JP2009180550A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor for suppressing decline of permeability in a high-temperature environment, and improving reliability by reducing a probability that a filter is damaged, while securing sufficient permeability. <P>SOLUTION: This gas sensor includes a filter unit 200 mounted on an air hole 121 so that at least a part of an opening 205 is exposed to the rear end side of a grommet 120, which includes an inside member 201 formed in a bottomed cylindrical shape, and having a plurality of apertures 202 along the circumferential direction; a filter member 203 provided on the outside of the inside member 201, for covering the outside part of the apertures 202; and an outside member 204 provided outside the filter member 203, holding the filter member 203 between itself and the inside member 201, and having the opening 205 corresponding to the apertures 202. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas sensor for detecting a specific gas (for example, oxygen or the like) contained in a measured gas such as an exhaust gas of an internal combustion engine.

  Conventionally, a gas sensor for detecting a specific gas in a gas to be measured, for example, a gas sensor for detecting oxygen or the like in exhaust gas of an internal combustion engine is known. As a gas sensor element used in such a gas sensor, a gas sensor element having a bottomed cylindrical shape with a closed tip and electrode layers on the inner and outer surfaces is known. In the gas sensor using the gas sensor element having such a structure, for example, the atmosphere is introduced as the reference gas inside the gas sensor element, the gas to be measured is brought into contact with the outside, and the electromotive force generated according to the gas concentration difference between the inside and outside of the gas sensor element is generated. The gas concentration is detected by measuring.

  In the above gas sensor, the gas sensor element is accommodated in the cylindrical metal housing so that the detection portion on the tip side is exposed, and a filter is provided on the side surface of the rear end portion of the cylindrical metal housing. There is known a structure in which a ventilation hole is arranged and air as a reference gas is introduced into the inside of a metal housing from the ventilation hole. In addition, this filter is for preventing infiltration of liquids, such as a water | moisture content, ensuring air permeability by having water repellency.

  However, in the gas sensor having the above structure, the air permeability of the filter may be impaired due to the influence of heat from the high-temperature exhaust gas. For this reason, as shown in FIG. 7, a vent member 13 is provided in a closing member for closing the rear end side opening of the cylindrical metal housing 11, for example, a rubber grommet 12, and the vent hole 13 is formed into a sheet-like shape. A structure that is covered with a filter member 14 is known. That is, in this gas sensor, as shown in FIG. 8, the sheet-like filter member 14 is fixed to the vent hole 13 of the grommet 12 so as to be sandwiched between the vent hole 13 and the cylindrical metal member 15. It has a structure (for example, see Patent Document 1). As shown in FIG. 8, the opening 16 on the upper surface of the metal member 15 is covered with the filter member 14. Further, a flange portion 17 is provided at the lower end portion of the metal member 15, and the flange portion 17 is locked to the bottom surface of the grommet 12. Further, the grommet 12 is provided with a plurality of (for example, four) through holes 18 for leading the electric cables of the gas sensor element to the outside of the metal housing.

7 and 8, the filter member 14 is positioned at the rearmost end portion of the gas sensor, and the rubber grommet 12 has lower thermal conductivity than the metal housing 11. For this reason, even if the front-end | tip part of a gas sensor becomes high temperature, the filter member 14 is maintained at a comparatively low temperature, and it can suppress that the air permeability is impaired.
JP 2000-249678 A

  However, since the filter member 14 is exposed toward the rear end side and a certain amount of tension is applied to the exposed surface of the filter member 14, an external force such as an object hitting the filter member 14 When this is added, the filter member 14 is easily damaged, and there is a problem that the reliability of the gas sensor may be impaired. Further, in order to avoid such a problem, if the thickness of the filter member 14 is increased, it is difficult to increase the diameter of the vent hole 13, and there is a problem that the air permeability may be insufficient. It was. Furthermore, if the thickness of the filter member 14 is increased, there arises a problem that assembly when the filter member 14 is sandwiched between the vent hole 13 and the cylindrical metal member 15 becomes difficult. It is not easy to increase the thickness. In other words, in the conventional gas sensor, the thermal effect on the filter for taking in the atmosphere as the reference gas is relaxed to ensure air permeability, and the possibility of damage to the external force of the filter is reduced to ensure reliability. There was a problem that it was difficult to achieve both.

