the present invention is to provide an oxygen sensor cover comprising: a surface smoothing treatment for suppressing the adhesion of soot on an inner peripheral wall surface of the introduction hole.

According to the above configuration, the inner peripheral wall surface of the introduction hole is
By performing the surface smoothing treatment, the unevenness of the surface is small, and there is no burr or the like serving as a nucleus at the time of soot adhesion, so that the adhesion of soot on the same surface is suppressed.

[0016] To achieve the above object, according to claim 2 or
The invention described in 3, respectively etched surface smoothing process for suppressing the deposition of soot in the configuration of the invention recited in claim 1, that it has a plating treatment and its spirit. Further, according to the invention described in claim 4, the oxygen concentration of the gas is reduced.
Covers the element of the oxygen sensor to be measured and the gas flows
Oxygen sensor cover made of metal material with inlet holes
The inner peripheral wall surface of the introduction hole is subjected to a surface smoothing treatment.
That the fluororesin coating treatment is applied
I do.

According to the inventions of claims 2 to 4,
The number of minute irregularities on the inner peripheral wall surface of the introduction hole is reduced, and adhesion of soot is suppressed. In particular, according to the invention of claim 4, since the affinity between the inner peripheral wall surface of the introduction hole and the soot decreases, the amount of soot adhering to the inner wall surface decreases.

According to a fifth aspect of the present invention, there is provided an oxygen sensor cover for covering an element of an oxygen sensor for measuring the oxygen concentration of a gas, the cover being made of a metal material having an introduction hole through which the gas flows. It is intended that the peripheral portion of the machined hole be formed into a shape in which the inner peripheral wall surface of the hole is not opposed to form an introduction hole.

In the above configuration, since the peripheral portion of the element hole is formed, the inner peripheral wall surface of the element hole in which minute uneven portions are formed during machining is not opposed. Therefore, even if soot adheres and deposits on the inner peripheral wall surface, the soot does not cause clogging of the introduction hole.

According to a sixth aspect of the present invention, there is provided an oxygen sensor cover according to the fifth aspect, wherein a peripheral portion of the element hole is formed into a shape extending toward the inside of the cover. The purpose is assumed.

According to the above configuration, since the inner peripheral wall surface of the element hole is located inside the cover, the amount of soot adhering to the same surface is further reduced. In order to achieve the above object, an invention according to claim 7 is an oxygen sensor cover for covering an element of an oxygen sensor for measuring the oxygen concentration of a gas and made of a metal material having an introduction hole through which the gas flows. The purpose is to locally reduce the thickness of the inner peripheral wall portion of the introduction hole.

In the above configuration, the inner peripheral wall portion of the introduction hole is locally thinned and the area of the wall surface is reduced, and consequently the irregularities such as burrs on the wall surface are relatively reduced. Thereby, adhesion of soot to the inner peripheral wall surface is suppressed.

In order to achieve the above object, an invention according to claim 8 is an oxygen sensor for covering an element of an oxygen sensor for measuring the oxygen concentration of a gas, the oxygen sensor comprising a metal material having an introduction hole through which the gas flows. In the cover, the inner peripheral wall surface of the introduction hole is covered by an annular member having a smooth inner peripheral surface.

According to the above configuration, even if there are irregularities such as burrs on the inner peripheral wall surface of the introduction hole, the irregularities are covered by the annular member having the smooth inner peripheral wall surface. Adhesion of soot to the wall surface is suppressed. Further, the gas passes through the inner peripheral side of the annular member and is introduced into the inside of the cover. However, since the member has a smooth inner peripheral surface, the adhesion of soot to the inner peripheral surface is suppressed. You.

According to a ninth aspect of the present invention, in the oxygen sensor cover according to the ninth aspect, the annular member is fitted and attached to an inner peripheral wall portion of the introduction hole. To that effect.

The invention according to claim 10 is the same as claim 8.
In the oxygen sensor cover described above, it is intended that the annular member is formed by fixing a resin material to an inner peripheral wall surface.

According to the structure described in claim 9 or 10, in addition to the function of the invention described in claim 8, an annular member for suppressing the adhesion of soot can be easily provided on the cover. .

[0028] In order to achieve the above object, an eleventh aspect of the present invention provides the oxygen sensor cover according to the tenth aspect, wherein the resin material is a thermosetting resin material.

According to the above construction, in addition to the effect of the tenth aspect, deformation of the annular member due to heat is suppressed.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment A first embodiment in which the present invention is embodied as a cover for an intake-side oxygen sensor provided in a diesel engine will be described below with reference to FIGS.

FIG. 1 shows a schematic configuration of a diesel engine (hereinafter, simply referred to as “engine”) 11 in the present embodiment. As shown in FIG. 1, an intake pipe 12 and an exhaust pipe 13 are connected to a combustion chamber (not shown) of the engine 11.

