JP2005010137A - Gas sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the using quantity of a sealing material for keeping airtightness between the hardware body of a sensor and an element, to improve sealing performance, and to shorten the sensor. <P>SOLUTION: A detection element 15 is positioned in the hardware body 2, and an electrode layer on the circumferential surface is electrically connected, and a terminal member 31 is inserted into the element 15 and electrically connected to an electrode layer on the inner circumferential surface, to thereby form this gas sensor. When keeping seal by compressing the sealing material 21 between the hardware body 2 and the detection element 15 to the tip side by a ceramic sleeve 25 having a flange 28, the sealing material 21 is arranged on the furthermore tip side than rear ends 2b, 15c of the hardware body and the detection element. Then, the sleeve tip 26 is positioned on the furthermore tip side than the rear end 15c of the detection element and the sealing material 21 is compressed. Since the sealing material 21 does not cross over a terminal member unlike before in the axis G direction, the quantity thereof is reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a gas sensor (hereinafter also simply referred to as a sensor) such as an oxygen sensor used for detecting the oxygen concentration in exhaust gas of an internal combustion engine.

  This type of gas sensor surrounds the outer peripheral surface of a detection element (hereinafter also simply referred to as an element) made of a cylindrical oxygen ion conductor having an electrode layer on each of the inner and outer peripheral surfaces and closed at the tip. It is positioned and fixed in the metal fitting body formed in the above. Then, the electrode layer on the outer peripheral surface is electrically connected to the metal fitting body, and a terminal member (metal terminal) is inserted into the opening at the rear end of the detection element from the inner connection terminal side on the front end side thereof, so that the electrode on the inner peripheral surface It is set as the structure which ensures the electrical connection (conduction) with a layer (for example, refer FIG. 2, 3 of patent document 1). This is attached to the exhaust pipe of the internal combustion engine from the outside, and the electrode layer (reference electrode layer) on the inner peripheral surface (inner surface) of the element is used as the reference oxygen gas (atmosphere), and the outer peripheral surface (outer surface). The electrode layer (measurement electrode layer) is brought into contact with the exhaust gas, and an electromotive force (potential difference) is generated between both electrodes corresponding to the oxygen concentration difference between the inner and outer peripheral surfaces of the element. A signal based on this electromotive force is sent to the control circuit. It outputs, detects oxygen concentration, and controls an air fuel ratio.

  In the gas sensor having such a configuration, when the seal (air tightness and liquid tightness) between the inner peripheral surface (inner surface) and the outer peripheral surface (outer surface) of the element is broken, the exhaust gas enters the inside of the element. . For this reason, the reference oxygen gas on the inner surface side of the element is contaminated, and the oxygen concentration detection ability is lowered. In addition, various problems occur such as oil contained in the exhaust gas causes corrosion of the electrode layer on the inner surface. Therefore, it is necessary to ensure a seal between the inner peripheral surface of the main body and the outer peripheral surface of the element, which may have an intrusion of exhaust gas.

Under such circumstances, the gas sensor described in FIG. 2 and FIG. 3 in Patent Document 1 is located inside the metal fitting body (mounting metal fitting), close to the rear end (upper end of the drawing) of the element, and in the element. A sealing material made of talc (talc powder) or the like is placed and filled in the annular space on the outer peripheral surface of the terminal member (metal terminal) with the tip end inserted therein, thereby holding the seal. That is, a ceramic sleeve is arranged at the rear end of the sealing material, and is sealed by a sleeve pressing fixing means that bends the rear end portion inward and presses the sleeve toward the front end side, for example, at the rear end portion of the metal fitting body. The material was compressed to ensure a seal.
Japanese Utility Model Publication No. 53-95884 (FIGS. 2 and 3)

  However, in the sensor shown in FIGS. 2 and 3 of Patent Document 1, since the sealing material straddles the two parts of the element and the terminal member in the axial direction, the arrangement region of the sealing material in the coaxial line direction is long. Become. As described above, in the sensor structure in which the axial length of the sealing material is increased, it is difficult to apply a uniform load to the sealing material when the sealing material is compressed (pressurized) and placed inside the metal fitting body. Therefore, it is easy to form a sealing material in which a portion where the specific gravity does not partially increase is present. And about the sealing material which has a site | part whose specific gravity does not rise partially, there exists a possibility that sufficient sealing performance may not be obtained but the sealing performance as a sensor may fall. On the other hand, it is conceivable to increase the filling density of the sealing material having a long axial direction length by applying a high load, but this is not realistic because the detection element may be broken by the load.

