JP2007224877A - Installation structure of exhaust sensor to exhaust pipe of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an exhaust sensor sensing part from getting wet by the splash of condensed water adhered to an exhaust pipe, and to start an engine normally even immediately after the formation of the condensed water. <P>SOLUTION: In the installation structure of the exhaust sensor to the exhaust pipe 11 of the internal combustion engine, an exhaust-emission control device 12 is provided in the exhaust pipe 11 of the internal combustion engine in order to remove a toxic substance in exhaust emission. The downstream part 11a of the exhaust-emission control device 12 in the exhaust pipe 11 is formed in a downstream tapered part 11b. The exhaust sensor 18 for sensing components in the exhaust emission is installed in the downstream of the exhaust-emission control device 12. In the exhaust pipe 11, a condensed water splash passage guide means 30 is provided so that the splash passage of the condensed water on the upstream side including the tapered part 11b of the exhaust pipe 11 is changed from an exhaust passing region W passing a component cover 47 covering the sensing part 45 of the exhaust sensor 18, and the passage is guided to a condensed water passing region Z. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust sensor mounting structure on an exhaust pipe of an engine (internal combustion engine), and is particularly suitable for an exhaust sensor mounting structure on an exhaust pipe in an exhaust purification system of a diesel engine.

  In recent years, exhaust regulations for vehicles equipped with diesel engines have become increasingly severe year by year to protect the global environment. As a countermeasure, oxygen concentration in the exhaust gas is detected, and the information is fed back to the engine control to compensate for variations in the fuel injection amount and EGR amount, thereby reducing fine carbon such as nitrogen oxides and soot in the exhaust gas. I am letting. As a sensor for detecting the oxygen concentration in exhaust gas, a zirconia solid electrolyte type exhaust oxygen concentration sensor using oxygen ion pumping is applied. This zirconia solid electrolyte type exhaust oxygen concentration sensor needs to be heated to about 650 ° C. or more in order to obtain a highly accurate sensor output because a zirconia solid electrolyte is used for the detection part. Usually, heating is performed by an electric heater built in the detection unit of the sensor.

  In addition, since this type of sensor for detecting the exhaust oxygen concentration is mounted in the exhaust pipe of an internal combustion engine, it has the following problems and hinders its application. That is, when the engine is started in a cold state, the exhaust pipe wall surface temperature is low, so the water vapor in the exhaust gas touches the exhaust pipe wall surface and condenses, and the condensed water adheres to the inner wall of the exhaust pipe. There is a problem that the zirconia solid electrolyte constituting the sensor detection unit is broken due to the excessive flow of heat stress generated on the sensor detection unit while the electric heater is in operation. If the sensor detection unit is damaged, not only the accuracy of the sensor output is deteriorated but also a normal output cannot be obtained, and there are problems such as malfunction of the exhaust purification system. In order to avoid this problem, the sensor was activated only after a long time since the engine was started because the electric heater built in the sensor was energized after the condensed water generated in the exhaust system after the engine started evaporating. I couldn't let you.

On the other hand, the structure for reducing the water exposure to the sensor detection part of the condensed water inside the exhaust pipe is formed in the following Patent Document 1 by forming a part of the exhaust pipe of the internal combustion engine lower than the upstream side and lowering it. A sensor is mounted at a position higher than the floor of the exhaust pipe, a storage section is provided at a position lower than the floor of the exhaust pipe, and the storage section and the exhaust pipe communicate with each other at two locations upstream and downstream of the sensor mounting position. The mounting structure is described. However, with this structure, when the engine is stopped, the condensed water generated inside the exhaust pipe can be stored in the storage section. However, it takes a long time to store all the condensed water in the storage section, and it still remains inside the exhaust pipe. When the engine is started while the condensed water remains attached, there is a problem that the remaining condensed water is scattered and the sensor detection unit gets wet. Further, in Patent Document 2 below, an extended portion having a large cross-sectional area is provided in a part of the exhaust pipe, and the floor portion of the expanded portion is located at a predetermined distance from the upstream end of the expanded portion to the downstream side. A sensor mounting structure in which the sensor is mounted at a higher position is described. However, this structure is a technology that reduces the exhaust flow velocity at the expansion part and shortens the condensate scattering reach distance, but although the exhaust flow rate around the wall surface of the exhaust pipe can be reduced by the expansion part, There is a problem in that the flow rate of the exhaust gas flowing through the central portion of the pipe hardly decreases, and condensed water is sucked into the exhaust gas flowing through the central portion where the flow rate is fast, so that the sensor detection unit gets wet.
JP 2004-124783 A JP 2005-127214 A

  As described above, in the prior art, the technology for preventing the sensor detection unit from being wetted by the condensate scattered on the exhaust pipe wall takes a long time to store the condensate, and a part of the condensate It only shortens the splashing distance and cannot reliably prevent the sensor detection unit from getting wet due to the splashing of the condensed water, and the engine starts normally with the condensed water adhering to the exhaust pipe wall. I can't do it. Therefore, the inventor forcibly changes the path through which the condensed water adhering to the exhaust pipe wall scatters due to the exhaust flow so that it does not pass through the exhaust intake hole of the element cover that covers the sensor detection unit. We focused on passing around the wall of the tube.

