JP2011145235A - Gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas sensor with a protector capable of effectively protecting a sensor element from being splashed with water without lowering responsiveness of the gas sensor. <P>SOLUTION: In the protector 8 of the gas sensor 1, a ring-shaped porous body 100 is attached to an outer periphery of a peripheral wall 92 on the leading end side of an inner protector 90. An exhaust gas flows inside through an outer inlet hole 85 in an outer protector 80. The exhaust gas flows along a guide 86 and produces a swirl flow, surrounding an outer circumference of the inner protector 90, while contacting the porous body 100. When this is done, the exhaust gas is separated into a gaseous component and moisture. The separated moisture is stored in holes in the porous body 100, preventing the moisture from entering the inner protector 90 through inner inlet holes 130 and 140. Accordingly, a leading end 11 of the sensor element 10 can be protected from breakage, and so on by a thermal shock resulting from water-splashing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gas sensor.

  Conventionally, a gas sensor that is provided in an internal combustion engine and detects an air-fuel ratio that is a ratio of air and fuel is known. The gas sensor includes a sensor element that detects a gas component, and the sensor element detects a gas component located around the sensor element, for example, the air-fuel ratio described above. Such a gas sensor element is usually formed of a ceramic such as zirconia and heated by a heater or the like, but water in the gas or water droplets such as condensed water adhering to a flow path tube through which the gas flows is this gas sensor. If it adheres to the element, it is cooled rapidly, and there is a risk that a crack will occur in the gas sensor element. Therefore, a protector is provided around the gas sensor element to prevent water droplets from adhering to the gas sensor element.

  In particular, in recent years, a plurality of protectors may be arranged around the gas sensor element. This is to prevent water droplets from passing through the introduction hole provided in the protector to introduce gas into the protector and from adhering to the gas sensor element. Specifically, a plurality of protectors are arranged, and gas introduction holes provided in the protectors are shifted and arranged. As a result, water drops that have passed through the introduction hole (hereinafter referred to as the outer introduction hole) of the protector (hereinafter referred to as the outer protector) disposed on the outside adhere to the wall surface of the protector (hereinafter referred to as the inner protector) disposed on the inside. Thus, the passage through the introduction hole of the inner protector (hereinafter referred to as the inner introduction hole) is suppressed.

  Furthermore, as in Patent Document 1, it is also known to arrange a filter in the gap between the inner protector and the outer protector. This is because even if the gas introduction holes provided in a plurality of protectors are shifted, water drops attached to the wall surface of the inner protector may pass through the wall surface and enter the inner protector from the inner introduction hole. Water droplets are stored to prevent the water droplets from entering the inner protector.

JP-A-5-149914

  However, in the gas sensor described in Patent Document 1, since the filter is disposed in the entire gap between the inner protector and the outer protector, the inner introduction hole is blocked by the filter, and water droplets stored in the filter are caused to flow into the inner introduction hole. Due to the effect of the gas passing through, there is a problem that the inside of the inner protector enters the inner protector, adheres to the sensor element, and element cracking occurs. In addition, since the filter is disposed in the entire gap between the inner protector and the outer protector, the gas entry into the gap between the outer protector and the inner protector is slow, and gas replacement is not performed well. There was also a problem that responsiveness deteriorated.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a gas sensor including a protector that can effectively protect the sensor element from moisture without lowering the responsiveness of the gas sensor. .

  According to an embodiment of the present invention, the sensor element that extends in the axial direction and detects a specific gas component in the gas to be detected on the tip side, and the sensor element while projecting the tip side of the sensor element from its tip A metal shell that surrounds the periphery of the element in the radial direction; and a protector that is attached to the metal shell and surrounds the periphery of the front end side of the sensor element, the protector facing the front end side of the sensor element. A cylindrical inner protector having an inner peripheral wall surrounding the periphery of the distal end side, wherein the inner peripheral wall is formed with an inner introduction hole for introducing the detected gas into the inner peripheral wall; An outer protector having an outer peripheral wall surrounding the inner peripheral wall while forming a gap with the inner peripheral wall of the inner protector, the outer peripheral wall having the outer peripheral wall An outer protector having an outer introduction hole for introducing the outer introduction hole into the gap, wherein the inner introduction hole and the outer introduction hole do not overlap each other in the axial direction, and the inner introduction hole and the A porous body is disposed on the outer surface of the inner peripheral wall located between the outer introduction hole and on the outer surface of the inner peripheral wall that is radially opposed to the outer introduction hole, and The porous body is arranged without blocking the inner introduction hole, and the porous body and the outer peripheral wall are arranged so that the detected gas introduced from the outer introduction hole does not pass through the porous body. A gas sensor is provided that is at least partially spaced to reach the inner introduction hole.

