JP4886006B2 - Gas sensor unit - Google Patents

Description

  The present invention relates to a gas sensor unit including a detection element that detects the concentration of oxygen in exhaust gas.

  2. Description of the Related Art Conventionally, an oxygen sensor that incorporates a detection element that detects the concentration of oxygen contained in automobile exhaust gas and is attached to an exhaust path of an internal combustion engine or the like is known. The detection element of the oxygen sensor is provided with a detection electrode that is exposed to exhaust gas and a reference electrode that is exposed to the atmosphere. A sensor cap having a cap terminal connected to the reference electrode and taking out the output of the detection element is detachably attached to the oxygen sensor. A gas sensor unit is formed by the oxygen sensor and the sensor cap.

  The sensor cap further includes an enclosing member that holds the cap terminal and is attached to the oxygen sensor. And in the state which attached the sensor cap to the oxygen sensor, in order to expose the atmosphere to the reference electrode, an internal space is formed between the surrounding member and the oxygen sensor, and the surrounding member includes the internal space and its own space. A communication hole that communicates with the outside is formed. In addition, a filter member having air permeability and water repellency is disposed in the communication hole, and foreign matter can be prevented from entering the internal space.

  By the way, so that the filter member can be positioned with respect to the communication hole, the communication hole communicates with the outside and has a filter arrangement surface on which the filter member is arranged, and a ventilation formed smaller than an opening area of the filter arrangement surface. And a connecting surface that connects the filter arrangement surface and the ventilation surface (see, for example, Patent Document 1).

JP 2006-162597 A

  However, in the gas sensor unit described in Patent Document 1, when the filter member is arranged on the filter arrangement surface, the filter member is pushed in from the outside of the surrounding member, so that the inner side surface of the filter member has the filter arrangement surface and the ventilation surface. In some cases, the connecting surface is touched. When the inner surface of the filter member comes into contact with the connecting surface, the ventilation area of the filter member cannot secure the area of the inner surface (that is, the opening area of the filter arrangement surface) and is substantially equal to the opening area of the ventilation surface. turn into. Then, the amount of ventilation in the filter member is reduced, and there is a concern that ventilation between the internal space and the outside may not be performed smoothly.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a gas sensor unit capable of smoothly venting between an internal space and the outside.

According to an embodiment of the present invention, a gas sensor having a gas detection element that is exposed to a gas to be measured, and a sensor terminal that is connected to an electrode formed on the gas detection element and transmits an output signal from the gas detection element; A sensor cap that is mounted on the gas sensor and transmits the output signal to an external device, the cap terminal being electrically connected to the sensor terminal, and the sensor cap and the gas sensor when the sensor cap is mounted on the gas sensor. An enclosing member that forms an internal space between them and has a communication hole that allows the gas to flow between the internal space and the outside, and a filter member that is disposed in the communication hole and has air permeability and water repellency A gas sensor unit comprising: a sensor cap having a filter arrangement surface on which the filter member is arranged; A ventilation surface having a smaller opening area than the filter arrangement surface, and a connecting surface connecting the filter arrangement surface and the ventilation surface, wherein a filter member is arranged in the filter arrangement surface, and the connection surface and the filter a gas flow passage formed by the inner surface facing the connecting surface side of the member, is a spacer to secure a gas channel for circulating the gas which has passed through the filter member to the site corresponding to the ventilation surface the first protrusion, the provided communication hole itself, the gas sensor unit according to claim Rukoto protruding from the connecting surface toward the inside of the filter member.

In the gas sensor unit of the present embodiment, since the first protrusion as a spacer is provided between the connecting surface and the inner surface of the filter member, the inner surface of the filter member and the connecting surface are not in direct contact with each other. A gas flow path can be secured between the connecting surface and the inner surface of the filter member. Therefore, the ventilation area of the filter member can be made larger than the opening area of the ventilation surface. Since the moving speed of the gas in the filter member depends on the ventilation area on the inner surface of the filter member, the amount of ventilation in the filter member can be maintained, and ventilation between the internal space and the outside can be performed smoothly.

Furthermore , the spacer and the surrounding member can be integrally formed by forming the first protrusion on the connecting surface. In this case, it is not necessary to prepare a separate spacer, and since the spacer can be molded without having to provide a manufacturing process for molding the spacer, the gas sensor unit can be manufactured easily and inexpensively. Further, in this case, since the first protrusion is fixed to the connecting surface, the contact position between the first protrusion and the filter member is difficult to shift. Therefore, the gas flow path secured by the first protrusion does not vary. Therefore, air can be smoothly ventilated between the internal space and the outside, and variation in the airflow amount for each product can be suppressed.

  Moreover, the area of the cross section of the said 1st projection part orthogonal to the protrusion direction of a said 1st projection part may be smaller than the area by the side of the said filter member of the said filter member side. In this case, the contact area between one surface of the filter member and the first protrusion can be reduced. Thereby, it can suppress that the ventilation area of a filter member is reduced by the 1st projection part, and the ventilation area of the inner surface of a filter member can be ensured reliably. Therefore, ventilation between the internal space and the outside can be performed more smoothly. Note that the area of the cross section in the direction orthogonal to the protruding direction of the first protrusion may be decreased stepwise from the connecting surface toward the inner surface of the filter member, or may be decreased asymptotically.

  In addition, when the connecting surface is partitioned 120 degrees in the circumferential direction, at least one or more of the first protrusions may be formed in each partition. By disposing at least one or more first protrusions in each section, it is possible to prevent the inner surface of the filter member from being inclined with respect to the connecting surface. Therefore, a gas flow path can be ensured reliably and the ventilation area in the inner surface of a filter member can be ensured. Therefore, ventilation between the internal space and the outside can be performed more smoothly.

As a reference form, the spacer may be a second protrusion that is provided in the communication hole itself and protrudes from the filter arrangement surface. By forming the second protrusion on the filter arrangement surface, the spacer and the surrounding member can be integrally molded. In this case, it is not necessary to prepare a separate spacer, and since the spacer can be molded without having to provide a manufacturing process for molding the spacer, the gas sensor unit can be manufactured easily and inexpensively. In this case, since the second protrusion is fixed to the connecting surface, the contact position between the second protrusion and the filter member is difficult to shift. Therefore, the gas flow path secured by the second protrusion does not vary. Therefore, air can be smoothly ventilated between the internal space and the outside, and variation in the airflow amount for each product can be suppressed.

