JP2000193632A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve ventilation when making functioning by means of introducing air from the outside. SOLUTION: An oxygen sensor 1, used as this gas sensor, is equipped with a first air hole 46 and a second air hole 58 opening toward the inside of a cylindrical cover 16 at respectively different positions in the axial direction of a cylindrical cover 16. Therefore, by installing the oxygen sensor 1 in a tube for forming a passage of the gas to be measured so that the cylindrical cover 16 is positioned, for example, facing roughly upward, a gas flow from the first air hole 46 to the second air hole 58 is generated, to thereby obtain satisfactory ventilation inside the oxygen sensor 1. Therefore, even if gas other than air (for example, vaporized oil at a high temperature or the like) penetrates the inside of the oxygen sensor 1, the gas can be rapidly discharged to the outside, to thereby maintain the original detection performance of the oxygen sensor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor which is attached to a pipe forming a flow path through which a gas to be measured such as exhaust gas flows, and which functions by introducing air as a reference gas from the outside.

[0002]

2. Description of the Related Art Conventionally, various types of gas sensors, such as an HC sensor and a NOx sensor, have been known as gas sensors for detecting the concentration of a specific gas component from a mixed gas. For example, as shown in FIG. 5, an oxygen sensor 501 including a detection element 502 made of an oxygen ion conductive solid electrolyte body is known.

The detection element 502 is formed in a bottomed cylindrical body having one end closed and the other end opened by a solid electrolyte body, and an inner electrode 503 and an outer electrode 504 formed on the inner and outer surfaces, respectively. An electromotive force is generated between the two electrodes 503 and 504 in accordance with the difference in oxygen concentration between the inside space and the outside of the detection element 502 formed in a cylindrical body. For example, in the exhaust pipe of an internal combustion engine, the closed end of the detection element 502 is projected through the cylindrical metal shell 505 to the inside of the exhaust pipe so that the outer electrode 504 is exposed to the exhaust gas, and the inner electrode 503 is exposed to the atmosphere. If touched, both electrodes 503, 50
The oxygen concentration in the exhaust gas can be detected by detecting the electromotive force generated between the four.

The detecting element 502 is housed in a casing made of a metal shell 505, a cylindrical cover 506, and the like so as not to be exposed to water or the like. In this case, introduction of the atmosphere into the oxygen sensor, that is, into the inner electrode 503 of the detection element 502 is performed as follows.
Although it can be performed through the gap between the twisted core wires of the lead wires 507 connected to the electrodes and the like, a vent hole 509 is provided on the side surface of the cylindrical cover 506 so that a large amount of air can be introduced, and water and the like can enter. In order to prevent this, for example, a vent hole 509 is formed by a water-repellent filter 508 made of fluororesin having air permeability.
The technique of closing the space has been used conventionally.

[0005]

When such an oxygen sensor 501 is used for detecting the concentration of oxygen in a high-temperature exhaust gas, the water-repellent filter 508 is placed at a high temperature. In this case, if oil, detergent liquid, or the like adheres to the water-repellent filter 508, they may evaporate and enter the inside of the casing together with the atmosphere. It is also conceivable that the performance will not be fully exhibited.

[0006] These problems occur not only in the above-described oxygen sensor, but also in other gas sensors such as a NOx sensor, an HC sensor, and the like, which require introduction of air as a reference gas. The present invention has been made in view of such a problem, and an object of the present invention is to improve the ventilation inside a gas sensor that functions by introducing the atmosphere from the outside.

[0007]

Means for Solving the Problems and Effects of the Invention A gas sensor according to the present invention (described in claim 1) made to solve the above problems is provided on the first and second surfaces of an oxygen ion conductive solid electrolyte body. A detection element having electrodes formed thereon, and a mounting portion mounted on a mounting hole provided on a wall surface of a tube forming a flow path of the gas to be measured, and further having the mounting portion through the mounting hole, A metal shell for holding the detection element such that the first surface is disposed inside the tube, and an air inlet is provided on the second surface, the metal shell being provided outside the tube with respect to the mounting portion of the metal shell. And a cylindrical cover having a ventilation portion for ventilating the cylindrical cover, wherein the ventilation portion has a plurality of ventilation holes that open into the interior of the cylindrical cover at at least two different positions in the axial direction of the cylindrical cover. Pores, closing the vents,
It is characterized by comprising a breathable water-repellent filter.