  The present invention has been made in view of the above-described points. Condensed water scattering path guidance for changing the path of condensed water scattered by the flow of exhaust gas from an area passing through the outer periphery of the element cover covering the sensor detection unit. By disposing the member in the exhaust pipe, it is possible to reliably prevent the condensate from getting wet with the detection part of the sensor, and the engine can be started normally even when the condensed water adheres to the exhaust pipe wall. An object of the present invention is to provide an exhaust sensor mounting structure for an exhaust pipe of an internal combustion engine.

  In the invention according to claim 1, an exhaust gas purification device for removing harmful substances in the exhaust gas is mounted in the exhaust pipe of the internal combustion engine, and the downstream portion of the exhaust gas purification device in the exhaust pipe is a downstream tapered portion. In the exhaust sensor mounting structure to the exhaust pipe of the internal combustion engine, the exhaust sensor being mounted on the downstream side of the exhaust purification device and detecting a component in the exhaust, the exhaust pipe Condensed water scattering path that condenses condensation on the upstream side including the tapered portion is changed from the exhaust passage area that passes through the outer periphery of the element cover that covers the detection section of the exhaust sensor, and leads to the condensed water passage area. Guiding means are provided.

  According to the above configuration, the condensate scattering path is condensed in this proposal compared to the conventional condensate dripping and storage caused by natural physics and the condensate splash rate being reduced by reducing the condensate splash rate. Because the water scattering path guiding means forcibly covers the exhaust sensor detection area, the exhaust passage area passing through the outer periphery of the element cover is surely changed and guided to the condensed water passage area. The condensate water can be prevented from entering, and the condensate water can be reliably prevented from entering the detection part of the exhaust sensor. Therefore, the engine can be normally started even immediately after the condensed water has condensed.

  In the invention according to claim 2, the condensate scattering path guiding means is constituted by a cylindrical guiding member arranged along the exhaust pipe, and the element that covers the detection part of the exhaust sensor in the exhaust passage region A cover is disposed, and the upstream end portion of the guide member is located at a crossing position between a surface forming an inner side of 30 ° from the tapered portion end portion of the exhaust pipe and the inner wall surface of the guide member. An exhaust intake hole of the element cover is located on the upstream side, and the downstream end of the guide member has a virtual plane that forms 30 ° in the downstream direction inside the exhaust pipe with the downstream end on the downstream side of the outer wall of the guide member as a base point. It arrange | positions so that it may be located in the upstream.

  According to the above configuration, since the condensate scattering path guiding means is a cylindrical guiding member, the gap between the exhaust pipe and the exhaust pipe is constant over the entire circumference. Can be good. Further, the total length of the guide member is the shortest length, and the manufacturing cost can be minimized.

  In the invention which concerns on Claim 3, the upstream edge part of the said guide member is located upstream from the taper-shaped part edge part of an exhaust pipe.

  According to the above configuration, the condensate scattering path that condenses and adheres to the tapered portion of the exhaust pipe is reliably changed from the exhaust passage area that passes the outer periphery of the element cover that covers the detection part of the exhaust sensor, and the condensed water passage area Can lead to.

  In the invention which concerns on Claim 4, the downstream edge part of the said guide cylinder is located downstream from the attachment position of the said exhaust sensor.

  According to the above configuration, the changed state of the condensed water passing area that is changed and scattered from the exhaust passing area passing through the outer periphery of the element cover that covers the detection part of the exhaust sensor is changed to the downstream area beyond the mounting position of the exhaust sensor. Since it is held, the intrusion of condensed water from the exhaust intake hole of the element cover can be more reliably prevented, and the condensate can prevent water from entering the detection part of the exhaust sensor.

  In the invention which concerns on Claim 5, the condensed water scattering path | route guide part which opens outside toward the upstream corresponding to the shape of an exhaust pipe is formed in the upstream edge part of a guide member.

  According to the above configuration, the condensed water splashing path guide part further passes through the outer periphery of the element cover that covers the detection part of the exhaust sensor more reliably on the condensed water scattering path that has condensed and adhered to the tapered shape part of the exhaust pipe. It can change from a passage area and can be led to a condensed water passage area.

  In the invention which concerns on Claim 6, the chamfering part is formed in the outer peripheral part of the upstream edge part of a guide member.

  According to the above configuration, by forming the chamfered portion, the exhaust flow resistance can be reduced, and the exhaust passage that passes through the outer periphery of the element cover that covers the detection portion of the exhaust sensor more reliably through the condensate scattering path. It can be changed from the area and led to the condensed water passage area.

  In the invention according to claim 7, the exhaust sensor is an oxygen concentration sensor having a built-in electric heater and having a zirconia solid electrolyte type sensing element.