  Furthermore, in such a gas sensor, it is set as the structure output to a control apparatus by connecting the connecting cord for output to the terminal member (metal terminal). Here, the outer side of the terminal fitting of the cord is usually covered with a rubber cap (rubber cover) to ensure the stability of the connection, water resistance, insulation, etc. There was a request. That is, since the metal fitting body constituting the sensor becomes high temperature due to the heat of the exhaust, the rubber cap also becomes high temperature due to this heat propagation and radiant heat. Therefore, even if a rubber material having high heat resistance is used for the rubber cap, it is necessary to take a protective measure against such heat damage. For this reason, in a state where the rubber cap is fitted (set) to the gas sensor, a predetermined dimension (distance) needs to be separated from the rear end of the metal fitting body to the front end of the rubber cap.

  On the other hand, there is a demand for such a sensor to be reduced in size and weight based on the relationship of the installation space. However, in the sensor described in FIG. 2 and FIG. 3 of Patent Document 1, a request for downsizing of the sensor is required based on such a requirement for maintaining the dimensions and a structure in which the arrangement region of the sealing material is increased as described above. There was a problem of not being able to respond.

  The present invention has been made in view of such problems of the conventional sensor, and is intended to improve the sealing performance by a seal material between the sensor metal fitting body and the element, and to shorten or miniaturize the sensor. That is the purpose.

In order to achieve the above object, the invention according to claim 1 is a metal fitting formed so as to surround the outer peripheral surface of a detection element having a cylindrical shape with its tip closed and having an electrode layer on the inner and outer peripheral surfaces. Positioning in the body and electrically connecting the electrode layer on the outer peripheral surface to the metal fitting body,
A gas sensor formed by inserting a terminal member into the opening at the rear end of the detection element from the front end side and electrically connecting to the polar layer of the inner peripheral surface,
Placing a sealing material in the annular space between the inner peripheral surface of the metal fitting body and the outer peripheral surface of the detection element;
A cylindrical ceramic sleeve having a convex portion on the outer peripheral surface is positioned rearward of the rear end of the metal fitting body and the detection element, and the sealing material is moved to the front end side by the end of the sleeve. Place it compressible,
At a portion near the rear end of the metal fitting body, the seal material is compressed by sleeve pressing fixing means for fixing the sleeve in a state where the sleeve is pressed to the front end side through the convex portion of the ceramic sleeve. In a configuration that holds a seal between the detection elements,
The sealing material is disposed only on the front end side from the rear end of the metal fitting main body and the detection element, and the ceramic sleeve is coaxial with the detection element and the sleeve front end from the rear end of the detection element. Also, the sealing material is compressed to the tip side by being positioned on the tip side.

  In this specification, the gas sensor or its constituent member (component) refers to the front end or the front, and refers to the lower end or the bottom of the gas sensor or the structural member in FIG. 1, and the rear end or the rear refers to the gas sensor in FIG. Refers to the top or top of the component.

  According to the above-described present invention, there are the following operations. That is, in the sensor seal structure shown in FIGS. 2 and 3 of Patent Document 1, the sealing material is provided between the outer peripheral surface of the part near the rear end of the element and the outer peripheral surface of the terminal member located behind the element. Therefore, the amount of the sealing material tends to increase, and the axial length of the sealing material becomes long. As a result, it is difficult to increase the packing density of the sealing material. . On the other hand, in the present invention, the sealing material is disposed only in a portion of the annular space between the inner peripheral surface of the metal fitting main body (hereinafter also simply referred to as the main body) and the outer peripheral surface of the element, and this is compressed by the sleeve. It has a structure.

  In other words, in the present invention, the ceramic sleeve is concentrically arranged with respect to the detection element and the rear end side of the detection element is arranged inside the front end of the ceramic element, and the seal material is compressed to the front end side by the sleeve front end. It was set as the structure to do. As a result, the axial length of the sealing material can be made shorter than that of the conventional sensor structure, and the sealing material under the condition of receiving the pressing force from the ceramic sleeve has a high density and a high specific gravity. can do. As a result, a gas sensor superior in sealing performance as compared with the conventional one can be obtained.

  In addition, according to the present invention, since the detection element is arranged at the rear end side inside the front end portion of the ceramic sleeve, the sleeve pressing member that compresses the sealing material toward the front end side is pressed near the rear end portion of the main body. The fixing means can be provided on the tip side of the conventional sensor. As a result, even if the dimension from the rear end of the main body to the rear end of the terminal member is ensured as in the conventional case, the position of the rear end of the main body can be set to the front end side, so that the sensor can be shortened. Can do.

  According to the gas sensor of the present invention, as described above, the axial length of the sealing material can be shortened as compared with the conventional one. Specifically, the axial length is in a range of 10 mm or less. It is preferable to set within. This is because if it is larger than 10 mm, it is difficult to apply a uniform load to the sealing material in a state where the sealing material is pressurized by the sleeve tip. The lower limit of the axial length is not particularly limited as long as the sealing performance between the inner peripheral surface of the detection element and the outer peripheral surface of the metal fitting body can be obtained satisfactorily. be able to. In the present specification, the “axial length of the sealing material” is the length between the end on the side of the sealing material that contacts the detection element and the end on the rear side. Yes, and refers to the length in the direction parallel to the axial direction of the detection element. Further, in the present invention, the shape of the convex portion provided on the outer peripheral surface of the sleeve may be discontinuous in the circumferential direction, for example, in the shape of an external gear when viewed from the axial direction. It is preferable that the flange has an annular shape. It is because the sleeve itself can be satisfactorily pressed toward the front end side in the axial direction by using the convex portion formed of the annular flange.

