JPH11248671A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor free of a caulking ring for fixing a filter and hardly causing loosening of the filter due to thermal expansion. SOLUTION: This gas sensor 1 has a detecting element 2 including an oxygen concentration cell element operated with outside air into an outer cylinder 18 as a reference gas and an elastic seal member 15 fitted to the opening at the rear end of the outer cylinder 18. A filter 40 is arranged in a form in contact with the outer face of the elastic seal member 15 and the inner face of the outer cylinder 18 at its both faces and fixed by caulking the outer cylinder 18 to the elastic seal member 15. At a position corresponding to the filter 40, a gas guide hole 19 is formed in the outer cylinder 18, thereby, outside air guided out of the gas guide hole 19 passes through the filter 40 and then is guided through a gas guide passage 90 formed in the elastic seal member 15 into an inside space of the outer cylinder 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an oxygen sensor, an HC sensor,
Sensor, such as NO _X sensor, it relates a gas sensor for detecting a test substance in the measurement object gas, in particular the sensing element, relates to a gas sensor comprising an oxygen concentration cell element that operates outside air as a reference gas.

[0002]

2. Description of the Related Art As a gas sensor as described above, for example,
2. Description of the Related Art In an internal combustion engine such as an automobile engine, various oxygen sensors for use in air-fuel ratio control and the like are known. As this type of oxygen sensor, there has been known an oxygen sensor in which an oxygen concentration cell element as a detecting unit is formed of an oxygen ion conductive solid electrolyte such as ZrO ₂ . The detection unit is generally provided at a tip of a detection element formed in a shaft shape. Such a detection element is accommodated in a metal outer cylinder, and the outer surface of the tip of the detection section is brought into contact with the atmosphere to be detected, while the air as a reference gas is introduced into the inner space of the outer cylinder to generate the detection element. The oxygen concentration in the detected atmosphere is measured by the electromotive force of the oxygen concentration cell. In recent years, in particular, in order to respond to environmental protection problems such as air pollution caused by exhaust gas, the demand for an oxygen sensor for detecting the oxygen concentration in the exhaust gas has been increasing, especially for a high-performance and long-life oxygen sensor. I have.

[0003] When the oxygen sensor as described above is mounted on an automobile, it is often mounted, for example, on an exhaust pipe near the vehicle's foot, in addition to the engine room. In such a situation, the oxygen sensor should be exposed to a severe environment such as being sprayed with water droplets during running in the rain or washing a car, adhering dirt such as oil, and receiving impact from splashed pebbles. Becomes In this case, in order to protect the oxygen sensing element from adhesion of water droplets and dirt, it is necessary to use a casing having a high strength and a high sealing property as much as possible. However, since it is necessary to introduce air into the casing as a reference gas for the detection element, a communication part with the outside must be provided. In other words, in order to operate the oxygen sensor stably in a severe environment for a long period of time, it is necessary to increase the liquid tightness to water or the like to a certain level or more, and at the same time, to contradict the problem of securing air permeability. Need to be resolved.

[0004] In order to meet such demands, for example, Japanese Patent Application Laid-Open No. Hei 8-201338 and the like disclose air holes in an outer cylinder and cover them with a water-repellent filter to prevent water droplets and the like from entering. There is disclosed an oxygen sensor having a structure in which the flow of the atmosphere can be ensured while preventing it.

[0005]

In the oxygen sensor disclosed in the above publication, an air hole is formed at the end of the outer cylinder, the periphery of which is covered with a cylindrical water-repellent filter, and then the air hole is formed. The filter is fixed by covering the outside with a metal cylindrical caulking ring having an air hole, and forming a caulking portion between the caulking ring and the casing. However, in this structure, a crimping ring for fixing the filter is required, and there is a problem that the number of parts increases and the cost increases. Further, in an environment where the temperature of the sensor becomes high, such as during high-speed operation, there is a concern that the caulked portion may undergo thermal expansion, loosening the caulked ring and the filter and impairing waterproofness.

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas sensor which can eliminate a caulking ring for fixing a filter and which is less likely to loosen due to thermal expansion or the like.

[0007]

The gas sensor according to the present invention has an outer cylinder and a detecting portion which is housed in the outer cylinder and detects a component to be detected in the gas to be measured. And a detection element including an oxygen concentration cell element that operates using outside air introduced into the outer cylinder as a reference gas, and a plurality of leads through which each lead wire from the detection element is inserted. A line insertion hole is formed penetrating in the axial direction, and an elastic seal member elastically fitted inside the opening at the rear end side of the outer cylinder, an outer surface of the elastic seal member, and an inner surface of the outer cylinder. A filter that is disposed so that both sides thereof are in contact with each other, and that is held between the elastic seal member and the outer cylinder; a gas introduction hole is formed in the outer cylinder at a position corresponding to the filter; Outside air introduced through holes After passing through the filter, characterized by being guided to the interior space of the outer cylinder through the gas inlet passage formed in the elastic seal member.

