JP2013104832A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor capable of securely fixing and protecting a ceramic member inside a casing.SOLUTION: An oxygen sensor 1 comprises: a cylindrical detection element 6; a primary metal fitting 5 for holding the detection element 6; a terminal metal fitting 70 for electrically connecting with the detection element 6; a lead wire 18 which extends from the terminal metal fitting 60 to form a current path; a separator 8 into which the lead wire 18 is inserted; an inner cylinder 3 for surrounding the periphery of the separator 8; a grommet 9 which is disposed inside a cylindrical hole of the inner cylinder 3 and into which the lead wire 18 is inserted; a filter 7 disposed on the outside in the radial direction of the inner cylinder 3; and an outer cylinder 100 for interposing the filter 7 between the inner cylinder 3. The separator 8 is sandwiched between the detection element 6 and the grommet 9 to be held in a separated state from the inner cylinder 3.

Description

  The present invention relates to a gas sensor for detecting a component to be detected in a gas to be measured, such as an oxygen sensor, an HC sensor, and a NOx sensor.

  2. Description of the Related Art Conventionally, a gas sensor is known in which a detection element in which a detection unit that detects a component to be detected is formed at the tip is arranged inside a metal casing. In such a gas sensor, a ceramic member (so-called separator) that holds a lead wire for taking out a detection signal from the detection element is provided inside the casing. Various methods for fixing the separator inside the casing have been proposed.

  For example, Patent Literature 1 discloses a gas sensor that fixes a separator by caulking the casing from the outside with a holding metal fitting interposed between the casing and the separator. Patent Document 2 discloses a gas sensor that fixes a separator with a holding fitting press-fitted into the casing. Patent Document 3 discloses a gas sensor in which a separator is sandwiched and fixed in an axial direction by a pair of elastic members (grommets and a seal member) provided inside a casing.

JP 2010-276337 A JP 2010-223750 A JP 2000-81412 A

  However, in the gas sensors disclosed in Patent Documents 1 and 2, when the gas sensor is vibrated or shocked, there is a possibility that the holding bracket is misaligned and the separator is misaligned. Furthermore, since a dedicated part (that is, a holding metal fitting) for fixing the separator is used, there is a risk that reduction in the number and manufacturing cost of the gas sensor, miniaturization of the gas sensor, and the like may be hindered. Further, in the gas sensor disclosed in Patent Document 3, the rear end side of the separator held between the pair of elastic members is protected only by the outer cylinder member surrounding the inner cylinder member. Therefore, when an external pressure is applied to the gas sensor, the separator may be easily damaged.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a gas sensor that can securely fix and protect a ceramic member inside a casing.

  A gas sensor according to an aspect of the present invention has a cylindrical shape that extends in the axial direction and has a closed distal end directed toward a measurement target, and includes an outer electrode on its outer peripheral surface and an inner electrode on its inner peripheral surface. A detection element, a metal shell that surrounds the detection element and holds the detection element, and a cylindrical terminal metal fitting that is inserted into a cylindrical hole of the detection element and is electrically connected to the inner electrode of the detection element And a lead wire connected to the terminal fitting and extending from the terminal fitting to the rear end side to form a current path, and disposed on the rear end side of the detection element, and at least the terminal fitting and the lead wire A ceramic member having an insertion hole into which either one is inserted, and a cylindrical metal member surrounding the ceramic member, the front end side being fixed to the rear end side of the metal shell, An inner cylinder in which a first introduction hole for introducing gas is formed, and a rear end side of the ceramic member in the cylinder hole of the inner cylinder, and presses the inner cylinder from the inner side to the outer side in the radial direction. And an elastic member having an insertion hole through which the lead wire is inserted, a filter arranged so as to close the first introduction hole on the radially outer side of the inner cylinder, and a cylindrical shape surrounding the periphery of the inner cylinder An outer cylinder in which the filter is interposed between the inner cylinder and a second introduction hole for introducing gas into the space is formed on the filter. The ceramic member is held in a state of being separated from the inner cylinder by being sandwiched between the detection element and the elastic member directly or via another member.

  According to the gas sensor of one aspect of the present invention, the ceramic member is sandwiched between the detection element and the elastic member in the axial direction directly or via another member, and the inner cylinder, the filter, and the outer cylinder are disposed radially outward. Arranged in order. Thereby, the movement to the axial direction and radial direction of a ceramic member is controlled, and a ceramic member is stably fixed inside a casing (an inner cylinder and an outer cylinder). Furthermore, since the ceramic member is held away from the inner cylinder and is triple protected by the inner cylinder, the filter, and the outer cylinder, the ceramic member is highly resistant to external pressure on the gas sensor. Therefore, the ceramic member can be reliably fixed and protected inside the casing.