[0008] In the gas sensor according to the present invention having the above-described structure (claim 1), the ventilation portions for introducing the air into the inside of the cylindrical cover are formed at different positions in the axial direction of the cylindrical cover. It is composed of at least two air holes that open inside the cover, and a gas-permeable water-repellent filter that closes the air holes.

When the gas sensor of the present invention is mounted on a pipe forming a flow path of a gas to be measured, if the cylindrical cover is directed substantially upward, for example, one of the plurality of ventilation holes, which is closer to the pipe, is provided. The pores are located at lower positions.
At a high temperature, the convection phenomenon occurs due to the warming of the gas inside the cylindrical cover, and a gas flow is generated from the lower position ventilation hole to the higher position ventilation hole. That is,
Atmosphere is introduced into the inside of the cylindrical cover through a ventilation hole near the pipe forming the flow path (that is, a ventilation hole at a low position), and is discharged from the ventilation hole far from the pipe (that is, a ventilation hole at a high position) to the outside of the cylindrical cover. As a result, the ventilation performance inside the cylindrical cover is improved.

Therefore, according to the gas sensor of the present invention (claim 1), since the ventilation inside the cylindrical cover can be improved, a gas other than the atmosphere (for example, vaporized at a high temperature) is temporarily stored inside the cylindrical cover. Oil, etc.) can be quickly discharged to the outside,
The original detection performance of the gas sensor can be maintained.

When the gas sensor is mounted on the exhaust pipe of an automobile, a tubular cover may be mounted substantially upward on the upper side of the exhaust pipe in order to reduce the possibility that a stone or the like hit by the tire will collide. Many. In that case, in the conventional gas sensor, even if it has a plurality of vents, since the position in the axial direction of the cylindrical cover is the same, the flow of gas from one vent to the other vent is unlikely to occur, Ventilation may not be sufficient. On the other hand, according to the gas sensor of the present invention, since a plurality of ventilation holes that open inside the cylindrical cover at different positions in the axial direction of the cylindrical cover are provided, efficient ventilation can be achieved by a convection phenomenon. is there.

When the gas sensor is used for detecting the concentration of a component to be detected in a high-temperature gas to be measured, the gas sensor is placed at a high temperature. The effect may be reduced. However, since heat is less likely to be transmitted as the distance from the flow path of the gas to be measured increases, it is less likely that the air permeability of the water-repellent filter that blocks the air hole decreases due to the influence of heat. According to the gas sensor of the present invention (claim 1), since the plurality of ventilation holes are provided at positions different from each other in the axial direction of the cylindrical cover, the gas permeability in the ventilation hole relatively closer to the pipe is provisionally assumed. Even if the air permeability decreases, it is highly possible that the ventilation hole located far from the pipe can maintain the air permeability in a normal state, and thus the ventilation performance inside the cylindrical cover can be maintained.

By the way, of the openings of the cylindrical cover, the opening opposite to the metal shell (that is, the opening directed outward in the radial direction of the tube forming the flow path) is connected to the electrode of the detecting element. Lead wire is pulled out of the gas sensor,
In order to prevent foreign matter such as water from entering the inside of the cover, a seal member having an insertion hole through which a lead wire passes is provided at the opening end. That is, the seal member is disposed at a position farthest from the flow path, and it is difficult for heat from the flow path to be transmitted.

