JP5147079B2 - Sensor unit - Google Patents

Description

  The present invention relates to a sensor unit to which an oil cover that restricts the adhesion of oil to an exhaust pipe is attached.

  Conventionally, a gas sensor for detecting the concentration of a specific gas component contained in a gas to be measured such as exhaust gas is known. This gas sensor includes a detection element on the tip side and a metal housing that holds the detection element. Further, the gas sensor draws out a lead wire for taking out the output of the detection element and energizing a heater for heating the detection element from the rear end side of the housing. In this gas sensor, the front end side of the detection element protrudes into the exhaust pipe, and the flange formed on the housing is locked to the exhaust pipe so that the rear end side is positioned outside the flange. Installed.

  Further, in such a gas sensor mounting structure, since it is necessary to ensure airtightness between the lead wire on the rear end side of the housing and the housing, an elastic member is filled around the lead wire on the rear end side of the housing. Is done. Such an elastic member is made of a resin material such as silicon rubber or fluorine rubber.

  By the way, this elastic member is likely to deteriorate due to heat transfer from the exhaust pipe to the housing, and the elastic member is exposed to high heat. Therefore, as in Patent Document 1, a substantially shallow dish-shaped protective cover is sandwiched between the exhaust pipe and the housing, and heat transfer from the exhaust pipe to the elastic member is suppressed by this protective cover. The protective cover has an insertion hole through which the front end side of the gas sensor is inserted, a mounting seat portion sandwiched between the exhaust pipe and the housing, a cylinder connected to the outer periphery of the mounting seat portion and surrounding the flange portion of the housing And a flare portion that is connected to the rear end of the cylindrical portion and expands in diameter toward the rear end side. The flare portion is further away from the exhaust pipe and the gas sensor, so that the heat from the exhaust pipe is radiated by the protective cover.

JP 2006-207403 A

  By the way, when oil adheres to the outer surface of the exhaust pipe, the oil may ignite due to heat of the exhaust pipe. For example, an internal combustion engine in which a silencer is formed on the outer surface of an exhaust pipe is known. As this silencer, it consists of high silicate glass fibers, such as siri glass (made by Nippon Inorganic Co., Ltd.). In such an exhaust pipe provided with a sound deadening material on the outer surface, the oil adhering to the sound deadening material may start and ignite to radiate heat from the outer surface of the exhaust pipe. If this ignition occurs in the vicinity of the gas sensor, the heat transfer from the exhaust pipe to the elastic member further increases, and there is a possibility that deterioration of the elastic member cannot be suppressed. On the other hand, when the protective cover described in Patent Document 1 is sandwiched between the gas sensor and the exhaust pipe, oil adheres to the protective cover, and the oil adheres to the outer surface of the exhaust pipe near the gas sensor. And ignition in the vicinity of the gas sensor can be suppressed.

  However, in the protective cover described in Patent Document 1, for example, the oil attached to the flare portion flows toward the cylindrical portion, and the oil stays between the cylindrical portion and the mounting seat portion. Then, oil enters the exhaust pipe from the insertion hole formed in the mounting seat, and the oil and the gas to be measured are mixed in the exhaust pipe. As a result, there is a possibility that the concentration of the specific gas component contained in the gas to be measured cannot be accurately detected.

  The present invention has been made in view of such conventional problems, and the protective cover disposed between the housing and the exhaust pipe regulates the adhesion of oil to the vicinity of the gas sensor in the exhaust pipe, and the protective cover. It is an object of the present invention to provide a sensor unit that can accurately detect the concentration of a specific gas component contained in a gas to be measured without adhering oil entering the exhaust pipe.

Therefore, the present invention has a detection element and a flange that accommodates the detection element and protrudes radially outward, and the front end surface of the flange faces the outer surface of the exhaust pipe through which exhaust gas flows. An oil cover that is disposed between the front end surface of the flange and the outer surface of the exhaust pipe and regulates the adhesion of oil to the exhaust pipe. A sensor unit comprising:
The oil cover has a plate-like extension portion that extends to the outside in the radial direction from the flange portion and extends in the entire radial direction of the housing, and the extension portion has an annular convex portion that surrounds the housing. , Formed toward the rear end side of the extension part.