The intake air taken into the intake pipe 12 through an air cleaner (not shown) or the like passes through the pipe 12 and is introduced into a combustion chamber (not shown) of the engine 11. A throttle valve 14 is provided in the intake pipe 12, and the amount of intake air introduced into the combustion chamber of the engine 11 is adjusted according to the opening of the throttle valve 14. Fuel injected from an injector (not shown) and intake air are mixed in the combustion chamber, and the air-fuel mixture explodes and burns, so that a driving force is obtained in the engine 11. After the combustion, the exhaust gas is introduced into the exhaust pipe 13 from the combustion chamber, and then discharged outside through a catalyst or the like (not shown).

The engine 11 is provided with an EGR device 15. The EGR device 15 includes an EGR passage 16 communicating the exhaust pipe 13 and a portion of the intake pipe 12 downstream of the throttle valve 14, and a flow regulating valve 17 provided in the passage 16. . Part of the exhaust gas in the exhaust pipe 13 passes through the EGR passage 16 and is returned into the intake pipe 12. The flow control valve 17 is an electronic control unit (not shown).
, The amount of exhaust gas passing through the EGR passage 16 is adjusted. As described above, part of the intake air introduced into the combustion chamber of the engine 11 is exhaust gas (EGR gas),
That is, an inert gas that is not used for combustion is mixed, and the maximum temperature of the combustion gas in the combustion chamber is reduced, so that N
Ox is reduced.

In the intake pipe 12, an oxygen sensor 20 is attached at a position downstream of the opening 16 a of the EGR passage 16, and the tip of the oxygen sensor 20 is connected to the intake pipe 1.
2 protrudes into The oxygen sensor 20 detects the oxygen concentration of the intake air composed of air and EGR gas that has passed through the throttle valve 14, and outputs a detection signal to the electronic control unit. The electronic control unit executes air-fuel ratio control of the engine 11 based on a detection signal from the oxygen sensor 20 and the like.

FIG. 2 is an enlarged cross-sectional view of the oxygen sensor 20 on the front end side. As shown in FIG.
Includes an element 21 and a cover 22 provided so as to cover the outer periphery of the element 21. Both the element 21 and the cover 22 are fixed to the housing 24 of the oxygen sensor 20.

The element 21 is formed in a hollow shape by a solid electrolyte such as a zirconia element, and electrodes (not shown) are provided on the inner and outer surfaces, respectively. The cover 22 is formed in a cylindrical shape with a bottom from stainless steel excellent in heat resistance and corrosion resistance, and is disposed so as to have a predetermined space between the cover 22 and the outer peripheral surface of the element 21. The cover 22 has a plurality of circular introduction holes 31 formed therein.

The intake air (including EGR gas) passing through the intake pipe 12 is introduced into the inside of the cover 22 through the introduction hole 31 and contacts the element 21. As a result, a detection signal corresponding to the oxygen concentration of the intake air is output from each electrode.

FIGS. 3A to 3C show a part of the cover 22 corresponding to the portion 3 surrounded by the dashed line in FIG. Hereinafter, a process of forming the introduction hole 31 in the present embodiment will be described with reference to FIG. When forming the introduction hole 31, first, a raw hole A to be the introduction hole 31 is formed in the cover 22 by a punching process. Here, as shown in FIG. 3A, a minute uneven portion (the size is exaggerated in FIG. 2) is formed on the inner peripheral wall of the element hole A. Is the outer part of the cover 22 (FIG. 3)
The inner part (the right part in FIG. 3A) is larger than the inner part (the left part in FIG. 3A). This is a hole A
Is formed by punching. That is, since the material is sheared in the initial stage of the punching process, the processed surface is a smooth shearing surface with relatively few uneven portions. On the other hand, if the processing has progressed to some extent, the material is broken and processed, so that the processed surface has a large uneven portion and a broken surface having many burrs and the like. As described above, the processing surface of the punched material (the cover 22) usually has a shear surface and a fracture surface. In the inner peripheral wall surface of the element hole A, the outer portion of the cover 22 corresponds to a shear surface, and the inner portion corresponds to a fractured surface.

Next, the entire cover 22 having the holes A thus punched is immersed in an etching solution such as hydrofluoric acid or aqua regia. By this etching treatment, burrs and the like on the inner peripheral wall surface of the element hole A are melted, and the surface is shown in FIG.
From the state of (a) to the state of (b) in the same figure, the surface becomes extremely small as shown in (c) of FIG. For example,
By immersing the cover 22 in the etching solution at 80 ° C. for 5 to 40 minutes, the surface roughness on the inner peripheral wall surface of the raw hole A can be made about 0.1 to 10 Rz.

As described above, the surface of the etched cover 22 is plated using electroless nickel or electrolytic nickel. As a result, the surface of the cover 22 including the inner peripheral wall surface of the element hole A has a thickness of 0.2 to 5.0 μm.
Is formed (not shown). At this time, since the surface of the cover 22 is etched and becomes a smooth surface,
The plating layer can be easily formed. By this plating process, the surface roughness of the inner peripheral wall surface of the element hole A is further reduced,
It is about 0.1 to 3.2 Rz.