  The convex portion may be provided on the outer peripheral surface of the sleeve. However, in the gas sensor according to claim 1, the convex portion is provided at the tip of the ceramic sleeve or as in the invention according to claim 2. It is good to be provided in the part near the tip. This is because, by doing this, the sleeve pressing and fixing means at the portion near the rear end of the main body can be positioned as little as possible at the front end side of the sensor, so that the axial length of the metal fitting main body can be shortened. This is because the cost of the sensor can be reduced and the sensor can be shortened.

  According to a third aspect of the present invention, there is provided the gas sensor according to the first or second aspect, wherein the ceramic sleeve surrounds an outer peripheral surface of the terminal member. In this way, in the case of surrounding the outer peripheral surface of the terminal member, in addition to protecting the inside of the sensor, the mounting of the terminal member can be stabilized. In addition, a rubber cap that covers the terminal fitting of the connecting cord connected to the terminal member is fitted on the part near the rear end of the sensor so that it is fitted on the ceramic sleeve. Therefore, based on the heat dissipation of ceramics, it is also effective as a heat damage countermeasure for rubber caps. In addition, what is necessary is just to let the range about the axial direction to surround be a range which does not have trouble in the connection of the terminal metal fitting of a connection cord.

  As the sleeve pressing and fixing means, as described in claim 4, the sleeve pressing and fixing means is configured by caulking the periphery of the portion close to the rear end of the metal fitting body to the rear of the convex portion of the sleeve. What is covered is preferable. However, what is necessary is just to fix the state which pressed this sleeve to the front end side via the said convex part of this ceramic sleeve, and it is not limited to this. In addition, although mentioned later in detail, for example, this annular member is attached to the rear end of the metal fitting main body in a state in which another metal annular member is put on the rear part of the sleeve and pressed to the front end side. It may be fixed to the side portion by welding or the like. That is, an appropriate means can be used.

  Moreover, the preferable manufacturing method of the gas sensor of this invention is as having described in Claims 5-7. According to a fifth aspect of the present invention, in manufacturing the gas sensor according to the fourth aspect, the ceramic sleeve is configured such that the rear end of the sleeve is positioned behind the rear end of the metal fitting body and the detection element, and the sleeve front end After the seal material is arranged to be compressible on the distal end side, the ceramic sleeve is pressed to the distal end side, and the seal material is compressed to the distal end side by the sleeve distal end, and the rear portion of the convex portion in the sleeve In addition, the gas sensor manufacturing method is characterized in that the peripheral edge of the portion close to the rear end of the metal fitting body is crimped and covered inside.

  According to a sixth aspect of the present invention, in manufacturing the gas sensor according to the fourth aspect, the ceramic sleeve is configured such that the rear end of the sleeve is positioned behind the rear end of the metal fitting body and the detection element, and the sleeve front end After the seal material is arranged to be compressible on the front end side, the ceramic sleeve is pressed to the front end side and the seal material is compressed to the front end side by the sleeve front end at the same time as the rear portion of the convex portion in the sleeve. In addition, the gas sensor manufacturing method is characterized in that the peripheral edge of the portion close to the rear end of the metal fitting body is crimped and covered inside.

  A seventh aspect of the present invention is the method according to the fifth or sixth aspect, wherein the terminal member is placed on the distal end side of the convex portion of the sleeve after the peripheral edge of the portion close to the rear end of the metal fitting body is crimped inward. The gas sensor is manufactured by inserting into the sleeve, and inserted into the opening at the rear end of the detection element and electrically connected to the electrode layer on the inner peripheral surface.

  As apparent from the above description, in the gas sensor of the present invention, the axial length of the sealing material can be made shorter than that of the conventional sensor structure. For this reason, since the sealing material under the state of receiving the pressing force from the ceramic sleeve can be made to have a high density and a high specific gravity, it is possible to provide a gas sensor with a superior sealing performance as compared with the conventional one. it can.

  In addition, since the gas sensor according to the present invention is arranged at the rear end side of the detection element inside the front end portion of the ceramic sleeve, the portion near the rear end of the main body that presses the sleeve that compresses the sealing material toward the front end side. The sleeve pressing and fixing means can be provided closer to the tip than the conventional sensor. As a result, even if the dimension from the rear end of the main body to the rear end of the terminal member is ensured as in the conventional case, the position of the rear end of the main body can be set to the front end side, so that the sensor can be shortened. Can do.