  In the gas sensor according to an aspect of the present invention, an edge portion that protrudes toward the tip end in the axial direction and is disposed in a gap between the ceramic member and the inner cylinder is formed at the tip portion of the elastic member. It is preferable. In this case, since the movement of the ceramic member in the radial direction is reliably restricted by the edge portion, the ceramic member can be more reliably fixed inside the casing. As a result, even when vibration or impact occurs in the gas sensor, for example, contact between the ceramic member and the inner cylinder is prevented, so that the ceramic member can be more reliably protected.

  In the gas sensor according to one aspect of the present invention, it is preferable that the first introduction hole is formed on a distal end side with respect to a contact position between the inner cylinder and the elastic member. A vent hole may be formed at the position of the elastic member corresponding to the first introduction hole of the inner cylinder to introduce outside air into the detection element. However, as in the present invention, the ceramic member and the inner cylinder are separated from each other. Therefore, by forming the front end side of the contact position of the elastic member, the separation between the ceramic member and the inner cylinder can be used as a ventilation path, and the filter can be formed without forming a vent hole in the elastic member. Thus, outside air can be easily introduced into the detection element. Note that it is preferable that the entire first introduction hole is formed on the tip side of the contact position between the inner cylinder and the elastic member, but a part of the first introduction hole is formed from the contact position between the inner cylinder and the elastic member. May also be formed on the tip side.

  Further, in the gas sensor according to one aspect of the present invention, the terminal fitting has a flange that extends radially outward from a rear end portion of the terminal fitting, and the flange of the terminal fitting includes the detection element, the ceramic member, and the like. May be sandwiched between them. In this case, the terminal fitting can be securely fixed with a simple structure without providing a dedicated component for fixing the terminal fitting.

  In the gas sensor according to one embodiment of the present invention, the detection element may include zirconia as a main component, and the ceramic member may include alumina as a main component. In this case, the above gas sensor can be applied to, for example, an oxygen sensor.

2 is a longitudinal sectional view of the oxygen sensor 1. FIG. It is a figure for demonstrating the process of arrange | positioning the protector 4 to the metal shell 5. FIG. It is a figure for demonstrating the process of arrange | positioning the detection element 6 to the metal shell 5. FIG. It is a figure for demonstrating the process of arrange | positioning the filling member 15 and the terminal metal fitting 70 to the metal shell 5. FIG. It is a figure for demonstrating the process of arrange | positioning the sleeve 16, packing 17, and the inner cylinder 3 to the metal shell 5. FIG. It is a figure for demonstrating the process of forming the crimping part. FIG. 10 is a diagram for explaining a process of arranging the filter 7 in the lower assembly 200. FIG. 10 is a diagram for explaining a process of placing an upper assembly 300 on the lower assembly 200. It is a figure for demonstrating the process of forming the crimping parts 102, 103, and 104. FIG.

  Hereinafter, an embodiment of a gas sensor embodying the present invention will be described with reference to the drawings. First, the structure of an oxygen sensor 1 as an example of a gas sensor will be described with reference to FIG. An oxygen sensor 1 shown in FIG. 1 is used by being attached to an exhaust pipe (not shown) of exhaust gas discharged from an engine of an internal combustion engine such as an automobile or an engine head. In the following, in the direction of the axis O of the oxygen sensor 1, the side toward the tip of the detection element 6 inserted into the exhaust pipe or the engine head (closed side, the lower side in the figure) is defined as the tip side, and opposite to this. The direction (the upper side in the figure) toward the direction will be described as the rear end side. A direction perpendicular to the direction of the axis O will be described as the radial direction of the oxygen sensor 1.

  An oxygen sensor 1 shown in FIG. 1 is a sensor for detecting the presence or absence of oxygen in exhaust gas flowing through an exhaust pipe. The oxygen sensor 1 has a structure in which a cylindrical detection element 6 having a long and closed end is surrounded and held by a metal shell 5. A lead wire 18 for extracting a signal output from the detection element 6 is drawn out from the oxygen sensor 1. The lead wire 18 is electrically connected to a sensor control device (not shown) provided at a position away from the oxygen sensor 1 or an automobile electronic control device (ECU).