Therefore, as described in claim 2, the vent hole is provided as follows.
It may be formed on the cylindrical cover side wall and the seal member. In the gas sensor according to claim 2 configured as described above, the water-repellent filter that closes the ventilation hole provided in the seal member is disposed at a position farthest from the pipe that forms the flow path, However, even when heat is received from the flow path, the heat is hardly transmitted, and there is little possibility that the air permeability is impaired by the influence of the heat.

Therefore, according to the gas sensor of the second aspect, even when heat is received from the flow path side, the ventilation performance inside the cylindrical cover can be more reliably maintained. According to the gas sensor of the second aspect, since the ventilation hole formed in the seal member opens at the end of the internal space of the cylindrical cover, it is possible to suppress gas from stagnating in the cylindrical cover, It also has the effect that efficient ventilation can be achieved.

Next, the ventilation hole may be formed on the side wall of the cylindrical cover provided directly on the metallic shell. However, when the gas sensor receives heat from the flow path, the repellent member closes the ventilation hole. It is highly possible that the air permeability of the aqueous filter is reduced by the influence of heat. Therefore, as described in claim 3, the cylindrical cover is attached to the first cover provided on the opposite side to the flow path of the metal shell, and the end of the first cover opposite to the metal shell. The second cover may be extended, and at least one of the ventilation holes may be formed on the side wall of the second cover. In the gas sensor according to claim 3 configured as described above, even if heat from the flow path is applied to the gas sensor,
Since heat is transmitted to the cover via the first cover, it is unlikely that the air permeability of the water-repellent filter that blocks the air holes formed in the second cover is reduced by the influence of the heat.

Therefore, according to the gas sensor of the third aspect, even when the gas sensor is attached to a high-temperature pipe, the ventilation performance inside the cylindrical cover can be maintained more reliably. The water-repellent filter may be formed in a sheet shape. That is, a rod-shaped porous foam may be embedded in the vent as a water-repellent filter, but the resistance when gas passes therethrough is large, and it is not very advantageous in terms of air permeability. On the other hand, according to the gas sensor of the fourth aspect, since the water-repellent filter is formed in a sheet shape, by providing the water-repellent filter so as to cover the opening of the ventilation hole or the flow passage inside the ventilation hole,
It is preferable because good air permeability can be obtained, ventilation inside the cylindrical cover can be efficiently performed, and waterproofness can be obtained.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the entire configuration of the oxygen sensor as the first embodiment. As shown in FIG.
The oxygen sensor 1 according to the first embodiment has a detection element 2 formed in a hollow shaft shape with a closed end made of a solid electrolyte containing ZrO ₂ as a main component, and a ceramic ceramic heater 3 disposed in the detection element 2. , A casing 10 for accommodating the detection element 2 and the like.

The detecting element 2 is electrically connected to a ceramic holder 6 and 7 made of insulating ceramic and a ceramic powder 8 made of talc on the outer periphery near the center in the axial direction. It is provided in a metal casing 10 in a state of being insulated. Detection element 2
The inner and outer surfaces of Pt are covered with Pt so as to cover almost the entire surface.
Are provided (inner electrode 2a, outer electrode 2b). Note that the outer surface and the inner surface of the detection element 2 correspond to the first and second surfaces, respectively.

The casing 10 has a metal shell 9 for fixing the oxygen sensor 1 to a mounting hole of a pipe (for example, an exhaust pipe) forming a flow path and projecting a closed end of the detecting element 2 toward the inside of the pipe. The metal shell 9 includes a cylindrical cover 16 that extends from an opening facing the outside of the exhaust pipe or the like and that introduces air into the inner surface of the detection element 2. The cylindrical cover 16 is
The first outer cylinder 14 is connected to one opening of the metal shell 9 so that the inside communicates with the first outer cylinder 14, and the upper part of the first outer cylinder 14 (that is, an outer part such as an exhaust pipe to which the oxygen sensor 1 is attached). Direction). The first outer cylinder 14 and the second outer cylinder 15 correspond to a first cover and a second cover, respectively.