  As described above, the oil cover has a plate-like extension portion that extends to the outside in the radial direction from the flange portion and extends over the entire radial direction of the housing. Thereby, it is possible to suppress oil from adhering to the outer surface of the exhaust pipe in the vicinity of the gas sensor, and to suppress ignition in the vicinity of the gas sensor. As a result, further increase in heat transfer from the exhaust pipe to the elastic member can be suppressed, and deterioration of the elastic member can be suppressed.

In addition, since the extension portion has a plate shape extending in the entire radial direction of the housing, oil flows from the extension portion into a portion (hereinafter referred to as an inner portion) disposed between the housing and the exhaust pipe, There is no stagnation in the inner part, oil can be prevented from entering the exhaust pipe, and the concentration of the specific gas component contained in the gas to be measured can be accurately detected.
In addition, "plate shape" refers to being formed substantially parallel to the tip surface of the collar portion.

Furthermore, by forming an annular convex part at the extension part, even if an impact from outside such as stepping stones is applied to the extension part formed in a plate shape, the oil cover can be prevented from being deformed, and the vicinity of the gas sensor Oil adhesion to the outer surface of the exhaust pipe can be suppressed. In addition, if a recess is formed in the extended part toward the rear end side, when the gas sensor is attached to the exhaust pipe, the recess obstructs the gas sensor, but the gas sensor is not attached to the exhaust pipe at a predetermined position. By setting it as a part, it can suppress that a gas sensor is not attached to a predetermined position with respect to an exhaust pipe.

  Furthermore, in the sensor unit of the present invention, the oil cover has an inner portion disposed radially inward of the flange portion, and an annular step portion surrounding the housing is formed on the inner portion. It is preferable to protrude toward the rear end side of the part. Accordingly, it is possible to prevent the oil from entering inward in the radial direction from the stepped portion of the oil cover, and it is possible to suppress the oil from entering the exhaust pipe.

  Furthermore, in the sensor unit of the present invention, it is preferable that an angle formed between the rear end surface of the extended portion of the oil cover and the convex portion is an obtuse angle than an angle formed between the stepped portion and the rear end surface. If a convex part is formed in the extension part of the oil cover toward the rear end side, oil may stay between the step part and the convex part. At this time, the angle formed between the rear end surface of the extended portion and the convex portion is set to an obtuse angle than the angle formed between the step portion and the rear end surface, so that oil can easily get over the convex portion rather than the step portion. Therefore, when the gas sensor receives vibrations of the exhaust pipe or the like, the oil flows radially outward from the convex portion. As a result, the oil can be prevented from entering radially inward from the stepped portion of the oil cover, and the oil can be prevented from entering the exhaust pipe. Moreover, there is no fear that oil will adhere to the outer surface of the exhaust pipe around the gas sensor.

  Furthermore, in the sensor unit of the present invention, it is preferable that the height of the stepped portion is higher than the height of the convex portion. As a result, the oil is more likely to get over the convex portion than the step portion, and even if the oil stays on the rear end surface of the oil cover, the oil flows from the convex portion toward the radially outer side when staying higher than the convex portion. As a result, the oil can be prevented from entering the radially inner side from the stepped portion.

  According to the present invention, the protective cover disposed between the housing and the exhaust pipe regulates the oil adhesion to the exhaust pipe in the vicinity of the gas sensor, and the oil attached to the protective cover does not enter the exhaust pipe and is measured. It is possible to provide a sensor unit that can accurately detect the concentration of the specific gas component contained in the gas.

1 is a longitudinal sectional view showing the structure of a gas sensor 1. FIG. 2 is a longitudinal sectional view of an oil cover 100. FIG. 3 is a top view of the oil cover 100. FIG. It is explanatory drawing of the sensor unit after the attachment to an exhaust pipe.

  Hereinafter, an embodiment of a sensor unit 106 embodying the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the structure of the gas sensor 1 of the present embodiment. FIG. 2 is a longitudinal sectional view of the oil cover. FIG. 3 is a top view of the oil cover. FIG. 4 is an explanatory diagram when the sensor unit is attached to the exhaust pipe.