  Furthermore, according to the method for manufacturing a gas sensor of the present invention, the ceramic sleeve is pressed to the tip side and the seal material is compressed to the tip side by the sleeve tip, or the seal material is moved to the tip side. At substantially the same time as the compression, the peripheral edge of the part close to the rear end of the metal fitting body is crimped inward and covered. For this reason, since the sealing material is compressed in the caulking, high sealing performance is ensured. In the gas sensor manufacturing method of the present invention, the sleeve end of the ceramic sleeve and the sealing material may be brought into contact with each other to press the ceramic sleeve toward the tip side, or the sleeve end of the ceramic sleeve An intermediate member (for example, an annular plate member having a constant thickness) may be interposed between the sealing member and the ceramic sleeve to press the tip side.

  Embodiments of the gas sensor according to the present invention will be described in detail with reference to FIGS. In the figure, 1 is a sensor of this example, the metal fitting body 2 is made of SUS430, and has a small-diameter hole 3 in which the inner periphery on the tip side (the lower side in the figure) is formed in a straight shape with a thin circular cross section, An inner peripheral step 4 having an upwardly expanding diameter taper is provided at the upper end of the small-diameter hole 3 and is larger than the small-diameter hole 3 behind the rear end (upper end in the figure) of the inner peripheral step 4. A straight cylindrical inner peripheral surface 5 is formed with a circular cross section having a diameter. The inner peripheral surface behind the rear end of the cylindrical inner peripheral surface 5 is increased in diameter upward from the cylindrical inner peripheral surface 5 via the tapered surface 6 having a diameter increasing upward, and the inside of the expanded cylindrical cylinder composed of the thin cylindrical portion 7. A peripheral surface 8 is provided. As shown in FIG. 2, the rear end portion 7b of the thin-walled cylindrical portion 7 is pushed and bent inward by pressing the die D with the force P toward the front end side from the cylindrical state coaxial with the sensor axis G. At the same time, it is crimped to the tip side. Such a metal fitting body 2 has an inner peripheral surface that is coaxially expanded from the front end (lower end in the drawing) 2a side to the rear end 2b side with respect to the sensor axis (same as the axis of the screw 10 described below) G. It has a stepped cylindrical shape with a diameter.

  On the other hand, a hexagonal portion 9 for mounting to the exhaust pipe H (for screwing) is provided in an expanded manner outside the portion corresponding to the cylindrical inner peripheral surface 5 and the tapered surface 6 in the metal fitting body 2. . And the screw | thread 10 for attachment is provided in the outer periphery of the lower part of the hexagonal part 9, and the reduced diameter part 11 by which the outer diameter was reduced is provided in the front end side of this screw 10 for attachment, A plurality of element protection caps 12 with gas flow holes are fitted and fixed by welding or the like. The thin cylindrical portion 7 is connected to the upper portion of the hexagonal portion 9.

  In this embodiment, a ring-shaped metal (made of SUS430) packing 13 is set on the inner peripheral step 4 inside the metal fitting body 2 from the rear end side. And the detection element 15 which makes the front-end | tip 15a obstruct | occluded and makes a cylindrical shape from the upper part in the inside of the metal fitting main body 2 is coaxially inserted from the front-end | tip 15a side. However, the detection element 15 includes an outer peripheral convex portion (flange) 16 that is provided so as to protrude outwardly from the intermediate position slightly above the intermediate position. 2 is positioned in a dead end manner through a metal packing 13 on the inner peripheral step portion 4 inside. In this embodiment, an electrode layer (not shown) formed on the outer peripheral surface on the tip end side of the element 15 extends to the outer peripheral convex portion 16 and is electrically connected to the metal fitting body 2 via the metal packing 13. It is connected to the. Further, the outer peripheral convex portion 16 is formed so that the tip side thereof corresponds to the taper angle of the inner peripheral step portion 4, and the outer diameter is set to be within the cylindrical inner peripheral surface 5. The width in the vertical (axis G) direction of the outer peripheral convex portion 16 is set to be smaller than the vertical dimension of the cylindrical inner peripheral surface 5. In addition, the outer peripheral surface on the front end side is formed in a gentle taper and a taper shape from the outer peripheral convex portion 16, and the outer peripheral surface on the rear end side is formed substantially straight. However, the inner and outer peripheral surfaces near the opening of the rear end 15b are chamfered.

  Now, packing 18 made of metal (Ni) wire is disposed above the outer peripheral convex portion 16 of the element 15 and between the outer peripheral surface 15 c of the element 15 and the cylindrical inner peripheral surface 5 of the main body 2. ing. In the annular space formed by the tapered surface 6 of the metal fitting body 2, the inside of the enlarged cylindrical inner peripheral surface 8 that is the inner peripheral surface of the thin cylindrical portion 7, and the outer peripheral surface 15 c of the element 15, Then, a sealing material 21 made of talc powder (or hexagonal boron nitride powder) is arranged (compressed and filled). However, the sealing material 21 is disposed so that the rear end thereof is located on the front end side from the rear end of the element 15 and the main body 2, and has a substantially wedge-shaped cross section in this embodiment.