  By the way, when the spacer is disposed in the middle of the gas flow path, the spacer itself becomes a resistance for the gas to flow. On the other hand, by providing the second projecting portion on the filter arrangement surface, the second projecting portion is not disposed in the middle of the gas flow path, and the gas does not flow. Thereby, the air permeability of the sensor cap can be further improved. Therefore, ventilation between the internal space and the outside can be performed more smoothly.

In the reference embodiment, when the filter arrangement surface is partitioned by 120 degrees in the circumferential direction, at least one or more of the second protrusions may be formed in each partition. By disposing at least one protrusion in each section, it is possible to suppress the inner surface of the filter member from being inclined with respect to the connecting surface. Therefore, a gas flow path can be ensured reliably and the ventilation area in the inner surface of a filter member can be ensured. Therefore, ventilation between the internal space and the outside can be performed more smoothly.

In the reference embodiment, the spacer may be provided between the connecting surface and the inner surface of the filter member, and may have a hardness higher than that of the filter member. By separately manufacturing the spacer without integrally molding with the surrounding member or the filter member, various spacer shapes can be formed without being affected by the existing surrounding member or filter member. Moreover, when the hardness of the spacer is higher than that of the filter member, the spacer is not crushed by the filter member when the filter member is disposed in the communication hole. Since the shape of the spacer can be secured, the gas flow path can be reliably secured. Therefore, ventilation between the internal space and the outside can be performed smoothly.

In the reference embodiment, the spacer may be disposed closer to the filter arrangement surface than the edge on the ventilation surface side of the connecting surface. As described above, when the spacer is also positioned in the middle of the gas flow path, the spacer itself becomes a resistance for gas flow. On the other hand, by arranging the spacer closer to the filter arrangement surface than the edge on the ventilation surface side of the connecting surface, the resistance of the gas flow by the spacer can be reduced. Thereby, the air permeability of the sensor cap can be further improved. Therefore, ventilation between the internal space and the outside can be performed more smoothly.

Moreover, in a reference form, the area of the cross section of the spacer in the direction parallel to the connecting surface may be such that the area on the filter member side is smaller than the area on the connecting surface side. In this case, the contact area between the inner surface of the filter member and the spacer can be reduced. Thereby, the ventilation area in the inner surface of a filter member is reliably securable. Therefore, ventilation between the internal space and the outside can be performed more smoothly. In addition, the step area in the direction parallel to the connecting surface of the spacer may be reduced stepwise from the connecting surface toward the inner surface of the filter member, or may be gradually reduced.

In the reference embodiment, when the connecting surface is partitioned 120 degrees in the circumferential direction, at least one spacer may be disposed in each partition. By arranging at least one spacer in each section, it is possible to prevent the inner surface of the filter member from being inclined with respect to the connecting surface. Therefore, a gas flow path can be ensured reliably and the ventilation area in the inner surface of a filter member can be ensured. Therefore, ventilation between the internal space and the outside can be performed more smoothly.

2 is a longitudinal sectional view showing the structure of the gas sensor unit 1. FIG. 2 is a longitudinal sectional view showing the structure of the oxygen sensor 100. FIG. 2 is a longitudinal sectional view showing a structure of a sensor cap 200. FIG. 2 is a partial cross-sectional view of a sensor cap 200. FIG. 5 is a graph showing a rate of decrease in air flow rate of the sensor cap 200. 3 is a partial cross-sectional view of a sensor cap 300. FIG. 4 is a partial cross-sectional view of a sensor cap 400. FIG. 5 is a perspective view of a spacer member 450. FIG. 5 is a perspective view of a spacer member 550. FIG. 3 is a partial cross-sectional view of a sensor cap 500. FIG.

  Hereinafter, a first embodiment of a gas sensor unit 1 embodying the present invention will be described with reference to the drawings. The gas sensor unit 1 is used by being attached to an exhaust path H of an automobile. Hereinafter, in the direction of the axis O, the side (lower side in FIG. 1) inserted into the exhaust path H of the gas sensor unit 1 is the tip side of the gas sensor unit 1, and the side (in FIG. The upper side) will be described as the rear end side.

  As shown in FIG. 1, the gas sensor unit 1 includes an oxygen sensor 100 and a sensor cap 200 that is detachably attached to the oxygen sensor 100 on the rear end side of the oxygen sensor 100. The oxygen sensor 100 includes a detection element 10 that is exposed to exhaust gas and outputs a detection signal corresponding to the oxygen concentration in the exhaust gas. The sensor cap 200 is attached to the oxygen sensor 100, and a cap terminal 210 provided in the sensor cap 200 is electrically connected to the detection element 10, and an output signal output from the detection element 10 is transmitted to an external device (for example, an engine control unit ( ECU)).

  First, the structure of the oxygen sensor 100 will be described with reference to FIG. The oxygen sensor 100 has a structure in which a cylindrical detection element 10 whose front end is closed is disposed in the housing 2. A connection terminal 71 for taking out a signal output from the detection element 10 is fitted inside the rear end of the detection element 10. A cylindrical ceramic enclosure 4 is provided so as to surround the outer periphery of the connection terminal 71. The ceramic enclosure 4 surrounds the connection terminal 71 together with the outer peripheral portion on the rear end side of the detection element 10. A cap terminal 210 (see FIG. 1) described later is connected to the connection terminal 71.

  The housing 2 has a metal shell 21 and a protector 22. The metal shell 21 is made of SUS430 and has a substantially cylindrical shape. A screw portion 24 for attaching the oxygen sensor 100 to the exhaust path H is formed on the outer peripheral surface of the distal end portion of the metal shell 21. On the rear end side of the screw portion 24, an attachment portion 29 for engaging with an attachment tool for screwing the screw portion 24 into the exhaust path H is provided.

