JP2008267192A - Exhaust passage structure for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust passage structure for an internal combustion engine, which smoothly controls an internal combustion engine, based on information from an oxygen concentration sensor, and prevents deterioration in detection accuracy or failure of the oxygen concentration sensor caused by deposition of condensate water. <P>SOLUTION: The oxygen concentration sensor 4 is interposed between catalysts 21, 22 of a tandem type exhaust cleaning catalyst disposed in the middle of an exhaust passage 1, and a sensor element part 41 is positioned above the center Q of an approximately center part in an exhaust flow direction of the casing 30. An approximately cylindrical guide 31 for guiding an exhaust flow to the sensor element part 41 is disposed immediately downstream of an upstream catalyst 21, a bore diameter of a downstream end opening 312a of the guide 31 is formed to be a diameter smaller than a diameter of an upstream end opening 311a. The center P of the downstream end opening 312a of the guide 31 is deviated to be closer to the sensor element part 41 than the center Q of the casing 30, and a plurality of exhaust ports 33, 33 are formed in a lower position of the guide 31. The exhaust ports 33, 33 discharge the condensate water in the exhaust condensed in contact with the guide 31, on the upstream from the downstream end opening 312a to the outside of the guide 31. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust passage structure of an internal combustion engine provided with a sensor for detecting a component in exhaust gas in the exhaust passage.

  Conventionally, a technique in which two catalysts are provided in series in an exhaust passage of an internal combustion engine is known. Specifically, in such a technique, a front catalyst (upstream catalyst) is disposed upstream of the exhaust passage, and an underfloor catalyst (downstream catalyst) is disposed downstream of the front catalyst. By arranging the catalysts in series in this way, the front catalyst can be activated early, and the catalyst can have a sufficient capacity.

  Further, for example, in Patent Document 1, two catalysts are provided in series and integrally (hereinafter, such a catalyst is referred to as a tandem catalyst), and components in exhaust gas are respectively provided in an upstream portion and a downstream portion of the tandem catalyst. There is disclosed a technique in which a sensor for detecting the engine is provided and the internal combustion engine is controlled based on information from these sensors.

  However, in such a tandem catalyst, when an internal combustion engine is controlled using an upstream sensor and a downstream sensor, a delay in information between the upstream sensor and the downstream sensor may increase. If the information delay between the two sensors is too large, the internal combustion engine may not be controlled smoothly.

Therefore, there is a type in which a single sensor is provided between two catalysts in a tandem catalyst, and the internal combustion engine is controlled based on information from the sensor.
JP 2000-120431 A

  By the way, even if a sensor is provided between the two catalysts in the tandem catalyst as described above, the exhaust from the upstream catalyst may be smoothly discharged to the sensor element portion of the sensor depending on the mounting position of the sensor. There are times when it cannot be guided. For this reason, the exhaust gas component cannot be accurately detected by the sensor, and it is difficult to smoothly control the internal combustion engine based on information from the sensor.

  In that case, it is conceivable to provide a guide for guiding the flow of exhaust gas from the upstream catalyst to the sensor element portion of the sensor, immediately downstream of the upstream catalyst. However, if the exhaust from the upstream catalyst is blown onto the cold guide when the internal combustion engine is cold started, condensation occurs when the exhaust comes into contact with the guide, and condensed water is produced. Is attached to the sensor element portion of the sensor, and thermal stress due to boiling (expansion) of the condensed water acts on the sensor element portion, causing a decrease in detection accuracy of the sensor and a failure.

  The present invention has been made in view of the above points, and an object of the present invention is to smoothly control an internal combustion engine based on information from the sensor and to detect the accuracy of the sensor by adhering condensed water. It is an object of the present invention to provide an exhaust passage structure for an internal combustion engine that can prevent deterioration and failure.

  In order to achieve the above object, according to the present invention, there is provided an internal combustion engine in which a catalyst is connected to each upstream and downstream of the exhaust passage in the exhaust flow direction, and a sensor for detecting a component in the exhaust is provided between the catalysts. On the premise of the exhaust passage structure, the sensor element portion of the sensor is positioned above the center of the exhaust passage portion between the two catalysts. A substantially cylindrical guide that guides the flow of exhaust gas to the sensor element portion of the sensor is provided immediately downstream of the upstream catalyst, and the diameter of the downstream end opening of the guide is larger than the diameter of the upstream end opening. Has a small diameter. Further, the center of the downstream end opening of the guide is decentered closer to the sensor element portion of the sensor than the center of the exhaust passage portion between the two catalysts, and condensation occurs in contact with the guide at the lower position of the guide. A discharge hole for discharging condensed water in the exhaust to the outside of the guide is provided upstream of the downstream end opening of the guide.