  The detection element 6 is formed by forming a solid electrolyte body 61 mainly composed of zirconia in a cylindrical shape extending in the direction of the axis O and having a closed tip, a reference electrode 62 provided on the inner peripheral side, and a detection electrode 63 provided on the outer peripheral side. It is provided. The reference electrode 62 is made of Pt or a Pt alloy, and is formed in a porous shape so as to cover almost the entire inner surface of the solid electrolyte body 61. Similarly, the detection electrode 63 is made of Pt or a Pt alloy, and is formed in a porous shape on the outer surface of the solid electrolyte body 61. Thereby, the front end side (closed side) of the detection element 6 functions as the detection unit 64. The gas concentration is detected by exposing the detection unit 64 to exhaust gas flowing through an exhaust pipe (not shown). Although not shown, the detection electrode 63 is covered with a porous electrode protection layer made of a heat-resistant ceramic, and is protected from poisoning by exhaust gas. In addition, an enlarged diameter portion 65 that protrudes in the circumferential direction toward the radially outer side is provided at a substantially intermediate position in the axis O direction of the detection element 6.

  The detection element 6 is held in the cylindrical hole 55 of the metal shell 5 in a state in which the circumference of the detection element 6 is surrounded by the cylindrical metal shell 5. The metal shell 5 is a cylindrical member made of stainless steel such as SUS430 or carbon steel such as S17C, and a male threaded portion 52 that is screwed into an exhaust pipe or a mounting portion (not shown) of the engine head is formed on the tip side. ing. The above-described detection unit 64 protrudes from the inside of the cylindrical hole 55 toward the tip side. On the rear end side of the male screw portion 52 of the metal shell 5, a tool engaging portion 53 that is expanded in the radial direction is formed. The tool engaging portion 53 is engaged with an attachment tool used when attaching the oxygen sensor 1 to an exhaust pipe or an attachment portion (not shown) of the engine head. An annular gasket 11 is inserted into a portion between the tool engaging portion 53 and the male screw portion 52 to prevent gas from being released through the exhaust pipe and the attachment portion of the engine head. A caulking portion 57 for fixing the detection element 6 and an inner cylinder 3 to be described later is provided at the rear end portion of the metal shell 5. The rear end portion 66 of the detection element 6 protrudes toward the rear end side from the crimping portion 57.

  In the cylindrical hole 55 of the metal shell 5, a step portion 59 is provided with its inner periphery protruding radially inward. The aforementioned enlarged diameter portion 65 is locked to the stepped portion 59 via a rear end portion 46 of the protector 4 described later. In other words, the stepped portion 59 sandwiches the rear end portion 46 of the protector 4 in the direction of the axis O between the enlarged diameter portion 65. The cylindrical hole 55 is filled with a filling member 15 made of talc powder so as to surround the detection element 6 on the rear end side of the enlarged diameter portion 65. Further, a cylindrical sleeve 16 made of alumina is disposed in the cylindrical hole 55 so as to surround the periphery of the detection element 6 on the rear end side of the filling member 15. On the rear end side of the sleeve 16, an annular packing 17 is arranged so that a distal end portion 31 of the inner cylinder 3 described later is sandwiched between the sleeve 16 and the sleeve 16.

  By crimping the rear end portion of the metal shell 5 in the inner front end direction to form the crimped portion 57, the front end portion 31 and the sleeve 16 are pressed against the filling member 15 via the packing 17. The filling member 15 is compressed and filled into the cylindrical hole 55 of the metal shell 5 so as to press the enlarged diameter portion 65 of the detection element 6 toward the stepped portion 59 of the metal shell 5. A gap between the inner peripheral surface of the cylindrical hole 55 and the outer peripheral surface of the detection element 6 is filled in an airtight manner by the filling member 15. As described above, the detection element 6 is fixed in the cylindrical hole 55 of the metal shell 5 through the members sandwiched between the crimping portion 57 and the step portion 59 of the metal shell 5.