  The present invention has been made to solve the above problems. The present invention provides a gas sensor capable of suppressing a decrease in air permeability in a high temperature environment and reducing the possibility of damage to a filter while ensuring sufficient air permeability to improve reliability. The purpose is to provide.

  The gas sensor of the present invention extends in the axial direction, the detection part on the tip side is exposed to the gas to be measured, and the difference between the concentration of the specific gas in the gas to be measured and the concentration of the specific gas in the atmosphere as the reference gas A gas sensor element that detects the specific gas from the gas sensor element, a cylindrical housing that surrounds a radially outer side of the gas sensor element, and projects the detection portion of the gas detection element from its front end, and a rear end opening of the housing. A gas sensor comprising a closing member that closes and has a vent hole for introducing air into the housing from the outside, with a portion protruding from the closing member toward the rear end side A filter unit that is inserted and arranged in a vent hole, and is formed in a bottomed cylindrical shape and has an inner member having a plurality of through holes along the circumferential direction, and at least provided outside the inner member. A filter member that covers an outer portion of the through hole, and an outer member that is provided on the outer side of the filter member, holds the filter member between the inner member and has an opening on the filter member, The filter unit is characterized in that at least a part of the opening is exposed on the rear end side of the closing member.

  In the gas sensor of the present invention, the filter unit disposed in the ventilation hole of the closing member (rubber grommet or the like) that closes the rear end opening of the housing is formed in a bottomed cylindrical shape and has a plurality of transparent portions along the circumferential direction. An inner member having a hole, a filter member provided outside the inner member and covering at least an outer portion of the through hole, and provided outside the filter member and holding the filter member between the inner member And an outer member having an opening on the filter member. That is, the overall shape is a substantially bottomed cylindrical shape, and an opening for ventilation (consisting of the through hole and the opening) provided with a filter member is formed in the side wall portion along the circumferential direction. It has been configured. And this filter unit is attached in the state which protruded from the said closure member to the rear-end side so that at least one part of the said opening might be exposed to the rear-end side rather than the said closure member. As described above, the filter unit protrudes from the closing member to the rear end side, and the ventilation opening is provided along the side wall thereof, so that the filter unit is sufficiently large regardless of the diameter of the ventilation hole of the closing member. An opening for ventilation can be provided.

  Therefore, even if the thickness of the filter member is increased, sufficient air permeability can be ensured. Therefore, it is possible to increase the thickness of the filter member and ensure its strength. Furthermore, by providing a plurality of ventilation openings, the opening area of each ventilation opening can be reduced compared to a case where only one ventilation opening is used, and an object or the like can be filtered. The possibility of hitting a member can be reduced. By these, possibility that a filter member will be damaged can be reduced. In addition, the filter member that covers the ventilation opening is positioned further to the rear end side than the closing member, so that the temperature rises even when the tip of the gas sensor is placed in a high temperature environment. Therefore, it is possible to suppress a decrease in the air permeability of the filter member. As a result, the reliability can be improved as compared with the prior art.

  Note that at least one or more openings may be provided, and a plurality of openings may be provided. Further, it is sufficient that at least one or more through holes are provided, and a plurality of through holes may be provided. Furthermore, it is preferable that at least a part of the opening and the through hole overlap when viewed from the radial direction of the gas sensor. If the opening and the through hole overlap in this way, sufficient air permeability can be ensured. Further, it is sufficient that at least a part of the opening is exposed on the rear end side of the closing member. When there are a plurality of openings, each of the openings may be fully exposed on the rear end side of the closing member. The opening may be partially exposed on the rear end side, or part of the opening may be fully exposed on the rear end side of the closing member and the other opening may be partially exposed on the rear end side of the closing member. good.