  Further, the cylindrical hole of the metal shell 21 has a three-stage step shape, and the tip side portion is formed as a tip cylindrical hole 28 having a minimum inner diameter. The rear end portion of the cylinder hole is formed as a rear end cylinder hole 25 having the maximum inner diameter, and an intermediate cylinder having an intermediate inner diameter between the front end cylinder hole 28 and the rear end cylinder hole 25. A hole 27 is formed.

  The rear end cylindrical hole 25 is disposed at a position surrounding the outer periphery of the front end portion 41 of the ceramic enclosure 4. Further, the step portion between the rear end cylindrical hole 25 and the intermediate cylindrical hole 27 is configured as a filler receiving portion 26, and the inner periphery of the cylindrical hole extending from the filler receiving portion 26 to the rear end cylindrical hole 25; A filler 102 is filled in a gap with the outer periphery of the detection element 10.

  The intermediate cylinder hole 27 is formed at a position where a later-described flange portion 12 of the detection element 10 is disposed. A step portion between the intermediate tube hole 27 and the tip tube hole 28 is configured as a flange receiving portion 23. The collar portion 12 of the detecting element 10 is supported by the collar receiving portion 23. Further, the distal end cylindrical hole 28 is formed at a position surrounding the detection element 10.

  A protector 22 is attached to the tip of the metal shell 21. The protector 22 has a bottomed cylindrical shape, and covers and protects the distal end side of the detection unit 11 described later of the detection element 10 exposed from the metal shell 21. The protector 22 includes a plurality of vent holes 54 for introducing the exhaust gas in the exhaust path H into the housing 2 and bringing it into contact with the detection element 10.

  As described above, the detection element 10 held inside the housing 2 has a bottomed cylindrical shape with a closed end, and the base 13 is a solid electrolyte mainly composed of zirconia. On the outer periphery of the detection element 10, a flange 12 protruding outward in the radial direction is provided. The detection element 10 is in a state where a metal packing 101 is interposed between a surface facing the distal end side of the flange portion 12 (hereinafter referred to as “front end facing surface”) and the flange receiving portion 23 of the metal shell 21. The metallic shell 21 is disposed.

  The detection unit 11 is disposed on the front end side of the detection element 10 with respect to the collar part 12, and the rear end side of the detection element 10 is configured as a rear end part 15. As described above, the detection unit 11 is exposed from the metal shell 21 and is exposed to the exhaust gas to detect the oxygen concentration in the exhaust gas. The rear end portion 15 extends in a cylindrical shape with substantially the same outer diameter. A detection electrode 51 formed by plating Pt or a Pt alloy is provided on the outer peripheral surface of the detection unit 11. The detection electrode 51 is electrically connected to the tip-facing surface of the flange 12 and is further electrically connected to the metal shell 21 via the packing 101. Therefore, the potential of the detection electrode 51 can be taken out from the metal shell 21. The surface of the detection unit 11 is covered with a porous electrode protection layer (not shown) made of heat resistant ceramics.

  A reference electrode 55 is provided on the inner peripheral side of the base 13 so as to cover the inner peripheral surface. The reference electrode 55 is formed by plating the entire inner peripheral surface of the detection element 10 with Pt or a Pt alloy. The reference electrode 55 and the detection electrode 51 are arranged at positions corresponding to each other with the base body 13 as a solid electrolyte body interposed therebetween, and this portion functions as a gas detection unit that detects the oxygen concentration in the exhaust gas. .

  A packing 103 is disposed on a surface facing the rear end side of the flange 12 of the detection element 10 (hereinafter referred to as “rear end facing surface”). Further, on the rear end side of the packing 103, a filler material 102 made of ceramic powder is attached to the outer peripheral surface of the rear end portion 15 of the detection element 10 and the filler receiving portion 26 of the metal shell 21 from the rear end cylindrical hole 25. It is filled between the inner peripheral surface.

  The ceramic enclosure 4 described above is arranged on the rear end side of the filler 102. The ceramic enclosure 4 is formed in a cylindrical shape from an insulating ceramic, and the tip 41 of the ceramic enclosure 4 protrudes radially outward. The distal end portion 41 is disposed between the outer peripheral surface of the rear end portion 15 of the detection element 10 and the inner peripheral surface of the rear end cylindrical hole 25 so as to be interposed at the position of the rear end of the filler 102. A packing 104 is disposed on the surface facing the rear end of the front end portion 41, and the crimping portion 31 formed at the rear end of the metal shell 21 is crimped toward the front end, whereby the front end portion 41 is interposed via the packing 104. Is pressed against the filler 102. Thereby, the gap between the inner peripheral surface of the metal shell 21 and the outer peripheral surface of the detection element 10 is airtightly filled with the filler 102. In this way, the detection element 10 is held inside the metal shell 21 via each member sandwiched between the flange receiving portion 23 and the crimping portion 31.

  A connection terminal 71 is inserted on the rear end side in the cylindrical hole of the detection element 10. The connection terminal 71 has a substantially cylindrical shape, an electrode contact portion 72 connected to the reference electrode 55 is provided on the front end side, and a cap connection portion 73 connected to a cap terminal 210 (described later) is formed on the rear end side. .

  Next, the structure of the sensor cap 200 will be described with reference to FIG. The sensor cap 200 includes a surrounding member 220 that surrounds the rear end side of the oxygen sensor 100 (see FIG. 2), a cap terminal 210 that is electrically connected to the oxygen sensor 100, and a lead wire that is caulked and fixed to the cap terminal 210. 260 and a filter member 250.

  First, the surrounding member 220 will be described. As shown in FIG. 3, the surrounding member 220 is made of a hollow insulating fluoro-rubber. The surrounding member 220 includes a bottomed cylindrical sensor surrounding portion 221 whose rear end side (upper side in the drawing) is closed, a filter surrounding portion 222 that projects radially from the rear end side of the sensor surrounding portion 221, and a sensor. A lead wire surrounding portion 223 that protrudes from the rear end side of the surrounding portion 221 to the side opposite to the filter surrounding portion 222 is provided.