  Then, on the rear end side of such a sealing material 21, an insulating ceramic sleeve 25 made of alumina or the like and having a substantially cylindrical shape is arranged and fixed as follows. That is, the ceramic sleeve 25 is coaxial with the element 15 at a portion near the tip 26 between the outer peripheral surface 15 c near the rear end 15 b of the element 15 and the inner peripheral surface 8 of the thin cylindrical portion 7 of the main body 2. Arranged in a shape. And the sealing material 21 is compressed to the front end side by the front-end | tip 26, and the seal | sticker between the metal fitting main body 2 and the element 15 is hold | maintained. However, the sleeve 25 is provided with a flange 28 that is a convex portion on the outer peripheral surface of the tip 26 in the circumferential direction, and the sleeve 25 is fixed by pressing the sleeve 25 toward the tip via the flange 28. Thus, the sealing material 21 is compressed, and the seal between the metal fitting body 2 and the detection element 15 is held. In this embodiment, an O-ring packing 30 made of a metal (SUS430) wire is disposed on the rear portion (rear end surface) 28b of the flange 28, and in this state, as described above, closer to the rear end in the thin cylindrical portion 7 The sleeve is pressed to the distal end side by covering the periphery of the portion 7b by caulking inside. At this stage, the work in progress shown on the left side of FIG. 3 is presented.

  In addition, before crimping the peripheral edge of the rear end portion 7b in the thin cylindrical portion 7 inward, as shown by an arrow K in FIG. 3, a predetermined load (for example, 10 to 30 kN) is used. ), The ceramic sleeve 25 is preferably pressed toward the distal end side, and the sealing material 21 is preferably compressed toward the distal end side by the sleeve distal end 26. That is, under such a compressed state, the die D is pushed to the front end side, and the periphery of the rear end portion 7b of the metal fitting body 2 is crimped and covered on the rear portion of the convex portion 28 of the sleeve 25. preferable. This is because the sealing material 21 can be sufficiently compressed separately from the caulking, so that higher sealing performance is ensured. However, substantially simultaneously with the compression of the sealing material 21 to the front end side, the rear end of the convex portion 28 of the sleeve 25 may be covered by crimping the periphery of the rear end portion 7b of the metal fitting body 2 inward.

  On the other hand, the ceramic sleeve 25 of this embodiment is provided with a flange 29 that protrudes inwardly on the inner peripheral surface on the rear end 27 side, and the output terminal member 31 is inserted inside the flange 29. Is formed. Further, the inner and outer peripheral surfaces of the sleeve 25 have the same diameter (straight) except for both flanges 28 and 29, and in this embodiment, more than half of the rear end portion is the rear end of the element 15 and the metal fitting body 2. It protrudes rearward from and is exposed to the outside.

  Then, a terminal member 31 formed in a tapered stepped cylindrical shape is passed through the inside of the ceramic sleeve 25 from the tip end side of the internal connection terminal 33 to the sensor work piece shown in FIG. 15 is assembled into the sensor shown in FIGS. 1 and 4 by press-fitting into the opening near the rear end 15b. The internal connection terminal 33 of the terminal member 31 is pressed against an electrode layer (not shown) formed on the inner peripheral surface 15d of the element 15 by its own spring property, and electrical connection (conduction) is maintained. Yes. As shown in FIG. 4, the length L1 in the axial direction from the rear end 2b of the main body 2 to the rear end 31b of the terminal member 31 in the sensor 1 assembled in this way is determined by the terminal fitting 43 constituting the connection cord 40. The rear end 2b of the main body 2 is prevented so that the rubber cap 45 formed by covering the terminal fitting 43 in the connection cord 40 is not subjected to the heat damage of the exhaust pipe when being connected to the terminal member 31. And the rubber cap 45 of the connecting cord 40 are set so that the necessary axial length S is maintained.

  In the assembly described above, the terminal member 31 is inserted in advance into the opening of the rear end 15b of the detection element 15 and electrically connected to the electrode layer on the inner peripheral surface thereof, and then the ceramic sleeve 25 is set. It is also possible to cover the peripheral edge of the portion 7b near the rear end of the metal fitting body 2 by crimping it inside. However, as described above, after the sleeve 25 is set and the peripheral edge of the rear end portion 7b of the metal fitting body 2 is crimped inward, the terminal member 31 is inserted into the sleeve 25 from the distal end side thereof, When the sensor element 15 is inserted into the opening of the rear end 15b of the detection element 15 and electrically connected to the electrode layer on the inner peripheral surface, the assembly becomes easy. This is because when the ceramic sleeve 25 is set after the terminal member 31 is inserted in the detection element 15 in advance, the ceramic sleeve 25 may interfere with the terminal member 31 due to the inclination of the terminal member 31. In some cases, setting may be difficult due to collision. However, when the terminal member 31 is inserted later, such a problem can be easily avoided.

