JP5931701B2 - Gas sensor - Google Patents

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.

  2. Description of the Related Art Conventionally, a gas sensor is known in which a cylindrical detection element having a detection portion for detecting a component to be detected formed at the tip is arranged inside a metal casing (see Patent Document 1). In such a gas sensor, the distal end side of the terminal fitting for taking out a detection signal from the detection element is inserted into the cylindrical hole of the detection element, and the rear end side of the terminal fitting is arranged closer to the rear end side than the detection element. ing. A separator that surrounds the rear end side of the terminal fitting and holds the terminal fitting is provided inside the casing. Further, an elastic member (grommet) for closing the casing and inserting the lead wire is provided on the rear end side of the casing. The lead wire and the rear end side of the terminal fitting are connected inside the separator.

JP 2010-223750 A

  However, in recent years, due to the demand for downsizing of the gas sensor, it has been considered to arrange the lead wire on the tip side and connect the lead wire and the terminal fitting in the cylindrical hole of the detection element. As a result, not only the length of the terminal fitting can be shortened, but also the need for providing a separator is eliminated, so that the distance between the detection element and the elastic member can be made as close as possible.

  On the other hand, the gas sensor can be most miniaturized by bringing the detection element and the elastic member into contact with each other. However, since heat from the exhaust gas, the internal combustion engine, or the like is transferred to the elastic member via the detection element, the elastic member may be thermally deteriorated. Therefore, it is necessary to separate the detection element and the elastic member from each other by a certain distance (although it is arranged on the distal end side as compared with the related art).

  At this time, only the lead wire is disposed in a region where the detection element and the elastic member are separated from each other. However, when vibration or impact occurs in the gas sensor, the lead wire swings in the radial direction of the gas sensor, As a result, stress is applied to the connection part between the terminal fitting and the lead wire, the contact failure between the lead wire and the terminal fitting, or the lead wire falls off from the terminal fitting, resulting in a decrease in detection accuracy of the gas sensor. There was a fear.

  The present invention has been made to solve the above-described problem, and suppresses the lead wire from swinging in the radial direction at a separation portion between the detection element and the elastic member, thereby suppressing a decrease in detection accuracy of the gas sensor. An object of the present invention is to provide a gas sensor.

  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 A lead wire connected to the terminal fitting and extending from the terminal fitting to the rear end side, a metal cylinder disposed on the rear end side of the metal shell and surrounding the lead wire, and the metal cylinder An elastic member that closes the rear end side and has the lead wire inserted in the axial direction, wherein the lead wire and the connection terminal are connected within the cylindrical hole of the detection element. The metal cylinder An insulating member having an insertion hole through which a lead wire is inserted in the axial direction is disposed between the metal shell and the elastic member, and is the smallest in the insertion hole of the insulating member. The diameter is smaller than the diameter of the opening located at the rear end of the cylindrical hole.

  According to the gas sensor of one aspect of the present invention, the insulating member having the insertion hole for inserting the lead wire is disposed between the metal shell and the elastic member, and the minimum diameter of the insertion hole of the insulating member is set. The diameter of the opening of the cylindrical hole of the detection element is made smaller. As a result, even if the lead wire tries to sway in the radial direction of the gas sensor, the stress applied to the connecting portion between the terminal fitting and the lead wire is reduced by restricting the insertion hole of the insulating member, and the lead wire and the terminal fitting Can prevent poor contact and lead wires falling off the terminal fittings. As a result, it can suppress that the detection accuracy of a gas sensor falls. In particular, since the minimum diameter of the insertion hole of the insulating member is smaller than the diameter of the opening of the cylindrical hole of the detection element, it is possible to effectively achieve the restriction of the lead wire swinging in the radial direction of the gas sensor. .

  Further, the metal shell and the elastic member are separated from each other by a certain distance by an insulating member. Thereby, it can suppress that heat | fever such as exhaust gas and an internal combustion engine transfers to an elastic member via a detection element, As a result, it can suppress that an elastic member heat-deteriorates.

  Furthermore, since the lead wire and the connection terminal are connected in the cylindrical hole of the detection element, there is no need to arrange the terminal fitting on the rear end side of the detection element, and the overall length of the terminal fitting can be shortened. It is possible to make the distance from the elastic member as close as possible. As a result, the gas sensor can be reduced in size.