  According to the above configuration, in particular, in the case of an oxygen concentration sensor used at a high temperature of 650 ° C. or higher, it is possible to prevent breakage such as thermal stress due to exposure to condensed water, and thus provide an exhaust purification system with good performance.

  In the invention according to claim 8, the exhaust sensor mounting structure to the exhaust pipe of the internal combustion engine is applied to the exhaust sensor mounting structure to the exhaust pipe of the internal combustion engine in the exhaust purification system of the diesel engine.

  According to the above configuration, since the exhaust sensor mounting structure to the exhaust pipe that can reliably prevent the condensate from being exposed to the exhaust sensor detection unit is mounted, a high-quality diesel engine exhaust purification system is provided. Can do.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 8 is an overall schematic configuration diagram of a diesel engine provided with an exhaust sensor mounting structure according to the present invention. The diesel engine 1 is a four-cylinder engine, and includes a common rail 2 common to each cylinder, and four injectors 3 that are connected to the common rail 2 and inject fuel into the combustion chamber of each cylinder. An intake manifold 4 of the engine 1 is connected to an intake pipe 5, and an intake air flow rate is adjusted by an intake throttle valve 6 provided at the connection portion. The intake air flowing through the intake pipe 5 is filtered by an air cleaner 7 and detected by an air flow meter 8.

  Exhaust gas from the engine 1 is discharged through an exhaust passage 9. The exhaust passage 9 includes an exhaust manifold 10 and an exhaust pipe 11 from the upstream side, and a particulate filter (DPF) 12 as an exhaust purification device is mounted in the middle of the exhaust pipe 11. The DPF 12 has a known configuration and is molded by heat-resistant porous ceramics such as silicon carbide and cordierite so that the exhaust outlets are alternately closed. The exhaust gas enters the DPF 12 from a cell having an opening at the inlet, and particulates (PM) are collected when passing through the porous partition wall. The inner surface of the DPF 12 that is in contact with the exhaust gas may have a structure that supports a catalyst that promotes the oxidation of PM, and stable PM can be burned and removed in a low temperature range of the DPF 12.

  The exhaust pipe 11 is provided with a turbine 14 of a turbocharger 13 on the upstream side of the DPF 12 and is connected to a compressor 15 provided in the intake pipe 5 via a turbine shaft. Thus, the compressor 15 is rotated using the kinetic energy of the exhaust, and the intake air introduced into the intake pipe 5 is compressed in the compressor 15. An intercooler 17 is provided in the intake pipe 5 upstream from the intake throttle valve 6, and the intake air that has been compressed by the compressor 15 to a high temperature is cooled here. In addition, a zirconia solid electrolyte type oxygen concentration sensor 18 for detecting the concentration of oxygen in the exhaust gas is attached to the exhaust pipe 11 on the downstream side of the DPF 12. The structure and operation of the oxygen concentration sensor 18 will be described later.

  The exhaust manifold 10 is connected to the intake manifold 4 by an EGR passage 19 so that a part of the exhaust is returned to the intake air through the EGR passage 19. An EGR valve 20 is provided at an outlet portion of the EGR passage 19 to the intake manifold 4, and the amount of exhaust gas recirculated to the intake air can be adjusted by adjusting the opening degree thereof. An EGR cooler 21 for cooling the refluxed EGR gas is provided in the middle of the EGR passage 19. An intake pressure sensor 22 detects the pressure of intake air in the intake manifold 4.

  The ECU 23 includes output signals from the air flow meter 8, the intake pressure sensor 22, the oxygen concentration sensor 18, the opening degree of the EGR valve 20, the engine speed, the vehicle speed, the coolant temperature, the accelerator opening degree, the crank position, the fuel pressure, and the like. Output signals from various sensors for detecting the engine are input, and the state (operating state) of each part of the engine 1 is known. The ECU 23 calculates the optimum fuel injection amount and EGR amount according to the operating state based on the operating state of the engine 1 known from the output signals of these various sensors, and the intake throttle valve 6, the injector 3, and the EGR valve 20 The turbocharger 13 and the like are feedback-controlled. The exhaust sensor mounting structure of the present invention relates to a structure in the exhaust pipe 11 ranging from the exhaust purification device 12 to the downstream exhaust sensor 18.

  Next, the structure and operation of the exhaust sensor 18 according to the present invention will be described with reference to FIGS. 9 is a longitudinal sectional view of the exhaust sensor 18, and FIG. 10 is an enlarged sectional view taken along line AA in FIG. The exhaust sensor 18 applied to the present invention is a known zirconia solid electrolyte type oxygen concentration sensor that is normally used. A detection element 43 having a zirconia solid electrolyte sheet 42 is housed in a metal cylindrical housing 40 while holding an outer periphery of an intermediate portion on an insulating member 41. An insulative sealing material 44 is filled in the recess at the center of the insulating member 41, and the exhaust in the exhaust pipe 11 and the atmosphere are blocked at this portion.