The elastic sealing member can be made of an organic elastic material such as rubber or elastomer, and can be made of, for example, a heat-resistant rubber such as fluorine rubber or silicon rubber. Further, as the filter, a waterproof and breathable filter made of a porous resin formed material made of a fluorine resin such as polytetrafluoroethylene can be used. Specifically, for example, polytetrafluoroethylene (hereinafter, PT
A porous fibrous structure (for example, Japanese Patent Publication No. 42-135) obtained by stretching a green compact of FE) in a uniaxial or more direction at a heating temperature lower than the melting point of PTFE.
60, JP-B-51-18991, JP-B-56-4577
3, JP-B-56-17216, JP-A-145735, JP-A-59-152825, JP-A-3-221541, JP-A-7-126428, JP-A-7-1966831, and the like. Co., Ltd.)) can be used.

In the configuration of the gas sensor according to the present invention, the filter is held between the elastic sealing member and the outer cylinder,
The outside air is introduced into the outer cylinder from the gas introduction hole on the outer cylinder via a gas introduction passage formed in the filter and the elastic seal member. In other words, by providing a filter, it is possible to secure the flow of outside air while preventing the intrusion of water droplets and the like, and since the caulking ring conventionally provided to fix this filter is abolished, the number of parts and thus the sensor Manufacturing costs can be reduced.

In the above configuration, the filter can be held in a form sandwiched between the outer cylinder and the elastic seal member by caulking the outer cylinder toward the elastic seal member. Thereby, the airtightness between the elastic seal member, the filter, and the outer cylinder is improved, and intrusion of water droplets or the like through these gaps can be effectively prevented. Further, since the elastic seal member is elastically deformed by being compressed in the radial direction by caulking, the elastic force causes the filter to be strongly held between the inner surface of the outer cylinder and the filter. in this case,
Even if the outer cylinder expands to some extent due to a rise in temperature or the like, the filter is kept pressed by the elastic return force of the elastic sealing member, so that the filter is unlikely to be loosened.

Next, the filter can be disposed so as to cover the outer periphery of the elastic seal member, and the gas introduction passage has an inlet opening on the outer peripheral surface of the elastic seal member and an outlet opening on the bottom surface. Can be configured as Thereby, the outside air introduced from the gas introduction hole of the outer cylinder can be smoothly guided into the outer cylinder via the elastic seal member.

A plurality of gas introduction holes can be formed at predetermined intervals along the circumferential direction of the outer cylinder. Thereby, outside air can be introduced into the outer cylinder without bias. Further, the outer cylinder has two annular caulked portions formed in the circumferential direction so as to sandwich the row of gas introduction holes in the axial direction, and a portion of the outer cylinder located between the caulked portions is provided. Bulging outward,
A gap may be formed between the filter and at least one of the outer cylinder and the elastic seal member at the bulging portion. With this configuration, the surface of the filter can be effectively used as an air passage, and for example, a sufficient amount of air whose detection characteristics do not deteriorate even in a fuel-rich atmosphere can be reliably introduced into the casing.

The elastic seal member may be constituted by two members adjacent to each other in the axial direction of the outer cylinder. Then, those located on the opening side of those outer cylinders are referred to as a first member, and those located on the opposite side are referred to as a second member, and the gas introduction path is formed on the joint surface between the first member and the second member. One end is opened at the outer peripheral surface of the elastic seal member to form an entrance, and the other end side extends radially inward of the elastic seal member, and the first passage extends through the second member in the axial direction. , One end of which communicates with the first passage, and the other end of which opens to the bottom surface of the second member to form an outlet.

In the above configuration, the elastic seal member is divided into two parts, and the gas introduction path having both ends opened at the side and the bottom is formed by the first path located at the joint surface between the two members, and the second member is formed in the axial direction. It was formed by combination with the penetrating second passage. Such members can be manufactured very easily by injection molding of rubber or the like, and are manufactured individually and then joined in the axial direction to form an elastic seal member having a gas introduction path of a desired shape. It can be obtained easily.

In this case, a projection is formed on at least one of the joining surfaces of the first member and the second member, a recess is formed on at least one of the joining surfaces, and the projection is formed on one of the first member and the second member. By fitting the raised convex portion into the concave portion formed on the other side, the two members can be configured to be joined to each other. By the joining, the first member and the second member are integrated to form an elastic seal member, and it is difficult for the two members to be disassembled by fitting the concave portion and the convex portion. This allows
Although the elastic seal member is composed of two parts, it can be easily assembled to the outer cylinder.

