JP2000088795A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor which is superior in productivity and built-in property without the fear of separating an electrode film and a coating layer of a gas concentration-detecting element such as an oxygen-detecting element or the like. SOLUTION: An oxygen sensor 1 as the sensor has a gas concentration- detecting element 10 with a touch gas part to be in touch with a gas to be measured, a housing 41 for holding the gas concentration-detecting element 10 and a protecting cover 21 for covering the touch gas part of the gas concentration-detecting element 10 with having a gas hole for circulation of the gas to be measured. A looped groove 45 is provided between a caulked projecting part 43 and an inner projecting part 44 at the side of the gas of the housing 41. An opening flange 213 of the protecting cover 21 is fitted in the looped groove 45 and moreover, the caulked projecting part 43 is caulked to a direction of the protecting cover 21. A projection length of the inner projecting part 44 of the housing 41 is shorter than a projection length of the caulked projecting part 43.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a gas sensor for detecting an air-fuel ratio state of an internal combustion engine such as an automobile internal combustion engine, an oxygen concentration of exhaust gas, a NOx concentration, a CO concentration, and the like.
In particular, the present invention relates to a caulking fixing structure for fixing a protective cover that covers a gas concentration detecting element.

[0002]

2. Description of the Related Art For example, adjustment of the air-fuel ratio of an internal combustion engine is extremely important for energy saving (fuel saving) and purification of exhaust gas. To control the air-fuel ratio, the exhaust system of the internal combustion engine is provided with an air-fuel ratio sensor that can detect the air-fuel ratio, which is a type of oxygen sensor. An electrochemical cell to which an electrode made of Pt or the like is added and which has a built-in sensing element made of an electrochemical cell is used.

That is, as shown in FIG. 14, for example, an oxygen sensor 90 comprises a bottomed cylindrical gas concentration detecting element 91 forming an electrochemical cell, and a container 92 containing the gas concentration detecting element 91. Have. The container 92 has a housing 93 that holds a gas concentration detection element 91. The housing 93 is formed with a screw portion 931 for mounting the sensor body in an exhaust passage of an exhaust system. The portion beyond the screw portion 931 is inserted into the exhaust passage and mounted. Further, the gas concentration detecting element 91 is fixed to the housing 93 via talc 932.

Further, inside the gas concentration detecting element 91,
Normally, a heater unit 96 is inserted, and the heater unit 96 is connected to the gas concentration detecting element 91 via a holder 961.
It is supported by. The gas concentration detection element 91 is heated by the heater unit 96, and the temperature distribution at the time of operation is high at a portion near the front end. The gas concentration detection element 91 has a bottomed cylindrical solid electrolyte and an electrode (not shown) for taking out output.

The electrodes of the gas concentration detecting element 91 are
The output line 97 is connected to the heater unit 96.
Are connected to a power supply line 972. The gas concentration detecting element 91 has a gas contact part 911 at the lower part thereof, which is in contact with the gas to be measured.

On the other hand, a protective cover 94 is swaged and fixed below the housing 93 (tip side) so as to cover the gas contact portion 911 of the gas concentration detecting element 91 (FIG. 1).
4, FIG. 17). On the side surface of the protective cover 94, a gas hole 944 for introducing exhaust gas to be measured is provided. In addition, cover members 951 to 953 that are in contact with the atmosphere are provided on the base end side above the housing 93.

On the other hand, the cover members 952 and 953 are provided with atmosphere ports 954 and 955 for introducing the atmosphere. In addition, a water-repellent ventilation filter 956 is provided between the cover members 952 and 953 in an air introduction passage that connects the air ports 954 and 955 to each other.
Further, as shown in FIG.
Is made of an oxygen ion conductive ceramic formed of zirconia or the like, has an inner electrode 917 made of Pt on the inner surface, and an outer electrode 918 made of Pt on the outer surface, and further has a surface protection ceramic formed thereon. Coating layer 919.

A description will be given of caulking and fixing of the housing 93 and the protective cover 94.
As shown in FIG. 17, first, the housing 93 has a caulking protrusion 935 for caulking and fixing the protective cover to the measured gas side, an inner protruding portion 936 for restraining the inside of the protective cover, and a ring provided between them. And a groove 937. On the other hand, the protective cover 94 is a cylindrical body with a bottom and has a plurality of gas holes 944 for flowing the gas to be measured. In addition, an opening flange 940 is provided at the upper end.