  In the gas sensor according to the present embodiment, by preventing the inner introduction hole and the outer introduction hole from overlapping each other, water droplets entering from the outer introduction hole are attached to the inner peripheral wall and are prevented from directly entering the inside from the inner introduction hole. it can. Note that “the inner introduction hole and the outer introduction hole do not overlap” means that the inner introduction hole and the outer introduction hole do not overlap in the axial direction, do not overlap in the radial direction, or overlap in both the axial direction and the radial direction. It means one of the things that must not be.

  Further, a part on the outer surface of the inner peripheral wall (a part on the outer surface of the inner peripheral wall that is radially opposed to the outer introduction hole and a part on the outer surface of the inner peripheral wall located between the outer introduction hole and the inner introduction hole) ), The water droplets adhering to the inner peripheral wall can be stored in the porous body, and the water droplets can be prevented from entering the inner introduction hole through the inner peripheral wall. Note that “on the outer surface of the inner peripheral wall facing the outer introduction hole in the radial direction” indicates the outer surface of the inner peripheral wall that is visible when the outer introduction hole is viewed from the radial direction. In addition, “on the outer surface of the inner peripheral wall located between the outer introduction hole and the inner introduction hole” means on the outer surface of the inner peripheral wall arranged in a section connecting the inner introduction hole and the outer introduction hole in a straight line. Means that.

  Furthermore, since the porous body does not block the inner introduction hole, water droplets stored in the porous body are prevented from entering the inner protector from the inner introduction hole due to the influence of gas passing through the inner introduction hole. it can. In addition, the porous body may be arranged so as not to block a part of the inner introduction hole, or may be arranged so as to open all the inner introduction holes.

  In addition, the porous body is porous by separating the outer peripheral wall and at least partly so that the gas to be detected introduced from the outer introduction hole reaches the inner introduction hole without passing through the porous body. Even if water droplets are stored in the body, the gas can successfully pass through the inner introduction hole and enter the inner protector. The outer peripheral wall and the porous body are preferably linearly separated along a path connecting the inner introduction hole and the outer introduction hole in a straight line, but a passage connecting the outer introduction hole to the inner introduction hole. What is necessary is just to be spaced apart so as to form.

  In this embodiment, the porous body may be disposed on at least a part of the outer surface of the inner peripheral wall that is radially opposed to the outer introduction hole. By disposing a porous body on the outer surface of the inner peripheral wall that is radially opposed to the outer introduction hole, water droplets entering from the outer introduction hole can be directly applied to the porous body, so that the porous body can be efficiently porous. Water droplets can be stored on the material.

  In this embodiment, the entire porous body and the outer peripheral wall may be separated from each other. By separating the entire porous body from the outer peripheral wall, the gas can pass through the inner introduction hole more satisfactorily and enter the inner protector.

  Further, in the present embodiment, the porous body is provided with a protruding portion that protrudes radially outward, and the protruding portion includes the outer introduction hole and the inner introduction hole in the gap. May be arranged at a position that blocks a route that connects the two straight lines. Since the protrusion is arranged at a position that blocks the path that linearly connects the outer introduction hole and the inner introduction hole, the gas that has passed through the outer introduction hole does not reach the inner introduction hole in a straight line. You will avoid it. On the other hand, some water droplets that do not adhere to the inner peripheral wall will adhere to the protruding portion, and this water droplet can also be stored in the porous body.

  In the present embodiment, the protrusion may be in contact with the inner surface of the outer peripheral wall. Thereby, the one part water droplet which a protrusion part does not adhere to an inner peripheral wall can be more effectively stored in a porous body.

  In this embodiment, the outer peripheral wall of the outer protector may be provided with a guide body that guides the flow path of the gas to be detected introduced from the outer introduction hole toward the porous body. Good. Since the guide body can reliably apply the gas to the porous body, water droplets contained in the gas can be reliably attached to the porous body.

  Further, in the present embodiment, the inner introduction hole is disposed on the rear end side with respect to the outer introduction hole, and the front end portion of the inner peripheral wall is reduced in diameter in the radial direction from the rear end portion. The porous body may be disposed on the outer surface of the tip portion. Thereby, the porous body can be easily held on the tip side without narrowing the gap between the inner peripheral wall and the outer peripheral wall. In addition, a porous body can be arrange | positioned at the front end side of an inner peripheral wall by press-fitting or adhering using an adhesive agent.

  In the present embodiment, the porous body may contain one or more of metal, ceramic, and glass. Thereby, heat resistance can be easily provided to a porous body.