More specifically, in the first member, a plurality of convex portions projecting toward the second member are formed at predetermined intervals in the circumferential direction on the joint surface with the second member, and each adjacent convex portion is formed. In between, the same number of concave portions as the convex portions can be formed. Further, the second member also has a plurality of convex portions protruding toward the first member on the joining surface with the first member at predetermined intervals in the circumferential direction, and the convex portions between the adjacent convex portions. The same number of recesses as can be formed. Then, each of the projections on the first member side is fitted into each of the recesses on the second member side, and each of the projections on the second member side is fitted into each of the recesses on the first member side, respectively. And the second member are joined to each other, and the first passage is between the top surface of the convex portion on the first member side and the bottom surface of the concave portion on the second member side where the convex portion is fitted, and on the second member side. A configuration may be formed between the top surface of the convex portion and the bottom surface of the concave portion on the first member side where the convex portion fits. By fitting the unevenness of the first member and the second member arranged in the circumferential direction to each other, the relative rotation of the first member and the second member around the axis is prevented. Can be performed more easily.
Further, since the plurality of first passages are formed radially with respect to the central axis of the elastic seal member, the flow of gas in the elastic seal member can be made smoother.

Next, in the second member, a portion including at least a part of the wall surface of the second passage can be a hard material portion made of a material harder than the remaining portion. Thus, when the outer cylinder is swaged toward the elastic seal member, the second passage is prevented from being crushed by the compressive force of the swage, and thus the flow of gas in the elastic seal member assembled to the outer cylinder is further improved. It can be assured.

In this case, the second member is composed of a main body having a bottomed cylindrical member mounting recess formed in the joint surface with the first member, and a harder material (for example, ceramic or metal) than the main body. ) Having a through hole in the axial direction, and a cylindrical member (hard material portion) mounted in the cylindrical member mounting concave portion. In this case, at the bottom of the cylindrical member mounting concave portion, a main body side through hole penetrating in the axial direction of the second member is formed, and the main body side through hole and the cylindrical member side through hole are formed. A second passage is formed by communicating with each other. According to this, simply mounting the cylindrical member in the cylindrical member mounting recess,
The hard material portion can be easily formed.

[0019]

Embodiments of the present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 shows an oxygen sensor 1 for detecting the concentration of oxygen in exhaust gas of an automobile or the like as an embodiment of the gas sensor of the present invention. The oxygen sensor 1 is commonly called a λ sensor or an O ₂ sensor, and has an elongated ceramic element 2 (detection element), and its tip end is exposed to high-temperature exhaust gas flowing in the exhaust pipe.

The ceramic element 2 is formed in an elongated plate shape having a square cross section, and as shown in FIG.
Oxygen concentration cell elements 21 each formed in a horizontally long plate shape
And a heater 22 for heating the oxygen concentration cell element 21 to a predetermined activation temperature. The oxygen concentration cell element 21 is made of a solid electrolyte having oxygen ion conductivity. As such a solid electrolyte, ZrO containing Y ₂ O ₃ or CaO as a solid solution is used.
_{Although 2} is a typical example, a solid solution of an oxide of another alkaline earth metal or rare earth metal and ZrO ₂ may be used. In addition, the ZrO ₂ as a base HfO ₂
May be contained. On the other hand, the heater 22 is a known ceramic heater in which a resistance heating element pattern 23 made of a high melting point metal or conductive ceramic is embedded in a ceramic base.

The oxygen concentration cell element 21 has porous electrodes 25 and 26 having oxygen molecule dissociation ability on both sides near one end (a part protruding from the tip of the metal shell 3) in the longitudinal direction. Electrodes 2
5, 26 and the solid electrolyte portion sandwiched therebetween form the detection portion D.

From each of the porous electrodes 25 and 26, electrode leads 25a and 26a extending toward the mounting base end side of the oxygen sensor 1 along the longitudinal direction of the oxygen concentration cell element 21 are formed integrally. I have. Among them, the electrode lead portion 25a from the electrode 25 on the side not facing the heater 22 is
The end is used as the electrode terminal portion 7. On the other hand, the electrode lead portion 26a of the electrode 26 on the side facing the heater 22
As shown in FIG. 2 (c), is connected to the electrode terminal portion 7 formed on the opposite element surface by a via 26b crossing the oxygen concentration cell element 21 in the thickness direction. That is, the oxygen concentration cell element 21 has a shape in which the electrode terminal portions 7 of the porous electrodes 25 and 26 are formed side by side at the end of the plate surface on the electrode 25 side. Each of the above electrodes, electrode terminal portions and vias is P
It is obtained by forming a pattern by screen printing or the like using a paste of a metal powder having a catalytic activity of an oxygen molecule dissociation reaction such as a t or Pt alloy and firing the paste.

On the other hand, the resistance heating element pattern 2 of the heater 22
The lead portions 23a, 23a for supplying current to
As shown in (d), the oxygen concentration cell element 2 of the heater 22
Electrode terminal portions 7, 7 formed at the end of the plate surface on the side not facing 1 are connected via vias 23b, respectively.