When the protective cover 94 is fixed to the housing 93 by caulking, first, an opening flange 940 of the protective cover 94 is fitted into the annular groove 937 of the housing 93 as shown in FIG. Next, as shown in FIGS. 14 and 16, the caulking protrusion 935 is bent in the direction of the opening flange 940 and caulked and fixed. In this manner, in the conventional oxygen sensor, the protective cover is caulked and fixed to the housing (actually, Japanese Patent Publication No. 6-3261).
6, Tokuhei 5-15221).

[0010]

However, the conventional oxygen sensor has the following problems. That is, in the conventional oxygen sensor 90, the protrusion length K of the caulking protrusion 935 of the housing 93 and the protrusion length U of the inner protrusion 936 are formed to be the same protrusion length (FIGS. 14 to 14). 16). Therefore, as shown in FIG. 17, the inner protruding portion 936 becomes longer than necessary, and the inner protruding portion 936 approaches the gas concentration detecting element 91 to generate a narrow and long gap 939.

The gap 939 between the inner protruding portion 936 and the gas concentration detecting element 91 is different from the measured gas side of the gas concentration detecting element 91 in that heat transfer of high-temperature exhaust gas and heat sink are not performed. The temperature is relatively low because of the balance.

Further, since the gap 939 is recessed, the gas flow of the gas to be measured is stagnated, and carbon from unburned components such as HC in the exhaust gas tends to adhere. Then, the deposited carbon reacts with the element electrode made of Pt and grows into whiskers. At this time, the outer electrode 1 formed on the surface of the gas
No. 8 platinum (Pt) electrode film is consumed together to cause electrode deterioration. In the part where the electrode was consumed and disappeared,
The coating layer (protective layer) 919 made of ceramic formed thereon is peeled off. This leads to a decrease in the performance of the gas concentration detection element 91.

The caulking protrusion 935 and the inner protrusion 9
36 is formed by cutting or the like. The depth of the annular groove 937 is processed from the end surface of the housing. If this depth is large, the abrasion of a processing blade or the like for forming the annular groove 937 is fast, and productivity is low. Also, caulking protrusion 935 and inner protrusion 93
6 has the same protruding length (K = U), as shown in FIG. 15, when the opening flange 940 of the protective cover 94 is inserted into the annular groove 937, the caulking protrusion 93 is formed.
5 and the inner projection 936 at the same time the opening flange 9
40 interferes with each other, and it is difficult to assemble the two.

Such a problem is a problem common to not only oxygen sensors and air-fuel ratio sensors but also various gas sensors (various gas sensors for detecting NOx, CO, HC) which are installed and used in an exhaust system of an internal combustion engine. .

The present invention has been made in view of the above-mentioned conventional problems, and provides a gas sensor which is excellent in productivity and assemblability without the possibility of peeling of an electrode film and a coating layer of a gas concentration detecting element such as an oxygen detecting element. What you want to do.

[0016]

According to a first aspect of the present invention, there is provided a gas concentration detecting element having a gas contact portion in contact with a gas to be measured, a housing for holding the gas concentration detecting element, and a gas contact portion of the gas concentration detecting element. And a protective cover having a gas hole for flowing the gas to be measured, and having an annular groove between the caulked projection and the inner projection on the side of the gas to be measured of the housing. In the gas sensor in which the protective cover is caulked and fixed to the housing by fitting the opening flange of the protective cover and caulking the caulking protrusion in the direction of the protective cover, the protruding length of the inner protruding portion of the housing is provided. In the gas sensor, U is shorter than the length K of the caulked projection.

The most remarkable point in the present invention is that, with respect to the caulking protrusion and the inner protrusion provided on both sides of the annular groove, the protrusion length of the inner protrusion is shorter than the protrusion length of the caulking protrusion. is there.

Next, the operation and effect of the present invention will be described.
In the present invention, the protrusion length U of the inner protrusion is shorter than the protrusion length K of the caulking protrusion (FIG. 2).
Therefore, the length of the gap between the inner protruding portion and the gas concentration detecting element such as the oxygen detecting element can be shortened. Therefore, the length of the gap is shorter than in the conventional case (FIG. 14).

Therefore, the growth of the deposited carbon in the element having the platinum (Pt) electrode is small, and there is no possibility of the electrode film deterioration and the peeling of the coating layer due to the deposited carbon. Therefore, the performance of the gas concentration detecting element can be maintained for a long time. The comparison between the lengths of the caulking protrusion and the inner protrusion is performed before the caulking protrusion is fixed.