  The sensor surrounding portion 221 surrounds the rear end side of the oxygen sensor 100 in a state where the sensor cap 200 is attached to the oxygen sensor 100 (see FIG. 2). As shown in FIG. 3, the sensor surrounding part 221 is formed in a substantially cylindrical shape. The inner wall 227 of the sensor surrounding part 221 is provided with a tapered step for guiding the rear end of the oxygen sensor 100 to the center of its cylinder hole when the sensor cap 200 is attached to the oxygen sensor 100.

  In addition, a cap terminal 210 is disposed in the sensor surrounding portion 221 so as to be electrically connected to the reference electrode 55 of the detection element 10 via the connection terminal 71 (see FIG. 2) of the oxygen sensor 100. The cap terminal 210 has a sensor connecting portion 256 that protrudes from the bottom side (upper side in the drawing) of the cylindrical hole of the sensor surrounding portion 221 toward the open side (lower side in the drawing) within the sensor surrounding portion 221. . The sensor connection portion 256 is inserted into the cap connection portion 73 (see FIG. 2) of the connection terminal 71 and makes electrical connection with the connection terminal 71. The sensor connecting portion 256 is formed in a cylindrical shape, and ventilation is possible in the sensor surrounding portion 221 through its own cylindrical hole 216.

  Further, the cap terminal 210 is provided with a positioning portion 255 for positioning and holding the cap terminal 210 on the inner wall 227 of the sensor surrounding portion 221 near the base of the sensor connecting portion 256. The positioning portion 255 is formed in an annular portion 211 formed in an annular shape from the root of the sensor connecting portion 256 toward the inner wall 227, and in a cylindrical shape protruding from the outer edge of the annular portion 211 toward the same side as the sensor connecting portion 256. Gripping portion 212. The inner wall 227 is provided with a concave engaging portion 225, and the lower end portion of the grip portion 212 is engaged with the engaging portion 225, so that the cap terminal 210 is prevented from coming off from the sensor surrounding portion 221. ing. In addition, at the bottom (upper side in the drawing) of the sensor surrounding part 221, the cap terminal 210 is mounted on the sensor surrounding part 221, and between the tube hole 216 of the sensor connecting part 256 and the filter surrounding part 222 described later. A groove portion 99 is formed so as to allow ventilation. Therefore, air can be passed from the filter surrounding part 222 (more specifically, a communication hole 230 described later) to the open side of the sensor surrounding part 221 through the groove part 99 and the inside of the cylindrical hole 216 of the cap terminal 210.

  Furthermore, a lead wire fixing portion 219 connected to the lead wire 260 extends from the cap terminal 210 in the radial direction from the vicinity of the rear end side of the sensor connection portion 256 toward the lead wire surrounding portion 223. The lead wire 260 is connected in the surrounding portion 223. The lead wire 260 is drawn out of the sensor cap 200 from a lead wire insertion hole 261 opened in the lead wire surrounding portion 223. The opening diameter of the lead wire insertion hole 261 is slightly smaller than the diameter of the lead wire 260. As a result, the lead wire insertion hole 261 and the lead wire 260 are in close contact with each other, and air and water can be prevented from being introduced from the lead wire insertion hole 261.

  The filter enclosure 222 will be described. The filter surrounding part 222 protrudes radially outward from the rear end side of the sensor surrounding part 221 and is formed in a substantially cylindrical shape. The filter enclosure 222 includes a communication hole 230 therein. The communication hole 230 allows the sensor surrounding part 221 to communicate with the outside of the surrounding member 220. The communication hole 230 includes a filter arrangement hole 231 having an opening 259 on the outer wall of the filter enclosure 222, and a ventilation hole 232 that allows the filter arrangement hole 231 and the sensor enclosure 221 to communicate with each other so as to allow ventilation.

  As shown in FIG. 4, the filter arrangement hole 231 is formed as a cylindrical hole having a circular cross section. The filter placement hole 231 is surrounded by a filter placement surface 234 that forms a circumferential surface, and an annular connecting surface 233 that is located at the end of the filter placement surface 234 on the sensor surrounding portion 221 side. A filter retainer 235 that protrudes inward in the radial direction and is annularly connected in the circumferential direction is formed at the end of the filter arrangement surface 234 on the opening 259 side. The filter retainer 235 prevents a filter member 250 (described later) from falling out of the filter placement hole 231. The filter arrangement surface 234 is formed with two filter holding portions 236 that protrude inward in the radial direction and are annularly connected in the circumferential direction. The protruding height of the filter holding part 236 is lower than the protruding height of the filter holding part 235.

  As shown in FIG. 4, the connecting surface 233 has an annular shape and has an opening 238 connected to the vent hole 232 at the center. A first protrusion 239 that protrudes from the connection surface 233 toward the opening 259 is formed on the connection surface 233. Four first protrusions 239 are arranged at intervals of 90 degrees in the circumferential direction with the position corresponding to the center of the opening 238 when the connecting surface 233 is viewed from the opening 259 side. Each of the first protrusions 239 has a hemispherical protruding tip. The protruding height of the first protrusion 239 is 0.5 mm as an example. As an example, the diameter of the end of the first protrusion 239 on the connecting surface 233 side is 0.7 mm.

  Next, the vent hole 232 is formed as a cylindrical hole having a smaller diameter than the filter arrangement hole 231, and communicates the filter arrangement hole 231 with the inside of the sensor surrounding portion 221 as described above. An opening 238 is located at the end of the ventilation hole 232 on the filter arrangement hole 231 side. The ventilation hole 232 is formed by the ventilation surface 237.

  Next, the filter member 250 arranged in the filter arrangement hole 231 of the surrounding member 220 will be described with reference to FIG. The filter member 250 is made of PTFE having a porous structure in which fine pores are continuous, and has water tightness and air permeability. The filter member 250 is formed in a cylindrical shape, and is disposed between the outer surface 251 disposed on the opening 259 side, the inner surface 252 disposed on the connecting surface 233 side, and the outer surface 251 and the inner surface 252. And a lateral surface 253 which is positioned.