A protector 11 is attached below the metallic shell 9 (ie, in the exhaust pipe or the like to which the oxygen sensor 1 is attached) so as to cover the distal end of the detecting element 2 with a certain space. The protector 11 has a plurality of gas transmission ports 12 through which the gas to be measured is transmitted.

The upper opening of the metal shell 9 is provided with the first outer cylinder 1.
4 is fixed to the ceramic holder 6 by caulking via the ring 5 and the first outer cylinder 14
Extends from the upper opening of the metal shell 9. on the other hand,
In the opening above the first outer cylinder 14, an insulating separator 18 formed in a cylindrical shape of ceramic is provided. A flange 18a is provided on the outer peripheral surface of the separator 18, and the flange 18a is engaged with the opening edge on the upper side of the first outer cylinder 14, so that the separator 18 is held inside the upper opening of the first outer cylinder 14. Is done. Further, a second outer cylinder 15 is further provided from above the separator 18, and is externally fitted to the first outer cylinder 14.

A cylindrical sealing member 17 made of rubber is provided in an opening on the upper end side of the second outer cylinder 15, and the detecting element 2 is inserted through the sealing member 17 and the separator 18. And a pair of lead wires (not shown) connected to the ceramic heater 3 are arranged.

The one lead wire 20 for the detecting element 2 includes a connector portion 24, a lead wire portion 25, and an internal electrode connection portion 2.
6, and is electrically connected to the inner electrode 2a of the detection element 2 via a terminal fitting 23 constituted by the same. The other lead 2
1 is electrically connected to the outer electrode 2b of the detection element 2 via a terminal fitting 33 composed of a connector portion 34, a lead wire portion 35, and an external electrode connection portion 36.

A pair of heater terminals 40 for energizing the ceramic heater 3 are fixed to the upper end of the ceramic heater 3, and the heating terminals (not shown) embedded in the ceramic heater 3 via the heater terminals 40. Power is supplied to the resistor circuit. Next, as shown in FIG. 2, ventilation of the internal space of the first outer cylinder 14 and the second outer cylinder 15 in the oxygen sensor 1 of the first embodiment is performed by fitting the second outer cylinder 15 and the second outer cylinder 15 to each other. This is performed via a first water-repellent filter 42 disposed between the protective outer cylinder 41 and the second water-repellent filter 62 provided inside the seal member 17.

The mounting structure of the first water repellent filter 42 and the second water repellent filter 62 will be described below. As described above, the second outer cylinder 15 is above the first outer cylinder 14 (that is, the side opposite to the metal shell 9 with respect to the first outer cylinder 14).
And the inside thereof communicates with the inside of the first outer cylinder 14. The second outer cylinder 15 is positioned from below (that is, from the metal shell 9 side).
The first outer cylinder 1 is swaged in the radial direction (positions A1 and A2).
4, a large-diameter cylindrical portion 43 fixed to the
The first water-repellent filter 42 has a cylindrical vent hole forming portion 44 externally fitted therein, and an opening end portion 47 externally fitted to the cylindrical seal member 17.

On the other hand, the protection outer cylinder 41 is formed so as to be able to be fitted externally to the upper structure of the second outer cylinder 15 (that is, the upper part of the large-diameter portion 43, the ventilation hole forming part 44 and the opening end 47). Specifically, the protection outer cylinder 41 is externally fitted to the large-diameter portion 51 that is externally fitted to and overlaps the large-diameter portion 43 of the second outer cylinder 15 and the ventilation hole forming portion 44 of the second outer cylinder 15 from below. First water-repellent filter 42
And a small-diameter portion 53 that is fitted to the open end 47 of the second outer cylinder 15.

The protection outer cylinder 41 is a large-diameter portion 4 of the second outer cylinder 15.
3 is caulked in the radial direction at the large diameter portion 51 (position A3), and is caulked in the radial direction at the small diameter portion 53 overlapping the open end 47 of the second outer cylinder 15 (position A4). , Is fixed to the second outer cylinder 15. Further, the caulking of the small-diameter portion 53 (position A4) causes the seal member 17 to move to the second outer cylinder 1.
5 is fixed to the inner peripheral surface of the open end 47 of the opening 5, and the sealing property between the inner peripheral surface of the second outer cylinder 15 and the outer peripheral surface of the seal member 17 is ensured.