  The detection portion 64 of the detection element 6 protruding from the cylindrical hole 55 of the metal shell 5 to the front end side is covered with the bottomed cylindrical protector 4. The protector 4 prevents a collision from the outside with respect to the detection unit 64 of the detection element 6 until the oxygen sensor 1 is attached to the exhaust pipe or the engine head (not shown). A rear end portion 46 which is a peripheral portion on the opened side of the protector 4 is bent into a tapered shape. As described above, the protector 4 is fixed in a state in which the detection unit 64 is accommodated by the rear end portion 46 being sandwiched between the enlarged diameter portion 65 and the stepped portion 59. On the peripheral surface of the protector 4, an introduction port 42 is formed for introducing exhaust gas into the interior and guiding the exhaust gas to the detection unit 64 of the detection element 6. The bottom surface of the protector 4 is formed with a discharge port 43 for discharging water droplets and exhaust gas that have entered the protector 4.

  A cylindrical inner tube 3 made of stainless steel such as SUS304 or carbon steel such as S17C is assembled to the rear end side of the metal shell 5. The inner cylinder 3 is formed in a cylindrical shape extending along the axis O direction. The tip 31 of the inner cylinder 3 is bent into a taper shape. The inner cylinder 3 is formed in such a manner that the crimping portion 57 is formed as described above, so that the front end portion 31 is sandwiched between the sleeve 16 and the packing 17 and protrudes from the cylindrical hole 55 of the metal shell 5 to the rear end side. It is fixed with. The inner cylinder 3 extending from the cylinder hole 55 toward the rear end side surrounds a rear end portion 66 of the detection element 6 and an outer periphery of a separator 8 described later.

  A terminal fitting 70 is inserted from the opening of the rear end portion 66 on the inner peripheral side of the detection element 6 surrounded by the inner cylinder 3 (that is, the cylinder hole 69). The terminal fitting 70 has a substantially cylindrical shape, and an electrode contact portion 71 connected to the reference electrode 62 is provided on the distal end side. A rear end portion of the terminal fitting 70 is a flange portion 72 protruding outward in the radial direction. The collar portion 72 is sandwiched between the rear end portion 66 of the detection element 6 and a separator 8 described later in the direction of the axis O.

  Further, the connection fitting 20 provided at the tip of the lead wire 18 is inserted into the cylindrical hole of the terminal fitting 70. The connection fitting 20 includes a base 21 that performs electrical connection by caulking a conducting wire (twisted wire) in the lead wire 18, a tapered continuous portion 22 that extends from the base 21 toward the rear end side, and a continuous portion 22. A substantially cylindrical connecting portion 23 extending from the connecting portion 23 to the rear end side, and a protruding portion 24 extending radially outward from the connecting portion 23 in the radial direction. The base portion 21 of the connection fitting 20 passes through the inside of the cylindrical hole 69 to the position where the protruding portion 24 contacts the flange portion 72 of the terminal fitting 70 (that is, the position where the flange portion 72 is locked to the rear end portion 66). Inserted into. At this time, the connection portion 23 comes into contact with the inner peripheral surface of the electrode contact portion 71, the connection fitting 20 and the terminal fitting 70 are electrically connected, and as a result, the lead wire 18 is electrically connected to the reference electrode 62. .

  A separator 8 is disposed on the rear end side of the rear end portion 66 of the detection element 6. The separator 8 is formed of insulating ceramic in a cylindrical shape, and has an insertion hole 81 that penetrates itself in the direction of the axis O. A lead wire 18 extending from the connection fitting 20 disposed in the detection element 6 to the rear end side is inserted into the insertion hole 81.

  A grommet 9 made of fluorine rubber, EPDM, or the like is disposed on the rear end side of the separator 8. The grommet 9 has a substantially cylindrical shape extending in the direction of the axis O, and has a flange 92 that protrudes from the approximate center position in the direction of the axis O to the outer side in the radial direction. In the grommet 9, the front column part 95 on the front end side of the flange part 92 is fitted in the opening 33 on the rear end side of the inner cylinder 3. Then, as will be described later, the grommet 9 is fixed to the inner cylinder 3 by caulking the vicinity of the opening 33 from the outside. In other words, the grommet 9 fixes the inner cylinder 3 to itself by the front pillar portion 95 pressing the inner cylinder 3 radially outward.

  Thereby, inside the inner cylinder 3, the separator 8 is clamped by the grommet 9 and the detection element 6 in the direction of the axis O. The separator 8 is supported by the grommet 9 so that movement toward the rear end side is restricted, and the separator 8 is detected by the detection element 6 via other members (the protruding portion 24 of the connection fitting 20 and the flange portion 72 of the terminal fitting 70). The movement to the tip side is regulated by being supported. In addition, since the rear end surface of the separator 8 is in surface contact with the front end surface of the grommet 9 and the adhesiveness with the rear end surface of the separator 8 is high due to elastic deformation of the front end surface of the grommet 9, Direction) is also restricted.