  The arrangement structure of the filter member 250 will be described with reference to FIG. When the filter member 250 is arranged in the filter arrangement hole 231, the filter member 250 is pushed into the filter arrangement hole 231 from the opening 259 of the filter arrangement hole 231. While the filter retainer 235 is elastically deformed, the filter member 250 is pushed into the filter placement hole 231 and placed in the filter placement hole 231.

  In a state in which the filter member 250 is disposed in the filter arrangement hole 231, the filter holding portion 235 returns from the deformation and contacts the outer surface 251 of the filter member 250, and the filter member 250 falls out of the filter arrangement hole 231 to the outside. To prevent. Further, the filter holding portion 236 holds the filter member 250 by pressing the horizontal surface 253 of the filter member 250 inward in the radial direction and seals the gap between the filter arrangement surface 234 and the horizontal surface 253. Thereby, the adhesiveness of the filter holding | maintenance part 236 and the filter member 250 can be improved, and the watertightness of the sensor cap 200 can be improved.

  The inner surface 252 of the filter member 250 is in contact with the tip of the first protrusion 239. Therefore, a gap 257 is formed between the inner side surface 252 and the connecting surface 233, thereby preventing the close contact therebetween. At this time, all portions of the inner surface 252 of the filter member 250 except the contact portion with the first protrusion 239 face the gap 257. Thereby, compared with the case where the inner surface 252 and the connecting surface 233 are in close contact, the ventilation area on the inner surface 252 can be increased.

  Next, a structure for attaching the sensor cap 200 configured as described above to the oxygen sensor 100 will be described. As shown in FIG. 1, in a state where the sensor cap 200 is attached to the oxygen sensor 100, the sensor connection portion 256 of the cap terminal 210 is inserted inside the connection terminal 71, abuts on the connection terminal 71, and the cap terminal 210 The connection terminal 71 is electrically connected.

  Further, the rear end side of the ceramic enclosure 4 is inserted into the gap between the grip portion 212 and the sensor connection portion 256, and the rear end face of the ceramic enclosure 4 abuts on the annular portion 211. The inner wall 227 of the surrounding member 220 is in close contact with the outer peripheral surface of the ceramic surrounding body 4 to hold the ceramic surrounding body 4. When the inner wall 227 and the outer peripheral surface of the ceramic enclosure 4 are in close contact with each other, air is prevented from being introduced into the sensor cap 200 from below the sensor cap 200. Thereby, the reference electrode 55 contacts only with the air introduced from the outside through the communication hole 230.

  Next, the flow of air that contacts the reference electrode 55 will be described. The atmosphere flows from the outside of the gas sensor unit 1 toward the reference electrode 55 and sometimes flows from the reference electrode 55 toward the outside. Here, the case of flowing from the outside toward the reference electrode 55 is taken as an example. I will explain.

  As shown in FIG. 4, the external atmosphere reaches the gap 257 via the filter member 250 from the opening 259 provided on the outer wall of the surrounding member 220. The atmosphere that has reached the gap 257 reaches the groove 99 formed on the rear end side (upper side in the drawing) of the cap terminal 210 from the opening 238 through the vent hole 232. Then, as shown in FIG. 1, it reaches the inside of the detection element 10 via the cylindrical hole 216 of the cap terminal 210 and the cylindrical hole formed in the connection terminal 71 and contacts the reference electrode 55. .

  Here, the moving speed of the atmosphere in the filter member 250 depends on the cross-sectional area (venting area) of the filter member 250 in the air circulation direction. In the present embodiment, as shown in FIG. 4, since the first protrusion 239 is provided on the connecting surface 233, the inner side surface 252 contacts only the tip of the first protrusion 239. Therefore, as compared with the case where the inner surface 252 and the connecting surface 233 are in direct contact with each other and the ventilation area on the inner surface 252 becomes substantially the same as that of the opening 238 as in the conventional case, the ventilation area on the inner surface 252. Can be increased. Therefore, the air flow rate in the filter member 250 can be improved.

  Further, by integrally molding the first protrusion 239 on the connecting surface 233, it is not necessary to prepare a separate spacer, and the first protrusion 239 can be formed without providing a manufacturing process for molding the spacer. Therefore, the gas sensor unit can be manufactured easily and inexpensively. In addition, since the first protrusion 239 is fixed to the connecting surface 233, the contact position between the first protrusion 239 and the filter member 250 is difficult to shift. Therefore, the gas flow path secured by the first protrusion 239 does not vary. Therefore, the dispersion | variation for every product can be suppressed.

In addition, the cross-sectional area of the first protrusion 239 that is orthogonal to the protruding direction of the first protrusion 239 (the left-right direction in FIG. 4) decreases from the connecting surface 233 toward the inner surface 252. Thereby, the contact area between the inner surface 252 of the filter member 250 and the first protrusion 239 can be reduced, and the reduction of the ventilation area of the filter member 250 by the first protrusion 239 can be suppressed.

  Further, when the connecting surface 233 is partitioned 120 degrees in the circumferential direction, at least one or more first protrusions 239 are formed in each section (in this embodiment, as described above, 90 degrees Therefore, it is possible to suppress the inner surface 252 of the filter member 250 from being inclined with respect to the connecting surface 233.

  The gas flow rate of the gas sensor unit 1 of the present embodiment in which the first protrusion 239 is provided on the connecting surface 233 was evaluated. An evaluation method and an evaluation result will be described with reference to FIG. For comparison, the air flow rate was also measured and evaluated for a conventional product that does not include the first protrusion 239 on the connecting surface 233.

  First, the evaluation method will be described. The evaluation is based on the filter member 250 in a state where the filter member 250 is disposed in the surrounding member 220 with respect to the air flow rate of the filter member 250 in a state where the filter member 250 is disposed in the silicon tube (hereinafter referred to as a reference air flow rate). This was done by evaluating the rate of decrease in air flow.

  The reference air flow was measured as follows. First, the filter member 250 is inserted into the silicon tube. Then, 50 kPa of air is pressurized on one end side of the silicon tube. Then, the amount of air flowing out from the other end side of the silicon tube in one minute is captured in water. The amount of trapped air was taken as the reference ventilation rate.