  The gas sensor 1 shown in FIG. 1 is used by being attached to an exhaust pipe 107 (see FIG. 4) for exhaust gas discharged from an engine of an internal combustion engine such as an automobile, and in the exhaust pipe in the direction of the axis O. The detection element 6 to be inserted will be described with the side toward the front end (closed side, lower side in the figure) as the front end side, and the side toward the opposite direction (upper side in the figure) as the rear end side. To do.

  The gas sensor 1 shown in FIG. 1 is a sensor for detecting the presence or absence of oxygen in the exhaust gas flowing through the exhaust pipe 107. The gas sensor 1 shown in FIG. It has the structure hold | maintained in the pipe | tube 3 and the protector 4. FIG. From the gas sensor 1, a lead wire 18 for taking out a signal output from the detection element 6 and energizing the heater 7 provided along with the detection element 6 is drawn out and separated from the gas sensor 1. It is electrically connected to a sensor control device (not shown) provided at the position or an electronic control device (ECU) of the automobile.

  The detection element 6 of the gas sensor 1 is formed by forming a solid electrolyte body 61 mainly composed of zirconia into a bottomed cylindrical shape extending in the axis O direction. On the inner surface of the solid electrolyte body 61, a reference electrode 62 made of Pt or a Pt alloy is formed in a porous shape so as to cover almost the entire surface thereof. Similarly to the reference electrode 62, the detection electrode 63 made of Pt or a Pt alloy is formed on the outer surface of the solid electrolyte body 61 in a porous shape. The front end side (closed side) of the detection element 6 is configured as a detection unit 64, and the detection electrode 63 on the outer surface is exposed to the exhaust gas flowing through the exhaust pipe 107. 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, a flange-like flange portion 65 protruding outward in the radial direction is provided at a substantially intermediate position in the axis O direction of the detection element 6. A rod-shaped heater 7 for heating and activating the solid electrolyte body 61 is inserted into the cylinder of the detection element 6.

  The detection element 6 is held in the cylindrical hole 55 of the metal shell 5 in a state where 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, and a male threaded portion 52 that is screwed into a mounting portion (not shown) of the exhaust pipe is formed on the distal end side. A distal end engaging portion 56 is formed on the outer periphery of the male screw portion 52 to engage a protector 4 described later on the outer periphery thereof. The detection portion 64 of the detection element 6 is protruded to the tip side from the tip engagement portion 56.

  A flange 53 having a diameter increased in the radial direction is formed on the rear end side of the male threaded portion 52 of the metal shell 5, and is an attachment tool used when attaching the gas sensor 1 to an attachment portion (not shown) of the exhaust pipe. Are engaged. An annular gasket 11 is inserted into a portion between the flange 53 and the male screw portion 52 to prevent gas escape through the attachment portion of the exhaust pipe. A caulking portion 57 for caulking and fixing the detection element 6 held in its cylindrical hole 55 is provided on the rear end side of the metal shell 5. The rear end portion 66 of the detection element 6 protrudes toward the rear end side from the caulking portion 57. A rear end engaging portion 58 is formed between the flange portion 53 and the caulking portion 57 on the outer periphery of the flange portion 53 and the caulking portion 57.

  Next, a step portion 59 is provided on the front end side in the cylindrical hole 55 of the metal shell 5 so that the inner periphery thereof protrudes radially inward, and the metal packing 12 is attached to the step portion 59. A cylindrical support member 13 made of alumina is engaged therewith. The inner periphery of the support member 13 is also formed in a step shape, and the flange portion 65 of the detection element 6 is supported by the support member 13 through a metal packing 14 disposed in the stepped portion. Further, the cylindrical hole 55 is filled with a filler member 15 made of talc powder on the rear end side of the support member 13, and the rear end side of the filler member 15 is sandwiched between the filler member 15 and the support member 13. A tubular sleeve 16 made of alumina is disposed on the surface.

  An annular ring 17 is disposed on the rear end side of the sleeve 16, and the sleeve 16 is connected to the filling member 15 via the ring 17 by caulking the caulking portion 57 of the metal shell 5 toward the inner distal end. It is pressed. When the filling member 15 is compressed and filled so as to press the flange portion 65 of the detection element 6 toward the support member 13 locked to the step portion 59 of the metal shell 5 through the crimping of the crimping portion 57. In addition, the gap between the inner peripheral surface of the cylindrical hole 55 of the metal shell 5 and the outer peripheral surface of the detection element 6 is filled in an airtight manner. As described above, the detection element 6 is held 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.