As described above, by performing the surface smoothing process such as the etching process and the plating process on the inner peripheral wall surface of the punched hole A, the smooth inner peripheral wall surface with very few irregularities is obtained. Is formed.

Next, the function and effect of the oxygen sensor cover of the present embodiment will be described. FIG. 4 (a), (b)
Shows the results of an endurance test performed to confirm the effects of the present embodiment. In this test, the EGR rate (volume ratio of the EGR gas circulating in the intake pipe 12 with respect to the intake) is 30%, and the diameter of the introduction hole 31 (initial value: 2 mm in diameter) when the engine 11 is continuously operated in an idling state. ) And responsiveness over time were measured.
Here, the diameter of the introduction hole 31 means a substantial diameter, and when soot adheres to the inner peripheral wall surface of the hole 31, the size decreases. In addition, the response is determined by setting the oxygen concentration of the intake air to 1
When increasing from 5% to 20%, the response time τ from the time of the increase until the current corresponding to 67% of the current value corresponding to the oxygen concentration of 20% is output from the oxygen sensor 20.
Has been evaluated by

The solid line shown in FIG. 4A shows the change over time of the diameter of the introduction hole 31 in the present embodiment, and the one-dot chain line shows
This shows the same change in a comparative example in which the above-described etching process and plating process are not performed. Similarly, the solid line shown in FIG. 4B shows the temporal change of the response (response time τ) in the present embodiment, and the one-dot chain line shows the same change in the comparative example.

From the test results, in the comparative example, the introduction hole 3
The diameter of 1 sharply decreases due to clogging with soot,
It can be seen that the hole 31 is closed after 00 hours. For this reason, in the comparative example, as shown in FIG. 4B, it can be seen that the response time τ increases to 300 msec or more after about 200 hours, and the predetermined responsiveness of the oxygen sensor 20 cannot be secured.

On the other hand, in this embodiment, 2000
Even after a lapse of time, the diameter of the introduction hole 31 is hardly reduced, which indicates that the predetermined responsiveness is secured. That is, the inner peripheral wall surface of the introduction hole 31 in the present embodiment does not have burrs or the like serving as nuclei when soot is deposited. In particular, due to the synergistic effect of performing each of the etching process and the plating process, the inner peripheral wall surface of the introduction hole 31 is a smooth surface with very few irregularities as described above. Therefore, the amount of soot adhering to the inner peripheral wall surface is extremely small, and even if soot temporarily adheres to the inner peripheral wall surface of the introduction hole 31, most of the soot is peeled off due to vibration or the like. It does not reach the point where it accumulates.

As a result, according to the present embodiment, the introduction hole 3
Clogging of the hole 31 by soot accumulated on the inner peripheral wall surface of the first inner wall surface can be reliably prevented. Then, as apparent from the above test results, the oxygen sensor 2
It is possible to avoid that the detection accuracy of 0, especially the responsiveness is deteriorated.

Next, second to fifth embodiments of the present invention will be described. In each embodiment, the description will focus on the differences from the first embodiment, and the same components will be denoted by the same reference numerals and description thereof will be omitted.

[Second Embodiment] Hereinafter, a second embodiment of the present invention will be described. In this embodiment,
The difference is that a coating process using a fluororesin is performed instead of the plating process described above. That is, in the present embodiment, after the cover 22 in which the raw holes A are formed by the punching process is subjected to an etching process, the surface of the cover 22 including the inner peripheral wall surface of the introduction hole 31 is coated with an ethylene tetrafluoride resin. (PTFE) is coated to a film thickness of 10 to 2
A 0 μm resin layer (not shown) is formed.

According to the present embodiment, by performing the etching process and the coating process on the cover 22, respectively, the inner peripheral wall surface of the introduction hole 31 can be made a smooth surface with almost no irregularities. Therefore, similarly to the above embodiment, it is possible to reliably prevent the soot accumulated on the inner peripheral wall surface of the introduction hole 31 from clogging the same.

Further, according to this embodiment, since the inner peripheral wall surface of the introduction hole 31 is formed with the PTFE resin film,
The affinity between the same surface and soot can be reduced. As a result, the adhesion of soot to the inner peripheral wall surface can be further suppressed,
Clogging of the introduction hole 31 can be reliably suppressed.

[Third Embodiment] Next, a third embodiment of the present invention will be described. In the present embodiment, the element holes A formed in the cover 22 by the punching process
However, the surface smoothing process such as the etching process described above is not performed. Therefore, the inner peripheral wall surface of the introduction hole 31 is in a state including a fractured surface having an uneven portion such as a burr.

FIG. 5 shows the cross-sectional shape of the introduction hole 31 in this embodiment. As shown in the drawing, an enlarged diameter portion 32 is formed in a portion of the cover 22 outside the introduction hole 31 (the left portion in the drawing). The enlarged diameter portion 32 is formed by forming the introduction hole 31 by a punching process and then compressing a portion around the hole 31 in the cover 22. Thus, the introduction hole 3 is formed by the enlarged diameter portion 32.
The area of the inner peripheral wall is reduced by locally reducing the thickness of the peripheral portion of 1. The thickness of the portion of the cover 22 that is not thinned is “0.3 mm”, and the thickness of the thinned portion is set to “0.1 mm”.