The first water repellent filter 42 is a sheet-like member formed in a cylindrical shape, and is disposed in a space formed between the vent hole forming portion 44 and the filter protecting portion 52 of the protective outer tube 41. ing. The first water-repellent filter 42 is made of, for example, a porous fibrous structure obtained by stretching an unfired molded body of polytetrafluoroethylene (PTFE) in a uniaxial or more direction at a heating temperature lower than the melting point of PTFE. (Product name: Gore-Tex (Japan Gore-Tex Co., Ltd.)) as a water-repellent filter that prevents the transmission of liquids mainly composed of water such as water droplets and allows the transmission of gas (air, water vapor, etc.). It is configured.

The filter protection portion 52 of the protection outer cylinder 41 is caulked in the radial direction above (position A5) and below (position A6) the first ventilation hole 46 of the second outer cylinder 15, thereby. , Water and the like are formed in the air hole forming portion 44 and the first water repellent filter 4.
2 is prevented from entering the inside of the oxygen sensor 1. In the filter protection section 52, a transmission hole 56 for introducing air into the first water-repellent filter 42 is provided between the caulking positions A5 and A6, that is, a position corresponding to the first ventilation hole 46. Have been. Thereby, the first ventilation hole 46, the first water-repellent filter 42, and the transmission hole 5
The gas can flow between the inside and the outside of the oxygen sensor 1 via 6.

As shown in FIG. 3, the seal member 17 provided inside the open end 47 of the second outer cylinder 15 has a second ventilation hole for allowing gas to flow between the inside and the outside of the oxygen sensor 1. 58, and insertion holes 60 (lead wires in the first embodiment) through which lead wires to be drawn out from the inside of the oxygen sensor 1 (that is, lead wires 20 and 21 for the detection element 2 and lead wires for the ceramic heater 3) pass. (4 places corresponding to the number).

The second water-repellent filter 6 formed in a sheet shape by the porous fiber structure is provided in the second vent hole 58.
2 is inserted and fixed by the cylindrical insertion member 64.
Both ends of the cylindrical insertion member 64 are opened, and the second ventilation holes 58 are formed.
It is formed in a tubular shape that can be fitted to the. The second water-repellent filter 62 is covered with the cylindrical insertion member 64 so as to cover one opening 64a of the cylindrical insertion member 64 and its outer peripheral surface (at least the outer peripheral surface near the opening end). It is inserted into the second ventilation hole 58 together with the insertion member 64. In this manner, the second water repellent filter 62 covers one opening 64 a of the cylindrical insertion member 64 and is sandwiched between the outer peripheral surface of the cylindrical insertion member 64 and the inner peripheral surface of the second ventilation hole 58. In the state
It is fixed to the second ventilation hole 58.

It should be noted that, of the two open ends of the cylindrical insertion member 64,
A flange 64b is formed on the outer peripheral portion of the opening end on the opposite side (lower in FIG. 3) with respect to the insertion direction (upper in FIG. 3) into the second ventilation hole 58. When the cylindrical insertion member 64 is inserted from below the second ventilation hole 58, the flange portion 64b is locked at the opening edge below the second ventilation hole 58, and as a result, the inside of the second ventilation hole 58 The positioning of the cylindrical insertion member 64 and the second water repellent filter 62 is performed.