Further, when forming the annular groove, it is sufficient to cut only the same depth as the length of the inner protruding portion. Therefore, as compared with the conventional example, the processing load on the processing blade is reduced by the difference (K−U) between the protruding length K of the caulked protruding portion and the protruding length U of the inner protruding portion (FIG. 4). . Therefore, wear of the blade is small and productivity is high.

Further, since the inner protruding portion is shorter than the caulking protruding portion, the inner protruding portion is formed deeper in the inside than the front end of the housing (FIGS. 2 and 3). Therefore, the opening flange of the protective cover can be easily fitted into the annular groove by being inserted into the inside of the caulking projection, and the assemblability between the protective cover and the housing is excellent. When the housing is formed by cold forging by adopting the housing shape of the present invention, the material can be reduced by the dimensional difference (K−U) between the caulked projection and the inner projection, and the productivity can be improved. .

Therefore, according to the present invention, it is possible to provide a gas sensor which is excellent in productivity and assembling property without causing the possibility of peeling of the electrode film and the coating layer of the gas concentration detecting element such as the oxygen detecting element. .

Next, as in the second aspect of the invention, the ratio U / K of the protrusion length U of the inner protrusion of the housing to the protrusion length K of the caulking protrusion is 0.2 to 0.85. Is preferably within the range. Thereby, the effect of the present invention can be reliably obtained.

If U / K is less than 0.2, the length of the inner protruding portion is short, so that the protection cover is not sufficiently restrained by the annular groove, and the durability of the caulking may be reduced. . On the other hand, if U / K exceeds 0.85, the productivity may be reduced because the amount of groove processing for the housing is increased in producing the annular groove.

The more preferable lower limit of U / K is 0.3.
5 or more. By setting U / K to a value larger than this, the curvature of the opening flange of the protective cover can be increased, and the workability of the protective cover can be improved. Further, since the thickness of the protective cover can be increased, the strength can be improved. The more preferable upper limit of U / K is 0.75 or less. By setting U / K to a value less than this, a space can be more reliably formed between the inner protruding portion and the gas concentration detecting element, and stagnation of the flow of the gas to be measured can be reduced.

Next, as in the third aspect of the present invention, the annular groove includes an inner wall surface formed by the inner protruding portion, an outer wall surface formed by the caulking protrusion portion, and a ceiling surface. It is preferable that a tapered portion is provided inside the annular groove from the inner wall surface to the ceiling surface.

By providing the tapered portion, the protective cover is restrained at three points of X, Y, and Z shown in FIG. 13, so that a bending force acts on these three points as fulcrums. For this reason, even when springback occurs after caulking of the caulking protrusion, the restraining force (pressing force by caulking) works reliably to stably fix the cover. As a result, the protective cover does not rotate along the annular groove and does not rattle after being fixed by caulking.

The tapered portion may be formed in a straight line or a plane as shown in FIG. 13 to be described later, or may be formed in a curved surface.

Next, as in the invention of claim 4, the projecting length of the inner projecting portion is larger than the thickness of the opening flange of the protective cover which comes into contact with the ceiling surface of the annular groove. Is preferred. In this case, the opening flange can be more securely restrained and fixed between the inner protruding portion and the caulking protruding portion.

Next, as in the fifth aspect of the present invention, the protective cover includes two or more covers, and the opening flanges of each cover are collectively swaged and fixed by the swaging projections. Is preferred. In this case, for example, the outer cover and the inner cover as a plurality of covers can be simultaneously fixed to the housing, so that the number of assembling steps can be reduced. Further, since two or more protective covers are provided, the gas concentration detecting element can be protected more reliably.

Next, as in the invention of claim 6, the protective cover comprises an outer cover and an inner cover, the opening flange of the outer cover is fixed by swaging with the swaging protrusion, and the inner cover is fixed to the outer cover. It is preferably fixed to the cover. In this case, the gas concentration detecting element can be more reliably protected by the outer cover and the inner cover as described above, and only the opening flange of the outer cover is caulked and fixed, so that the caulking operation is facilitated.

Next, the outer cover and the inner cover are provided with a plurality of gas holes for introducing a gas to be measured. It is preferable that the gas hole located at a position closer to the housing is provided at a position closer to the housing than the gas hole provided at the outer cover at the position closest to the housing. As a result, the inflow and outflow of the gas to be measured into and out of the protective cover is performed in the entire space surrounded by the protective cover, and the exchange of the gas to be measured in this space is improved, and the output characteristics of the gas sensor are improved. It will be good.