As shown in FIGS. 2A and 2B, a spacer portion 28 is interposed between the oxygen concentration element 21 and the heater 22, and the whole is integrated by firing. In the spacer section 28, an oxygen reference chamber 28a is formed at a position corresponding to the porous electrode 26. Also, the spacer portion 28
An air introduction passage (reference gas supply passage) 28b is formed at the center in the width direction along the longitudinal direction thereof, and one end thereof communicates with the oxygen reference chamber 28a, and the other end thereof is a rear end surface of the spacer portion 28. And an air inlet 29 is formed. Thereby, as shown in FIG. 4B, in the ceramic element 2, the atmosphere is introduced from the atmosphere introduction port 29 through the atmosphere introduction path 28b into the oxygen reference chamber 28a, and the porous electrode 26 functions as an oxygen reference electrode. It will be.

As shown in FIG. 1, such a ceramic element 2 is inserted into the insertion hole 30 of the insulator 4 disposed inside the metal shell 3, and the detecting portion D at the tip is fixed to the exhaust pipe. The metal shell 3 is fixed in the insulator 4 so as to protrude from the tip of the metal shell 3. One end of the insulator 4 communicates with the rear end of the insertion hole 30 in the axial direction, and the other end is open to the rear end surface of the insulator 4 and has a shaft section 31 whose axial cross section is larger in diameter than the insertion hole 30. Are formed. And the void 3
1 and the outer surface of the ceramic element 2 are sealed by a sealing material layer 32 mainly composed of glass (for example, crystallized zinc silica borate glass).

As shown in FIG. 1, the insulator 4 and the metal shell 3
Between them, a talc ring 36 and a caulking ring 37 are fitted adjacent to each other in the axial direction, and the outer peripheral portion on the rear end side of the metal shell 3 is caulked to the insulator 4 side via the caulking ring 37. By tightening, the insulator 4 and the metal shell 3 are fixed. On the outer periphery of the distal end of the metal shell 3, double protective covers 6a and 6b made of metal are formed by laser welding or resistance welding (for example, spot welding) to cover the protruding portion of the ceramic element 2. The covers 6a and 6b have a cap-like shape, and a high-temperature exhaust gas flowing in the exhaust pipe is covered with the cover 6a and 6b at the tip and the periphery thereof.
Openings 6c and 6d leading to the inside are formed. On the other hand, the rear end portion of the metal shell 3 is inserted inside the front end portion of the metal outer cylinder 18, and a welded portion (for example, a laser welded portion) 35 is formed as a connecting portion formed in a circular shape in the circumferential direction at the overlapping portion. They are joined together in an airtight manner. In addition, the welded portion 35 may be formed by an annular caulked portion instead of laser welding. However, in a case where a particularly high waterproof property is desired, laser welding is more liquid-tight. Therefore, it is more desirable. Further, in the present specification, in the axial direction of the metal shell 3, the protruding side of the detecting portion D is defined as a front side, and the opposite side is defined as a rear side.

Next, as shown in FIG. 10, a plurality of gas introduction holes 19 are formed in the rear end side wall of the outer cylinder 18 at predetermined intervals along the circumferential direction. A grommet 15 as an elastic sealing member made of an elastic material such as rubber is provided at the rear end opening of the outer cylinder 18 through a filter 40 that closes the gas introduction hole 19 in a gas-permeable state. It is located inside. The filter 40 and the grommet 15 are fixed to the outer cylinder 18 by annular caulking portions 38 and 39 formed on both sides of the row of the gas introduction holes 19.

The portion of the outer cylinder 18 located between the caulking portions 38 and 39 bulges outwardly in a convex shape, and a circumferential annular gap is provided between the outer surface of the filter 40 and the inner surface of the outer cylinder 18. g1 is formed. Further, an annular concave portion 87a is formed in the middle of the grommet 15 in the axial direction so as to correspond to a position where a connecting portion 87 described later is formed. The gap g1 and the recess 87a
The function serves as a stagnation space for the outside air guided from the gas introduction hole 19, and furthermore, plays a role of smoothly flowing the outside air to the filter 40.

As shown in FIG. 4, the grommet 15 has a cylindrical shape as a whole corresponding to the inner surface shape of the outer cylinder 18, and the lead wires 14 (four in this embodiment) for the ceramic element 2 are inserted. Lead hole 45 (FIG. 4)
(B)) is formed penetrating in the axial direction. The grommet 15 has a two-part structure of a first member 41 and a second member 51 in the axial direction, and as shown in FIGS. 4B and 5, the first member 41 and the second member 5
1 are combined with each other and integrated, and a cylindrical filter 40 is extrapolated outside thereof. In addition, as shown in FIG. 1, the gas introduction hole 19 is opened on the outer peripheral surface of the grommet 15 at the connecting portion 87 (FIG. 4B) between the first member 41 and the second member 51.