  Due to this specific matter, the flow of exhaust from the upstream catalyst is made higher than the center of the exhaust passage portion between the upstream and downstream catalysts by a substantially cylindrical guide on the downstream side of the upstream catalyst. The sensor element portion of the sensor located at At this time, the center of the downstream end opening having a smaller diameter than the diameter of the upstream end opening of the guide is decentered closer to the sensor element portion of the sensor than the center of the exhaust passage portion between the two catalysts. As a result, the exhaust from the upstream catalyst is smoothly guided to the sensor element portion by the guide, the exhaust component is accurately detected by the sensor, and the internal combustion engine is smoothly controlled based on the information from the sensor. It becomes possible.

  In addition, when the internal combustion engine is cold started or the like, the condensed water produced when the exhaust from the upstream catalyst is blown onto the cold guide and comes into contact with the guide is upstream of the downstream end opening of the guide. It is discharged out of the guide through a discharge hole that opens to the lower position of the guide on the side. This prevents the condensed water from being guided by the guide together with the exhaust and attached to the sensor element portion of the sensor, so that the thermal stress due to the boiling (expansion) of the condensed water does not act on the sensor element portion. It is possible to prevent a decrease in detection accuracy and failure.

  Further, when the guide is formed with a thickness thinner than the thickness of the exhaust passage portion between the two catalysts, the guide from which the exhaust from the upstream catalyst is cold at the time of cold start of the internal combustion engine or the like When it is sprayed on, the guide is warmed quickly because the thickness of the guide is thin. For this reason, when the exhaust from the upstream catalyst comes into contact with the guide, the amount of condensed water produced by condensation is small. Thereby, it is possible to effectively prevent the condensed water from adhering to the sensor element portion of the sensor, and it is possible to reliably prevent a decrease in detection accuracy or failure of the sensor.

  When the discharge hole that opens to the lower position of the guide is formed in a portion that is point-symmetric with the sensor element portion of the sensor with respect to the center of the exhaust passage portion between the two catalysts, the discharge hole Is opened at a position that is point-symmetric with the sensor element portion of the sensor with respect to the center of the exhaust passage portion between the two catalysts, that is, a portion that is farthest from the sensor element portion of the sensor. For this reason, the condensed water produced by condensation when the exhaust from the upstream catalyst contacts the guide is smoothly discharged from the discharge hole at the lower position of the guide farthest from the sensor element portion of the sensor. As a result, the condensed water hardly adheres to the sensor element portion of the sensor, and it becomes possible to more reliably prevent a decrease in detection accuracy or failure of the sensor.

  Further, when the exhaust hole is opened upstream of the sensor element portion of the sensor in the exhaust flow direction, dew condensation is produced when exhaust from the upstream catalyst contacts the guide. Condensed water is smoothly discharged from the discharge hole that opens to the lower position of the guide on the upstream side in the exhaust flow direction from the sensor element portion of the sensor. Thus, the condensed water is reliably discharged out of the guide before adhering to the sensor element portion of the sensor, which is very advantageous for reliably preventing a decrease in sensor detection accuracy and failure.

  In short, the center of the downstream end opening of the guide is decentered closer to the sensor element portion of the sensor than the center of the exhaust passage portion between the two catalysts, and the discharge hole for discharging the condensed water in the exhaust is formed at the lower position of the guide. By providing, the flow of the exhaust from the upstream catalyst is smoothly guided to the sensor element portion of the sensor by the guide, and the internal combustion engine is smoothly controlled based on the information from the sensor by accurately detecting the exhaust component. be able to. In addition, condensed water that comes into contact with the guide during cold start of the internal combustion engine, etc., is discharged outside the guide through the discharge hole at the lower position of the guide to prevent the condensed water from adhering to the sensor element part of the sensor. Further, it is possible to prevent the sensor element portion from being subjected to the thermal stress caused by the condensed water, and to prevent the detection accuracy of the sensor from being lowered or broken.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing a schematic configuration when an exhaust passage structure according to Embodiment 1 of the present invention is applied to an internal combustion engine for an automobile.