As described above, in the present embodiment, the area of the inner peripheral wall surface of the introduction hole 31 having the uneven portion is reduced. Therefore, the uneven portion serving as a nucleus when soot is attached is relatively reduced, and the amount of soot attached to the inner peripheral wall surface of the introduction hole 31 is reduced. As a result, clogging of the introduction hole 31 due to soot can be suppressed, and it is possible to prevent the detection accuracy of the oxygen sensor 20, particularly, the responsiveness from being deteriorated.

Further, in this embodiment, only the peripheral portion of the introduction hole 31 is locally thinned. Therefore, unlike the configuration in which the entire thickness of the cover 22 is reduced,
The clogging of the introduction hole 31 by soot can be suppressed without greatly reducing the rigidity of the cover 22 or impairing the heat retaining ability.

Further, when forming a thinned portion in the cover 22, in the pressing step, in addition to the punching process of the introduction hole 31, a compression process of compressing the peripheral portion of the hole 31 may be performed. . For this reason, according to the present embodiment, without making significant design changes or production process changes,
Clogging of the introduction hole 31 can be suppressed.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described. In the present embodiment, the shape of a portion corresponding to the periphery of the introduction hole 31 in the cover 22 is different from that of the first embodiment. FIG. 6 shows a cross section of a portion where the introduction hole 31 is formed in the cover 22. As shown in the figure, the peripheral portion of the introduction hole 31 has a shape curved toward the inside of the cover 22.

In the present embodiment, the introduction hole 31 is formed as shown in FIG.
It is formed through the steps shown in (a) to (d). First, by performing drawing, a portion where the introduction hole 31 is formed on the surface of the cover 22 is depressed. Accordingly, a bottomed cylindrical portion 33 is formed on the surface of the cover 22 shown in FIG. 7A, corresponding to the position of the introduction hole 31, as shown in FIG. 7B. Next, a tip side portion of the cylindrical portion 33 (a portion on the right side of a dashed line in FIG. 7B).
7, the cylindrical portion 33 is opened inside the cover 22 as shown in FIG. In the present embodiment, the introduction hole 3 is formed by the inner peripheral wall surface of the cylindrical portion 33.
1 will be formed. Further, by bending the peripheral wall portion of the cylindrical portion 33, the cylindrical portion 3 is formed.
3 is slightly enlarged at the tip side. By performing this bending process, the distal end surface 33 a of the cylindrical portion 33 is directed to the outside of the introduction hole 31.

In many cases, the cut surface 33a of the cylindrical portion 33 has an uneven portion such as a burr, and soot tends to adhere and deposit. In this regard, according to the present embodiment, since the cut surface 33a is located inside the cover 22 where the amount of soot is relatively small, the amount of soot adhering to the same surface 33a is small. Even if soot is deposited and deposited, the cut surface 33a
Is directed to the outside of the introduction hole 31, so that the accumulation of soot does not cause clogging of the hole 31.

Further, according to the present embodiment, the introduction hole 31 is surrounded by the inner peripheral wall surface of the cylindrical portion 33. Cylindrical part 3
3 is formed by drawing, so that its inner peripheral wall surface becomes a smooth surface whose surface roughness is extremely small as compared with, for example, a shear surface and a fracture surface in punching or a cut surface in cutting. Has become. That is, the introduction hole 31
Has almost no burrs or the like serving as nuclei when soot is attached. Therefore, the intake air flows through the cover 22 through the introduction hole 31.
When it is introduced into the inside, the soot contained in the intake air is prevented from adhering to the inner peripheral wall surface of the hole 31. Also, even if soot adheres, its adhesion is weak,
The soot tends to peel off due to vibration of the cover 22 or the like.

As a result, according to the present embodiment, clogging of the introduction hole 31 by soot can be suppressed, and the detection accuracy of the oxygen sensor 20, particularly, responsiveness can be prevented from deteriorating. .

[Fifth Embodiment] Next, a fifth embodiment of the present invention will be described. FIG. 8 shows the introduction hole 3
1 shows a cross-sectional shape of the cover 22 in the vicinity of 1. As shown in the figure, an annular member 34 having an arc-shaped cross section is attached to the introduction hole 31. The annular member 34 is made of a metal material, and its inner peripheral surface is finished to a smooth surface by, for example, extrusion. As shown in FIG. 9, after the annular member 34 is inserted into the introduction hole 31 in a tubular shape, both sides thereof are separated from the hole 31 by expanding the diameter as shown by arrows in FIG. It is improperly mounted.

According to the present embodiment configured as described above, since the inner peripheral wall surface of the introduction hole 31 is covered with the annular member 34, the intake air hardly comes into contact with the inner peripheral wall surface. Therefore, according to the present embodiment, the adhesion of soot on the inner peripheral wall surface of the introduction hole 31 is reliably suppressed.