  The air flow rate of the filter member 250 in a state where the filter member 250 is disposed on the surrounding member 220 was measured as follows. First, the filter member 250 is arranged in the filter arrangement hole 231 of the surrounding member 220. Then, the lead wire insertion hole 261 opened in the lead wire surrounding portion 223 of the surrounding member 220 is closed. Then, air of 50 kPa is pressurized to the opening of the surrounding member 220 on the sensor surrounding portion 221 side. Under this condition, the amount of air that flows out from the opening 259 formed in the filter enclosure 222 in one minute is captured in water. The amount of trapped air was defined as the air flow rate of the filter member 250 in a state where the filter member 250 is disposed on the surrounding member 220.

  The filter member 250 was placed in the surrounding member 220 in the following two ways, and each was evaluated. Specifically, there are two methods: a method of pushing the center of the outer surface 251 of the filter member 250 from the opening 259 side toward the vent 232 and a method of pushing the vicinity of the edge of the outer surface 251 of the filter member 250. By the method, the filter member 250 was arrange | positioned to the filter arrangement | positioning hole 231, and each evaluated. When the filter member 250 is arranged by the former method, as shown in FIG. 1, the filter member 250 has an inner surface 252 that is in contact with all four first protrusions 239, and the column axis is the filter member. It arrange | positions so that it may become the same as the hole axis | shaft of the arrangement | positioning hole 231. FIG. Further, when the filter member 250 is arranged by the latter method, the filter member 250 has the inner surface 252 in contact with at least one of the four first protrusions 239 and the column axis is a filter. The arrangement holes 231 are arranged so as to be inclined with respect to the hole axis.

  Hereinafter, the center of the outer surface 251 of the filter member 250 is pushed in, and the ventilation amount of the filter member 250 arranged in the filter arrangement hole 231 is arranged by pushing the sample 1 and the vicinity of the edge of the outer surface 251 of the filter member 250. The ventilation rate of the filter member 250 will be described as the ventilation rate of the sample 2, and the ventilation rate when the filter member 250 is disposed on the conventional surrounding member will be described as the ventilation rate of the sample 3.

The rate of decrease in the air flow rate of Sample 1, Sample 2, and Sample 3 relative to the reference air flow rate was calculated by the following equation.
(Rate of decrease in air flow rate of sample 1) = (1− (air flow rate of sample 1) / (reference air flow rate)) × 100
(Rate of decrease in airflow rate of sample 2) = (1− (airflow rate of sample 2) / (reference airflow rate)) × 100
(Rate of decrease in air flow rate of sample 3) = (1− (air flow rate of sample 3) / (reference air flow rate)) × 100

  The result of evaluation will be described. As shown in FIG. 5, for Sample 1, the rate of decrease in the air flow rate with respect to the reference air flow rate was 6% to 18%. For sample 2, the rate of decrease in the air flow rate relative to the reference air flow rate was 8% to 18%. On the other hand, for sample 3, the rate of decrease in the air flow rate relative to the reference air flow rate was 39% to 60%.

  Thereby, it was shown that the air flow rate of Sample 1 and Sample 2 is larger than the air flow rate of Sample 3. The reason is considered as follows. In Sample 1 and Sample 2, since a gap 257 is formed between the connecting surface 233 of the filter arrangement hole 231 and the inner surface 252 of the filter member 250, an air pressure of 50 kPa is applied to almost the entire inner surface 252. The pressurized air is introduced into the filter member 250 from almost the entire inner surface 252 and flows out from the outer surface 251. On the other hand, in the sample 3, the inner side surface 252 of the filter member 250 is in contact with the connecting surface 233 of the filter arrangement hole 231. Air pressure is not applied to the portion of the inner surface 252 that is in contact with the connecting surface 233. Therefore, the pressurized air is not introduced into the filter member 250 from the portion of the inner surface 252 that is in contact with the connecting surface 233 but is introduced only from the portion facing the opening 238. Thereby, it is considered that the sample 1 and the sample 2 have a larger air flow rate than the sample 3.

  Moreover, it was shown that the variation in the air flow rate of Sample 1 and Sample 2 was smaller than the variation in the air flow rate of Sample 3. The reason is considered as follows. As described above, the amount of ventilation depends on the ventilation area of the inner surface 252 of the filter member 250. In Sample 1 and Sample 2, the inner surface 252 of the filter member 250 is in contact with the tip of the first protrusion 239. Therefore, the ventilation area on the inner surface 252 can be approximated as being approximately equal to the area of the inner surface 252. On the other hand, in the sample 3, the inner surface 252 and the connecting surface 233 are in contact with each other. The contact area between the inner side surface 252 and the connecting surface 233 varies due to unevenness that can be formed on the inner side surface 252 and the connecting surface 233 in the manufacturing process. As a result, a variation occurs in the ventilation area on the inner surface 252. Therefore, it is considered that Sample 1 and Sample 2 have less variation than Sample 3.

  From the above, it was suggested that in this embodiment, the air flow rate can be increased as compared with the conventional product, and the variation in the air flow rate can be reduced.

  The detection element 10 in the first embodiment corresponds to a “gas detection element” in the claims of the present invention, the reference electrode 55 corresponds to an “electrode”, and the connection terminal 71 corresponds to a “sensor terminal”. The oxygen sensor 100 corresponds to a “gas sensor”, the gap 257 corresponds to a “gas channel”, and the first protrusion 239 corresponds to a “spacer” and a “first protrusion”.

Next, the sensor cap 300 in the second reference embodiment of the present invention will be described with reference to FIG. In the sensor cap 300 of the second reference form, the shape of the filter arrangement hole 331 formed in the filter surrounding part 322 of the surrounding member 320 is different from that of the first embodiment. Hereinafter, the filter arrangement hole 331 different from that of the first embodiment will be mainly described, and the same parts as those of the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted or simplified.