  The front end portion (lower end portion in the figure) of the detection element 43 serving as the oxygen detection portion 45 protrudes from the housing 40 and extends downward in the figure, and is housed in container-like element covers 46 and 47 fixed to the lower end of the housing 40. Has been. The element covers are doubled, and an outer cover 47 is disposed outside the inner cover 46. Each of the covers 46, 47 has a plurality of exhaust intake holes 46a, 47a for taking in the exhaust flowing in the exhaust pipe 11. It is formed. The exhaust intake holes 46a and 47a are arranged with their centers inconsistent so that the flow of exhaust does not directly hit the detection unit 45, and the position of the exhaust intake hole 47a of the outer cover 47 is the exhaust intake hole 46a of the inner cover 46. It is arranged on the tip side from the position (when attached to the exhaust pipe 11, the position is approximately 7/10 of the radius from the pipe wall).

  A rear end portion (upper end portion in the drawing) of the detection element 43 protrudes from the housing 40 and extends upward in the drawing, and is housed in a cylindrical atmospheric cover 48 fixed to the upper end of the housing 40. The upper half of the atmospheric cover 48 is formed in a double cylinder shape, and has atmospheric introduction ports 48a and 48b at positions opposed to the inner and outer cylinders 48c and 48d, and the atmospheric air for the reference electrode 42b from these atmospheric introduction ports 48a and 48b. Is taken into the atmosphere cover 48. A water-repellent filter 49 is disposed between the inner and outer cylinders 48c and 48d of the atmospheric cover 48 at the positions where the atmospheric introduction ports 48a and 48b are formed for waterproofing. Accordingly, moisture does not enter the sensor and only the atmosphere is introduced.

  A substantially ring-shaped insulating holding member 50 is disposed in the center of the atmospheric cover 48, and one end of the insulating holding member 50 has a lead portion 51 at the rear end of the detection element 43 and the other end has an external lead. Plate spring-like metal terminals 52 and 53 electrically connected to the wires 54 and 55 are provided. In addition, a communication port 50 a is formed in the upper part of the insulating holding member 50 to allow the air introduced from the air introduction ports 48 a and 48 b to communicate with the atmospheric passage 57 (FIG. 10) provided in the sensor element cell 43. ing.

  Since the external lead wires 54 and 55 and the metal terminals 52 and 53 are shown in cross-section in FIG. 9, only two external lead wires and two metal terminals are shown, but in reality, the external lead wires 54 and 55 are external in the vertical direction There are two lead wires and two metal terminals. That is, there are four external lead wires and four metal terminals. Then, the external lead wire 55 and the metal terminal 53 (in fact, one pair each) illustrated on the left side are electrically connected to a working electrode and a reference electrode, which will be described later, and the external lead wire 54 and the metal terminal illustrated on the right side. 52 (actually one pair exists) is electrically connected to a pair of lead wires of an electric heater described later.

  As shown in FIG. 10, the detection element 43 is provided with a plate-like zirconia solid electrolyte sheet 42, a working electrode 42 a that is exposed to exhaust gas on the outside thereof, and a reference electrode 42 b that is provided on the inner side. Thus, the lead 51 of the detection element 42 is electrically connected to the metal terminal 53 (the other metal terminal is not shown). The reference electrode 42b is exposed to an air passage 57 formed by an air introduction duct 56 into which air is introduced.

  Electrodes 42a and 42b are arranged on both sides of the zirconia solid electrolyte sheet 42 so as to face each other to form an electrochemical cell. The electrochemical cell constituting the sensing element 43 needs to have a sufficiently low internal resistance in order to obtain an accurate output, and therefore must be heated to 650 ° C. or higher. Therefore, an electric heater 58 for heating the detection unit 45 of the detection element 43 is provided and embedded in the insulating sheet 59. It should be noted that the cross section of the electric heater 58 is usually shown in four places, but this is because the electric heater 58 is bent and bent at the cut surface (AA line). In addition, as described above, the electric heater 58 is energized with a pair of external lead wires 54 (the other external lead wire is not shown) and a pair of metal terminals 52 (the other metal terminal is shown). Not through).

  In addition to the working electrode 42a, an exhaust transmission layer 60 and an exhaust shielding layer 61 are sequentially stacked on the surface exposed to the exhaust of the zirconia solid electrolyte sheet 42 constituting the detection element 43. The exhaust permeable layer 60 is a porous sheet for introducing exhaust into the working electrode 42a, and is formed by sheet-forming ceramics such as alumina, spinel, zirconia. The entire sensing element 43 is covered with a protective layer 62 of high specific surface area alumina to prevent the exhaust transmission layer 60 from being clogged by poisoning components in the exhaust.

  In the exhaust sensor 18, the element covers 46 and 47 and the detection portion 45 protrude into the exhaust pipe 11, and a screw portion 40 a formed at the lower end of the housing 40 is screwed and fixed to a female screw seat 11 c provided in the exhaust pipe 11. Is done. The exhaust sensor 18 prevents the looseness of the screwing between the screw portion 40a and the female screw seat 11c and the exhaust leakage by the gasket 63 due to vibration or the like.