1 is an external view of a gas sensor 1. FIG. 1 is a longitudinal sectional view of a gas sensor 1. FIG. 3 is a longitudinal sectional view of the front end side of the gas sensor 1. FIG. FIG. 4 is a cross-sectional view taken along the line I-I in FIG. 3. 3 is a longitudinal sectional view of the front end side of the gas sensor 150. FIG. It is II-II arrow direction sectional drawing shown in FIG. 3 is a longitudinal sectional view of the front end side of the gas sensor 250. FIG. FIG. 6 is a longitudinal sectional view of a distal end side of a modified example of the gas sensor 1. FIG. 11 is a cross-sectional view taken along the line II-II of a modification of the gas sensor 150.

  Hereinafter, a first embodiment of a gas sensor embodying the present invention will be described with reference to the drawings. First, the structure of the gas sensor 1 as an example will be described with reference to FIGS. 1 and 2, the axis O direction of the gas sensor 1 (indicated by a one-dot chain line) is shown as the vertical direction, and the tip end 11 side of the sensor element 10 held inside is the tip end side of the gas sensor 1 and the rear side. The end 12 side will be described as the rear end side of the gas sensor 1.

  A gas sensor 1 shown in FIG. 1 is attached to an exhaust pipe (not shown) of an automobile. As shown in FIG. 2, the gas sensor 1 is exposed to the exhaust gas flowing through the exhaust pipe at the tip 11 of the sensor element 10 held therein, and the air-fuel ratio of the exhaust gas is determined from the oxygen concentration in the exhaust gas. This is a so-called full-range air-fuel ratio sensor to detect.

  As shown in FIG. 2, the sensor element 10 has a strip shape extending in the direction of the axis O as is well known, a detection element that detects the oxygen concentration, and a heater that heats the detection element for early activation Are laminated together and integrated as a laminated body having a substantially prismatic shape. The detection element is composed of a solid electrolyte body mainly composed of zirconia and a detection electrode mainly composed of platinum (both not shown), and the detection electrode is disposed at the distal end portion 11 of the sensor element 10.

  And in order to protect a detection electrode from poisoning by exhaust gas, the protective layer 15 is formed in the front-end | tip part 11 of the sensor element 10 so that the outer peripheral surface may be wrapped. Further, five electrode pads 16 (two of which are shown in FIG. 2) are formed on the rear end portion 12 on the rear end side of the sensor element 10 to take out electrodes from the detection element and the heater. ing.

  Around the central portion 13 of the sensor element 10, a metal cup 20 having a bottomed cylindrical shape allows the sensor element 10 to be inserted into itself, and the tip portion 11 of the sensor element 10 is opened to the opening 25 at the bottom of the cylinder. It is arrange | positioned in the state protruded from. The metal cup 20 is a member for holding the sensor element 10 in the metal shell 50, and the tip peripheral edge 23 of the edge portion of the cylinder bottom is formed in a taper shape toward the outer peripheral surface.

  In the metal cup 20, an alumina ceramic ring 21 and a talc ring 22 obtained by compressing and solidifying talc powder are accommodated in a state where the sensor element 10 is inserted. The talc ring 22 is crushed in the metal cup 20 so as to be filled in detail, whereby the sensor element 10 is positioned and held in the metal cup 20.

  The sensor element 10 integrated with the metal cup 20 is surrounded and held by a cylindrical metal shell 50. The metal shell 50 is for mounting and fixing the gas sensor 1 to an exhaust pipe (not shown) of an automobile, and is made of low carbon steel such as SUS430, and a male screw portion 51 for mounting to the exhaust pipe is formed on the outer peripheral tip side. Has been. A distal end engaging portion 56 to which a protector 8 described later is engaged is formed on the distal end side of the male screw portion 51.

  Further, a tool engaging portion 52 with which a tool for attachment is engaged is formed at the center of the outer periphery of the metal shell 50. A gasket 55 is inserted between the front end surface of the tool engaging portion 52 and the rear end of the male screw portion 51 to prevent gas escape when attached to the exhaust pipe. Further, a rear end engaging portion 57 to which an outer cylinder 30 described later is engaged is formed on the rear end side of the tool engaging portion 52, and the sensor element 10 is added to the metal shell 50 on the rear end side. A caulking portion 53 for tightening and holding is formed.