  Further, inside the inner cylinder 3, the separator 8 is held in a state of being pressed against the grommet 9, and the grommet 9 is elastically deformed corresponding to the rear end portion of the separator 8. At this time, a concave portion 93 in which the rear end portion of the separator 8 is buried is formed at the center of the front end portion of the grommet 9. An edge portion 94 that protrudes toward the distal end side along the outline of the recess 93 and is disposed in the gap between the separator 8 and the inner cylinder 3 is formed on the periphery of the distal end portion of the grommet 9. Accordingly, the movement of the separator 8 in the radial direction is further restricted by the edge portion 94 in a state where the rear end portion is accommodated in the concave portion 93.

  The grommet 9 also has an insertion hole 91 that penetrates itself in the direction of the axis O, like the separator 8. The lead wire 18 extending from the insertion hole 81 of the separator 8 to the rear end side is inserted into the insertion hole 91. That is, the lead wire 18 connected to the reference electrode 62 through the connection fitting 20 and the terminal fitting 70 in the detection element 6 is drawn out of the oxygen sensor 1 through the insertion holes 81 and 91.

  The plurality of holes penetrating the peripheral surface of the inner cylinder 3 are first introduction holes 34 for introducing the atmosphere (outside air) as the reference gas into the inner cylinder 3. The first introduction hole 34 is formed on the tip side of the contact position between the inner cylinder 3 and the grommet 9 in order to ensure the introduction of outside air into the inner cylinder 3. A cylindrical filter 7 is disposed outside the inner cylinder 3 in the radial direction so as to close the first introduction hole 34. The filter 7 is a water-repellent filter that prevents the transmission of liquids mainly composed of water droplets and the like and allows the transmission of gases such as air and / or water vapor by using, for example, a polytetrafluoroethylene porous fiber structure. .

  Outside the inner cylinder 3 in the radial direction, a filter 7 is interposed between the inner cylinder 3 and an outer cylinder 100 which is a cylindrical metal member surrounding the inner cylinder 3 is provided. At the rear end portion of the outer cylinder 100, the entire grommet 9 is fitted therein, and an annular crimping portion 104 is formed. The caulking portion 104 presses and fixes the outer cylinder 100 to the rear column portion 96 of the grommet 9 on the rear end side of the flange portion 92.

  The plurality of holes that penetrate the peripheral surface of the outer cylinder 100 are second introduction holes 101 for introducing the atmosphere (outside air) as the reference gas into the outer cylinder 100. The second introduction hole 101 is formed at a position corresponding to the filter 7 in order to ensure the supply of outside air to the filter 7. In the peripheral surface of the outer cylinder 100, annular crimping portions 102 and 103 are formed on the front end side and the rear end side of the second introduction hole 101, respectively. The crimping portions 102 and 103 are crimped and fixed with the outer cylinder 100 facing the inner cylinder 3 on both sides in the axis O direction across the second introduction hole 101, and the filter 7 is connected between the outer cylinder 100 and the inner cylinder 3. Hold between them.

  In addition, since the outer cylinder 100 is crimped with respect to the inner cylinder 3 as mentioned above, it is suitable for the outer cylinder 100 to have the softness | flexibility which is easier to crimp than the inner cylinder 3. As an example, in the oxygen sensor 1 of the present embodiment, the inner cylinder 3 and the outer cylinder 100 are provided with a hardness difference by heat treatment.

  With the above structure, the outside air introduced into the outer cylinder 100 from the second introduction hole 101 is further introduced into the inner cylinder 3 from the first introduction hole 34. At this time, water or the like contained in the outside air is prevented from entering the inner cylinder 3 by the filter 7. Note that a gap 19 through which outside air can be introduced is formed between the separator 8 and the rear end portion 66 of the detection element 6 by the projecting portion 24 of the terminal fitting 70 having a radial shape. The outside air introduced into the inner cylinder 3 is introduced into the detection element 6 (that is, the cylinder hole 69) via the gap 19.

  As described above, in the oxygen sensor 1 of the present embodiment, outside air is introduced as the reference gas into the detection element 6, while introduced to the outer surface (specifically, the detection unit 64) of the detection element 6 from the introduction port 42. The exhausted gas comes into contact. An oxygen concentration cell electromotive force is generated according to the difference in oxygen concentration between the inner and outer surfaces of the detection element 6. By extracting the oxygen concentration cell electromotive force from the reference electrode 62 through the lead wire 18 as a detection signal of the oxygen concentration in the exhaust gas, the oxygen concentration in the exhaust gas can be detected.