  The filter unit may be inserted into the closing member, and may be press-fitted into the closing member, or may be fixed by crimping the closing member in the radial direction after being inserted into the closing member. You may join between filter units using an adhesive agent etc.

  In the gas sensor of the present invention configured as described above, the filter member can be formed in a cylindrical shape that can be mounted on the outside of the inner member. With such a configuration, the filter unit can be easily assembled.

  Moreover, in the gas sensor of the present invention configured as described above, the outer member and the filter member may be fixed to the inner member by caulking both axial side portions sandwiching the opening of the outer member along the circumferential direction. it can. With such a configuration, the filter unit can be easily assembled. Further, in this case, by making the Vickers hardness of the outer member lower than the Vickers hardness of the inner member, fixing by caulking can be performed easily and reliably.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to suppress the fall of the air permeability in a high temperature environment, it is possible to improve reliability by reducing the possibility that the filter is damaged while ensuring sufficient air permeability. Gassen can be provided.

  Hereinafter, an embodiment in which a gas sensor of the present invention is applied to an oxygen sensor will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a schematic configuration of an oxygen sensor according to an embodiment of the gas sensor of the present invention, and FIG. 2 is an exploded perspective view showing a main configuration of the gas sensor of FIG.

  As shown in FIG. 1, the gas sensor 100 includes a bottomed cylindrical gas sensor element (oxygen detection element) 1 having a closed tip, and a rod-shaped heater 101 inserted into a cylindrical portion of the gas sensor element 1.

  The gas sensor element 1 is made of an oxygen ion conductive solid electrolyte mainly composed of zirconia or the like, and its front end 3 side (lower side in the figure) serves as a detection part, and on the rear end side (upper side in the figure) of the detection part. The flange portion 2 is formed so as to protrude outward in the radial direction.

  Further, as shown in FIG. 2, an outer electrode formed porous, for example, of Pt or a Pt alloy is formed on the outer side 4 of the gas sensor element 1, and the outer electrode covers the substantially entire surface of the detection unit. The formed detection part electrode 5, the vertical lead part electrode 6 that is electrically connected to the detection part electrode 5 and leads the electrode to the rear end side, and the rear end side of the vertical lead part electrode 6 in a ring shape The ring lead portion electrode 7 is formed. Further, inside the gas sensor element 1, for example, an inner electrode 8 formed in a porous shape by Pt or a Pt alloy is formed. A protective layer made of a ceramic sprayed layer such as spinel is formed outside the detection unit electrode 5.

  As shown in FIG. 1, the flange portion 2 of the gas sensor element 1 is engaged with a holder 102 made of an insulating ceramic, and the gas sensor element 1 is formed of talc disposed on the rear end side of the flange portion 2. The cylindrical metal shell 105 is hermetically held by the ceramic powder 104 and the sleeve 103 disposed on the rear end side of the ceramic powder 104. In addition, in this specification, the direction which goes to the front-end | tip part 3 side (downward in FIG. 1) among the directions (up-down direction in FIG. 1) along the axis | shaft of the gas sensor element 1 is made into the "front end side. The side toward the opposite direction (upward in FIG. 1) is referred to as the “rear end side”.

  The metal shell 105 has a screw portion 106 and a tool engagement portion 107 for attaching the gas sensor 100 to an attachment portion such as an exhaust pipe, and the protector 108 is connected to the protector connection portion 109 by laser welding. The protector 108 is attached so as to cover the distal end portion 3 of the gas sensor element 1 protruding from the distal end side opening of the metal shell 105. The gas sensor 100 is used in such a manner that the front end side of the screw portion 106 is located in an engine such as an exhaust pipe, and the rear end side thereof is located in the outside atmosphere. The protector 108 is formed with a plurality of gas permeation ports 180 through which the exhaust gas permeates.