  In the exhaust sensor 18 having the above-described configuration, exhaust gas enters from the exhaust intake hole 47a of the outer cover 47, passes through the exhaust intake hole 46a of the inner cover 46, and further passes through the exhaust transmission layer 60 in the detection element 43 to the zirconia solid electrolyte sheet 42. touch. When a predetermined voltage is applied between the reference electrode 42b exposed to the atmosphere in the atmosphere passage 57 and the working electrode 42a exposed to the exhaust, a limit current appears between the electrodes 42a and 42b according to the oxygen concentration in the exhaust. The limit current is output as an output current through the pair of external lead wires 55 (the other external lead wire is not shown), and is input to the ECU 23 (FIG. 8) as oxygen concentration information in the exhaust pipe 11. .

  Next, an embodiment of the present invention will be described based on FIG. 1, FIG. 2, FIG. 3, and FIG. FIG. 1 is a front sectional view of an exhaust sensor mounting structure to an exhaust pipe of an internal combustion engine according to the present invention, FIG. 2 is a sectional view taken along the line AA in FIG. 1, and FIG. 4 and 4 are enlarged views of a portion C in FIG. In the substantially cylindrical metal exhaust pipe 11, a DPF constituting an exhaust purification device 12 is mounted. The diameter of the exhaust pipe 11 at the position where the exhaust purification device 12 is mounted is larger than the other parts because the exhaust purification device 12 has a larger outer diameter in order to obtain an exhaust passage effective area. . Therefore, the downstream portion 11a of the exhaust gas purification device 12 in the exhaust pipe 11 is connected to the exhaust pipe 11 that continues downstream, so that a tapered forming portion 11b is formed in the downstream direction. A zirconia solid electrolyte type oxygen concentration sensor 18 is screwed and fixed as an exhaust sensor through a female screw seat 11c attached to the exhaust pipe 11 on the downstream side of the exhaust purification device 12 by welding. When the exhaust sensor 18 is fixed to the exhaust pipe 11, the exhaust intake hole 47 a of the outer element cover 47 is located at a radius of about 7/10 from the tube wall of the exhaust pipe 11.

  Further, high-temperature exhaust gas purified (removal of particulate carbon such as soot) by the exhaust gas purification device 12 flows in the exhaust pipe 11 in the downstream direction (right direction in FIG. 1). When the engine is stopped at a time when the outside air temperature is low, such as in winter, the water vapor in the exhaust gas staying in the exhaust pipe 11 touches the wall of the exhaust pipe 11 which has become low temperature due to the low temperature outside air and condenses. Phenomenon of condensation on the inner wall 11d occurs. Further, when the engine in the cold state is started, water vapor touches the low temperature exhaust pipe 11 to condense and adhere to the inner wall 11 d of the exhaust pipe 11. This condensed water is also condensed and attached to the tapered forming portion 11b of the exhaust pipe 11. And the condensed water which has condensed and adhered to the taper forming portion 11b is scattered along the wall surface of the taper forming portion 11b by the flow of high-speed exhaust gas, and is scattered to the exhaust pipe 11 in the downstream direction. In particular, in the region where the taper forming portion 11b is connected to the exhaust pipe 11b, the exhaust gas gradually flows from the direction along the taper forming portion 11b toward the center of the exhaust pipe 11, and the condensed water is broken along with the flow of the exhaust gas. Spatter as shown by the arrows. Therefore, at the position where the exhaust sensor 18 is attached, the condensed water passes through the central region of the exhaust pipe 11, and the detection unit 45 of the exhaust sensor 18 is likely to receive water from the condensed water entering from the exhaust intake hole 47 a of the element cover 47.

  Reference numeral 30 denotes a thin plate-shaped guide member having a circular cross-section, which is a heat-resistant and corrosion-resistant metal member and serves as a condensed water scattering path guiding means. The guide member 30 is arranged along the exhaust pipe 11 on the downstream side of the exhaust purification device 12 so that the axes thereof coincide with each other, and is fixed to the exhaust pipe 11 by fixing members 31 at three locations in the circumferential direction. Therefore, when viewed from the side, the exhaust pipe 11 and the guide member 30 are concentric circles as shown in FIG. 2, and the gap t between them is constant over the entire circumference. Note that the fixing member 31 is also formed of the same material as that of the guide member 30. Further, the guide member 30 may be held in the exhaust pipe 11 by filling the gap t between the two with a metal wool having air permeability. Furthermore, the material of the guide member 30 may be a metal mesh or a punching metal. Furthermore, although the exhaust purification device 12 is a DPF, it may be a catalytic converter.