The insertion hole of the insulating member may be provided in a straight shape (that is, the same diameter) along the axial direction, for example, a tapered shape that narrows toward the front end side or a narrowing toward the rear end side. The taper shape may be partially included. When the insertion hole is tapered, the diameter of the insertion hole is compared with the diameter of the opening of the cylindrical hole of the detection element.
Also, the cylindrical hole of the detection element may be provided in a straight shape (that is, the same diameter) along the axial direction, or may be provided in a tapered shape that narrows toward the tip side, for example. . When the cylindrical hole has a tapered shape that narrows toward the tip, the diameter of the opening at the rearmost end of the cylindrical hole is compared with the diameter of the insertion hole of the insulating member.

  Moreover, the gas sensor which concerns on 1 aspect of this invention WHEREIN: It is preferable that the said insulating member is spaced apart and arrange | positioned from the said metal cylindrical body. As described above, the insulating member is arranged away from the metal cylindrical body, so that the insulating member is not affected by the deformation of the metal cylindrical body even if the metal cylindrical body is deformed by a stepping stone from the outside. It is possible to suppress the insulating member from being deformed or damaged.

  In the gas sensor according to one aspect of the present invention, it is preferable that the insulating member is sandwiched between the metal shell and the elastic member. Thereby, it becomes possible to arrange | position an insulating member easily in a metal cylinder. In particular, when the insulating member is disposed apart from the metal cylindrical body, the insulating member can be easily disposed in the metal cylindrical body by adopting this configuration.

  Moreover, the gas sensor which concerns on 1 aspect of this invention WHEREIN: It is preferable that the said lead wire and the said terminal metal fitting are connected in the front-end | tip part of the said terminal metal fitting. Since the lead wire is connected at the tip end of the terminal fitting, the lead wire and the terminal fitting are connected within the cylindrical hole of the detection element simply by inserting the terminal fitting into the cylindrical hole of the detection element. It becomes possible. As a result, the gas sensor can be reduced in size.

2 is a longitudinal sectional view of the oxygen sensor 1. FIG. FIG. 6 is a view for explaining a 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.

  On the rear end side of the metal shell 5, a cylindrical inner cylinder 3 (corresponding to the “metal cylinder” in the claims) made of stainless steel such as SUS304 or carbon steel such as S17C is assembled. 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 an insulating member 8 described later. Further, 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 connecting fitting (corresponding to “terminal fitting” in the claims) 20 provided at the tip of the lead wire 18 is inserted into the cylindrical hole 69 of the detection element 6 surrounded by the inner cylinder 3. The connection fitting 20 extends from the connection portion 21 to the rear end side, and a connection portion 21 (corresponding to the front end portion of the claims) that performs electrical connection by caulking a conducting wire (twisted wire) in the lead wire 18. It has a tapered continuous portion 22, a substantially cylindrical contact portion 23 extending from the continuous portion 22 toward the rear end side, and a protrusion 24 extending radially outward from the contact portion 23 in the radial direction. That is, the connection portion 21 of the connection fitting 20 is provided on the most distal side of the connection fitting 20. At this time, the contact portion 23 is connected to the reference electrode 62, and as a result, the lead wire 18 is electrically connected to the reference electrode 62.

  An insulating member 8 is disposed on the rear end side of the rear end portion 66 of the detection element 6 in a state of being separated from the inner cylinder 3. The insulating member 8 is formed of insulating ceramic in a cylindrical shape, and has an insertion hole 81 that passes through the insulating member 8 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.

  The minimum diameter A of the insertion hole 81 is smaller than the diameter B of the opening of the cylindrical hole 69 of the detection element 6. In this embodiment, the opening of the cylindrical hole 69 of the detection element 6 is chamfered in consideration of the insertability of the terminal fitting 20, but in this case, the diameter B is on the rear end side of the chamfer. Refers to the opening provided.

  On the rear end side of the separator 8, a grommet 9 (corresponding to “elastic member” in the claims) made of fluorine rubber, EPDM or the like is disposed. 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.