  On the other hand, the rear end portion 110 of the metal shell 105 is crimped between the sleeve 103 and the sleeve 103 via the ring packing 111 and is kept airtight. In addition, a distal end portion 114 of a cylindrical metal outer tube 113 is fixed to the connecting portion 112 on the rear end side of the tool engaging portion 107 from the outside by laser welding. The metal shell 105 and the metal outer tube 113 constitute the main part of the metal housing in the gas sensor 100.

  Further, the rear end side opening of the metal outer cylinder 113, that is, the rear end side opening of the substantially metal housing is sealed by inserting and tightening a grommet 120 made of a rubber member or the like. Has been.

  At the center of the grommet 120, a filter unit 200 that introduces air into the metal outer cylinder 113 and prevents moisture from entering is disposed. Further, a separator 122 made of an insulating alumina ceramic is provided on the tip side of the grommet 120. Sensor output lead wires 130 and 131 and heater lead wires 132 and 133 are disposed through the separator 122 and the grommet 120.

  Here, the configuration of the filter unit 200 will be described. As shown in FIG. 3, the filter unit 200 is made of metal, such as SUS304, and includes a bottomed cylindrical inner member 201. A plurality of through holes 202 are provided in a predetermined axial position of the inner member 201 along the circumferential direction. Further, a flange 208 protruding in the outer peripheral direction is provided at the opening side end (the lower end in FIG. 3) of the inner member 201. The thickness of the inner member 201 is preferably 0.2 to 0.8 mm.

  A cylindrical filter member 203 is provided outside the inner member 201, and an outer portion of the through hole 202 is covered by the filter member 203. The filter member 203 has water repellency to prevent ingress of liquid such as moisture while ensuring air permeability. As this filter member 203, for example, a porous fiber structure obtained by stretching an unfired molded body of polytetrafluoroethylene (PTFE) in a direction of one axis or more at a temperature lower than the melting point of PTFE, for example, Gore-Tex (trade name: Japan Gore-Tex Co., Ltd.) or the like can be used. Further, an oil repellent coated porous fiber structure such as an oleovent filter (trade name: Japan Gore-Tex Co., Ltd.) can be used. The thickness of the filter member 203 is preferably about 0.8 mm, for example. Thereby, the required strength can be ensured.

Further, an outer member 204 made of metal, for example, SUS304 that has been heat-treated and formed in a substantially cylindrical shape, is provided outside the filter member 203. Each outer member 204 is provided with an opening 205 at a position corresponding to the through hole 202. The filter member 203 is held between the outer member 204 and the inner member 201, and the filter member 203 is pressed inward along the circumferential direction at both side portions in the axial direction across the through hole 202. However, this structure ensures airtightness in this part. The thickness of the outer member 204 is preferably 0.2 to 0.8 mm.

  In the present embodiment, the outer member 204 is crimped at both sides in the axial direction across the through hole 202 to form small diameter portions 206 and 207 in this portion, thereby pressing the filter member 203 inward. It is supposed to be kept in the state. Thus, in this embodiment, since the outer member 204 is caulked to hold the filter member 203, the outer member 204 is set to have a Vickers hardness lower than that of the inner member 201.

  The Vickers hardness of the inner member 201 is preferably 350 to 360, for example, and the Vickers hardness of the outer member 204 is preferably about 150 to 160, for example. In order to reduce the Vickers hardness of the outer member 204, a material having a lower Vickers hardness than that of the inner member 201 can be selected, or a heat treatment method using the same material as that of the inner member 201 can be used. Instead of caulking as described above, adhesive layers 401 are provided between the inner member 201 and the filter member 203 and between the outer member 204 and the filter member 203, respectively, as in the filter unit 400 shown in FIG. The inner member 201, the filter member 203, and the outer member 204 may be fixed by an adhesive or the like. In FIG. 6, parts corresponding to those in FIG.

  After assembling the filter unit 200 having the above configuration, as shown in FIG. 4, the filter unit 200 is inserted into the vent hole 121 provided in the center of the grommet 120, and at least a part of the through hole 202 and the opening 205 is It arrange | positions so that it may become a position exposed to the rear end side from the grommet 120. FIG. At this time, the flange 208 of the inner member 201 serves as a stopper, and the filter unit 200 is positioned in the axial direction. As shown in FIG. 4, four lead wires (only two are shown in FIG. 4) for inserting the sensor output lead wires 130 and 131 and the heater lead wires 132 and 133 into the grommet 120 are inserted. A hole 220 is provided.