Next, it is preferable that the opening flange of at least one of the protective covers is uneven. In this case, since the opening flange has irregularities in its thickness direction, an elastic action occurs, and even when springback occurs after caulking of the caulking projection, the restraining force (pressing force due to caulking) works reliably. Is fixed stably. As a result, the protective cover does not rotate along the annular groove and does not rattle after being fixed by caulking.

Next, it is preferable that the housing is a forged product. In this case,
The material can be reduced by the size difference (KU in FIG. 2) between the caulked protrusion and the inner protrusion, and the productivity is improved.

Next, it is preferable that the housing is made of a material having a lower hardness than the protective cover. This makes it easier for the protective cover to bite into the housing after caulking, making it difficult for the protective cover to be loosened in the circumferential direction of the housing.

Further, since the housing is softer, the housing is easily deformed by caulking, but the protective cover is harder and hardly deformed. That is, since a restoring force acts on the protective cover, the protective cover is fixed by caulking in the annular groove of the housing in a state where it is unlikely to be loosened in the axial direction of the housing or the like.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment An oxygen sensor as a gas sensor according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 2, the oxygen sensor 1 of the present embodiment has an oxygen sensing element 10 having a gas contact portion 11 that comes into contact with a gas to be measured, a housing 41 holding the oxygen sensing element 10, and the oxygen sensing element. The protective cover 21 covers the gas contact part 11 of the element 10 and has a gas hole 211 for flowing the gas to be measured.

The housing 41 has an annular groove 45 between the caulking projection 43 and the inner projection 44 on the measured gas side, and the opening flange 213 of the protective cover 21 is fitted into the annular groove 45. At the same time, the caulking projection 43 is caulked in the direction of the protective cover 21, thereby caulking and fixing the protective cover 21 to the housing 41.
In FIG. 2, reference numeral 46 denotes a ceiling surface. The protruding length U of the inner protruding portion 44 of the housing 41 is shorter than the protruding length K of the caulking protruding portion 43, and the protruding length K of the caulking protruding portion 43 is smaller than that of the opening flange 213 of the protective cover 21. It is larger than the thickness.

The protective cover 21 has an opening flange 213 at an upper end, and a plurality of gas holes 211 for flowing a gas to be measured in a cylindrical portion 210 as a main body (FIGS. 1, 2, and 5). . Further, in this example, the protruding length U of the inner protruding portion 44 is 1.4 mm, the protruding length K of the caulking protruding portion 43 is 2.4 mm, and U / K is about 0.58. In addition,
The protrusion length K of the caulking protrusion 43 is the length before caulking.

In this embodiment, the housing 41 is made of stainless steel SUS430 having a hardness of about Hv: 220, and the protective cover 21 is made of stainless steel SUS310SCP having a hardness of about 350 Hv. That is, the housing 41 is softer than the protective cover 21.

Next, the operation of this embodiment will be described. In the present example, the protrusion length U of the inner protrusion 44 is formed shorter than the protrusion length K of the caulking protrusion 43 (FIG. 2). The length of the gap between them is shorter than that of the conventional case (FIG. 15). Therefore, a phenomenon such as growth due to mutual reaction of the carbon adhered to the element with platinum (Pt) of the element electrode is less likely to occur, and there is no risk of electrode film deterioration due to the deposition of the carbon adhered or peeling of the coating layer. Therefore,
The performance of the oxygen sensing element can be maintained for a long time.

Further, as shown in FIG. 4, the annular groove 45 is formed by a step 450 on the side of the measured gas of the housing 41.
A forged housing having a step is prepared.
50 is performed by cutting to the same depth as the protruding length U of the inner protruding portion 44. Therefore, as compared with the conventional example, the processing load on the processing blade is reduced by the difference (K−U) between the protrusion length K of the caulked protrusion and the protrusion length U of the inner protrusion. Therefore, wear of the blade is small and productivity is high. If the housing is made from the beginning only by cutting, the step 450 must also be cut. However, in this example, since the housing is a forged product, a greater effect is exhibited as described above.

Further, the inner protruding portion 44 is
3 is formed at the back of the housing (FIGS. 2 and 3). Therefore, the opening flange 213 of the protective cover 21 can be guided only inside the caulking projection 43. Therefore, it can be inserted smoothly and can be easily fitted into the annular groove 45.
It is also excellent in the assemblability of both.