  As a result, the insulating member 8 is sandwiched between the grommet 9 and the detection element 6 in the direction of the axis O inside the inner cylinder 3. The insulating member 8 is supported by the grommet 9 and restricted from moving toward the rear end side, and supported by the detection element 6 via the protruding portion 24 of the connection fitting 20 and restricted from moving toward the front end side. The Further, since the rear end surface of the insulating member 8 is in surface contact with the front end surface of the grommet 9 and the adhesiveness with the rear end surface of the insulating member 8 is high due to elastic deformation of the front end surface of the grommet 9, the circumferential direction of the separator 8 (that is, , Movement in the radial direction) is also restricted.

  Further, inside the inner cylinder 3, the insulating member 8 is held while being pressed against the grommet 9, and the grommet 9 is elastically deformed corresponding to the rear end portion of the insulating member 8. At this time, a concave portion 93 in which the rear end portion of the insulating member 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 along the contour of the recess 93 and is disposed in the gap between the insulating member 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 insulating member 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 a through-hole 91 that penetrates itself in the direction of the axis O, like the insulating member 8. The lead wire 18 extending from the insertion hole 81 of the insulating member 8 to the rear end side is inserted into the through hole 91. That is, the lead wire 18 connected to the reference electrode 62 through the connection fitting 20 in the detection element 6 is drawn out of the oxygen sensor 1 through the insertion hole 81 and the through hole 91.

  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.

  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 is formed between the insulating member 8 and the rear end portion 66 of the detection element 6 by the protruding portion 24 of the connecting fitting 20 that forms a radial shape. The outside air introduced into the inner cylinder 3 is introduced into the cylinder hole 69 of the detection element 6 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, the protector 4 is press-fitted into the cylindrical hole 55 from the rear end side opening 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, the detection element 6 is inserted into the cylindrical hole 55 from the rear end side opening 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, the filling member 15 is filled around the detection element 6 from the rear end side opening 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 sleeve 16, the inner cylinder 3, and the packing 17 are sequentially attached around the detection element 6 from the rear end side opening 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.

  Then, the caulking portion 57 is formed by caulking the rear end side 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, a lower assembly 200 in which the metal shell 5, the protector 4, the detection element 6, the inner cylinder 3, and the like are integrally assembled as shown in FIG. 2 is produced.

  Next, 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. 3, 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 insulating member 8, and the like are integrally assembled, 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 through 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 insulating member 8. The connecting portion 21 is crimped to the lead wire (stranded wire) in the lead wire 18 drawn out from the insulating member 8, and the connection fitting 20 is fixed to the lead wire 18. Thereby, the insulating member 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. 3, 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 connection portion 21 is inserted toward the tip until the protruding portion 24 of the connection fitting 20 is locked to the rear end portion 66 of the detection element 6. The contact portion 23 is fixed to the cylindrical hole 69 in a state in which the contact portion 23 is in contact with the inner peripheral surface of the detection element 6 by its own spring force acting radially outward.

  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 a state where the protruding portion 24 of the connection fitting 20 is locked to the rear end portion 66 of the detection element 6, the upper assembly is moved to a position where the rear end portion of the inner cylinder 3 is locked to the collar portion 92 of the grommet 9. 300 can be pushed further forward. When the upper assembly 300 is pushed in this way, the grommet 9 is pressed against the insulating member 8 and elastically deformed, so that the concave portion 93 and the edge portion 94 are formed in the front pillar portion 95. In the present embodiment, the grommets 9 are pressed against the insulating member 8 and elastically deformed to form the recesses 93 and the edge portions 94 in the front pillar portion 95, but the grommets 9 are pressed against the insulating member 8. The concave portion 93 and the edge portion 94 may be formed in the front pillar portion 95 from before.