  Then, as shown in FIG. 5, the grommet 120 on which the filter unit 200 is arranged as described above is inserted into the rear end side opening of the metal outer cylinder 113, and the caulking portion 155 at the rear end portion of the metal outer cylinder 113 is inserted. By caulking, the grommet 120 is fixed to the metal outer cylinder 113, and the filter unit 200 is fixed to the grommet 120. The caulking portion 155 after caulking as described above has a shape recessed toward the inner side in the circumferential direction, and the inner wall portion of the vent hole 121 of the grommet 120 is also elastically deformed toward the inner circumferential direction. As a result, the filter unit 200 is held and fixed in the vent hole 121.

  In the present embodiment, as described above, the filter unit 200 is disposed on the most rear end side of the gas sensor 100 and is fixed to the rubber grommet 120 having low thermal conductivity. Even if the side is exposed to a high-heat atmosphere, the air permeability of the filter member 202 can be prevented from being impaired by heat.

  Further, the filter unit 200 protrudes from the grommet 120 toward the rear end side, and a ventilation opening made of a through hole 202 and an opening 205 is provided along the side wall thereof, whereby the diameter of the ventilation hole 121 of the grommet 120 is provided. Regardless of this, it is possible to provide a sufficiently large opening for ventilation. Therefore, even if the thickness of the filter member 203 is increased, sufficient air permeability can be ensured. Therefore, the thickness of the filter member 203 can be increased to, for example, 0.8 mm to ensure its strength. It becomes. Furthermore, by providing a plurality of ventilation openings, the opening area of each ventilation opening can be reduced compared to a case where only one ventilation opening is used, and an object or the like can be filtered. The possibility of hitting the member 203 can be reduced. By these, possibility that the filter member 203 will be damaged can be reduced. As a result, the reliability can be improved as compared with the prior art.

  Further, a cylindrical filter member 203 is placed on the outer side of the bottomed cylindrical inner member 201, and a cylindrical outer member 204 is placed on the outer side of the filter member 203, and these are fixed by caulking or adhesive. As a result, the filter member 203 can be easily assembled even when the filter member 203 is thick.

  Here, returning to FIGS. 1 and 2, the overall configuration of the gas sensor 100 will be described. As shown in FIG. 2, the separator 122 includes a rear end side portion 123, a front end side portion 124, and a flange portion 125 having a larger diameter than these. An outer cylinder abutting surface 126 is formed between the flange portion 125 and the rear end side portion 123 so as to increase in diameter toward the front end side (downward in the drawing) to form a tapered surface. On the other hand, a tip side surface 127 forming a stepped step is formed between the tip side portion 124 and the tip side portion 124.

  The separator 122 is formed with lead wire insertion holes 230 and 231 that pass through the lead wires 130, 131, 132, and 133 in the axial direction. Further, on the end face on the rear end side, a ventilation groove 232 is formed in a cross shape and in a direction perpendicular to the axis at a position where it does not interfere with the four lead wire insertion holes 230, 231. Also, a bottomed holding hole 234 that is opened in the front end surface of the separator 122 is formed in the axial direction.

  As shown in FIGS. 1 and 2, the lead wires 130, 131, 132, 133 are inserted into the holding holes 234 and the lead wire insertion holes 230, 231, and the first and second sensor terminal fittings 140, 240 are inserted. The connector portions 141 and 241 and the heater terminal members 340 and 341 are held in the separator 122 while being insulated from each other.

  As shown in FIG. 2, the first sensor terminal fitting 140 includes a connector part 141, a separator contact part 142, and an insertion part 143 that are integrally formed. Among these, the connector part 141 holds the core wire of the sensor output lead wire 130 and electrically connects the first sensor terminal fitting 140 and the sensor output lead wire 130.