Then, the seal member 17 is arranged inside the open end 47 of the second outer cylinder 15 and is caulked in the radial direction via the second outer cylinder 15 and the protective outer cylinder 41 (position A4).
In addition, the sealing property between the cylindrical insertion member 64 and the sealing member 17 is further ensured. The oxygen sensor 1 configured as described above is mounted on the screw 9 formed on the outer periphery of the metal shell 9.
a, when the cylindrical cover 16 is attached to the mounting hole of the pipe forming the flow path of the gas to be measured so that the cylindrical cover 16 faces substantially upward, the tip of the detection element 2 protected by the protector 11 is placed inside the pipe. It protrudes and is exposed to the gas to be measured. On the other hand, the atmosphere is introduced into the inside of the detection element 2 through the cylindrical cover 16 by ventilation through the first ventilation hole 46 and the second ventilation hole 58. As a result, the inner electrode 2 of the detection element 2
A voltage corresponding to the ratio of the oxygen concentration in the atmosphere to the oxygen concentration in the gas to be measured is generated between the a and the outer electrode 2b, and is output to the outside as detection signals by the lead wires 20 and 21. Note that the screw portion 9a corresponds to a “mounting portion” in the claims.

Since the second ventilation hole 58 is arranged at a position higher than the first ventilation hole 46, when the atmosphere inside the cylindrical cover 16 is heated at a high temperature, the second ventilation hole 58 is removed from the first ventilation hole 46 by a convection phenomenon. A flow toward the second ventilation hole 58 is generated, and the atmosphere is introduced into the inside of the cylindrical cover 16 from the first ventilation hole 46 and discharged from the second ventilation hole 58. Due to such ventilation, even if a gas other than the atmosphere (for example, vaporized oil or the like) enters the inside of the oxygen sensor 1 (that is, the inside of the cylindrical cover 16), it is quickly discharged to the outside of the sensor.

According to the oxygen sensor 1 of the first embodiment configured as described above, the following effects are obtained. The first air hole 46 and the second air hole 46 opening inside the cylindrical cover 16 at different positions in the axial direction of the cylindrical cover 16.
Since the ventilation hole 58 is provided, the oxygen sensor 1 is attached to a pipe forming a flow path of the gas to be measured so that the cylindrical cover 16 is directed substantially upward, for example, so that good ventilation property inside the oxygen sensor 1 is obtained. Can be obtained. Therefore, if a gas other than the atmosphere (for example,
Even if oil vaporized under high temperature enters, it can be quickly discharged to the outside, and the oxygen sensor 1
The original detection performance can be maintained.

A first ventilation hole 46 and a second ventilation hole 58 are provided at different positions in the axial direction of the cylindrical cover 16. Therefore, even if the air permeability of the first water-repellent filter 42 that closes the first air hole 46 is reduced due to the influence of heat from the flow path, the second air hole that closes the second air hole 58 far from the flow path. The air permeability of the water repellent filter 62 is likely to be maintained, and the ventilation performance inside the cylindrical cover 16 can be maintained.

Since the second ventilation hole 58 is provided in the seal member 17 located farthest from the flow path, the second water repellent filter 62 for closing the second ventilation hole 58 is provided in the position furthest from the flow path. Is done. Therefore, even when the oxygen sensor 1 receives heat from the flow path, the second water repellent filter 62
There is no fear that the air permeability of the cylindrical cover 16 is reduced by the influence of heat, and the possibility that the ventilation performance inside the tubular cover 16 is impaired can be further reduced.

The second water repellent filter 62 is formed of rubber and is provided inside the seal member 17 having low thermal conductivity. Therefore, even when the oxygen sensor 1 receives heat from the flow path, the possibility that the air permeability of the second water-repellent filter 62 decreases due to the heat can be further reduced.

Since the second ventilation hole 58 is opened at the end of the internal space of the cylindrical cover 16, it is possible to suppress stagnation of gas in the cylindrical cover 16 and to achieve efficient ventilation. The second outer cylinder 15 extends at the end of the first outer cylinder 14 on the opposite side to the metal shell 9. Even when heat from the flow path is applied to the oxygen sensor 1, the second outer cylinder 15 Has the first outer cylinder 14
The heat is indirectly transmitted through the heat exchanger. Therefore, even when the oxygen sensor 1 receives heat from the flow path, the air permeability of the first water-repellent filter 42 that blocks the first air hole 46 formed in the side wall of the second outer cylinder 15 may be reduced due to heat. Thus, the ventilation performance inside the cylindrical cover 16 can be more reliably maintained.