  Next, the manufacturing process of the oxygen sensor 1 will be described with reference to FIGS. First, as shown in FIG. 2, the protector 4 is press-fitted into the cylindrical hole 55 from the opening of the rear end portion 56 of the metal shell 5. At this time, the discharge port 43 is press-fitted toward the tip until the rear end portion 46 of the protector 4 is locked to the stepped portion 59, and the protector 4 is temporarily fixed in the metal shell 5.

  Next, as shown in FIG. 3, the detection element 6 is inserted into the cylindrical hole 55 through the opening of the rear end portion 56 of the metal shell 5. At this time, the detecting portion 64 is inserted toward the front end until the enlarged diameter portion 65 of the detecting element 6 is locked to the rear end portion 46 of the protector 4, and the detecting element 6 is temporarily fixed in the metal shell 5. .

  Next, as shown in FIG. 4, the filling member 15 is filled around the detection element 6 through the opening of the rear end portion 56 of the metal shell 5. Thereby, the filling member 15 fills the gap between the metal shell 5 and the detection element 6 on the rear end side of the enlarged diameter portion 65. Further, the terminal fitting 70 is inserted into the cylindrical hole 69 through the opening of the rear end portion 66 of the detection element 6. At this time, the electrode contact portion 71 is inserted toward the tip until the collar portion 72 of the terminal fitting 70 is locked to the rear end portion 66 of the detection element 6. The electrode contact portion 71 is fixed to the cylindrical hole 69 while being in contact with the reference electrode 62 by its own spring force acting on the radially outer side.

  Next, as shown in FIG. 5, the sleeve 16, the inner cylinder 3, and the packing 17 are sequentially attached around the detection element 6 through the opening of the rear end portion 56 of the metal shell 5. As a result, the sleeve 16 abuts against the filling member 15 from the rear end side, and the front end portion 31 of the inner cylinder 3 is sandwiched between the sleeve 16 and the packing 17 in the axis O direction. It will be in the state erected toward the side.

  Next, as shown in FIG. 6, a caulking portion 57 is formed by caulking the rear end portion 56 of the metal shell 5 radially inward to a position where it contacts the outer peripheral surface of the inner cylinder 3. The external pressure applied to the packing 17 by the formation of the crimping portion 57 presses the sleeve 16 and the filling member 15 toward the distal end side via the distal end portion 31 of the inner cylinder 3. Thereby, the enlarged diameter part 65 is firmly clamped between the filling member 15 and the step part 59, and the detection element 6 is fixed. Further, the rear end portion 46 is firmly sandwiched between the enlarged diameter portion 65 and the stepped portion 59, and the protector 4 is fixed. Further, the tip portion 31 is firmly sandwiched between the sleeve 16 and the packing 17 and the inner cylinder 3 is fixed. Through the above steps, the lower assembly 200 in which the metal shell 5, the protector 4, the detection element 6, the inner cylinder 3 and the like are assembled together is manufactured.

  Next, as shown in FIG. 7, the filter 7 is attached to the lower assembly 200 so as to cover the outer peripheral surface of the inner cylinder 3 on the rear end side of the crimping portion 57. Further, as shown in FIG. 8, the prefabricated upper assembly 300 is assembled to the lower assembly 200 to which the filter 7 is attached. The upper assembly 300 is a member in which the grommet 9, the outer cylinder 100, the lead wire 18, the separator 8, and the like are assembled together, and may be manufactured as follows.

  The outer cylinder 100 before assembly includes a rear cylinder part 106 that is a cylindrical part having substantially the same diameter as that of the rear column part 96, and a cylinder having a diameter that is substantially the same as that of the flange part 92 provided on the front end side of the rear cylinder part 106. A front cylindrical portion 105 that is a shape portion, and a connecting portion 107 that extends radially outward from the front end edge of the rear cylindrical portion 106 and is connected to the rear end edge of the front cylindrical portion 105. The aforementioned second introduction hole 101 is formed in the front tube portion 105. The grommet 9 is inserted into the outer cylinder 100 through the front end side opening of the continuous portion 107. At this time, the rear column portion 96 is inserted toward the rear end until the collar portion 92 of the grommet 9 is locked to the continuous portion 107 of the outer cylinder 100, and the rear column portion 96 is inserted into the rear cylinder portion 106. Fit.