The protruding length U of the inner protruding portion 44
Is larger than the thickness of the opening flange 213 of the protective cover 21. Therefore, the opening flange 213 can be reliably restrained from the inside by the inner protruding portion 44, and
Caulking can be more securely fixed.

Further, the housing 41 is provided with the protective cover 2.
Since the protective cover 21 is made of a softer material than that of the protective cover 2, the protective cover 21 easily bites into the housing 41 after caulking, and the protective cover 2 extends in the circumferential direction of the housing 41.
1 can be hardly generated.

Also, when the housing 41 is fixed by caulking,
Is soft and easily deformed, but the protective cover 21 is hardly deformed. That is, since a restoring force acts on the protective cover 21, the protective cover 21 is fixed by caulking in the annular groove 45 of the housing 41 in a state in which the housing 41 and the like are not easily loosened in the axial direction.

The oxygen sensor 1 of this embodiment is used as an air-fuel ratio sensor for detecting the air-fuel ratio of an automobile engine, and its outline will be described below. That is, as shown in FIG. 1, the housing 41 of the container 40 has a screw portion 41 which is screwed into a screw hole provided in an exhaust passage of an automobile engine.
4 and a mounting flange 415 that contacts the exhaust passage.

The cover member 44 located on the base end side
2, 443 are provided with air intakes 444, 445 for introducing air into the oxygen sensing element 10. In addition, in the atmosphere introduction passage between the atmosphere intakes 444 and 445,
A water-repellent ventilation filter 446 is provided.

The oxygen sensing element 10 is held in the inner cavity of the housing 41 via a packing 417 and talc 416. In FIG. 1, reference numeral 462 denotes a gasket, and reference numeral 4 denotes a gasket.
Reference numeral 63 denotes a metallic ring, and reference numeral 161 denotes an output lead line.
Further, inside the oxygen detecting element 10, a heater unit 20 is provided.
Are inserted, and the heater unit 20 is
Is supported by the oxygen sensing element 10 via the

A heating wire is attached to the heater unit 20, and the heating wire is connected to a power supply line (not shown). The output line 161 and the power supply line are fixed by cover members 442 and 443 via a bush 447. Further, an air passage is provided (not shown) for guiding the air taken in from the air inlets 444 and 445 to the inside of the oxygen detection element 10.

Embodiment 2 In this embodiment, as shown in FIG. 6, an inner cover 22 is further provided inside a protective cover 21 so that both opening flanges 213 and
This is an example in which 223 are collectively caulked and fixed by the caulking protrusion 43. In the case of this example, the protective cover 21 functions as an outer cover. The inner cover 22 also has a plurality of gas holes 221. According to this example, the outer cover and the inner cover as the plurality of protective covers can be firmly fixed to the housing 41 at the same time. Thereby, the number of assembling steps can be reduced. Further, since the protective cover is provided in duplicate, the oxygen detecting element 10 can be protected more reliably. Others are the same as the first embodiment, and the same effects can be obtained.

Third Embodiment As shown in FIG. 7, this embodiment has a protective cover 21 as an outer cover and an inner cover 22 as in the second embodiment. This is an example in which an opening flange 213 of the protective cover 21 is fixed by caulking with a welding portion 28.

According to this embodiment, the oxygen detecting element can be more securely protected by the outer cover and the inner cover as described above, and only the opening flange 213 of the outer cover is fixed by caulking, so that the caulking operation is easy. Becomes Further, the welding position may be not only the position of the welded portion 28 in FIG. 7 but also another position (for example, a bottom or the like). Others are the same as those of the second embodiment, and similar effects can be obtained.

Embodiment 4 As shown in FIG. 8, this embodiment is an example in which a bent and widened portion 225 facing the opening flange 223 is provided on the upper part of the inner cover 22 in Embodiment 2 as shown in FIG. Thereby, the inner cover 2
The range of the second cylindrical portion 220 can be widened, and the degree of freedom in designing gas holes formed here can be improved. Others are the same as those of the second embodiment, and the same operation and effect can be obtained.