Here, the filter 40 is made of, for example, a porous material obtained by stretching an unsintered molded body of polytetrafluoroethylene (hereinafter, referred to as PTFE) in a uniaxial or more direction at a heating temperature lower than the melting point of PTFE. The porous fiber structure (trade name: Gore-Tex (Japan Gore-Tex Co., Ltd.)) prevents permeation of liquid mainly composed of water such as water droplets and allows permeation of gas such as air and / or water vapor. The filter is configured as a water-repellent filter. This allows the filter 40 to pass through the gas introduction hole 19 of the outer cylinder 18.
Then, the atmosphere (outside air) as a reference gas is introduced into the outer cylinder 18 (details will be described later), and water in a liquid state such as water droplets is prevented from entering the outer cylinder 18. ing.

As shown in FIG. 1, the outer cylinder 18 is connected to the grommet 15 and further inwardly to the connector portion 1.
3 are provided. The rear end side of the lead wire 14 extends through the grommet 15 to the outside, and a connector plug 16 is connected to the tip end thereof. 17
Is covered. On the other hand, the distal end side of the lead wire 14 is electrically connected to each electrode terminal portion 7 (collectively four poles) of the ceramic element 2 shown in FIG.

As shown in FIG. 3, the connector portion 13 is provided with a female contact 8 connected to the lead wire 14 and a two-part ceramic contact portion for connecting the electrode terminal portion 7 of the ceramic element 2 to the lead wire 14. A housing 9, which is also a two-piece fixing bracket 10, a pair of pressing springs 11, 11, and a plug-in member consisting of one caulking ring 12 are inserted into the electrode terminal portion 7 of the ceramic element 2, and the outer periphery of the caulking ring 12 is inserted. Is crimped to apply a displacement to each pressing spring 11 and press the female contact 8 against the electrode terminal portion 7 with a predetermined pressure. That is, when the caulking ring 12 is caulked at a plurality of locations from the outside, the inner pressing springs 11 and 11 are elastically compressed, and the inner fixing metal 10 is further compressed based on the spring force of the pressing spring 11. Then, the female contact 8 is pressed against the electrode terminal portion 7 of the ceramic element 2 via the ceramic housing 9 (see also FIGS. 4B and 4C).

Next, the structure of the grommet 15 will be described in detail. As shown in FIG. 4, an insertion hole 45 '(four in this embodiment) for inserting the lead wire 14 is formed through the first member 41 in the axial direction. Insertion hole 4
As shown in FIG. 6, plural 5's (four in this embodiment) are formed at predetermined angular intervals (approximately 90 degrees in this embodiment) around the axis of the main body 43, as shown in FIG. A plurality of (two in this embodiment) convex portions 42, 42 projecting in the axial direction from the end surface 43a are formed on the end surface 43a of the main body 43, and between the convex portions 42, 42. Has a plurality (two in this embodiment) of recesses 44, 44 formed therein. Each of the convex portions 42 and the concave portions 44 has, for example, a substantially fan-shaped planar shape, and the plurality of insertion holes 45 ′ are formed at positions corresponding to the convex portions 42 and the concave portions 44, respectively. In addition, a radial groove 4 is formed on the distal end surface of each of the convex portions 42, 42.
7 are formed.

On the other hand, as shown in FIGS. 4 and 7, the second member 51 also has an insertion hole 45 'similar to that of the first member 41, and its end face 53a has projections 52, 52 and a recess 5'.
4 and 54 are formed, and a groove 57 is formed in the distal end surface of each of the protrusions 52 and 52 along the radial direction. FIG.
As shown in FIG. 7, a flange portion 59 as a filter receiving portion protruding outward is formed on the outer peripheral surface of the distal end portion of the main body portion 53 along the circumferential direction. On the other hand, a tubular member 95 as a second passage forming member is embedded in the center of the main body 53 in the axial direction. The grommet 15 is used for the tubular member 95.
Is made of a material harder than rubber, such as ceramic, for example, and has a cylindrical member side through-hole 61 penetrating in the axial direction. The cylindrical member 95 is mounted by being pushed into a cylindrical member mounting concave portion 53b serving as a second passage forming member mounting portion that opens on the end surface 53a of the main body portion 53. Further, the main body portion 53 has a main body side through-hole 5 penetrating through the bottom of the cylindrical member mounting concave portion 53a.
3c are formed substantially concentrically. Then, the cylindrical member side through hole 61 of the cylindrical member 95 and the main body side through hole 53c of the main body 53 communicate with each other, and the second through hole of the air introduction passage (gas introduction part) 90 shown in FIG. The passage 90b is formed.