  With respect to the positions of the upstream end 30a and the downstream end 30b of the guide member 30, the inventors have obtained the following results through experiments. As shown in FIG. 3, when the diameter of the guide member 30 is changed, the position of the end 30a where the condensed water does not enter the guide member 30 is plotted. It has been found that the plot surface X forms 30 ° with respect to the exhaust pipe inner wall 11f, and the extension reaches the end portion 11e of the tapered portion 11b of the exhaust pipe 11. That is, the position of the upstream end 30a of the guide member 30 is such that the end X of the tapered portion 11b of the exhaust pipe 11 and the surface X that forms 30 ° inward with respect to the exhaust pipe inner wall 11f and the guide member 30 It is a crossing position M with the inner wall 30b, and when the diameter of the guide member 30 is determined, it is necessary to be located upstream from the crossing position M. In this case, even when the inclination of the tapered portion 11b of the exhaust pipe 11 is large or small, the path through which the condensed water scatters from the tapered portion 11b of the exhaust pipe 11 to the exhaust pipe 11 has a high exhaust flow velocity. Therefore, it was confirmed by experimental observation that the condensate scattering path follows almost the same path.

  On the other hand, as to the position of the downstream end 30b of the guide member 30, as shown in FIG. 4, when the diameter of the guide member 30 is changed, the scattering path is changed by the guide member 30 and the condensation has passed through the guide member 30. When the boundary position of the downstream end 30b where water does not enter the exhaust intake hole 47a of the element cover 47 of the exhaust sensor 18 is plotted, the plot surface Y forms 30 ° with respect to the outer wall surface 30c of the guide member 30, It has been found that the extension reaches the position of the exhaust intake hole 47 a of the element cover 47. That is, the position of the downstream end portion 30b of the guide member 30 is 30 ° in the exhaust pipe inner downstream direction with respect to the extension line 30c of the outer wall surface with the outer wall downstream end portion 30b of the guide member 30 as a base point. It is necessary that the exhaust intake hole 47a of the element cover 47 is positioned on the exhaust upstream side with respect to the virtual plane Y. In addition, regarding the positions of the upstream end portion 30a and the downstream end portion 30b of the guide member 30, the plot pipe X formed in the inner side with respect to the exhaust pipe inner wall 11f and the extension line 30c of the outer wall surface on the exhaust pipe inner downstream side. As a result of further experiments regarding the angle of the virtual plane Y formed in the direction, it was confirmed that the effect was obtained when the angle formed by the plot plane X and the virtual plane Y was 30 °.

  In this way, by setting the positions of the upstream end 30a and the downstream end 30b of the guide member 30, the downstream end 11a of the exhaust purification device 12 in the exhaust pipe 11 is formed on the upstream end 30a side. The condensed water condensed on the tapered portion 11b is scattered downstream by the flow of exhaust as described above, but the exhaust passage region through which the condensed water scatters through the element cover 47 covering the detection unit 45 of the exhaust sensor 18. W (FIG. 1) is forcibly changed by the guide member 30, and the condensed water passes through the condensed water passage region Z (FIG. 1), that is, in the gap t between the exhaust pipe 11 and the guide member 30, as indicated by the solid arrow. It can be scattered and passed. The condensed water that has passed through the condensed water passage area Z and passed through the downstream end 30b of the guide member 30 is sucked into the exhaust passage area W that passes through the element cover 47 that covers the detection part 45 of the exhaust sensor 18, Since the position of the downstream end 30b of the guide member 30 is set as described above with respect to the position of the exhaust intake hole 47a of the element cover 47, condensed water does not enter from the exhaust intake hole 47a.

  Thus, compared to the conventional condensate water dripping and storage due to natural physics and the condensate splash rate being reduced, the condensate splash path is defined as a guide member. Since the exhaust passage region W passing through the outer periphery of the element cover 47 forcibly covering the detection unit 45 of the exhaust sensor 18 at 30 is completely changed to pass the condensed water passage region Z, the exhaust intake hole of the exhaust cover 47 is It is possible to prevent the condensed water from entering from 47a, and to reliably prevent the condensed water from entering the detection unit 45 of the exhaust sensor 18. In particular, in the case where the detection unit 45 of the exhaust sensor 18 is a zirconia solid electrolyte type oxygen concentration sensor that is used by being heated to 650 ° C. or more by a built-in electric heater, it is possible to prevent thermal stress damage due to condensate water exposure, A good exhaust purification system can be provided. Therefore, the engine can be normally started even immediately after the water vapor in the exhaust gas is condensed. Further, since the guide member 30 has a common center line with the exhaust pipe 11, the gap t between them is constant over the entire circumference, and the flow of condensed water can be made favorable over the entire circumference. . Furthermore, the guide member 30 described in the present embodiment has the shortest overall length in the shape that can achieve the invention effect, and can minimize the manufacturing cost.

  In addition, the width of the condensed water passage area Z, that is, the gap t between the exhaust pipe 11 and the guide member 30 requires a minimum of 0.5 mm through which condensed water can pass according to experiments. On the other hand, the upper limit of the gap t can be increased (the diameter of the guide member 30 is reduced) according to the setting procedure of the positions of the upstream end 30a and the downstream end 30b of the guide member 30 described above. That is, the diameter of the guide member 30 can be reduced and the gap t can be increased to a position where the exhaust intake hole 47a of the element cover 47 exists in the inner diameter region of the guide member 30 when viewed from the state shown in FIG.