  Further, a step portion 54 is formed in the vicinity of the male screw portion 51 on the inner periphery of the metal shell 50. The step 54 is engaged with the peripheral edge 23 of the tip of the metal cup 20 that holds the sensor element 10. Furthermore, a talc ring 26 is loaded on the inner periphery of the metal shell 50 from the rear end side of the metal cup 20 in a state where the talc ring 26 is inserted through the sensor element 10. A cylindrical sleeve 27 is fitted into the metal shell 50 so as to hold the talc ring 26 from the rear end side.

  A shoulder portion 24 having a step shape is formed on the outer periphery of the rear end side of the sleeve 27, and an annular caulking packing 29 is disposed on the shoulder portion 24. In this state, the crimping portion 53 of the metal shell 50 is crimped so as to press the shoulder portion 24 of the sleeve 27 toward the distal end side via the crimping packing 29. The talc ring 26 pressed by the sleeve 27 is crushed in the metal shell 50 and filled in details. The metal cup 20 and the sensor element 10 are positioned and held in the metal shell 50 by the talc ring 26 and the talc ring 22 loaded in the metal cup 20 in advance. The airtightness in the metal shell 50 is maintained by the caulking packing 29 interposed between the caulking portion 53 and the shoulder portion 24 of the sleeve 27, and the outflow of combustion gas is prevented.

  The sensor element 10 has a rear end portion 12 protruding rearward from the rear end (caulking portion 53) of the metal shell 50, and the rear end portion 12 is covered with a cylindrical separator 60 made of insulating ceramics. It has been. The separator 60 has five connection terminals 61 (two of which are shown in FIG. 2) that are electrically connected to the five electrode pads 16 formed on the rear end portion 12 of the sensor element 10, respectively. Each of the connection portions of the connection terminals 61 and the five lead wires 65 (three of which are shown in FIGS. 1 and 2) drawn out of the gas sensor 1 are held inside. Contain and protect.

  And the cylindrical outer cylinder 30 is arrange | positioned so that the circumference | surroundings of the rear-end part 12 of the sensor element 10 with which the separator 60 was fitted may be enclosed. The outer cylinder 30 is made of stainless steel (for example, SUS304), and the opening end 36 on its front end side is engaged with the outer periphery of the rear end engaging portion 57 of the metal shell 50. The open end 36 is caulked from the outer peripheral side, and further laser-welded around the outer periphery and joined to the rear end engaging portion 57, and the outer cylinder 30 and the metal shell 50 are fixed integrally. ing.

  Further, a metal-made cylindrical holding metal fitting 70 is disposed in the gap between the outer cylinder 30 and the separator 60. The holding metal fitting 70 has a support portion 71 formed by bending the rear end of the holding member 70 inward, and a support portion 71 is provided with a flange portion 62 provided in a hook shape on the outer periphery of the rear end side of the separator 60 inserted into the holding metal fitting 70. And the separator 60 is supported. In this state, the outer peripheral surface of the outer cylinder 30 where the holding metal fitting 70 is disposed is crimped, and the holding metal fitting 70 that supports the separator 60 is fixed to the outer cylinder 30.

  A fluorine rubber grommet 75 is fitted into the opening on the rear end side of the outer cylinder 30. The grommet 75 has five insertion holes 76 (one of which is shown in FIG. 2), and the five lead wires 65 drawn from the separator 60 are inserted into each insertion hole 76 in an airtight manner. ing. In this state, the grommet 75 is crimped from the outer periphery of the outer cylinder 30 while pressing the separator 60 toward the front end side, and is fixed to the rear end of the outer cylinder 30.

  The sensor element 10 held by the metal shell 50 is in a state in which the tip portion 11 protrudes from the tip portion (tip engagement portion 56) of the metal shell 50. The tip engaging portion 56 protects the tip portion 11 of the sensor element 10 from contamination caused by deposits (toxic substances such as fuel ash and oil components) in exhaust gas, breakage due to moisture, and the like. A protector 8 is fitted and fixed by laser welding. The protector 8 has a cylindrical shape that surrounds the periphery of the inner protector 90 in the radial direction with a gap between the bottomed cylindrical inner protector 90 having a plurality of holes on the side surface and the outer peripheral surface of the inner protector 90. None, having a double structure composed of an outer protector 80 having a plurality of holes on the side.

  The inner protector 90 will be described. As shown in FIG. 3, the inner protector 90 has a cylindrical shape and an outer diameter of the rear end side peripheral wall 91 formed smaller than the front end engaging portion 56 of the metal shell 50, and the rear end side peripheral wall 91. It has a front end side peripheral wall 92 provided on the front end side and having a diameter smaller than that of the rear end side peripheral wall 91 and a bottom wall 93 provided so as to close the opening on the front end side of the front end side peripheral wall 92. The base end portion 95 formed on the rear end side of the rear end side peripheral wall 91 is expanded in diameter so as to engage with the front end engaging portion 56.