As shown in FIG. 4 and FIG.
And the second member 51 has the protrusions 42, 42 of the first member 41 in the recesses 54, 54 of the second member 51, and the protrusions 52, 52 of the second member 51 in the recesses 44, 44 of the first member, respectively. The two members 41,
The respective convex portions 42, 42 and 52, 52 of 51 are integrated,
A columnar connecting portion 87 having a smaller diameter than the main body portions 43 and 53 is formed. Then, as shown in FIGS. 8C and 8D, the first member 41 and the second member 51 are fitted together in the connecting portion 87 in a state in which the two convex portions 42 and 52 are in close contact with each other.
Are prevented from rotating about the axis, and the respective insertion holes 45 'of the two members 41, 51 communicate with each other to form the lead wire insertion holes 45, respectively.

Each of the projections 42, 5 of both members 41, 51
As shown in FIG. 5, the grooves 47, 57 (FIGS. 6 and 7) formed on the front end surface of the front end 2 are closed on the bottom surfaces of the concave portions 54, 44 in which the convex portions 42, 52 fit. And the first passage 90a of the air introduction passage 90 (four places in this embodiment).
(FIG. 8B). The first passage 90a is connected to the connecting portion 8
7 (that is, the grommet 15) is formed in the radial direction so as to open to the outer peripheral surface thereof, and the second passage 9 on the second member 51 side is formed.
0b and each other. Thereby, as shown in FIG. 10, the air introduction path 90 plays a role of guiding the air introduced from the outside through the air introduction hole 19 and the filter 40 to the inside of the outer cylinder 18.

When assembling the grommet 15 to the outer cylinder 18, first, as shown in FIG. 4, a filter 40 is attached to the outer periphery of the grommet 15 from the first member 41 side, and the lead wire is inserted into the lead wire insertion hole 45. 14 is inserted. here,
The flange portion 59 of the second member 51 plays a role in preventing the filter 40 from being displaced in the axial direction with respect to the grommet 15. Then, as shown in FIG. 3C, with the grommet 15 in contact with the rear end of the connector 13,
As shown in FIGS. 9A and 9B, the outer cylinder 18 is located in the rear end opening 18a.

In this state, the outer cylinder 18 is circumferentially crimped from the outside toward the filter 40 and the grommet 15 on both sides in the axial direction of the air introduction hole 19 to form annular crimping portions 38 and 39 (FIG. 9). (C)) is formed. As a result, the grommet 15 is compressed and deformed with the caulking of the outer cylinder 18, and is fixed in the outer cylinder 18 in a state where the lead wire 14 and the lead wire insertion hole 45 are in close contact with each other. The second member 51 of the grommet 15 has a caulking portion 39.
The above-mentioned cylindrical member 95 is buried in correspondence with the formation position. Since the cylindrical member 95 is made of a hard material such as ceramic (or may be metal), even if the grommet 15 is compressed by caulking, the cylindrical member side through-hole 61 forming a part of the air introduction passage 90 is formed. Crushing is prevented.

Hereinafter, the operation of the oxygen sensor 1 will be described. As shown in FIG. 1, the oxygen sensor 1 is fixed to a vehicle exhaust pipe or the like at a screw portion 3a of a metal shell 3, and a connector plug 16 is connected to a controller (not shown) for use. When the detection unit D is exposed to the exhaust gas, the porous electrode 25 of the oxygen concentration cell element 21 is exposed.
(FIG. 2) comes into contact with the exhaust gas, and an oxygen concentration cell electromotive force is generated in the oxygen concentration cell element 21 according to the oxygen concentration in the exhaust gas. The electromotive force is applied to the electrode lead portions 25a and 26a.
a through the electrode terminal portions 7, 7 and the lead wires 14, 1
4 and is taken out as a sensor output. This kind of λ
Sensors (or O ₂ sensors) are widely used for air-fuel ratio detection because they exhibit characteristics in which the concentration cell electromotive force changes abruptly in the vicinity where the exhaust gas composition reaches the stoichiometric air-fuel ratio.

As shown in FIG. 10, the atmosphere for introducing the reference atmosphere is introduced from the gas introduction hole 19, and is guided to the atmosphere introduction port 29 of the ceramic element 2 through the filter 40 and the atmosphere introduction path 90 of the grommet 15. .

In the oxygen sensor 1, the air introduction passage 90 is formed in the grommet 15, the filter 40 is disposed outside the grommet 15, and the caulking portions 38 and 39 are formed in the outer cylinder 18. Is fixed between the grommet 15 and the outer cylinder 18 so to speak. This reduces the number of parts by eliminating the need for a caulking ring, compared to a conventional structure in which a filter is placed outside the outer cylinder and the filter is held from the outside with a caulking ring. As a result, the assembly efficiency is improved. Further, since the grommet 15 is radially compressed by the caulking force of the caulking portions 38 and 39, even if the outer cylinder 18 slightly expands due to a temperature rise or the like, the filter 40 is pressed by the elastic return force of the grommet 15. Since the state is maintained, the filter 40 is unlikely to be loosened.