  Then, the lead wire 18 is inserted into the insertion hole 91 from the rear end side, and the lead wire 18 is pulled out to the front end side of the grommet 9. Further, the lead wire 18 drawn out from the grommet 9 is inserted into the insertion hole 81 from the rear end side, and the lead wire 18 is drawn out to the front end side of the separator 8. The base 21 is crimped to the lead wire (stranded wire) in the lead wire 18 drawn out from the separator 8, and the connection fitting 20 is fixed to the lead wire 18. Thereby, the separator 8 is clamped between the protrusion part 24 of the connection metal fitting 20 and the grommet 9, and the upper assembly 300 is produced.

  As shown in FIG. 8, when the upper assembly 300 is assembled to the lower assembly 200, the connection fitting 20 attached to the distal end side of the lead wire 18 is connected to the cylindrical hole of the detection element 6 through the opening 33 of the inner cylinder 3. 69 is inserted. At this time, the base 21 is inserted toward the tip until the protruding portion 24 of the connection fitting 20 is locked to the flange 72 of the terminal fitting 70. The connection portion 23 is fixed to the cylindrical hole 69 in a state in which the connection portion 23 is in contact with the inner peripheral surface of the electrode contact portion 71 by its own spring force acting on the radially outer side.

  On the other hand, the inner cylinder 3 to which the filter 7 is attached is inserted into the outer cylinder 100 through the front end side opening of the front cylinder part 105 in accordance with the insertion of the connection fitting 20 and the front cylinder part 105 and the grommet. 9 enters the gap with the front pillar portion 95. In the state in which the protruding portion 24 of the connection fitting 20 is locked to the flange 72 of the terminal fitting 70, the upper assembly 300 reaches a position where the rear end portion of the inner cylinder 3 is locked to the flange 92 of the grommet 9. Can be pushed further into the tip side. When the upper assembly 300 is pushed in this way, the grommet 9 is pressed against the separator 8 and elastically deformed, so that a recess 93 and an edge portion 94 are formed in the front pillar portion 95. In this embodiment, the recess 93 and the edge portion 94 are formed in the front pillar portion 95 by the grommet 9 being pressed against the separator 8 and elastically deformed, but before the grommet 9 is pressed against the separator 8. Accordingly, the concave portion 93 and the edge portion 94 may be formed in the front pillar portion 95.

  Finally, in the assembled state shown in FIG. 8, as shown in FIG. 9, the front end side and the rear end side of the second introduction hole 101 in the front cylinder part 105 are respectively added in the circumferential direction toward the radially inner side. The annular caulking portions 102 and 103 are formed by tightening. As a result, the outer cylinder 100 is crimped to the inner cylinder 3, the upper assembly 300 is fixed to the lower assembly 200, and the filter 7 is fixed between the outer cylinder 100 and the inner cylinder 3. Further, the rear cylinder portion 106 is caulked in the circumferential direction toward the inside in the radial direction to form an annular caulking portion 104. Thereby, the outer cylinder 100 is pressure-bonded and fixed to the grommet 9 (specifically, the rear column portion 96), and the oxygen sensor 1 is completed.

  As described above, according to the oxygen sensor 1 according to the present embodiment, the separator 8 is sandwiched in the direction of the axis O by the detection element 6 and the grommet 9, and the inner cylinder 3, the filter 7, The outer cylinder 100 is arrange | positioned in order. Thereby, the movement to the axial direction and radial direction of the separator 8 is controlled, and the separator 8 is stably fixed inside the casing (the inner cylinder 3 and the outer cylinder 100). Furthermore, since the separator 8 is held away from the inner cylinder 3 and is triple protected by the inner cylinder 3, the filter 7, and the outer cylinder 100, the separator 8 is highly resistant to the external pressure on the oxygen sensor 1. Therefore, the separator 8 can be reliably fixed and protected inside the casing.

  Moreover, since the edge part 94 formed in the front-end | tip part of the separator 8 restrict | limits the movement to the radial direction of the separator 8 reliably, the separator 8 can be more reliably fixed inside a casing. As a result, even when vibration or impact occurs in the oxygen sensor 1, for example, contact between the separator 8 and the inner cylinder 3 is prevented, so that the separator 8 can be more reliably protected.