The inner peripheral surface of the annular member 34 is formed to be a smooth surface, so that the adhesion of soot to the same surface is suppressed. Therefore, clogging does not occur in the annular member 34, and the intake air passes through the inner peripheral side of the annular member 34 and
Will be quickly introduced inside the As a result, according to the present embodiment, good responsiveness of the oxygen sensor 20 can be ensured.

Further, according to the present embodiment, by attaching the annular member 34 to the existing cover 22, the introduction hole 31 is formed.
Since the clogging of the cover 22 can be prevented, a design change for changing the shape of the cover 22 is unnecessary, and in that sense, an increase in the manufacturing cost of the cover 22 can be avoided.

[Sixth Embodiment] Next, a sixth embodiment of the present invention will be described. In this embodiment,
The fifth embodiment is different from the fifth embodiment in that the shape of the annular member 34, the point that the member 34 is formed of a resin material, and the point that the member 34 is fitted and attached to the introduction hole 31 are provided.

FIG. 10 shows the cover 2 near the introduction hole 31.
2 shows a cross-sectional shape. The annular member 34 is formed of a heat-resistant resin having water repellency (in the present embodiment, polyphenylene sulfide (PPS) containing fluorine). The annular member 34 includes a flange 35 disposed outside the cover 22, a cylindrical portion 36 inserted into the introduction hole 31,
The cover 22 is formed over the entire outer periphery of the cylindrical portion 36 and includes the cover 22.
And a locking portion 37 disposed inside the inside. The outer diameter of the flange 35 is larger than the diameter of the introduction hole 31,
The outer diameter of 6 is set smaller than the diameter of the hole 31.
The outer peripheral surface of the locking portion 37 is a tapered surface 37 a inclined with respect to the axis of the annular member 34.

A circulation hole 38 is formed inside the annular member 34. The inner peripheral surface of this flow hole 38 is the first tapered surface 3
8a and the second tapered surface 38b. In the present embodiment, since the annular member 34 is made of a resin material, each of the tapered surfaces 38a and 38b is processed into a sufficiently smooth surface. Further, each tapered surface 38a, 38b is located at each end side of the annular member 34 (inside or outside of the cover 22).
, So that the inner diameter of the flow hole 38 increases.

When the annular member 34 is fitted into the introduction hole 31, one end portion including the locking portion 37 is inserted into the hole 31 from the direction shown by the arrow in FIG. At this time, since the outer peripheral surface of the locking portion 37 is a tapered surface 37a, the annular member 34
The locking portion 37 is elastically deformed by the force acting on the same surface 37a with the insertion of. Thus, the annular member 34 is inserted into the introduction hole 31 while the locking portion 37 is elastically deformed. When the one end portion of the annular member 34 projects into the cover 22, the locking portion 3 which has been elastically deformed is formed.
7 returns to its original shape again. As a result, as shown in FIG. 10, since the locking portion 37 is locked to the peripheral portion of the introduction hole 31, the annular member 34 is fixed so as not to be detached from the hole 31. Then, the inner peripheral wall surface of the introduction hole 31 is covered with the cylindrical portion 36.

According to the present embodiment configured as described above, even when the inner peripheral wall surface of the introduction hole 31 is formed with irregularities such as burrs, the same surface is covered by the annular member 34, It is possible to suppress the adhesion of soot to the surface.

Further, the inner peripheral surface of the flow hole 38 is processed into a smooth surface, so that adhesion of soot to the same surface is suppressed. Accordingly, clogging does not occur in the flow hole 38, and the intake air is quickly introduced into the cover 22 through the hole 38. As a result, good responsiveness in the oxygen sensor 20 can be secured.

Further, according to this embodiment, similarly to the fifth embodiment, without changing the shape of the cover 22,
Since the clogging of the introduction hole 31 can be prevented only by attaching the annular member 34 to the existing cover 22, an increase in the manufacturing cost of the cover 22 can be avoided.

Further, according to the present embodiment, the annular member 34
An elastically deformable resin material was selected as the material of the first member 34, and the engaging portion 37 was provided on the member 34. Therefore, the annular member 34 can be easily attached to the cover 22 by elastically deforming the annular member 34 and inserting and fitting the same into the introduction hole 31.

Normally, as the temperature of the cover 22 increases, soot is burned by the heat of the cover 22.
Although the amount of adhering soot is reduced, when the temperature of the cover 22 rises extremely (for example, when it becomes 700 ° C. or more),
Conversely, the amount of adhering soot tends to increase.

In this regard, in this embodiment, the annular member 34 is formed of a member separate from the cover 22 and the member 34 is formed of a resin material, so that the temperature of the member 34 is lower than that of the cover 22. can do. Therefore, according to the present embodiment, the annular member 34 is maintained at a relatively lower temperature than the cover 22, and an extreme rise in temperature of the member 34 is suppressed, so that the amount of soot adhering to the member 34 is further reduced. Can be reduced.