  Next, the protector 4 that covers the detection portion 64 of the detection element 6 protruding from the front end engagement portion 56 toward the front end side in the axis O direction is assembled to the front end engagement portion 56 of the metal shell 5 by welding. ing. The protector 4 protects the detection portion 64 of the detection element 6 that protrudes into the exhaust pipe when the gas sensor 1 is attached to the exhaust pipe (not shown) from collision of water droplets or foreign matters contained in the exhaust gas. It is. The protector 4 has a bottomed cylindrical shape and an outer protector 41 whose peripheral edge on the opened side is joined to the tip engaging portion 56, and a bottomed cylindrical inner protector 45 fixed inside the outer protector 41. It is comprised so that the double structure which consists of these may be made. On the outer peripheral surfaces of the outer protector 41 and the inner protector 45, there are respectively introduced inlets 42 for introducing exhaust gas into the interior and guiding them to the detection part 64 of the detection element 6 (the gas inlets of the inner protector 45 are Not shown). In addition, on the bottom surfaces of the outer protector 41 and the inner protector 45, discharge ports 43 and 48 for discharging water droplets and exhaust gas that have entered the inside are opened.

  Further, as described above, the rear end portion 66 of the detection element 6 protrudes rearward from the rear end (caulking portion 57) of the metal shell 5. A cylindrical separator 8 made of an insulating ceramic is disposed on the rear end side in the axis O direction from the rear end portion 66. The separator 8 has a pair of electrodes 71 exposed on the rear end side for energizing the reference electrode 62 and the detection electrode 63 of the detection element 6 and the heating resistor of the heater 7 (in FIG. In order to separate the four connection terminals 19 (three of which are shown in FIG. 1) that are electrically connected to one electrode 71 so as not to contact each other. And has a housing portion 82 in which each connection terminal 19 is independently housed. The accommodating portion 82 penetrates the separator 8 in the direction of the axis O, and is configured to be able to communicate with the atmosphere between the front end side and the rear end side with respect to the separator 8. The core wires of four lead wires 18 are caulked and joined to each connection terminal 19 (three lead wires 18 are shown in FIG. 1), and each lead wire 18 is a grommet described later. 9 is pulled out to the outside of the gas sensor 1. Further, a flange portion 81 protruding radially outward is provided on the outer peripheral surface of the separator 8, and a substantially cylindrical holding metal fitting 85 is fitted on the outer peripheral surface on the tip side of the flange portion 81. .

  Next, the front end portion 31 of the cylindrical outer cylinder 3 made of stainless steel such as SUS304 is engaged with the rear end engaging portion 58 of the metal shell 5. The front end portion 31 is crimped from the outer peripheral side, and is further laser-welded around the outer periphery and joined to the rear end engaging portion 58. The outer cylinder 3 extends toward the rear end side along the direction of the axis O, and radially surrounds the outer periphery of the rear end portion 66 of the detection element 6 and the separator 8 disposed on the rear end side of the detection element 6. Yes. The outer peripheral surface of the outer cylinder 3 corresponding to the arrangement position of the separator 8 is caulked in the radial direction, so that the holding metal fitting 85 holds the separator 8 inside itself, while inside the outer cylinder 3. It is held by crimping.

  A grommet 9 made of fluorine rubber is fitted in the opening 32 on the rear end side of the outer cylinder 3. As shown in FIG. 2, the grommet 9 is a plug member formed in a substantially cylindrical shape with the axis O direction as the height direction, and closes the rear end side of the outer cylinder 3. At the center in the radial direction, an atmospheric communication hole 91 that penetrates in the direction of the axis O is formed. Four lead wire insertion holes 92 that penetrate in the direction of the axis O also on the outer peripheral side of the atmospheric communication hole 91. Are formed at equal intervals in the circumferential direction. The grommet 9 corresponds to the “elastic member” in the present invention.