  A plurality (six in this embodiment) of inner introduction holes 130 are formed in the circumferential direction near the base end portion 95 of the rear end side peripheral wall 91. On the other hand, a plurality (six in this embodiment) of inner introduction holes 140 are formed in the circumferential direction in the same manner near the distal end side peripheral wall 92. The inner introduction holes 130 and the inner introduction holes 140 are arranged in a staggered manner. In addition, a plurality of drain holes 96 that are opened in a cut shape toward the inside are provided on the distal end side of the distal end side peripheral wall 92. A discharge port 97 is opened at the center of the bottom wall 93. The base end portion 95 of the rear end side peripheral wall 91 of the inner protector 90 having such a shape is engaged with the outer periphery of the distal end engaging portion 56 of the metal shell 50, and in this state, the outer periphery makes a round and laser welding is performed. The inner protector 90 is fixed to the metal shell 50.

  The outer protector 80 will be described. As shown in FIG. 3, the outer protector 80 has a cylindrical shape, and its outer diameter is smaller than the front end engaging portion 56 of the metal shell 50 and larger than the outer diameter of the rear end side peripheral wall 91 of the inner protector 90. A peripheral wall 82 is formed. A proximal end portion 81 formed on the rear end side of the peripheral wall 82 is expanded in diameter so as to engage with the distal end engaging portion 56 and the proximal end portion 95 of the inner protector 90.

  A plurality of rectangular outer introduction holes 85 (see FIGS. 1 and 3) are formed on the distal end side of the peripheral wall 82, respectively. These outer introduction holes 85 are arranged at positions that do not overlap with the inner introduction holes 130 and 140 in the axis O direction in the axis direction of the protector 8. Thereby, since the water droplet which enters from the outer side introduction hole 85 can be made to adhere to the inner side protector 90, it can suppress that a water droplet directly enters the inside of the inner side protector 90 from the inner side introduction holes 130 and 140. These outer introduction holes 85 are provided with guide bodies 86 extending inward. These guide bodies 86 have a function of generating a swirling flow in a state of surrounding the outer peripheral surface of the distal end side peripheral wall 92 of the inner protector 90 in the exhaust gas introduced into the outer protector 80 from the outside through the outer introduction hole 85. Bear.

  The base end portion 81 of the peripheral wall 82 of the outer protector 80 having such a shape is engaged with the outer periphery of the base end portion 95 of the inner protector 90, and laser welding is performed on the outer periphery in this state. Thereby, the outer protector 80 is also fixed to the metal shell 50 together with the inner protector 90. And the front-end | tip part 83 of the outer side protector 80 is bend | folded inside toward the front end side surrounding wall 92 of the inner side protector 90 so that the clearance gap between the outer side protector 80 and the inner side protector 90 may be closed.

  As shown in FIGS. 3 and 4, in the protector 8 having the above structure, a ring-shaped porous body 100 is attached to the outer peripheral surface of the distal end side peripheral wall 92 of the inner protector 90. The material of this porous body 100 should just contain any 1 or more types, such as a metal, a ceramic, and glass, and should just have heat resistance at least.

  Further, as shown in FIG. 4, the distal end portion of each guide body 86 is in contact with the outer peripheral surface of the porous body 100. Thereby, the porous body 100 is urged | biased by radial direction and is hold | maintained in the position. As for the method for holding the porous body 100, other than this, for example, the porous body 100 may be fixed to the outer peripheral surface of the inner protector 90 with an adhesive or the like. Alternatively, it may be held by another holding member or the like. In this embodiment, the tip portions of all the guide bodies 86 are in contact with the outer peripheral surface of the porous body 100, but the tip portions of some of the guide bodies 86 are in contact with the outer peripheral surface of the porous body 100. You may contact.

  Next, a process in which exhaust gas is introduced into the protector 8 will be described. As shown in FIG. 3, first, the exhaust gas flows inward from the outer introduction hole 85 of the outer protector 80. The exhaust gas flows along the guide body 86 and generates a swirling flow in a state of surrounding the outer periphery of the front end side peripheral wall 92 and the rear end side peripheral wall 91 of the inner protector 90 while contacting the porous body 100. At this time, the exhaust gas is separated into a gas component and moisture. The gas component is introduced into the inner protector 90 from the inner introduction holes 130 and 140, contacts the sensor element 10, and is discharged to the outside from the discharge port 97.