Since the first water repellent filter 42 and the second water repellent filter 62 are formed in a sheet shape, gas can easily pass therethrough, good air permeability can be obtained, and ventilation inside the cylindrical cover 16 can be improved. Can be improved. Next, an oxygen sensor 101 according to a second embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 4, in the oxygen sensor 101 of the second embodiment, a flange 118a is provided inside the upper opening of the first outer cylinder 114 extending to the upper opening of the metal shell.
Is disposed. That is, the flange 118 a of the separator 118 is
The separator 118 is retained on the upper part of the first outer cylinder 114 by the upper end of the first outer cylinder 114.
Then, from above the separator 118, the protective outer cylinder 14
1 is externally fitted to the first outer cylinder 114. In the second embodiment, the first outer cylinder 114 and the protection outer cylinder 141 constitute a cylindrical cover 116.

A seal member 17 similar to that of the first embodiment is inserted into an opening on the upper end side of the protective outer cylinder 141. Then, a pair of lead wires (not shown) connected to the lead wires 120 and 121 and the ceramic heater 3 are arranged so as to penetrate the separator 118 and the seal member 17. The lead wires 120 and 121 are connected to terminal fittings 123,
Via 133, they are connected to the inner and outer electrodes on the inner and outer surfaces of the detecting element 2, respectively. In addition, the ceramic heater 3
A pair of heater terminals 140 for energizing the ceramic heater 3 are fixed to the upper end of the ceramic heater 3.

In the oxygen sensor 101 according to the second embodiment, as shown in FIG. 4, the first outer cylinder 114 extending from the upper opening of the metal shell is provided with the vent hole forming portion 144 (ie, the second outer cylinder 114). The first water-repellent filter 142 has a first air hole 146 and a first water-repellent filter 142). That is, ventilation in the oxygen sensor 101 of the second embodiment is performed by the inside of the first water-repellent filter 142 and the seal member 17 disposed between the first outer cylinder 114 and the protective outer cylinder 141 fitted to the first outer cylinder 114. This is performed via the second water-repellent filter 62 provided in the filter.

Hereinafter, the mounting structure of the first water repellent filter 142 will be described. Note that the seal member 17, the second water repellent filter 62 provided inside the seal member 17, and the cylindrical insertion member 64 are the same as those used in the oxygen sensor 1 of the first embodiment, and therefore description thereof is omitted. .

The first outer cylinder 114 has a cylindrical base 143 connected to the metal shell from below (that is, from the metal shell side).
And the first water repellent filter 1 having the first ventilation hole 146 and
42 and a cylindrical ventilation hole forming portion 144 which is fitted to the outside. The protection outer cylinder 141 has an upper structure of the first outer cylinder 114 (that is, an upper portion of the base 143 and the ventilation hole forming portion 14).
4) is formed so that it can be fitted outside. More specifically, the protection outer cylinder 141 includes, from below, a large-diameter portion 151 that overlaps an upper portion of the base 143 of the first outer cylinder 114 and a first repellent externally fitted to the ventilation hole forming portion 144 of the first outer cylinder 114. The filter includes a filter protection portion 152 that covers the outer periphery of the aqueous filter 142 and an open end 153 that is fitted to the seal member 17.

The protection outer cylinder 141 is caulked in the radial direction at a large diameter portion 151 overlapping the base 143 of the first outer cylinder 114 (position B1), and is fixed to the first outer cylinder 114. Then, by caulking (position B2) in the radial direction at the opening end 153 of the protective outer cylinder 141, the sealing member 17
41 is fixed inside the open end 153, and the airtightness between the inner peripheral surface of the open end 153 and the outer peripheral surface of the seal member 17 is ensured.