  As shown in FIG. 6, a communication hole 330 is formed in the filter surrounding part 322. The communication hole 330 includes a filter arrangement hole 331 and a vent hole 232 having the same shape as that of the first embodiment. The filter arrangement hole 331 is formed as a cylindrical hole having a circular cross section. Similarly to the first embodiment, the filter arrangement hole 331 includes a filter arrangement surface 334 that forms a circumferential surface of the filter arrangement hole 331, and an annular shape that is located at the end of the filter arrangement surface 334 on the sensor surrounding portion 221 side. It is surrounded by the connecting surface 333. On the filter arrangement surface 334, in addition to the filter pressing portion 235 and the filter holding portion 236 formed in the same manner as in the first embodiment, four second protrusions formed in a substantially cylindrical shape projecting radially inward. A portion 339 is provided.

  The four second protrusions 339 are formed on the same circumference in the filter arrangement surface 334. The second protrusions 339 are arranged on the filter arrangement surface 334 at intervals of 90 degrees in the circumferential direction when the connecting surface 333 is viewed from the opening 259 side. Each of the second protrusions 339 has a hemispherical protruding tip.

  The connecting surface 333 has an annular shape and has an opening 338 connected to the vent hole 232 at the center. Unlike the first embodiment, no projection is formed on the connecting surface 333.

  The filter member 250 arranged in the filter arrangement hole 331 has the same shape and material as in the first embodiment. In a state where the filter member 250 is arranged in the filter arrangement hole 331, the inner side surface 252 of the filter member 250 abuts on the side surface of the second protrusion 339. Therefore, a gap 357 is formed between the inner surface 252 and the connecting surface 333, thereby preventing the close contact therebetween. At this time, all portions of the inner surface 252 of the filter member 250 except the contact portion with the second protrusion 339 face the gap 357. Thereby, compared with the case where the inner surface 252 and the connecting surface 333 are in close contact with each other, the ventilation area on the inner surface 252 can be increased.

Moreover, the second protrusion 339 protrudes from the filter arrangement surface 334. As a result, the second protrusion 339 is not disposed in the middle of the gap 357, and the gas does not flow. From the above, the air flow rate can be reliably ensured even in the sensor cap of the second reference embodiment.

Next, the sensor cap 400 in the third referential embodiment of the present invention will be described with reference to FIGS. In the sensor cap 400 of the third reference embodiment, the shape of the filter arrangement hole 431 formed in the filter surrounding portion 422 of the surrounding member 420 is different from that of the first embodiment. Moreover, the point from which the spacer member 450 is arrange | positioned in the filter arrangement | positioning hole 431 differs from 1st embodiment. Hereinafter, the filter arrangement hole 431 and the spacer member 450 different from those in the first embodiment will be mainly described, and the same parts as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted or simplified. And

  As shown in FIG. 7, a communication hole 430 is formed in the filter surrounding part 422. The communication hole 430 includes a filter arrangement hole 431 and a vent hole 232 having the same shape as that of the first embodiment. The filter arrangement hole 431 is formed as a cylindrical hole having a circular cross section. A filter holding portion 235 and a filter holding portion 236 formed in the same manner as in the first embodiment are provided on the filter arrangement surface 434 that forms the circumferential surface of the filter arrangement hole 431.

  The connecting surface 433 has an annular shape as in the first embodiment, and has an opening 438 connected to the vent 232 at the center. Unlike the first embodiment, no projection is formed on the connecting surface 433.

  The spacer member 450 arrange | positioned at the filter arrangement | positioning hole 431 is demonstrated with reference to FIG. In the description of the spacer member 450, the upper part of FIG. The spacer member 450 is made of a plastic material or an inorganic material having a hardness higher than that of the filter member 250.

  The spacer member 450 includes an annular portion 451 formed in an annular shape in plan view, and a protrusion 439 projecting upward from the upper surface 452 of the annular portion 451. The outer diameter of the annular portion 451 is the same as the outer diameter of the connecting surface 433. The inner diameter of the annular portion 451 is larger than the opening diameter of the opening 238. The four protrusions 439 are arranged at intervals of 90 degrees in the circumferential direction when the annular portion 451 is viewed in plan. The protrusions 439 each have a protruding hemispherical tip.

  A method of arranging the spacer member 450 and the filter member 250 in the filter arrangement hole 431 will be described with reference to FIG. First, the spacer member 450 is arranged in the filter arrangement hole 431, and then the filter member 250 is arranged. When arranging the spacer member 450 in the filter arrangement hole 431, first, an adhesive is applied in advance to the lower surface 453 of the spacer member 450. Then, the spacer member 450 is inserted from the opening 259 and the lower surface 453 of the spacer member 450 and the connecting surface 433 are bonded. In this state, the protrusion 439 is disposed at a position closer to the outer peripheral edge than the inner peripheral edge of the connecting surface 433.

  Then, the filter member 250 is inserted from the opening 259. The filter member 250 arranged in the filter arrangement hole 431 has the same shape and material as the first embodiment. In a state where the filter member 250 is arranged in the filter arrangement hole 331, the inner side surface 252 of the filter member 250 comes into contact with the tip of the protruding portion 439. Therefore, a gap 457 is formed between the inner surface 252 and the upper surface 452 and between the inner surface 252 and the connecting surface 433. At this time, all portions of the inner surface 252 of the filter member 250 except the contact portion with the protruding portion 439 face the gap 457. Therefore, the ventilation area in the inner surface 252 can be increased as in the first embodiment.

  Moreover, the protrusion 439 is provided on the spacer member 450 and is not disposed on the surrounding member 420 or the filter member 250. Therefore, the ventilation area on the inner side surface 252 of the filter member 250 can be ensured only by arranging a separately created spacer member 450 in the filter arrangement hole 431 of the existing surrounding member 420.

The shape of the spacer member 450 described above is not limited to the shape having the protrusion 439. A sensor cap 500 including a modified spacer member 550 will be described with reference to FIGS. 9 and 10. Hereinafter, only portions different from the third reference embodiment will be described mainly, and the same portions will be denoted by the same reference numerals, and description thereof will be omitted or simplified.