  On the other hand, the separated water is stored in the pores of the porous body 100. Although the water stored in the porous body 100 evaporates due to ambient heat, even when the water leaks from the porous body 100, the water is stored outside from the gap between the tip of the outer protector 80 and the outer peripheral surface of the tip of the inner protector 90. To be discharged. Further, the water that has not been stored in the porous body 100 and has entered the inner protector 90 from the drain hole 96 is discharged to the outside through the discharge port 97.

  Thus, by disposing the porous body 100 on the outer peripheral surface of the distal end side peripheral wall 92, water droplets attached to the distal end side peripheral wall 92 can be stored in the porous body 100, and the water droplets are stored in the distal end side peripheral wall 92. Further, it is possible to suppress the inside from the inner introduction holes 130 and 140 along the rear end side peripheral wall 91.

  In particular, the porous body 100 is disposed in the circumferential direction on the outer surface of the distal end side peripheral wall 92 that faces the outer introduction hole 85 of the outer protector 80 in the radial direction. As a result, the water droplets that have entered from the outer introduction hole 85 can be directly applied to the outer peripheral surface of the porous body 100, so that the water droplets can be efficiently stored in the porous body 100.

  Further, the porous body 100 is provided on the outer peripheral surface of the distal end side peripheral wall 92 of the inner protector 90 and is disposed at a position where the inner introduction holes 130 and 140 are not blocked. Thereby, it is possible to prevent water droplets stored in the porous body 100 from entering the inner protector 90 from the inner introduction holes 130 and 140 due to the influence of the exhaust gas passing through the inner introduction holes 130 and 140.

  In addition, the porous body 100 and the peripheral wall 82 of the outer protector 80 are spaced apart. Therefore, the exhaust gas introduced from the outer introduction hole 85 can reach the inner introduction holes 130 and 140 without passing through the porous body 100. Thereby, even if water droplets are stored in the porous body 100, the exhaust gas can pass through the inner introduction holes 130 and 140 and enter the inner protector 90.

  Furthermore, as described above, the tip of each guide body 86 is guided toward the porous body 100. Thereby, exhaust gas can be reliably applied to the porous body, and water droplets contained in the exhaust gas can be reliably attached to the porous body 100.

  Furthermore, as described above, the front end side peripheral wall 92 of the inner protector 90 is smaller in diameter than the rear end side peripheral wall 91, and the porous body 100 is disposed on the outer surface of the front end side peripheral wall 92. Yes. Thereby, the porous body 100 can be easily held by the distal end side peripheral wall 92 of the inner protector 90 without narrowing the gap between the inner protector 90 and the outer protector 80.

  Next, the gas sensor 150 which is 2nd Embodiment of this invention is demonstrated with reference to FIG. 5, FIG. The second embodiment is a modification of the first embodiment. The gas sensor 150 includes a protector 18 having a structure different from that of the first embodiment and a porous body 200 having a different shape, and other structures are the same as those of the gas sensor 1 of the first embodiment. Therefore, here, the structure of the protector 18 and the shape of the porous body 200 will be mainly described. In addition, about the same part as the gas sensor 1 of 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected and demonstrated.

  First, the structure of the protector 18 will be described. As shown in FIG. 5, the protector 18 is, as in the first embodiment, an outer side that surrounds the inner periphery of the inner protector 190 in a state where there is a gap between the inner protector 190 and the outer peripheral surface of the inner protector 190. It has a double structure composed of a protector 180.

  The inner protector 190 includes a rear end side peripheral wall 191, a front end side peripheral wall 192, and a bottom wall 193 as in the first embodiment. Inner introduction holes 130 and 140 are respectively provided in the rear end side peripheral wall 191, and a discharge port 197 is provided in the center of the bottom wall 193. On the other hand, the outer protector 180 includes a peripheral wall 182 similar to that of the first embodiment, and the distal end side thereof is closed by a bottom wall 183. An outer introduction hole 185 is provided in the peripheral wall 182. The bottom wall 183 is provided with a plurality of discharge ports 187 (two of which are shown in FIG. 5). A gap is formed between the bottom wall 183 of the outer protector 180 and the bottom wall 193 of the inner protector 190.

  Next, the shape of the porous body 200 will be described. As shown in FIGS. 5 and 6, the ring-shaped porous body 200 is mounted on the outer peripheral surface of the distal end side peripheral wall 192 of the inner protector 190. As shown in FIG. 6, eight projecting portions 201 projecting obliquely rearward toward the radially outer side are provided at the rear end portion in the axial direction of the porous body 200. Each protrusion 201 is located at a position corresponding to the outer introduction hole 185 provided in the outer protector 180, and within the gap between the outer protector 80 and the inner protector 90, the outer introduction hole 185 and the inner introduction holes 130, 140 Are respectively arranged at positions that block the path connecting the two straight lines. Each tip portion of the protruding portion 201 is in contact with the inner surface of the outer protector 180. The material of the porous body 200 is the same as that of the porous body 100 of the first embodiment.