  In this embodiment, the terminal member 31 has a rear end 31a through a small diameter insertion guide portion 32, an internal connection terminal 33 portion, an intermediate tube portion 34, and a constricted portion 35 from the front end 31a to the rear end 31b. A thin metal plate made of SUS304 is rounded so as to form a close external connection terminal 36, and one side is cut along the axis (see the right figure in FIG. 3). However, the cut in the internal connection terminal 33 is formed uneven in the axial direction, and the portion of the internal connection terminal 33 is pressed against the electrode layer on the inner peripheral surface 15d of the element 15 due to its spring property when set to the element 15. It is formed as follows. The rear end of the outer peripheral surface forming the external connection terminal 36 is formed in a chamfered shape so that the terminal fitting 43 constituting the connection cord 40 is easily covered. The connection cord 40 is electrically connected to the terminal fitting 43, a rubber cap 45 (for example, made of fluorine-based rubber) that covers the terminal fitting 43, the lead wire 41, and one end side of which is in contact with the terminal fitting 43. The other end side is crimped to the lead wire 41 and has a crimping terminal 42 for electrical connection. Among these, the terminal metal fitting 43 is a material having a rigidity (for example, Inconel) that reduces the diameter of the external connection terminal 36 of the terminal member 31 without being deformed when it is connected to the outside of the terminal member 31. 178). By attaching such a connection cord 40 to the gas sensor 1, an output signal from the detection element 15 of the gas sensor 1 can be transmitted to an external device (for example, ECU) through the lead wire 41.

  The connection cord 40 shown in FIG. 4 is provided with a rubber cap 45 having an L shape in the cross section shown in the drawing so as to cover the terminal fitting 43 as described above. The inner side of the cap 45 close to the opening is formed so as to be elastically fitted to the sleeve 25. Reference numeral 38 in the terminal member 31 is a stopper for preventing excessive insertion into the element 15 and is formed to project outward so as to be engaged with the rear end 27 of the sleeve 25. Reference numeral 39 in the figure denotes a retaining member after the terminal member is inserted. When the terminal member is inserted, the terminal member 39 is squeezed by the inner peripheral surface of the flange 29 at the rear end 27 of the ceramic sleeve 25 and passes through the flange 29. After passing, it is opened by a spring at the tip of the flange 29, and is formed in a cut-out shape in the intermediate cylindrical portion 34 in a tongue-like shape spreading upward.

  As shown in FIG. 4, such a sensor 1 is attached to the exhaust pipe H through a washer W by a screwing method. Then, the external connection terminal 36 of the terminal member 31 is covered with the terminal metal fitting 43 of the connection cord 40 so that the electrical connection therebetween is maintained and used as a sensor. On the other hand, in the sensor 1 of this embodiment, the portion near the tip of the ceramic sleeve 25 is coaxially disposed and assembled so as to overlap the outer peripheral surface 15c near the rear end 15b of the element 15. That is, since the sealing material 21 exists only around the outer peripheral surface of the element 15 inside the main body 2 and is not disposed across the element and the terminal member in the axial direction as in the prior art, the sealing material 21 The axial length L3 can be shortened. For this reason, it is possible to increase the filling density in the sealing material 21 that is compressed and filled by the pressing force of the sleeve 25, and it is possible to obtain the gas sensor 1 that is superior in sealing performance as compared with the conventional sensor structure. In this embodiment, the length L3 of the sealing material is 4 mm.

  In addition, since the formation position of the flange 28 of the sleeve 25 is set on the outer peripheral surface of the tip 26 while reducing the arrangement region in the axial direction of the sealing material 21, the position of the rear end 2 b of the main body 2 is set on the tip side of the element 15. Therefore, the sensor can be shortened and thus miniaturized. Further, since the length can be reduced, the length L2 from the exhaust pipe to the rear end of the sensor when the sensor 1 is attached to the exhaust pipe H can be shortened, so that the installation space can be reduced.

  Further, in this embodiment, the rubber cap 45 in the connecting cord 40 is elastically fitted (contacted) with the outer circumferential surface of the ceramic sleeve 25 holding the axial length S. For this reason, the heat damage to the rubber cap 45 can be reduced, the mounting thereof can be stabilized, and the effect of preventing water and oil from entering the sensor can be kept high.