  The separator contact portion 142 elastically contacts the holding hole 234 of the separator 122 to hold the first sensor terminal fitting 140 in the separator 122. The insertion portion 143 is inserted into the cylindrical portion of the gas sensor element 1 and is electrically connected to the inner electrode (reference electrode) 8.

  The insertion portion 143 includes a lower pressing portion 144 and an upper pressing portion 145. When the insertion portion 143 is inserted into the cylindrical portion of the gas sensor element 1, the heater 101 surrounded by the insertion portion 143 is pressed. The posture of the heater 101 is adjusted so that the axis of the heater 101 is decentered with respect to the central axis of the gas sensor element 1 and the heat generating part 161 is in contact with the inner wall (inner electrode 8) of the cylinder part of the gas sensor element 1. Further, a flange 146 is provided on the rear end side of the insertion portion 143 in order to prevent the insertion portion 143 from entering the cylinder portion of the gas sensor element 1.

  The heat generating portion 161 formed in the heater 101 is eccentric and comes into contact with the inner wall of the cylindrical portion of the gas sensor element 1, so that heat energy is concentrated in a smaller volume, and the activation time of the gas sensor 100 is shortened. Effective above.

  On the other hand, the second sensor terminal fitting 240 includes a connector part 241, a separator contact part 242, and a grip part 243 that are integrally formed. Among these, the connector part 241 grips the core wire of the sensor output lead wire 131 and electrically connects the second sensor terminal fitting 240 and the sensor output lead wire 131. The separator contact portion 242 elastically contacts the holding hole 234 of the separator 122 to hold the second sensor terminal fitting 240 in the separator 122. The gripping part 243 grips the outer periphery near the rear end of the gas sensor element 1.

  Here, the grip portion 243 is electrically connected to the ring lead portion electrode 7 formed on the outer side 4 of the gas sensor element 1, thereby being connected to the detection portion electrode 5 formed on the outer side 4 of the gas sensor element 1. In addition, a flange portion 244 is provided on the front end side of the grip portion 243 so that the rear end portion of the gas sensor element 1 can be easily inserted into the grip portion 243.

  The heater 101 is a rod-shaped ceramic heater, and a heat generating portion 161 having a resistance heat generating element (not shown) is formed on a core mainly made of alumina. When the heater 101 is energized through the heater terminal fittings 340 and 341 and the heater lead wires 132 and 133 brazed to the electrode pads 163 and 164, the tip of the gas sensor element 1 is heated. The heater terminal fitting 341 has a connector portion 342 that holds the core wire of the heater lead wire 132 and electrically connects the heater terminal fitting 143 and the heater lead wire 132. Although not shown in FIG. 2, the heater terminal fitting 340 also has a connector portion that holds the core wire of the heater lead 133 by the connector portion.

  As shown in FIG. 1, the metal outer cylinder 113 is made of metal and has a substantially cylindrical shape, and is positioned on the distal end side (lower side in the figure). As described above, the distal end portion 114 on the distal end side is the metal shell 105. And a second outer cylinder portion 116 positioned on the rear end side and having a smaller diameter than the first outer cylinder portion 115. In the intermediate portion in the axial direction of the second outer cylindrical portion 116, four convex portions are formed evenly in the circumferential direction, and the inner convex portion 117 is projected radially inwardly with the convex top surface protruding in a square shape. Of the inner convex portion 117, a hook contact surface 118 that forms a slope is formed on the tip side from the top surface of the convex portion. The flange contact surface 118 contacts the outer cylinder contact surface 126 of the separator 122.

  Further, as shown in FIG. 1, an urging metal fitting 150 is attached around the front end side portion 124 of the separator 122. In addition to the cylindrical metal tube portion 151, the urging metal member 150 has a J-type elastic holding portion 152 formed integrally with the metal tube portion 151 at the rear end portion of the metal tube portion 151.