  First, a modified spacer member 550 will be described with reference to FIG. In the description of the spacer member 550, the upper part of FIG. 9 is described as the upper part of the spacer member 550. The modified spacer member 550 has a C shape in a plan view and includes a cut 552. The spacer member 550 has an upper surface 551 and a lower surface 553 (see FIG. 10). The outer diameters of the upper surface 551 and the lower surface 553 are smaller than the diameter of the inner surface 252 of the filter member 250 (see FIG. 10). The inner diameters of the upper surface 551 and the lower surface 553 are larger than the opening diameter of the opening 438 (see FIG. 10). Therefore, the areas of the upper surface 551 and the lower surface 553 are smaller than the area of the connecting surface 433.

The arrangement structure of the spacer member 550 will be described with reference to FIG. When the spacer member 550 is arranged in the filter arrangement hole 431, an adhesive is applied in advance to the lower surface 553 of the spacer member 550. Then, the spacer member 550 is inserted from the opening 259 and the lower surface 553 of the spacer member 450 and the connecting surface 433 are bonded. The filter member 250 arranged in the filter arrangement hole 431 has the same shape and material as the third reference embodiment.

  In a state where the filter member 250 is disposed in the filter arrangement hole 331, the inner surface 252 of the filter member 250 is in contact with the upper surface 551 of the spacer member 550. Therefore, the gap 557 formed between the inner surface 252 and the connecting surface 433 of the filter member 250 is partitioned by the spacer member 550 into the radially outer side and the inner side of the spacer member 550. The gap 557 formed on the radially outer side of the spacer member 550 and the gap 557 formed on the radially inner side communicate with each other through a cut 552. Therefore, the gap 557 and the ventilation hole 232 formed on the outer side in the radial direction of the spacer member 550 can be ventilated through the cut 552. Therefore, the substantial decrease in the ventilation area of the inner surface 252 of the filter member 250 is the area of the upper surface 551.

  In the modified example described above, all the portions of the inner surface 252 of the filter member 250 except the contact portion with the upper surface 551 of the spacer member 550 face the gap 557. Therefore, also in the modified example, the ventilation area on the inner surface 252 can be increased as compared with the case where the inner surface 252 of the filter member 250 and the connecting surface 433 are in contact with each other.

In addition, it cannot be overemphasized that the structure shown by the said embodiment and reference form is an illustration, and various changes are possible. For example, the shape and arrangement position of the spacer for securing the gas flow path between the inner surface 252 of the filter member 250 and the connecting surface 233 are not limited to the embodiment and the reference mode .

  For example, in the first embodiment, the first protrusion 239 is formed on the connecting surface 233 of the filter arrangement hole 431. However, the first protrusion 239 is not formed on the connecting surface 233, and the inner surface 252 of the filter member 250 is formed. In addition, a protrusion protruding from the inner surface 252 may be formed. Even in this case, contact between the inner surface 252 and the connecting surface 233 can be prevented, and a ventilation area on the inner surface 252 can be secured.

Moreover, the shape of the 1st projection part 239 and the 2nd projection part 339 is not limited to embodiment mentioned above and a reference form . For example, the first protrusion 239 and the second protrusion 339 may be formed in a columnar shape, or may be formed in a conical shape or a columnar shape.

In the second reference embodiment, the substantially cylindrical second protrusion 339 that protrudes radially inward from the filter arrangement surface 334 is formed. However, the second protrusion 339 is not substantially cylindrical. Also good. For example, instead of providing the second protrusion 339 formed in a columnar shape, a protrusion that protrudes radially inward from the filter placement surface 334 and that is annularly connected in the circumferential direction may be provided.

  Further, the number of the first protrusions 239 and the second protrusions 339 is not limited to four, and the arrangement interval may not be constant. For example, in the first embodiment, when the connecting surface 233 is partitioned 120 degrees in the circumferential direction when viewed from the opening 259 side, one or more first protrusions 239 are formed in each section. This is suitable for preventing the filter member 250 from being inclined. Further, even when the number of the first protrusions 239 is one, a gap can be formed between the inner surface 252 and the connecting surface 233 of the filter member 250, so that the ventilation area on the inner surface 252 is increased. Can be made.

DESCRIPTION OF SYMBOLS 1 Gas sensor unit 10 Detection element 71 Connection terminal 72 Electrode contact part 73 Cap connection part 99 Groove part 100 Oxygen sensor 200, 300, 400 Sensor cap 210 Cap terminal 220 Surrounding member 230 Communication hole 231, 331, 431 Filter arrangement hole 232 Vent hole 233 333, 433 Connecting surface 234, 334, 434 Filter arrangement surface 237 Ventilation surface 239 First protrusion 250 Filter member 339 Second protrusion 450, 550 Spacer member

Claims (3)

A gas sensor having a sensor terminal connected to an electrode formed on the gas detection element and transmitting an output signal from the gas detection element;
A sensor cap that is mounted on the gas sensor and transmits the output signal to an external device, the cap terminal being electrically connected to the sensor terminal, and the sensor cap and the gas sensor when the sensor cap is mounted on the gas sensor. An enclosing member that forms an internal space between them and has a communication hole that allows the gas to flow between the internal space and the outside, and a filter member that is disposed in the communication hole and has air permeability and water repellency And a sensor cap having
In the gas sensor unit with
The communication hole includes a filter arrangement surface on which the filter member is arranged, a ventilation surface having an opening area smaller than the filter arrangement surface, and a connecting surface that connects the filter arrangement surface and the ventilation surface,
A filter member is arranged in the filter arrangement surface,
A spacer that secures a gas flow path formed by the connecting surface and an inner side surface of the filter member facing the connecting surface, and allows the gas that has passed through the filter member to flow into the ventilation surface. gas sensor unit first protrusion is provided in the communication hole itself, characterized by Rukoto protruding from the connecting surface toward the inside of the filter member is. The area of the cross section of the first protrusion first orthogonal to the projecting direction of the projections, the area of the filter member side, according to claim 1, characterized in that less than the area of the connecting surface side Gas sensor unit. When compartmentalized by 120 ° the connecting surface in the circumferential direction, the first protrusion, the gas sensor unit according to claim 1 or 2, characterized in that it is formed at least one on each respective compartment .

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