  In the above-described embodiment, the case where the flange (convex portion) 28 of the sleeve 25 is pressed toward the tip side by caulking at the portion near the rear end of the main body 2 as the sleeve pressing and fixing means is illustrated in FIG. Even so, it can be embodied. FIG. 5 shows another example of the sleeve pressing and fixing means, and only the difference from that of the above-described embodiment will be described, and the same portions are only given the same reference numerals. The same applies to the following. That is, a ring 51 having an L-shaped cross section as shown in the figure is fitted on the outer peripheral surface of the rear end portion 7 b of the main body 2 through the vertical cylindrical portion 52, and the O ring is inserted through the flat ring portion 53. It arrange | positions so that the packing 30 may be pressed. Then, the sleeve is pressed toward the distal end side as indicated by an arrow P through the ring 51 to compress the sealing material 21. Under this state, the inner peripheral surface of the vertical cylindrical portion 52 and the rear end of the main body 2 are compressed. The sleeve 25 is fixed to the main body 2 by welding between the outer peripheral surface of the offset portion 7b.

  Further, as shown in FIG. 6, a screw 7c is provided on the outer peripheral surface of the rear end portion 7b of the main body 2, and the inner peripheral surface of the vertical cylindrical portion 62 in the ring 61 having an L-shaped cross section as shown in the figure. A female screw is provided on the main body 2 and screwed into the screw 7 c of the main body 2, so that the sleeve 25 is pressed by pressing the O-ring packing 30 through the flat ring portion 63 protruding inside the upper end of the vertical cylindrical portion 62. You may make it compress to the front end side.

  Moreover, in the said form, although the convex part in the ceramic sleeve 25 was made into the annular flange, it is not limited to such a thing. Furthermore, in the said form, although the convex part in the ceramic sleeve 25 was provided in the front-end | tip, this position is good also as a back end position rather than the front-end | tip 26 of the same sleeve 25, for example, as shown in FIG. In FIG. 7, the sealing material is arranged so as to compress the sealing material 21 also at the tip surface 28 a of the convex portion 28.

  In FIG. 7, the sealing material 21 is also compressed at the front end surface 28a of the flange (convex portion) 28. However, such a convex portion may not be responsible for compression of the sealing material. FIG. 8 shows an example thereof, in which the inner diameter of the portion 8b near the tapered surface 6 of the enlarged diameter cylindrical inner peripheral surface 8 is reduced and the outer diameter of the sealing material 21 is reduced. In the structure shown in FIG. 8, the seal material 21 is compressed only by the sleeve tip 26 except for the flange (convex portion) 28 near the tip of the sleeve 25. Although understood also from this, the position in the axis line G direction of the convex part 28 may be any from a viewpoint of reduction of the usage-amount of a sealing material. However, the rear end portion of the main body is located rearward as the rear end side is set. The same applies to the case where the convex portion 28 is thick in the direction of the axis G.

  Further, in each of the above-described embodiments, the structure in which the tip 26 of the sleeve 25 directly compresses the sealing material 21 is exemplified. However, as shown in FIG. 9, in FIG. You may make it compress by interposing the annular plate member 71 which consists of mica, SUS430, etc. of fixed thickness between the rear ends (rear end surface) 22 of the material 21. When such an annular plate member 71 is interposed, the following effects are obtained. This is because when the gap between the inner peripheral surface of the sleeve 25 and the outer peripheral surface 15c of the detection element 15 is set small, the detection element 15 is positioned relative to the axis of the metal fitting body 2 when the sleeve 25 is placed (set). If there is an eccentric arrangement, the element 15 may be damaged due to excessive stress applied to the element 15. In order to prevent such damage, it is necessary to provide a certain gap between the outer peripheral surface of the element 15 and the inner peripheral surface of the sleeve 25. On the other hand, as the gap becomes larger, there is a risk of causing problems such as protrusion or leakage of the sealing material 21 from the gap. However, as shown in FIG. 9, when an annular plate member 71 is interposed between the front end 26 of the sleeve 25 and the rear end 22 of the sealing material 21, the inner peripheral surface of the annular plate member 71 Generation | occurrence | production of such a malfunction can be prevented by making the clearance gap with the outer peripheral surface of the element 15 small. In other words, even when the annular plate member 71 is interposed as shown in FIG. 9, the gap between the outer peripheral surface of the element 15 and the inner peripheral surface of the sleeve 25 must be increased. There is an effect that it is possible to prevent the sealing material from sticking out from the surface.

  Further, in the above embodiment, the ceramic sleeve is configured to project the portion near the rear end of the terminal member from the rear end thereof so as to surround the outer peripheral surface of the terminal member. It is not limited to anything. That is, the length of the sleeve may be set appropriately, and the terminal member only needs to be connected to the terminal of the cord for connection to the terminal member. Therefore, the terminal member does not necessarily protrude from the rear end of the ceramic sleeve. You don't need to be.

  Moreover, about the ceramic sleeve, although the outer peripheral surface was materialized as the thing of the same diameter (straight) except a convex part, the taper may be attached. In particular, when a taper with a narrow gentle slope toward the rear end (the upper end in the figure) is formed, when the rubber cap of the terminal fitting of the cord is fitted, the taper is fitted, so that stable fixing can be obtained.