  In the protector 18 having such a structure, the exhaust gas flows from the outer introduction hole 185 of the outer protector 180 toward the inner introduction holes 130 and 140 of the inner protector 190. Since the projecting portion 201 of the porous body 200 is disposed in the path, the exhaust gas reaches the inner introduction holes 130 and 140 while avoiding the projecting portion 201. On the other hand, some water droplets that do not adhere to the front end side peripheral wall 192 of the inner protector 190 adhere to the protruding portion 201 of the porous body 200. Therefore, some water droplets that do not adhere to the distal end side peripheral wall 192 of the inner protector 190 can also be stored in the porous body 200. Furthermore, since each tip of the protrusion 201 is in contact with the inner surface of the outer protector 180, some water droplets that do not adhere to the tip side peripheral wall 92 of the inner protector 190 are more effectively stored in the porous body 200. be able to. Further, water droplets leaking from the porous body 200 are discharged to the outside from the discharge port 187 of the outer protector 180. In addition, you may provide the porous body 200 of 2nd Embodiment in the protector 8 of 1st Embodiment.

  Next, the gas sensor 250 of 3rd Embodiment is demonstrated with reference to FIG. The third embodiment is a modification of the second embodiment. The gas sensor 250 is provided with a porous body 300 in which the shape of the porous body 200 of the second embodiment is changed in the protector 28. About other structures, it is the same as that of the gas sensor 1 of 1st Embodiment. Therefore, here, the shape of the porous body 300 will be mainly described. The same parts as those of the gas sensors 1 and 150 of the first and second embodiments will be described with the same reference numerals as those of the first and second embodiments.

  First, the structure of the protector 28 will be described. As shown in FIG. 7, the protector 28 includes an inner protector 190 that is the same as that of the second embodiment, and an outer protector 280 that is different in shape from the second embodiment. One discharge port 287 is provided at the center of the bottom wall 283 of the outer protector 280. The position of the discharge port 287 faces the position of the discharge port 197 provided on the bottom wall 193 of the inner protector 190. A plurality of outer introduction holes 285 are provided in the peripheral wall 282 of the outer protector 280. About another shape, it is the same as the protector 18 of 2nd Embodiment.

  Next, the shape of the porous body 300 will be described. As shown in FIG. 7, the porous body 300 is formed in a bottomed cylindrical shape, and includes a cylindrical peripheral wall 301, a bottom wall 302 provided at an axial end portion of the peripheral wall 301, and an axial direction of the peripheral wall 301. It is composed of eight projecting portions 303 provided at the rear end portion and projecting obliquely rearward toward the radially outer side. That is, the point provided with the bottom wall 302 is different from the porous body 200 of the second embodiment. The bottom wall 302 is disposed so as to fill a gap between the bottom wall 283 of the outer protector 280 and the bottom wall 193 of the inner protector 190. A discharge port 305 is provided in the center of the bottom wall 302 of the porous body 300. The discharge port 305 corresponds to the discharge port 287 of the outer protector 280 and the discharge port 197 of the inner protector 190. The material of the porous body 300 is the same as that of the porous body 100 of the first embodiment.

  In the protector 28 having such a structure, since the discharge port 287, the discharge port 305, and the discharge port 197 are arranged in a straight line and communicate with each other, the gas component that has contacted the sensor element 10 in the inner protector 190 is removed. The discharge port 287, the discharge port 305, and the discharge port 197 can be discharged to the outside. Further, water droplets leaking from the porous body 300 are discharged from the discharge port 305 to the outside through the discharge port 287 of the outer protector 280.

  In addition, the gas sensor of this invention is not restricted to 1st Embodiment, 2nd Embodiment, and 3rd Embodiment, A various change is possible. For example, in the first embodiment, the second embodiment, and the third embodiment, the oxygen sensor is described as an example of the gas sensor in the above, but the present invention can also be applied to a full-range air-fuel ratio sensor, NOx sensor, HC sensor, and the like. .

  Further, in the above embodiment, the inner protector 90 is provided with the inner introduction holes 130 and 140 in two upper and lower stages, but either one may be provided, or three or more upper and lower stages may be provided. Further, the number of the outer introduction holes 85 provided in the outer protectors 80, 180, and 280 is not limited to the above embodiment.