  Finally, in the assembled state shown in FIG. 3, as shown in FIG. 4, the front end side and the rear end side of the second introduction hole 101 in the front cylinder portion 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 insulating member 8 having the insertion hole 81 through which the lead wire 81 is inserted is disposed between the metal shell 5 and the grommet 9. The minimum diameter A of the insertion hole 81 of the insulating member 8 is made smaller than the diameter B of the opening of the cylindrical hole 69 of the detection element 6. Thereby, even if the lead wire 81 tries to swing in the radial direction of the oxygen sensor 1, the insertion hole 81 of the insulating member 8 is restricted, so that the stress applied to the connection portion between the connection fitting 20 and the lead wire 81 is reduced. Further, it is possible to suppress the contact failure between the lead wire 81 and the connection fitting 20 or the drop of the lead wire 81 from the connection fitting 20. As a result, it can suppress that the detection accuracy of the oxygen sensor 1 falls.
In particular, since the minimum diameter A of the insertion hole 81 of the insulating member 8 is smaller than the diameter B of the opening of the cylindrical hole 69 of the detection element 6, the lead wire 81 swings in the radial direction of the oxygen sensor 1. Regulating can be effectively achieved.

  Further, the metal shell 5 and the grommet 9 are separated from each other by a certain distance by the insulating member 8. Thereby, it can suppress that heat | fever such as exhaust gas and an internal combustion engine heat-transfers to the grommet 9 via the detection element 6, As a result, it can suppress that the grommet 9 heat-degrades.

  Furthermore, since the lead wire 81 and the connection fitting 20 are connected in the cylindrical hole 69 of the detection element 6, there is no need to arrange the connection fitting 20 on the rear end side of the detection element 6. The overall length can be shortened, and the distance between the detection element 6 and the grommet 9 can be as close as possible. As a result, the oxygen sensor 1 can be reduced in size.

  Further, according to the oxygen sensor 1 according to the present embodiment, since the insulating member 8 is arranged away from the inner cylinder 3, even if the inner cylinder 3 is deformed by a flying stone from the outside, the insulating member 8 is It is possible to prevent the insulating member 8 from being deformed or damaged without being affected by the deformation of the inner cylinder 3.

  Further, according to the oxygen sensor 1 according to the present embodiment, since the insulating member 8 is sandwiched between the metal shell 5 and the grommet 9, the insulating member 8 can be easily disposed in the inner cylinder 3. Become. In particular, when the insulating member 8 is disposed away from the inner cylinder 3, the insulating member 8 can be easily disposed in the inner cylinder 3 by adopting this configuration.

  Moreover, according to the oxygen sensor 1 according to the present embodiment, the lead wire 81 and the connection fitting 20 are preferably connected by the connection portion 21 provided on the distal end side of the terminal fitting 20. Since the lead wire 81 is connected to the connecting portion 21 of the connection fitting 20, the lead wire 81 and the connection fitting 20 can be connected to the detection element 6 simply by inserting the connection fitting 20 into the cylindrical hole 69 of the detection element 6. It becomes possible to take the structure connected in the cylindrical hole 69 of this. As a result, the oxygen sensor 1 can be reduced in size.

  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.

  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 Insulation member 9 Grommet 18 Lead wire 20 Connection metal fitting 34 First introduction hole 62 Reference electrode 63 Detection electrode 72 ridge part 81 Insertion hole 91 Insertion hole 100 Outer cylinder 101 First Two introduction holes

Claims (4)

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 that surrounds the detection element and holds the detection element; a cylindrical terminal metal fitting that is inserted into the cylindrical hole of the detection element and is 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 the rear end side;
A metal cylinder disposed on the rear end side of the metal shell and surrounding the lead wire;
An elastic member that closes a rear end side of the metal cylindrical body and has the lead wire inserted in the axial direction;
A gas sensor comprising:
The lead wire and the terminal fitting are connected in the cylindrical hole of the detection element,
An insulating member having an insertion hole through which the lead wire is inserted in the axial direction is disposed inside the metal cylindrical body and between the metal shell and the elastic member,
The gas sensor according to claim 1, wherein a minimum diameter of the insulating member in the insertion hole is smaller than a diameter of an opening located at a rear end of the cylindrical hole.   The gas sensor according to claim 1, wherein the insulating member is disposed apart from the metal cylindrical body.   The gas sensor according to claim 1 or 2, wherein the insulating member is sandwiched between the metal shell and the elastic member.   The gas sensor according to any one of claims 1 to 3, wherein the lead wire and the terminal fitting are connected at a distal end side of the terminal fitting.