  FIG. 5 shows another embodiment of the present invention, which is an example in which the upstream end 30a and the downstream end 30b of the guide member 30 are extended to the upstream side and the downstream side, respectively. The structure is the same as that shown in FIG. The upstream end 30a of the guide member 30 is extended upstream from the position of the downstream end 11e of the tapered portion 11b. On the other hand, the downstream end 30b extends to the downstream side beyond the attachment position of the exhaust sensor 18. In this case, a hole 30 c is formed at a position where the exhaust sensor 18 is attached to the guide member 30, and the detection unit 45 and the element cover 47 of the exhaust sensor 18 are disposed in the guide member 30 through the hole 30 c.

  In this way, the upstream end 30a of the guide member 30 extends upstream from the position of the downstream end 11e of the tapered portion 11b, and the downstream end 30b extends downstream from the position where the exhaust sensor 18 is attached. The condensate scattering path is changed from the exhaust passage region W passing through the outer periphery of the element cover 47 covering the detection unit 45 of the exhaust sensor 18 to the downstream region beyond the mounting position of the exhaust sensor 18. Since the state is maintained, the detection unit 45 of the exhaust sensor 18 of the condensed water can be prevented more reliably than the embodiment shown in FIGS. 1 and 2. In addition, since condensed water usually flows along the lower part of the exhaust pipe 11 (lower part of the drawing) and adheres, a slit in the longitudinal direction is formed over the entire length of the guide member 30 instead of the hole 30c. The detection unit 45 and the element cover 47 of the exhaust sensor 18 may be disposed in the guide member 30 through the same effect, and the same effect can be obtained. In addition, if the upstream end 30a of the guide member 30 is extended to the vicinity of the exhaust purification device 12 as indicated by a virtual line, the condensate scattering path can be completely changed from the exhaust passage region W. What is necessary is just to set suitably the extending | stretching length of the upstream edge part 30a of the guide member 30 according to an exhaust flow velocity etc. FIG.

  FIG. 6 shows still another embodiment of the present invention. The upstream end 30a of the guide member 30 is set at the position of the downstream end 11e of the tapered portion 11b, and the upstream end 30a This is an example in which the condensed water scattering path guide portion 30d that opens outward toward the upstream side is formed. The inclination of the guide portion 30d is the same as the inclination of the tapered portion 11b, that is, both are parallel and the material is the same as that of the guide member 30. Further, the guide portion 30d may be formed integrally with the guide member 30, or connected by welding after forming a separate body. Other parts and structures are the same as those shown in FIG.

  If comprised in this way, the flow of exhaust_gas | exhaustion will be rectified along the inclined surface of the guide part 30d, and the scattering of condensed water can be passed through the condensed water passage area | region Z. FIG. The extension length of the guide portion 30d may be set as appropriate according to the exhaust flow velocity or the like.

  FIG. 7 shows still another embodiment of the present invention, and is an enlarged cross-sectional view of the upstream end 30 a of the guide member 30. FIG. 7A shows an example in which a 45 ° chamfer 30e is formed on the outer peripheral portion of the upstream end 30a of the guide member 30 by cutting or pressing. FIG. 7B is an example in which an R-shaped chamfer 30 f is formed on the outer peripheral portion of the upstream end 30 a of the guide member 30 by cutting or pressing. FIG. 7C is an example in which an R-shaped chamfer 30 f is formed on the outer peripheral portion of the upstream end 30 a of the guide member 30 and an R-shaped protruding portion 30 g is formed on the inner peripheral portion. The R-shaped chamfer 30f and the R-shaped protruding portion 30g are simultaneously formed when the position of the end portion 30a of the guide member 30 is cut from the outer periphery with a parting roller.

  Since the chamfers 30e and 30f are formed on the outer periphery of the upstream end 30a of the guide member 30 in this way, the chamfers 30e and 30f can reduce the flow resistance of the exhaust gas, and the condensed water scattering path. Can be reliably guided to the condensed water passage region Z. Further, by forming the above-described R-shaped protruding portion 30g, it is possible to prevent the condensed water from entering the exhaust passage region W by the protruding portion 30g. The chamfers 30e and 30f may be formed on the outer periphery of the guide part 30d described with reference to FIG. The upstream end portion 30a of the guide member 30 includes the upstream end portion of the guide portion 30d.

  Note that, regarding the exhaust passage region W and the condensed water passage region Z described above, the exhaust passage region W means a region where the condensed water does not scatter and passes through the outer periphery of the element cover 47 that covers the detection unit 45 of the exhaust sensor 18. The condensed water passage area Z means a gap t between the guide member 30 and the exhaust pipe 11 through which condensed water and exhaust gas pass together. In the above embodiment, the exhaust sensor 18 is a zirconia solid electrolyte type oxygen concentration sensor. However, the exhaust sensor 18 is not limited to this, and is attached to the exhaust pipe 11 downstream of the tapered portion 11b of the exhaust purification device 12 downstream side 11a. The sensor may be a nitrogen oxide concentration sensor, a hydrocarbon concentration sensor, a carbon monoxide concentration sensor, or the like. In the above embodiment, the present example is applied to an exhaust gas purification system for a diesel engine, but may be applied to an exhaust gas purification system for a gasoline engine.