  Further, in the gas sensor 1 of the first embodiment, the guide body 86 may not be provided in the outer introduction hole 85 of the outer protector 80. Moreover, you may provide a guide body (guide body 86 shown in FIG. 4) in the outer introduction hole 185 of the outer protectors 180 and 280 of the second and third embodiments.

  Further, in the first and second embodiments, the porous bodies 100 and 200 extend in the circumferential direction on the outer surfaces of the distal end side peripheral walls 92 and 192 that are radially opposed to the outer introduction holes 85 and 185 of the outer protectors 80 and 180. Although it is arranged, a porous body 400 may be arranged as shown in FIG. Since FIG. 8 is a modification of the first embodiment, portions other than the porous body 400 are omitted or simplified. The porous body 400 is disposed only in the section on the outer peripheral surface of the distal end side peripheral wall 92 from the outer introduction hole 85 to the inner introduction holes 130 and 140. Even if the porous body 400 is disposed only in such a section, water droplets adhering to the front end side peripheral wall 92 can be stored in the porous body 400, and the water drops can be attached to the front end side peripheral wall 92 and the rear end side peripheral wall 91. Accordingly, it is possible to suppress the inside from entering through the inner introduction holes 130 and 140.

  Furthermore, in the first and second embodiments, the porous bodies 100 and 200 are spaced apart from the outer protectors 80 and 180 in the circumferential direction. However, as shown in FIG. 9, at least the porous body 500 and the outer protector 180 are not separated. Some may be separated.

1, 150, 250 Gas sensor 8, 18, 28 Protector 10 Sensor element 11 Tip 50 Metal shell 80, 180, 280 Outer protector 82, 182 Peripheral wall 85, 185 Outer introduction hole 86 Guide body 90, 190 Inner protector 91, 191 Rear End side peripheral wall 92, 192 Tip side peripheral wall 93, 193 Bottom wall 97, 197 Discharge port 100, 200, 300 Porous body 130, 140 Inner introduction hole 183 Bottom wall 187 Discharge port 201, 303 Protruding portion 283 Bottom wall 287 Discharge port 301 Perimeter wall 302 Bottom wall

Claims (8)

A sensor element that extends in the axial direction and detects a specific gas component in the gas to be detected on the tip side;
While protruding the tip side of the sensor element from its tip, the metal shell surrounding the sensor element in the radial direction,
A protector attached to the metal shell and surrounding the tip of the sensor element;
The protector is
A cylindrical inner protector having an inner peripheral wall that surrounds the periphery of the front end side while facing the front end side of the sensor element, and an inner side for introducing the detected gas into the inner peripheral wall An inner protector formed with an introduction hole;
An outer protector having an outer peripheral wall surrounding the inner peripheral wall while forming a gap with the inner peripheral wall of the inner protector, wherein the gas to be detected is introduced into the outer peripheral wall. In a gas sensor having an outer protector formed with an outer introduction hole,
The inner introduction hole and the outer introduction hole do not overlap each other in the axial direction,
A porous body is formed on the outer surface of the inner peripheral wall located between the inner introduction hole and the outer introduction hole and on at least a part of the outer surface of the inner peripheral wall that is radially opposed to the outer introduction hole. Has been placed,
The porous body is arranged without closing the inner introduction hole,
The porous body and the outer peripheral wall are at least partially separated so that the gas to be detected introduced from the outer introduction hole reaches the inner introduction hole without passing through the porous body. A gas sensor characterized by comprising:   2. The gas sensor according to claim 1, wherein the porous body is disposed on at least a part of the outer surface of the inner peripheral wall that is radially opposed to the outer introduction hole.   The gas sensor according to claim 1 or 2, wherein the entire porous body and the outer peripheral wall are separated from each other.   The porous body is provided with a protruding portion that protrudes outward in the radial direction, and the protruding portion has a path that linearly connects the outer introduction hole and the inner introduction hole in the gap. The gas sensor according to any one of claims 1 to 3, wherein the gas sensor is disposed at a blocking position.   The gas sensor according to claim 4, wherein the protruding portion is in contact with an inner surface of the outer peripheral wall.   The guide body for guiding the flow path of the detection gas introduced from the outer introduction hole toward the porous body is provided on the outer peripheral wall of the outer protector. The gas sensor according to any one of 5. The inner introduction hole is arranged on the rear end side with respect to the outer introduction hole,
The front end portion of the inner peripheral wall is reduced in diameter in the radial direction from the rear end portion, and the porous body is disposed on the outer surface of the front end portion. A gas sensor according to any one of the above.   The gas sensor according to any one of claims 1 to 7, wherein the porous body contains at least one of metal, ceramic, and glass.

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