In addition, in this embodiment, since the annular member 34 is formed of PPS containing fluorine, the member 34 is given water repellency. Therefore, particularly, the affinity between the inner peripheral surface of the flow hole 38 and the soot can be reduced, and the adhesion of the soot to the same surface can be further suppressed. as a result,
The clogging of the flow holes 38 can be reliably suppressed, and the intake air can be quickly introduced into the inside of the cover 22.

Further, in this embodiment, since the tapered surfaces 38a and 38b are formed on the inner peripheral wall of the flow hole 38, oil or the like adhering to the inner peripheral surface of the hole 38 does not stop and the cover 22 does not stop. It flows down inside or outside.
Therefore, it is possible to suppress soot adhesion from being promoted by using oil or the like attached to the inner peripheral surface of the flow hole 38 as a core.

[Seventh Embodiment] Next, a seventh embodiment of the present invention will be described. FIG. 11 shows a cross-sectional shape of the cover 22 near the introduction hole 31.
In the present embodiment, an annular member 34 is formed by attaching a liquid thermosetting resin (in this embodiment, epoxy resin) to the inner peripheral wall of the introduction hole 31 and then solidifying the same. The inner wall surface of the introduction hole 31 is covered with the member 34. Here, since the thermosetting resin solidifies in a state in which minute irregularities on the surface have disappeared due to surface tension, the surface of the annular member 34 has a smooth surface having no burrs or the like that can be a nucleus to which soot adheres. It has become.

According to this embodiment, substantially the same functions and effects as those of the sixth embodiment can be obtained, and the annular member 34 can be provided.
Is formed of a thermosetting resin, the deformation of the member 34 due to heat can be suppressed. For example, the member 34 can be prevented from being deformed by heat and falling off the cover 22.

Each of the above embodiments can be implemented by changing the configuration as in the other embodiments described below. In these other embodiments, substantially the same operation and effects as those of the above embodiments can be obtained.

(1) In the above embodiments, the oxygen sensor 2
0 is the intake pipe 12 of the engine 11 equipped with the EGR device 15.
It is designed to be attached to. On the other hand, the oxygen sensor 20 according to the present invention may be attached to the intake pipe 12 of the engine 11 including the PCV device or both the device and the EGR device 20.

(2) In each of the above embodiments, the oxygen sensor 2
0 is attached to the intake pipe 12 of the diesel engine 11. On the other hand, the oxygen sensor 20 may be attached to the exhaust pipe 13 of the diesel engine 11. Further, the oxygen sensor may be attached to an exhaust pipe of a gasoline engine or an intake / exhaust pipe of a gasoline engine provided with an EGR device or a PCV device. Further, the present invention is not limited to an internal combustion engine such as a diesel engine and a gasoline engine, and can be embodied as a cover of an oxygen sensor used for a general combustor.

(3) In each of the above embodiments, the circular introduction hole 31 is formed in the cover 22. However, the shape of the introduction hole 31 is not limited to a circular shape. Other shapes, such as a shape, may be sufficient.

(4) In the first or second embodiment,
By etching, plating or coating the entire cover 22, the inner peripheral wall surface of the introduction hole 31 is smoothed. On the other hand, the introduction hole 31
Only the vicinity of the inner peripheral wall surface may be etched. Similarly, plating or coating may be performed only on the inner peripheral wall surface of the introduction hole 31.

(5) In the third embodiment, the enlarged diameter portion 3
2 is formed outside the cover 22. On the other hand, as shown in FIG. 12, the enlarged diameter portion 32 may be formed inside the cover 22. That is, in the introduction hole 31 formed by punching, the inner side portion of the cover 22 often has a broken surface on the inner peripheral wall surface. Therefore, by forming the enlarged diameter portion 32 on the inner side of the cover 22, it is possible to reduce the area of a broken surface (indicated by a two-dot chain line in the figure) on the inner peripheral wall surface of the introduction hole 31. Thus, the adhesion of soot can be reliably suppressed.

(6) In the third embodiment, the cover 2
By forming the enlarged diameter portion 32 on the outer side of 2, the peripheral portion of the introduction hole 31 is made thinner. On the other hand, for example, as shown in FIGS. 13A and 13B, the enlarged diameter portion 32 has a shape in which the inner peripheral wall surface is inclined with respect to the axis of the introduction hole 31. Is also good.

As shown in FIG. 14, the inner diameter of the introduction hole 31 is continuously reduced from the outside to the inside (or from the inside to the outside), whereby
The peripheral portion of 1 may be thinned. Inlet 3
When 1 has the above shape, as shown in FIG.
Soot may be attached to the inner peripheral edge portion of the convex hole 31 in some cases. However, according to this configuration, the soot is deposited in an extremely unstable state as compared with the case where the inner peripheral wall surface of the introduction hole 31 is formed flat (see FIG. 2B). When the amount increases, it tends to peel off due to its own weight. Therefore, clogging of the introduction hole 31 can be suppressed even with the above configuration.