  Further, the terminal member is formed by rounding a thin metal plate and forming a cylindrical shape having an end in the circumferential direction, but it may be formed by an endless tube material in the circumferential direction. The ceramic sleeve in the present invention is not limited to alumina as long as it is an insulating ceramic. Further, the sealing material is not limited to talc or hexagonal boron nitride powder.

The half section front view showing the embodiment of the gas sensor of the present invention. The A section (main part) enlarged view of FIG. The cross-sectional front view which shows the work-in-process item (before the assembly of a terminal member) of the gas sensor of FIG. The half cross-sectional front view of the state which attached the gas sensor of FIG. 1 to the exhaust pipe, and connected the terminal metal fitting of a cord with a rubber cap to the terminal member. The principal part expanded sectional view which shows another example of the sleeve press fixing means in the gas sensor of this invention. The principal part expanded sectional view which shows another example of the sleeve press fixing means in the gas sensor of this invention. The principal part expanded sectional view which shows another example of the convex part in a ceramic sleeve. The principal part expanded sectional view which shows another example of the convex part in a ceramic sleeve. In FIG. 2, the principal part expanded sectional view which interposed the annular plate member between the front-end | tip of a ceramic sleeve, and a sealing material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas sensor 2 Metal fitting body 2b Metal fitting main body rear end 7b Rear metal fitting main body rear end part 15 Detection element 15b Detection element rear end 21 Sealing material 25 Ceramic sleeve 26 Ceramic sleeve front end 27 Ceramic sleeve rear end 28 Ceramic sleeve flange (convex)
31 Terminal member H Exhaust pipe

Claims (7)

A sensing element having a cylindrical shape with its tip closed and an electrode layer on the inner and outer peripheral surfaces is positioned in a metal fitting body formed so as to surround the outer peripheral surface, and the electrode layer on the outer peripheral surface is positioned on the metal fitting body. Electrically connect to
A gas sensor formed by inserting a terminal member into the opening at the rear end of the detection element from the front end side and electrically connecting to the electrode layer on the inner peripheral surface,
Placing a sealing material in the annular space between the inner peripheral surface of the metal fitting body and the outer peripheral surface of the detection element;
A cylindrical ceramic sleeve having a convex portion on the outer peripheral surface is positioned rearward of the rear end of the metal fitting body and the detection element, and the sealing material is moved to the front end side by the end of the sleeve. Place it compressible,
At a portion near the rear end of the metal fitting body, the seal material is compressed by sleeve pressing fixing means for fixing the sleeve in a state where the sleeve is pressed to the front end side through the convex portion of the ceramic sleeve. In a configuration that holds a seal between the detection elements,
The sealing material is disposed only on the front end side from the rear end of the metal fitting main body and the detection element, and the ceramic sleeve is coaxial with the detection element and the sleeve front end from the rear end of the detection element. The gas sensor is also configured to be positioned on the distal end side and compress the sealing material to the distal end side.   The gas sensor according to claim 1, wherein the convex portion is provided at a tip of the ceramic sleeve or a portion near the tip.   3. The gas sensor according to claim 1, wherein the ceramic sleeve surrounds an outer peripheral surface of the terminal member.   4. The sleeve pressing and fixing means is formed by covering the rear portion of the convex portion of the sleeve with the periphery of the portion close to the rear end of the metal fitting body by caulking inwardly. The gas sensor according to any one of the above.   5. The gas sensor according to claim 4, wherein the ceramic sleeve has a sleeve rear end positioned behind the metal fitting main body and the rear end of the detection element, and the sleeve tip is used to move the seal material to the tip side. After the ceramic sleeve is pressed in a compressible manner, the ceramic sleeve is pressed to the distal end side and the sealing material is compressed to the distal end side by the sleeve distal end, and the metal fitting main body is disposed at the rear portion of the convex portion of the sleeve. A method of manufacturing a gas sensor, wherein the peripheral edge of the portion near the rear end is crimped and covered inside.   5. The gas sensor according to claim 4, wherein the ceramic sleeve has a sleeve rear end positioned behind the metal fitting main body and the rear end of the detection element, and the sleeve tip is used to move the seal material to the tip side. After being arranged to be compressible, the ceramic sleeve is pressed to the distal end side, and the seal material is compressed to the distal end side by the sleeve distal end. A method of manufacturing a gas sensor, wherein the peripheral edge of the portion near the rear end is crimped and covered inside.   7. The sleeve according to claim 5, wherein the terminal member is inserted into the sleeve from its distal end side after the rear edge of the convex portion of the sleeve is covered with the periphery of the portion close to the rear end of the metal fitting body. A method for manufacturing a gas sensor, wherein the gas sensor is inserted, inserted into an opening at a rear end of the detection element, and electrically connected to the electrode layer on the inner peripheral surface.

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