  Further, since the first introduction hole 34 is formed on the tip side from the contact position between the inner cylinder 3 and the grommet 9, the separation portion between the separator 8 and the inner cylinder 3 can be used as an air passage, and the filter 7 The outside air can be easily introduced into the oxygen sensor 1 via

  Further, since the flange 72 that extends radially outward from the rear end portion of the terminal fitting 70 is sandwiched between the detection element 6 and the separator 8, without providing a dedicated component for fixing the terminal fitting 70, The terminal fitting 70 can be reliably fixed with a simple structure.

  By the way, in the said embodiment, the oxygen sensor 1 corresponds to the "gas sensor" of this invention. The separator 8 corresponds to the “ceramic member” of the present invention. The present invention is not limited to the embodiment described in detail above, and various modifications may be made without departing from the scope of the present invention.

  In the above embodiment, the separator 8 holds one lead wire 18. Alternatively, the separator 8 may insulate and hold a plurality of lead wires. In the above embodiment, the separator 8 has the insertion hole 81 through which the lead wire is inserted. Instead of this, the separator 8 may have an insertion hole 81 through which at least one of the terminal fitting 70 and the lead wire 18 is inserted. Further, in the above-described embodiment, the separator 8 is sandwiched between the detection element 6 and the grommet 9 via other members (such as the flange 72 of the terminal fitting 70 and the protruding portion 24 of the connection fitting 20). Instead, the separator 8 may be directly sandwiched between the detection element 6 and the grommet 9.

  Moreover, in the said embodiment, the oxygen sensor 1 which is an oxygen sensor was illustrated as one aspect | mode of the sensor which concerns on this invention. However, the present invention can be applied to a sensor in which a ceramic member that holds a lead wire for taking out a detection signal from a detection element is provided inside the casing. Therefore, the present invention may be applied to gas sensors other than oxygen sensors, such as HC sensors and NOx sensors.

DESCRIPTION OF SYMBOLS 1 Oxygen sensor 3 Inner cylinder 5 Main metal fitting 6 Detection element 7 Filter 8 Separator 9 Grommet 18 Lead wire 34 First introduction hole 62 Reference electrode 63 Detection electrode 70 Terminal metal fitting 72 Eight hole 81 Insertion hole 91 Insertion hole 100 Outer cylinder 101 Second Introduction hole

Claims (5)

A detection element that extends in the axial direction and has a cylindrical shape with the tip side directed toward the measurement object closed, and has an outer electrode on its outer peripheral surface and an inner electrode on its inner peripheral surface;
A metal shell surrounding the detection element and holding the detection element;
A cylindrical terminal fitting inserted into the cylindrical hole of the detection element and electrically connected to the inner electrode of the detection element;
A lead wire connected to the terminal fitting and extending from the terminal fitting to a rear end side to form a current path;
A ceramic member that is disposed on the rear end side of the detection element and has an insertion hole through which at least one of the terminal fitting and the lead wire is inserted;
An inner cylinder that is a cylindrical metal member that surrounds the periphery of the ceramic member, the front end side of which is fixed to the rear end side of the metal shell, and a first introduction hole for introducing gas into the interior is formed When,
An elastic member that is disposed on the rear end side of the ceramic member in the cylindrical hole of the inner cylinder, has an insertion hole through which the lead wire is inserted, while pressing the inner cylinder from the inner side to the outer side in the radial direction;
A filter disposed on the radially outer side of the inner cylinder so as to close the first introduction hole;
A cylindrical metal member surrounding the inner cylinder, the filter being interposed between the inner cylinder and a second introduction hole for introducing gas into the space is formed on the filter And an outer cylinder,
The said ceramic member is hold | maintained in the state spaced apart from the said inner cylinder by being clamped by the said detection element and the said elastic member directly or via another member.   2. The gas sensor according to claim 1, wherein an edge portion is formed at a distal end portion of the elastic member so as to protrude toward the distal end side in the axial direction and is disposed in a gap between the ceramic member and the inner cylinder.   3. The gas sensor according to claim 1, wherein the first introduction hole is formed on a distal end side with respect to a contact position between the inner cylinder and the elastic member. The terminal fitting has a flange extending radially outward from its rear end,
The gas sensor according to any one of claims 1 to 3, wherein the flange portion of the terminal fitting is sandwiched between the detection element and the ceramic member.   5. The gas sensor according to claim 1, wherein the detection element has zirconia as a main component, and the ceramic member has alumina as a main component.

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