The first water-repellent filter 142 is made of a material similar to that of the first water-repellent filter 42 of the first embodiment and is formed in a cylindrical shape.
It is arranged in a space formed between the first filter protection section 152 and the first filter protection section 152. Filter protection section 152 of protection outer cylinder 141
Is located above the first ventilation hole 146 of the first outer cylinder 114 (position B
3) and caulking in the radial direction at the lower side (position B4), whereby water or the like enters the inside of the oxygen sensor 101 through the space between the vent hole forming section 144 and the first water repellent filter 142. Is prevented. And the filter protection unit 1
At 52, a transmission hole 156 for introducing air to the first water-repellent filter 142 is provided between the caulking positions B 3 and B 4, that is, a position corresponding to the first air hole 146. Thus, gas can flow between the inside and the outside of the oxygen sensor 101 via the first ventilation hole 146, the first water-repellent filter 142, and the transmission hole 156.

The rest of the configuration of the oxygen sensor 101 of the second embodiment is the same as that of the oxygen sensor 1 of the first embodiment, and a description thereof will be omitted. The second constructed in this way
According to the oxygen sensor of the embodiment, the same effects as and in the first embodiment can be obtained.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various embodiments can be adopted. For example, in the above embodiment, the oxygen sensor has been described as an example of the gas sensor, but the gas sensor is not limited to this.
For example, the present invention may be applied to a NOx (nitrogen oxide) sensor or a CH (hydrocarbon) sensor.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an oxygen sensor as a first embodiment as a whole;

FIG. 2 is an explanatory diagram showing a configuration near a cylindrical cover in the first embodiment.

FIG. 3 is an explanatory diagram showing a configuration inside a seal member in the first embodiment.

FIG. 4 is an explanatory diagram showing a configuration near a cylindrical cover in an oxygen sensor as a second embodiment.

FIG. 5 is an explanatory diagram showing an oxygen sensor as a conventional example.

[Explanation of symbols]

1, 101 oxygen sensor, 2 detection element, 2a inner electrode, 2b outer electrode, 9 metal shell, 9a screw part, 1
4, 114: first outer cylinder, 15: second outer cylinder, 16, 116
... cylindrical cover, 17 ... sealing member, 20, 21, 12
0, 121: lead wire, 42, 142: first water-repellent filter, 46, 146: first air hole, 47, 153: open end, 58: second air hole, 60: insertion hole, 62: second Water-repellent filter, 64: cylindrical insertion member, 141: protective outer cylinder.

Claims (4)

[Claims] 1. A detection element having electrodes formed on first and second surfaces of an oxygen ion conductive solid electrolyte body, and a mounting hole provided on a wall surface of a tube forming a flow path through which a gas to be measured flows. A metal shell that has a mounting portion to be mounted, and further holds the detection element such that the first surface is arranged on the inner side of the tube with respect to the mounting portion via the mounting hole; It is provided on the outside of the tube than the mounting part,
A cylindrical cover having a ventilation section for introducing air into the second surface, wherein the ventilation section has at least two locations at different positions in the axial direction of the cylindrical cover. A gas sensor comprising: a plurality of air holes that open inside the cylindrical cover; and a gas-permeable water-repellent filter that closes the air holes. 2. The gas sensor according to claim 1, wherein the cylindrical cover is provided at an opening end of the cylindrical cover opposite to the metal shell and passes a lead wire connected to an electrode of the detection element. A gas sensor comprising a seal member having a hole, wherein the vent hole is formed in the cylindrical cover side wall and the seal member. 3. The gas sensor according to claim 1, wherein the cylindrical cover is provided on a side of the metal shell opposite to the flow path.
And a second cover extending from an end of the first cover opposite to the metal shell, wherein at least one of the ventilation holes is formed in the side wall of the second cover. A gas sensor characterized in that: 4. The gas sensor according to claim 1, wherein the water-repellent filter is formed in a sheet shape.