Next, as shown in FIG. 11, buffer layers are provided at both ends of the sealing material layer 32 in the axial direction of the ceramic element 2 so as to fill the space between the outer surface of the ceramic element 2 and the inner surface of the cavity 31. 33 and 34 can be formed respectively. Each of the buffer layers 33 and 34 is formed of a porous inorganic substance, and specifically, filler particles having better heat resistance than the glass contained in the sealing material layer 32 and a gap between the filler particles. It is configured to include a part of the filler particles and binder particles having a softening temperature lower than that of the filler particles. Of these, the buffer layer 34 located on the side closer to the tip of the ceramic element 2 with respect to the sealing material layer 32 in the axial direction of the ceramic element 2 is such that the filler particles are made of Al ₂ O ₃ particles and The particles are made of particles having higher heat resistance than the glass contained in the sealing material layer 21 and having a lower softening temperature than the filler particles, for example, clay particles. As the clay particles, those mainly composed of hydrous aluminosilicate can be used. Two or more types can be mainly constituted. In addition, from the viewpoint of the contained oxide-based components, it contains SiO ₂ and Al ₂ O ₃ , and further contains Fe ₂ O ₃ , TiO ₂ ,
Those mainly containing one or more of O, MgO, Na ₂ O and K ₂ O can be used.

In the above embodiment, the gas sensor is configured as a λ sensor using only an oxygen concentration cell element as a detection element (ceramic element). However, the gas sensor may be configured as another type of gas sensor element. It is. The following are some examples. First, FIG. 12 is a conceptual diagram in the case where the oxygen sensor element is the whole area. in this case,
The ceramic element 60 has a structure in which an oxygen pump element 61 and an oxygen concentration cell element 62 each composed of an oxygen ion conductive solid electrolyte are arranged to face each other with a measurement chamber 65 interposed therebetween. It is introduced into the measurement chamber 65 through the diffusion hole 67 configured. Note that reference numeral 69
Is a heater for heating the oxygen pump element 61 and the oxygen concentration cell element 62. The oxygen concentration cell element 62 measures the oxygen concentration in the measurement chamber 65 by the concentration cell electromotive force generated between the electrode 63 embedded in the element and the electrode 64 on the measurement chamber 65 side as an oxygen reference electrode. I do. On the other hand, a voltage is applied to the oxygen pump element 61 from an external power source (not shown) via the electrodes 66 and 68, and oxygen is pumped into or out of the measurement chamber 65 at a speed determined by the direction and magnitude of the voltage. It has become. And
The operation of the oxygen pump element 61 is controlled by an oxygen concentration cell element 62.
Is controlled by a control unit (not shown) based on the detected oxygen concentration in the measurement chamber 65 so that the oxygen concentration in the measurement chamber 65 is kept constant.
The oxygen concentration of the exhaust gas is detected based on the first pump current.

[0044] Further, FIG. 13 shows an example in which the ceramic element and the NO _X sensor element of two-chamber system. The ceramic element 70 is composed of an oxygen ion conductive solid electrolyte such as ZrO ₂ , in which first and second measurement chambers 71 and 72 are formed with a partition wall 71a interposed therebetween. A second diffusion hole 73 formed of a high-quality ceramic or the like and connecting them to each other is formed. Further, the first measurement chamber 71 is in communication with the surrounding atmosphere through the first diffusion hole 74. And the first measurement room 7
1 is provided with a first oxygen pump element 75 having electrodes 76 and 77, and for the second measurement chamber 72, an electrode 79 is provided.
A second oxygen pump element 78 having a second and a second oxygen pump element 80 is located opposite the wall 71a. The oxygen concentration cell element 83 (the oxygen reference electrode 81 in the partition 71a) for detecting the oxygen concentration in the first measurement chamber 71 is provided on the partition 71a.
And a counter electrode 82 facing the first measurement chamber 71). Reference numeral 86 denotes a heater for heating the first oxygen pump element 75, the second oxygen pump element 78, and the oxygen concentration cell element 83.

In operation, first, a gas in the surrounding atmosphere is introduced into the first measurement chamber 71 through the first diffusion hole 74. Then, oxygen is pumped from the introduced gas by the first oxygen pump element 75. The oxygen concentration in the measurement chamber is detected by the oxygen concentration cell element 83, and the first oxygen pump element 75 controls the oxygen concentration in the gas in the first measurement chamber 71 by a control unit (not shown) based on the detected value. , so that a constant value of a degree that does not cause decomposition of nO _X, working for the oxygen pumping is controlled. As Thus oxygen is reduced by gas travels through the second diffusion hole 73 into the second measurement chamber 72, where and the NO _X and oxygen in the gas is completely decomposed, the second oxygen pump element 78 Pumps out oxygen. Detecting the concentration of the NO _X in the gas based on the pump current of the second oxygen pump element 78 at this time.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an oxygen sensor showing an example of a gas sensor of the present invention.

FIG. 2 is an explanatory view showing a structure of a ceramic element as the detection element.