  Here, as shown in FIG. 1, the atmosphere communication hole 91 is provided to introduce the atmosphere into the outer cylinder 3 closed by the grommet 9. In the outer cylinder 3, the detection element 6 is held by the metal shell 5 in a form protruding from the rear end portion 66, but the reference electrode 62 formed in the cylinder of the detection element 6 is connected to the atmosphere communication hole 91 and It is configured to be exposed to the atmosphere via the accommodating portion 82 of the separator 8. The four lead wire insertion holes 92 electrically connect the detection electrode 63 of the detection element 6, the reference electrode 62 and the pair of electrodes 71 of the heater 7 to a sensor control device or ECU (not shown). The lead wires 18 are inserted independently of each other (FIG. 1 shows a state where two of the lead wires 18 are inserted into the lead wire insertion holes 92).

  On the other hand, as shown in FIG. 1, a filter member 87 and a fastener 88 are inserted into the air communication hole 91 of the grommet 9. The filter member 87 is a thin-film filter having a micron-sized network structure made of a fluororesin such as PTFE (polytetrafluoroethylene), and is configured to allow air to communicate without passing water droplets. is there. The clasp 88 is a member formed in a cylindrical shape, and the filter member 87 is sandwiched between the outer periphery of itself and the inner periphery of the air communication hole 91 and fixed to the grommet 9.

  As described above, the grommet 9 in which the filter member 87 and the fastener 88 are inserted into the air communication hole 91 and the lead wire 18 is inserted into the lead wire insertion hole 92 is in contact with the separator 8 from the rear end side. 3 is fitted in the opening 32. In this state, a portion slightly distal to the opening 32 of the outer cylinder 3 is crimped radially inward from the outer peripheral side, and the grommet 9 is fixed to the outer cylinder 3. The caulking portion 35 formed by caulking has a groove shape that makes one round in the circumferential direction while being recessed in the radial direction on the outer circumferential surface of the outer cylinder 3.

  Next, the oil cover 100 that is a main part of the present embodiment will be described. The oil cover 100 in the present embodiment is sandwiched between the distal end surface 53a of the flange portion 53 and the gasket 11. As shown in FIG. 2 or 3, the oil cover 100 has a circular thin plate shape made of stainless steel such as SUS304L, and has an insertion hole 108 for inserting the distal end side of the gas sensor 1 into the center. The inner portion 101 surrounding the periphery of the insertion hole 108 and the extending portion 102 that surrounds the inner portion 101 and extends radially outward are provided. The inner portion 101 is a portion facing the tip surface 53a of the flange portion 53 when the oil cover 100 is sandwiched between the tip surface 53a of the flange portion 53 and the gasket 11, and the extension portion 102 is This is a portion located radially outside the portion 53 (see FIG. 4). As described above, the oil cover 100 has the extended portion 102 that extends to the outside in the radial direction from the flange portion 53 and extends in the entire radial direction, so that the outer surface of the exhaust pipe 107 in the vicinity of the gas sensor 1 is provided. It is possible to suppress oil from adhering to the gas, and to suppress ignition near the gas sensor.

  Further, as shown in FIG. 2, since the extension part 102 has a plate shape, the oil does not flow into and stay in the inner part 101, and the oil is prevented from entering the exhaust pipe 107, so The concentration of the specific gas component contained in the measurement gas can be accurately detected.

  Further, as shown in FIG. 2, a hemispherical convex portion 103 is formed in an annular shape toward the rear end side in the extended portion 102. In this way, by forming the annular convex portion 103 in the extension portion 102, even when an impact is applied to the extension portion 102 from the outside, deformation of the oil cover 100 can be suppressed, and the vicinity of the gas sensor can be suppressed. Oil adhesion to the outer surface of the exhaust pipe can be suppressed. Furthermore, when the sensor unit is attached to the exhaust pipe, it is possible to prevent the gas sensor from being attached to a predetermined position with respect to the exhaust pipe. In the present embodiment, the metal shell 5 and the outer cylinder 3 correspond to a “housing” in the claims.

  Further, as shown in FIG. 2, the inner portion 101 is formed with an annular step 104 that protrudes toward the rear end side. This step portion 104 can prevent oil from entering inward in the radial direction and, as a result, prevent oil from entering the exhaust pipe 107.