(7) In the fourth embodiment, the cylindrical portion 3
The bending process is performed on the cover 22 so that the tip side portion of the cover 3 is enlarged in diameter. On the other hand, the bending process may be omitted, and the peripheral portion of the introduction hole 31 may be formed in a shape as shown in FIG. Even with such a configuration,
The soot adhering to the distal end surface of the cylindrical portion 33 accumulates toward the inside of the cover 22, so that the introduction hole 31 is not clogged.

(8) In the third embodiment, after the introduction hole 31 is formed by punching, the enlarged-diameter portion 32 is formed so that the peripheral portion of the hole 31 is thinned. On the other hand, after forming the enlarged diameter portion 32, the introduction hole 3 is formed.
1 may be formed.

(9) In the first or second embodiment,
A plating process or a coating process is performed in addition to the etching process. For example, only the etching process, or only the plating process and the coating process are performed.
2 may be performed.

(10) In the first embodiment, plating is performed using electroless nickel or electrolytic nickel. On the other hand, the same process may be performed using copper or chromium.

(11) In the second embodiment, the PTF
A film was formed on the surface of the cover 22 with the E resin. On the other hand, for example, a film may be formed using another resin having heat resistance higher than the intake air temperature (300 ° C.).

The technical ideas that can be grasped from the above embodiments will be described below together with their effects. (A) The oxygen sensor cover according to claim 1, wherein the oxygen sensor is attached to an intake pipe of an internal combustion engine provided with at least one of an exhaust gas recirculation device and a blow-by gas reduction device.

As described above, in the cover of the oxygen sensor attached to the intake pipe of the internal combustion engine, as described above, since the soot contained in the intake air has high adhesiveness, the introduction hole tends to be clogged. is there. The configuration described in (a) is suitable in that the clogging of the introduction hole in the oxygen sensor cover, which tends to be as described above, is suppressed.

(B) The oxygen sensor cover according to claim 1, wherein the inner peripheral wall surface of the introduction hole is subjected to plating treatment or fluororesin coating treatment after etching treatment.

According to the configuration described in (b) above, the inner peripheral wall surface of the introduction hole can be further smoothed, so that clogging of the hole can be reliably suppressed.

[0096]

According to the first aspect of the present invention, a surface smoothing process is performed on the inner peripheral wall surface of the introduction hole to suppress the adhesion of soot . Therefore, since the inner peripheral wall surface of the introduction hole has few irregularities on the surface and does not have burrs or the like serving as nuclei when soot is attached, accumulation of soot is suppressed. As a result, according to the present invention, it is possible to prevent the soot accumulated on the inner peripheral wall surface of the inlet hole from clogging the hole.

In the present invention, the inner peripheral wall surface of the introduction hole is subjected to an etching process, a plating process, and a fluororesin coating process as a surface smoothing process. Therefore, according to the inventions of claims 2 to 4, minute irregularities on the inner peripheral wall surface of the introduction hole are reduced, and the accumulation of soot is suppressed. As a result, it is possible to suppress the hole from being clogged by soot deposited on the inner peripheral wall surface of the introduction hole.

In particular, according to the fourth aspect of the present invention, since the affinity between the inner peripheral wall surface of the introduction hole and the soot is reduced, the amount of soot attached to the inner wall surface is reduced. As a result, according to the invention described in claim 4, clogging of the introduction hole can be suppressed more reliably.

According to the fifth aspect of the present invention, the peripheral portion of the machined raw hole is formed into a shape in which the inner peripheral wall surface of the hole does not face, and the formed peripheral portion forms the inner peripheral wall surface of the introduction hole. I am trying to do it. Therefore, according to the present invention, even if soot adheres and accumulates on the inner peripheral wall surface, clogging of the introduction hole due to the accumulated soot can be suppressed.

According to a sixth aspect of the present invention, in the configuration of the fifth aspect of the present invention, the peripheral portion of the element hole is formed into a shape extending to the inside of the cover. Therefore,
The amount of soot adhering to the inner peripheral wall surface of the hole is further reduced. As a result, in addition to the effect of the invention described in claim 5, clogging of the introduction hole due to soot attached to the inner peripheral wall surface of the element hole can be reliably suppressed.

According to the seventh aspect of the present invention, the inner peripheral wall portion of the introduction hole is locally thinned. Therefore, since the area of the inner peripheral wall surface of the introduction hole is reduced, uneven portions such as burrs on the wall surface are relatively reduced. As a result, the amount of soot adhering to the inner peripheral wall surface can be reduced, and clogging of the introduction hole can be suppressed.

According to the eighth aspect of the invention, the inner peripheral wall surface of the introduction hole is covered by an annular member having a smooth inner peripheral surface. Therefore, even if there is an uneven portion such as a burr on the inner peripheral wall surface of the introduction hole, since the uneven portion is covered by the annular member having the smooth inner peripheral wall surface, adhesion of soot to the inner peripheral wall surface is suppressed. You. On the other hand, the gas to be measured passes through the inside of the annular member and is introduced into the cover, but since the member has a smooth inner peripheral surface, the adhesion of soot to the surface is suppressed. You. As a result, gas can be quickly introduced into the cover while suppressing clogging of the introduction hole.