FIG. 3 is an exploded perspective view of a connector section.

FIG. 4 is an exploded perspective view of the grommet and a perspective view showing an assembled state of the ceramic element, the connector, and the grommet.

FIG. 5 is a perspective view of a grommet and a perspective view in a state where a filter is extrapolated.

FIG. 6 is a perspective view of a first member, and a three side view thereof.

FIG. 7 is a perspective view of a second member, and a three side view thereof.

FIG. 8 is a front view of the grommet and a cross-sectional view of each part thereof.

FIG. 9 is an operation explanatory view showing an assembled state of the grommet to the outer cylinder.

FIG. 10 is a partially enlarged view of FIG. 1;

FIG. 11 is a cross-sectional view showing a modification of the form of forming the buffer layer in the oxygen sensor of FIG. 1;

FIG. 12 is a schematic cross-sectional view showing an example in which a ceramic element is formed of an entire-area oxygen sensor element.

FIG. 13 is a schematic cross-sectional view showing an example similarly constituted by a NO _X sensor element.

[Explanation of symbols]

 Reference Signs List 1 oxygen sensor (gas sensor) 2, 60, 70 ceramic element (detection element) 3 metal shell 15 grommet (elastic sealing member) 18 outer cylinder 19 gas introduction hole 40 filter 38, 39 crimping part 41 first member 45 lead wire insertion Hole 51 Second member 90 Gas introduction passage 90a First passage 90b Second passage 95 Cylindrical member (hard material portion)

Claims (8)

[Claims] 1. An outer cylinder and a detection unit that is housed in the outer cylinder and that detects a component to be detected in a gas to be measured are formed on the distal end side, and the detection unit is formed of the outer cylinder. A detection element including an oxygen concentration cell element that operates using outside air introduced therein as a reference gas, and a plurality of lead wire insertion holes into which respective lead wires from the detection element are inserted are formed to penetrate in the axial direction. An elastic seal member elastically fitted inside the outer cylinder at the rear end side opening thereof, and an outer surface of the elastic seal member and an inner surface of the outer cylinder are arranged so that both surfaces are in contact with each other, A filter held between the elastic seal member and the outer cylinder, a gas introduction hole is formed in the outer cylinder at a position corresponding to the filter, and external air introduced from the gas introduction hole is provided. Through the filter The gas sensor is configured to be guided to a space inside the outer cylinder through a gas introduction path formed in the elastic seal member after the gas sensor has been operated. 2. The filter according to claim 1, wherein said filter is held between said outer cylinder and said elastic seal member by caulking said outer cylinder toward said elastic seal member. Gas sensor. 3. The filter is disposed so as to cover the outer periphery of the elastic seal member, and the gas introduction path has an entrance portion on the outer peripheral surface of the elastic seal member and an exit portion on the bottom surface. The gas sensor according to claim 1, wherein 4. A plurality of said gas introduction holes are formed at a predetermined interval along a circumferential direction of said outer cylinder, and said outer cylinder has two gas introduction holes sandwiching said row of said gas introduction holes in an axial direction. While an annular caulking part is formed in the circumferential direction,
A portion of the outer cylinder located between the caulked portions bulges outward, and a gap is formed between the filter and at least one of the outer cylinder and the elastic seal member at the bulge portion. The gas sensor according to claim 3, wherein 5. The elastic seal member is composed of two members adjacent to each other in the axial direction of the outer cylinder, the one located on the opening side of the outer cylinder being the first member, and the one located on the opposite side as well. As a second member, the gas introduction path is formed on the joint surface between the first member and the second member, one end of which is open to the outer peripheral surface of the elastic seal member to form the entrance portion, The other end has a first passage extending radially inward of the elastic seal member, and penetrates the second member in the axial direction. One end communicates with the first passage, and the other end is open to the bottom surface of the second member. The gas sensor according to claim 3, further comprising a second passage forming the outlet portion. 6. A projection is formed on at least one of the joining surfaces of the first member and the second member, and a recess is formed on at least one of the joining surfaces, and one of the first member and the second member is formed. 6. The two members are joined to each other by fitting the convex portion formed on the other side into the concave portion formed on the other side.
A gas sensor as described. 7. The second member, wherein a portion including at least a part of a wall surface of the second passage is a hard material portion made of a harder material than the remaining portion. A gas sensor according to claim 1. 8. The second member is formed of a main body having a bottomed tubular member mounting recess formed in a joint surface with the first member, and a material harder than the main body. A cylindrical member as the hard material portion, which has an axial through hole and is mounted in the cylindrical member mounting concave portion; and a bottom portion of the cylindrical member mounting concave portion has an axial line of the second member. 8. The main body part side through-hole which penetrates this in the direction is formed, The said main body part side through hole and the said through hole of the said cylindrical member communicate with each other, and the said 2nd passage is formed. Gas sensor.