Fifth Embodiment As shown in FIG. 9, this embodiment is an example in which the middle cover 23 is disposed between the outer cover 21 and the inner cover 22 in the second embodiment. The middle cover 23 has a plurality of gas holes 231 and an opening flange 233. The opening flanges 213, 233, 223 of the outer cover 21, the middle cover 23, and the inner cover 22 are caulked and fixed together by the caulking protrusion 43. Others are the same as the second embodiment. According to this example, the same effect as that of the second embodiment can be obtained. Further, since three covers are used, the oxygen detecting element 10 can be protected more reliably.

Embodiment 6 In this embodiment, as shown in FIG. 10, the opening flange 214 of the protective cover 21 is formed in a corrugated shape. Other configurations are the same as those of the first embodiment. According to the present example, since the opening flange 214 has an uneven shape in the thickness direction, an elastic force acts to return to the uneven shape when the caulking protrusion 43 is caulked and fixed. Therefore, the protective cover 21 does not rattle between the caulking protrusion 43 and the annular groove 45, and the protective cover 21 does not rotate along the annular groove 45 of the housing 41. In addition, the same functions and effects as those of the first embodiment can be obtained.

Seventh Embodiment As shown in FIG. 11, the oxygen sensor of this embodiment has a protective cover 21 as an outer cover and an inner cover 22 as in the second embodiment. Holes 221 and 22
2 are provided. The gas hole 223 provided at the position closest to the housing in the inner cover 22 in FIG.
Is the center line of C1, and the center line of the gas hole 224 provided on the outer cover 21 closest to the housing is C2.
In the oxygen sensor of the present embodiment, the center line C1 is closer to C2.
Rather than on the housing side. Gas hole 2
24 and the gas holes 223 are mutually connected to the outer cover 21 and the inner cover 2.
The projection positions for 2 do not overlap.

With this configuration, the outer cover 2
1, the inflow and outflow of the gas to be measured into and out of the inner cover 22 are performed in the entire space surrounded by the gas, and the exchange of the gas to be measured in this space is improved, and the output characteristics of the oxygen sensor are improved. It will be good. Otherwise, the same operation and effect as those of the first embodiment can be obtained.

When the oxygen sensor of this embodiment is installed in the exhaust system of an automobile engine, the output periodically rises and falls according to the air-fuel ratio of the engine, as shown in FIG. In the figure, the range indicated by R corresponds to the output when the air-fuel ratio of the engine is on the rich side, and the range indicated by L corresponds to the lean side. As shown in FIG. 11, the amplitude Va of the output was measured by preparing an oxygen sensor having C1 on the housing side and an oxygen sensor having C2 on the housing side.

As a result of this measurement, as shown in FIG. 12B, a larger Va could be obtained with the oxygen sensor having C1 on the housing side. Thus, it was found that the replacement of the exhaust gas into the cover was more reliably performed as shown in FIG.

Eighth Embodiment As shown in FIG. 13, the oxygen sensor of this embodiment has a protective cover 21 as an outer cover and an inner cover 22 as in the second embodiment. The annular groove 45 to which the outer cover 21 and the inner cover 22 are caulked is fixed.
4 and an inner wall surface 440 and a caulking projection 43
, And a ceiling surface 46, and a flat tapered portion 49 is provided inside the annular groove 45 from the inner wall surface 440 to the ceiling surface 46.

By fixing the outer cover 21 and the inner cover 22 in such an annular groove 45 by caulking, as shown in FIG.
5 and is fixed by being restrained at this point. Accordingly, a bending force acts on these three points X, Y, and Z as fulcrums.

For this reason, even when springback occurs after the caulking of the caulking protrusion 43, the restraining force (pressing force by caulking) works reliably to stably fix the outer cover 21 and the inner cover 22. This prevents the outer cover 21 and the inner cover 22 from rotating along the annular groove 45 or rattling after being fixed by caulking. Otherwise, the same operation and effect as those of the first embodiment can be obtained.

In the present invention, the shape of the gas concentration detecting element is not limited to the cup shape shown in the embodiment, but may be a laminated plate. In each embodiment, the oxygen sensor has been described as an example. However, it is needless to say that the present invention can be applied to other gas sensors such as a NOx sensor. Furthermore, the gas hole of the protective cover has been described as an example of a round hole, but the hole shape is a long hole, slit shape, etc.
Anything is good and the hole position can be arbitrarily designed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an oxygen sensor according to a first embodiment.

FIG. 2 is an explanatory view of caulking and fixing a protective cover to a housing in the first embodiment.

FIG. 3 is a sectional perspective view of a housing in the first embodiment.

FIG. 4 is an explanatory view of processing an annular groove on a measured gas side of a housing in the first embodiment.