  The J-shaped elastic holding portions 152 are scattered at four locations at equal intervals in the circumferential direction, and extend inward in the radial direction and gradually change direction to extend toward the distal end and bend in a substantially J shape. The J-type elastic holding portion 152 is elastically deformed and holds the urging metal fitting 150 on the front end side portion 124 when the urging metal fitting 150 is attached to the front end side portion 124 of the separator 122.

  The gas sensor 100 having the above configuration is used in a state where the front end side (lower side in FIG. 1) of the screw portion 106 is located in the exhaust pipe and the rear end side (upper side in FIG. 1) is located in the outside atmosphere. Is done. The gas sensor element 1 is heated and activated by a heater 101 disposed inside thereof. Then, the atmosphere as the reference gas is introduced from the filter unit 200 into the metal outer cylinder 113 and is introduced into the gas sensor element 1. On the other hand, exhaust gas is introduced to the outside of the gas sensor element 2 through the gas permeation port 180 of the protector 108.

  As a result, an oxygen concentration cell electromotive force is generated in the gas sensor element 1 in accordance with the difference in oxygen concentration between the inner and outer surfaces. The oxygen concentration cell electromotive force is taken out as a detection signal for the oxygen concentration in the exhaust gas, thereby detecting the oxygen concentration in the exhaust gas.

  As described above, according to the gas sensor 100 of the present embodiment, it is possible to suppress a decrease in air permeability under a high temperature environment, and reduce the possibility that the filter is damaged while ensuring sufficient air permeability. Reliability can be improved. Of course, the present invention is not limited to the above-described embodiment, and various modifications and the like are possible.

1 is a longitudinal sectional view showing an overall schematic configuration of a gas sensor according to an embodiment of the present invention. The disassembled perspective view which shows a part of gas sensor of FIG. The longitudinal cross-sectional view which shows the structure of the filter unit of the gas sensor of FIG. The longitudinal cross-sectional view which shows the state which attached the filter unit of FIG. 3 to the grommet. The longitudinal cross-sectional view which shows the state which attached the filter unit and grommet of FIG. 4 to the metal housing. The longitudinal cross-sectional view which shows the structure of the modification of a filter unit. The longitudinal cross-sectional view which shows the principal part structure of the conventional gas sensor. The figure for demonstrating the principal part structure of the gas sensor of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Gas sensor element, 100 ... Gas sensor, 120 ... Grommet, 121 ... Vent hole, 200 ... Filter unit, 201 ... Inside member, 202 ... Through-hole, 203 ... Filter member, 204 ... Outside Member, 205... Opening, 206, 207.

Claims (4)

It extends in the axial direction, and the detection part on the tip side is exposed to the gas to be measured, and the specific gas is detected from the difference between the concentration of the specific gas in the gas to be measured and the concentration of the specific gas in the atmosphere as the reference gas A gas sensor element to
A cylindrical housing that surrounds the radially outer side of the gas sensor element and projects the detection portion of the gas detection element from its tip;
A closing member for closing the rear end side opening of the housing, the closing member having a ventilation hole for introducing air into the housing from the outside;
In the gas sensor with
A filter unit that is inserted and arranged in the vent hole in a state in which a part projects from the closing member to the rear end side,
An inner member formed in a bottomed cylindrical shape and having a plurality of through holes along the circumferential direction;
A filter member provided outside the inner member and covering at least the outer portion of the through hole;
An outer member provided on the outside of the filter member, holding the filter member between the inner member and an opening on the filter member;
A gas sensor comprising a filter unit in which at least a part of the opening is exposed to the rear end side of the closing member. The gas sensor according to claim 1, wherein
The gas sensor according to claim 1, wherein the filter member has a cylindrical shape that can be attached to the outside of the inner member. The gas sensor according to claim 1 or 2,
The gas sensor according to claim 1, wherein the outer member and the filter member are fixed to the inner member by crimping axially opposite sides of the outer member along the circumferential direction. The gas sensor according to claim 3, wherein
The gas sensor according to claim 1, wherein a Vickers hardness of the outer member is lower than a Vickers hardness of the inner member.

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