In the ninth aspect of the present invention, the annular member of the oxygen sensor cover according to the eighth aspect is attached to the inner peripheral wall portion of the introduction hole by fitting. Also,
In the tenth aspect of the present invention, the annular member of the oxygen sensor cover according to the eighth aspect is formed by fixing a resin material to an inner peripheral wall surface. Therefore,
According to the ninth or tenth aspect, in addition to the effect of the eighth aspect, the annular member can be easily provided on the cover.

In the eleventh aspect of the present invention, the resin material in the oxygen sensor cover according to the tenth aspect is a thermosetting resin material. Therefore, in addition to the effect of the invention described in claim 10, since the deformation of the annular member due to heat is suppressed, it is possible to suppress, for example, the member from being deformed and falling off the cover.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a diesel engine system.

FIG. 2 is a cross-sectional view showing a tip portion of the oxygen sensor.

FIG. 3 is a schematic process diagram showing a process of forming an introduction hole.

FIG. 4 is a graph showing an endurance test result of the oxygen sensor.

FIG. 5 is a cross-sectional view of a cover showing the vicinity of an introduction hole according to a third embodiment.

FIG. 6 is a cross-sectional view of a cover showing the vicinity of an introduction hole according to a fourth embodiment.

FIG. 7 is a schematic process diagram showing a process of forming an introduction hole.

FIG. 8 is a sectional view of a cover showing the vicinity of an introduction hole according to a fifth embodiment.

FIG. 9 is a cross-sectional view of the cover for illustrating a forming process of the annular member.

FIG. 10 is a sectional view of a cover showing the vicinity of an introduction hole according to a sixth embodiment.

FIG. 11 is a sectional view of a cover showing the vicinity of an introduction hole according to a seventh embodiment.

FIG. 12 is a sectional view showing the vicinity of an introduction hole according to another embodiment.

FIG. 13 is a sectional view showing the vicinity of an introduction hole according to another embodiment.

FIG. 14 is a sectional view showing the vicinity of an introduction hole according to another embodiment.

FIG. 15 is a cross-sectional view showing the vicinity of the periphery of an introduction hole according to another embodiment and a comparative example.

FIG. 16 is a sectional view showing the vicinity of an introduction hole according to another embodiment.

FIG. 17 shows an EGR device and a PCV provided in an internal combustion engine.
FIG. 1 is a schematic configuration diagram showing an apparatus.

[Explanation of symbols]

20 ... oxygen sensor, 22 ... cover, 31 ... introduction hole, A ...
Raw hole.

Continuation of the front page (56) References Japanese Utility Model Showa Sho 53-46891 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 27/409 G01N 27/00-27/12

Claims (11)

(57) [Claims] An oxygen sensor cover for covering an element of an oxygen sensor for measuring the oxygen concentration of a gas and made of a metal material having an introduction hole through which the gas flows, wherein an inner peripheral wall surface of the introduction hole has An oxygen sensor cover, which has been subjected to a surface smoothing treatment for suppressing the adhesion of soot . 2. The oxygen sensor cover according to claim 1, wherein the surface smoothing process is an etching process. 3. The oxygen sensor cover according to claim 1, wherein the surface smoothing process is a plating process. 4. An oxygen sensor for measuring the oxygen concentration of a gas.
Metal material covering an element and having an introduction hole through which the gas flows
Oxygen sensor cover, comprising:
Fluororesin coating on inner wall surface for surface smoothing
A cover for an oxygen sensor, wherein a cover is provided. 5. An oxygen sensor cover for covering an element of an oxygen sensor for measuring an oxygen concentration of a gas, the cover being made of a metal material having an introduction hole through which the gas flows, and a peripheral portion of the machined element hole. The cover for an oxygen sensor is characterized in that the inlet hole is formed by shaping an inner peripheral wall of the homogenous hole so as not to face each other. 6. The cover for an oxygen sensor according to claim 5, wherein a peripheral portion of said element hole is formed in a shape extending toward an inside of said cover. 7. A cover for an oxygen sensor which covers an element of an oxygen sensor for measuring an oxygen concentration of a gas and is made of a metal material having an introduction hole through which the gas flows, wherein an inner peripheral wall portion of the introduction hole is localized. An oxygen sensor cover characterized in that it is made thinner. 8. An oxygen sensor cover for covering an element of an oxygen sensor for measuring the oxygen concentration of a gas and made of a metal material having an introduction hole through which the gas flows, wherein an inner peripheral wall surface of the introduction hole is smoothed. A cover for an oxygen sensor, wherein the cover is covered by an annular member having a suitable inner peripheral surface. 9. The oxygen sensor cover according to claim 8, wherein the annular member is fitted and attached to an inner peripheral wall portion of the introduction hole. 10. The oxygen sensor cover according to claim 8, wherein the annular member is formed by fixing a resin material to the inner peripheral wall surface. 11. The oxygen sensor cover according to claim 10, wherein said resin material is a thermosetting resin material.