FIG. 5 is a perspective view of a protective cover according to the first embodiment.

FIGS. 6A and 6B are an overall view and a partially enlarged explanatory view of a swaged fixing portion of a protective cover to a housing in a second embodiment.

FIG. 7 is an explanatory view of caulking and fixing a protective cover to a housing in a third embodiment.

FIG. 8 is an explanatory view of caulking and fixing a protective cover to a housing in a fourth embodiment.

FIG. 9 is an explanatory view of caulking and fixing of a protective cover to a housing in a fifth embodiment.

FIG. 10 is a perspective view of a protective cover according to a sixth embodiment.

FIG. 11 is an explanatory diagram of a protective cover according to a seventh embodiment.

FIG. 12 is a diagram showing the relationship between the time and the output of the oxygen sensor according to the seventh embodiment, (b) C1 is an oxygen sensor located on the housing side, and C2 is located on the housing side. FIG. 9 is a diagram showing measured values of a value of Va according to (a) with a certain oxygen sensor.

FIG. 13 is an explanatory view of an annular groove having a tapered portion and a crimp-fixed protective cover in the eighth embodiment.

FIG. 14 is a sectional view of a conventional oxygen sensor.

FIG. 15 is an explanatory view of inserting a protective cover into a housing in a conventional oxygen sensor.

FIG. 16 is an explanatory diagram of a projection length of an inner projection and a caulking projection in a conventional oxygen sensor.

FIG. 17 is an explanatory view of a gap between an inside protruding portion and an oxygen detection element in a conventional oxygen sensor.

[Explanation of symbols]

 1. . . Oxygen sensor, 10. . . 10. oxygen sensing element, . . 21. Gas contact part, . . Protective cover, 213. . . Opening flange, 22. . . Inner cover, 41. . . Housing, 43. . . Swaging, 44. . . Inward projection, 45. . . Annular groove, 49. . . Tapered part,

Continued on the front page (72) Inventor Takashi Kojima 1-1-1, Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 2G004 BB01 BF11 BF18 BF27 BM04 BM07

Claims (10)

[Claims] A gas concentration detecting element having a gas contacting portion in contact with a gas to be measured; a housing for holding the gas concentration detecting element; A protective cover having a gas hole, and an annular groove between the caulking projection and the inner projection on the measured gas side of the housing, and an opening flange of the protective cover is fitted into the annular groove. In the gas sensor in which the protective cover is caulked and fixed to the housing by caulking and caulking the caulking protrusion in the direction of the protective cover, the protruding length U of the inner protruding portion of the housing is determined by the protruding length of the caulking protrusion. A gas sensor characterized by being shorter than the length K. 2. The projection length U of the inner projection of the housing and the projection length K of the caulking projection according to claim 1.
The ratio U / K of the gas sensor is in the range of 0.2 to 0.85. 3. The annular groove according to claim 1, wherein the annular groove includes an inner wall surface defined by the inner protruding portion, an outer wall surface defined by the caulked projection portion, and a ceiling surface. A gas sensor, wherein a tapered portion is provided from the inner wall surface to the ceiling surface inside the gas sensor. 4. The method according to claim 1, wherein:
The gas sensor according to claim 1, wherein a length of the inner protruding portion is equal to or greater than a thickness of an opening flange of the protective cover that comes into contact with a ceiling surface of the annular groove. 5. The protective cover according to claim 1, wherein the protective cover comprises two or more covers, and the opening flanges of each cover are fixed together by the caulking projection. Characteristic gas sensor. 6. The method according to claim 1, wherein:
The gas sensor according to claim 1, wherein the protective cover includes an outer cover and an inner cover, an opening flange of the outer cover is fixed by the caulking protrusion, and the inner cover is fixed to the outer cover. 7. The outer cover and the inner cover according to claim 5, wherein the outer cover and the inner cover are provided with a plurality of gas holes for introducing a gas to be measured, and are provided in the inner cover at a position closest to the housing. A gas hole provided in the outer cover is provided at a position closer to the housing than a gas hole provided at the outer cover and located closest to the housing. 8. The method according to claim 1, wherein:
The gas sensor according to claim 1, wherein an opening flange of at least one of the protective covers is uneven. 9. The method according to claim 1, wherein:
The said housing is a forged product, The gas sensor characterized by the above-mentioned. 10. The gas sensor according to claim 1, wherein the housing is made of a material having a lower hardness than the protective cover.