1 is a front sectional view of an exhaust sensor mounting structure for an exhaust pipe of an internal combustion engine showing an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. The B section enlarged view of FIG. It is the C section enlarged view of FIG. The front sectional view of the exhaust sensor attachment structure to the exhaust pipe of the internal combustion engine which shows other embodiments of the present invention. The front sectional view of the exhaust sensor attachment structure to the exhaust pipe of the internal combustion engine which shows further another embodiment of the present invention. (A), (b), (c) shows the embodiment of the upstream edge part of the guide tube in this invention, respectively, and is the D section enlarged view of FIG. 1 is an overall schematic configuration diagram of a diesel engine provided with an exhaust sensor mounting structure to an exhaust pipe of an internal combustion engine according to the present invention. The longitudinal section of the zirconia solid electrolyte type oxygen concentration sensor as an exhaust sensor in the present invention. FIG. 10 is a cross-sectional view taken along line AA in FIG. 9.

Explanation of symbols

1 engine (internal combustion engine)
DESCRIPTION OF SYMBOLS 11 Exhaust pipe 11a The downstream part of the exhaust gas purification apparatus 12 in the exhaust pipe 11 11b The taper-shaped part 11e of the exhaust pipe 11 11e End part of the taper-shaped part 11b 12 Exhaust gas purification apparatus 18 Oxygen concentration sensor as an exhaust sensor 30 Condensate scattering path separation means Inducting member 30a Upstream end 30b of guiding member 30 Downstream end 45 of guiding member 45 Detection unit 47 Element cover 47a Exhaust intake hole W Exhaust passage region Z Condensate passage region

Claims (8)

An exhaust purification device for removing harmful substances in exhaust gas is mounted in an exhaust pipe of an internal combustion engine, and a downstream portion of the exhaust purification device in the exhaust pipe is formed in a tapered shape in the downstream direction, and the exhaust purification device In the exhaust sensor mounting structure to the exhaust pipe of the internal combustion engine in which the exhaust sensor for detecting the component in the exhaust is mounted on the downstream side of the exhaust gas,
In the exhaust pipe, the condensed water splashing path condensed on the upstream side including the tapered portion of the exhaust pipe is changed from the exhaust passage area passing through the outer periphery of the element cover covering the detection part of the exhaust sensor, and the condensed water passes An exhaust sensor mounting structure for an exhaust pipe of an internal combustion engine, characterized in that a condensed water scattering path guiding means for leading to an area is provided.   The condensed water scattering path guiding means is a cylindrical guiding member disposed along the exhaust pipe, and an element cover that covers a detection part of the exhaust sensor is disposed in the exhaust passage region, and the guidance The upstream end portion of the cylinder is located upstream from the crossing position of the inner wall surface of the guide member and the surface that forms 30 ° inside the downstream exhaust pipe wall surface from the tapered shape end portion of the exhaust pipe, The downstream end of the guide member is arranged such that the exhaust intake hole of the element cover is located on the upstream side with respect to a virtual plane that forms 30 ° in the downstream direction inside the exhaust pipe with the downstream end on the downstream side of the guide member as a base point. 2. An exhaust sensor mounting structure for an exhaust pipe of an internal combustion engine according to claim 1, wherein the exhaust sensor is mounted on the exhaust pipe.   The exhaust sensor mounting structure for an exhaust pipe of an internal combustion engine according to claim 2, wherein the upstream end portion of the guide member is located upstream of the tapered portion end portion of the exhaust pipe.   The exhaust sensor mounting structure for an exhaust pipe of an internal combustion engine according to claim 2 or 3, wherein the downstream end portion of the guide member is positioned downstream of the exhaust sensor mounting position.   The exhaust sensor to the exhaust pipe of the internal combustion engine according to claim 3, wherein a condensate scattering path guide portion corresponding to the shape of the exhaust pipe and opening outward toward the upstream side is formed at an upstream end portion of the guide member. Mounting structure.   The exhaust sensor mounting structure for an exhaust pipe of an internal combustion engine according to any one of claims 2 to 5, wherein a chamfered portion is formed on an outer peripheral portion of an upstream end portion of the guide member.   The exhaust sensor mounting structure for an exhaust pipe of an internal combustion engine according to any one of claims 1 to 6, wherein the exhaust sensor is an oxygen concentration sensor including an electric heater and having a zirconia solid electrolyte type sensing element. The exhaust sensor attachment structure to the exhaust pipe of the internal combustion engine is applied to an exhaust sensor attachment structure to the exhaust pipe of the internal combustion engine in an exhaust purification system of a diesel engine. An exhaust sensor mounting structure for an exhaust pipe of an internal combustion engine.