  Further, as shown in FIG. 2, the angle θ1 formed between the rear end surface 105 of the oil cover 100 and the convex portion 103 is formed to be an obtuse angle than the angle θ2 formed between the rear end surface 105 of the oil cover 100 and the stepped portion 104. ing. Thereby, even if oil stays between the step part 104 and the convex part 103, it becomes easier for oil to get over the convex part 103 than the step part 104. Therefore, when the sensor unit 106 receives vibration of the exhaust pipe 107 or the like, the oil flows from the convex portion 103 toward the radially outer side. As a result, oil can be prevented from entering radially inward of the step 104 of the oil cover 100, and oil can be prevented from entering the exhaust pipe 107. The angles θ1 and θ2 indicate acute angles formed by two virtual lines drawn in the normal direction from the apexes of the convex portion 103, the stepped portion 104, and the rear end surface 105 of the oil cover 100, respectively.

  Further, as shown in FIG. 2, the height t <b> 1 of the stepped portion 104 is formed higher than the height t <b> 2 of the convex portion 103. As a result, even if the oil stays between the step 104 and the protrusion 103, if the oil stays higher than the height of the protrusion 103, the oil flows radially outward from the protrusion 103. As a result, oil can be prevented from entering radially inward of the step 104 of the oil cover 100, and oil can be prevented from entering the exhaust pipe 107. The heights t <b> 1 and t <b> 2 indicate the height from the rear end surface 105 of the oil cover 100 to the rear end of the stepped portion 104 and the height from the rear end surface 105 of the oil cover 100 to the convex portion 103.

  Next, the sensor unit 106 in which the oil cover 100 is attached to the gas sensor 1 will be described with reference to FIG. The sensor unit 106 is attached by fitting a sleeve wrench on the outside of the flange portion 53 and screwing the tip portion into the exhaust pipe 107 from the gasket 11. At this time, the oil cover 100 is sandwiched and fixed between the flange portion 53 and the gasket 11.

Needless to say, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the present embodiment, the convex portion 103 is formed so as to protrude toward the rear end surface of the extension portion 102, but is not limited thereto, and a concave portion is formed toward the rear end side (that is, on the front end side). A convex portion protruding toward the top).
Moreover, in this embodiment, although the convex part 103 had hemispherical shape, it is not restricted to this, You may form in cone shape.
Moreover, in this embodiment, although the convex part 103 was formed in the annular | circular shape, it is not restricted to this, You may form in the cyclic | annular form connected to the circumferential direction, and it is formed in the cyclic | annular form where one part interrupted. May be.
Moreover, in this embodiment, although the convex part 103 was formed in one annular shape over the circumferential direction, it is not restricted to this, You may be formed in the some annular shape.

DESCRIPTION OF SYMBOLS 1 Gas sensor 9 Elastic member 11 Gasket 53 Grow part 100 Oil cover 101 Inner part 102 Extension part 103 Projection part 104 Step part 106 Sensor unit 107 Exhaust pipe

Claims (4)

The exhaust pipe has a detection element and a flange that accommodates the detection element and protrudes radially outward, and the front end surface of the flange faces the outer surface of the exhaust pipe through which exhaust gas flows. A housing having a housing attached thereto, and
An oil cover that is disposed between the tip surface of the flange and the outer surface of the exhaust pipe and regulates the adhesion of oil to the exhaust pipe,
The oil cover has a plate-like extension portion that extends to the outside in the radial direction from the flange portion and extends in the entire radial direction of the housing, and the extension portion has an annular convex portion that surrounds the housing. The sensor unit is formed toward the rear end side of the extension part.   The oil cover has an inner portion disposed radially inward of the flange portion, and an annular stepped portion surrounding the housing projects toward the rear end side of the inner portion in the inner portion. The sensor unit according to claim 1. 2. The sensor unit according to claim 1 , wherein an angle formed between a rear end surface of the extended portion of the oil cover and the convex portion is larger than an angle formed between the stepped portion and the rear end surface. Height of the stepped portion, the sensor unit according to any one of claims 1 to 3, characterized in that greater than the height of the convex portion.