  In FIG. 1, reference numeral 1 denotes an exhaust passage, and the exhaust passage 1 is connected to a downstream end in which exhaust manifolds extending from an exhaust port of an automobile internal combustion engine having a plurality of cylinders are gathered into one. A converter 3 in which the catalyst 2 is accommodated in a substantially cylindrical casing 30 is interposed on the upstream side of the exhaust passage 1. The catalyst 2 is arranged in series downstream of the upstream catalyst 21 (upstream catalyst) having a substantially cylindrical shape slightly smaller than the inner diameter of the casing 30 and the upstream catalyst 21 through an appropriate gap, and is arranged upstream. The tandem type exhaust purification catalyst is provided with two catalysts, a catalyst 21 and a downstream catalyst 22 (downstream catalyst) having the same diameter. The upstream catalyst 21 and the downstream catalyst 22 are attached to the inner peripheral surface of the casing 30 with the mat 20 interposed therebetween. In this case, the casing 30 of the converter 3 is formed to have a larger diameter than the exhaust passage 1, and thus both ends are formed by spinning. In addition, the shaping | molding of the casing 30 (both ends) is not limited to spinning processing, You may shape | mold by press work.

  As shown in FIG. 2, an oxygen concentration sensor 4 is provided between the upstream catalyst 21 and the downstream catalyst 22 as a sensor for detecting the oxygen concentration in the exhaust gas that has passed through the upstream catalyst 21. . The oxygen concentration sensor 4 is attached to a recessed portion 32 that is recessed downward at the upper end position of a substantially central portion of the casing 30 that serves as an exhaust passage portion between the two catalysts 21 and 22, and passes through the recessed portion 32. The sensor element portion 41 protrudes toward the center Q of the substantially central portion of the casing 30 in the exhaust flow direction. In this case, the tip of the sensor element portion 41 is positioned above the center Q of the substantially central portion (exhaust passage portion) of the casing 30 between the catalysts 21 and 22 in the exhaust flow direction. In addition, the arrow in FIG. 1 and FIG. 2 has shown the distribution direction of exhaust_gas | exhaustion.

  A substantially cylindrical guide 31 that guides the flow of exhaust gas to the sensor element portion 41 of the oxygen concentration sensor 4 is provided immediately downstream of the upstream catalyst 21 in the casing 30. The guide 31 includes an upstream cylindrical portion 311 formed slightly larger in diameter than the upstream catalyst 21, a downstream cylindrical portion 312 formed smaller in diameter than the upstream cylindrical portion 311, and an upstream cylindrical portion 311. And the downstream cylindrical portion 312 are integrally formed with a funnel-shaped tapered portion 313. Accordingly, the diameter of the downstream end opening 312a of the downstream cylindrical portion 312 as the downstream end opening of the guide 31 is smaller than the diameter of the upstream end opening 311a of the upstream cylindrical portion 311 as the upstream end opening of the guide 31. Is formed.

  Further, the guide 31 (the upstream cylindrical portion 311, the downstream cylindrical portion 312 and the tapered portion 313) has a thickness t1 (for example, 1.5 mm) at a substantially central portion in the exhaust gas flow direction of the casing 30 between the two catalysts 21 and 22. Is also formed with a thin wall thickness t2 (for example, 1.0 mm). In this case, when the casing 30 is formed, the tapered portion 313 is formed by spinning. In addition, shaping | molding of the casing 30 (taper part 313) is not limited to spinning processing, You may shape | mold by press work.

  Furthermore, the center P of the downstream end opening 312 a of the downstream cylindrical portion 312 in the guide 31 is biased toward the upper side closer to the sensor element portion 41 of the oxygen concentration sensor 4 than the center Q of the substantially central portion of the casing 30 in the exhaust flow direction. I have a heart. In addition, a plurality of discharge holes for discharging condensed water in the exhaust gas condensing in contact with the guide 31 to the outside of the guide 31 on the upstream side of the downstream end opening 312a of the downstream cylindrical portion 312 are provided at a lower position of the guide 31. 33, 33, ... are provided. Each of the discharge holes 33 opens at a position below the tapered portion 313 to prevent the condensed water from flowing into the downstream cylindrical portion 312. Each exhaust hole 33 is opened upstream of the sensor element portion 41 of the oxygen concentration sensor 4 in the exhaust flow direction.

  Therefore, in the first embodiment, the flow of the exhaust gas from the upstream side catalyst 21 is caused by the substantially cylindrical guide 31 on the downstream side of the upstream side catalyst 21 to the casing 30 between the upstream side and the downstream side catalysts 21 and 22. Is guided to the sensor element portion 41 of the oxygen concentration sensor 4 located above the center Q of the substantially central portion of the exhaust gas flow direction. At this time, the center P of the downstream end opening 312a of the downstream cylindrical portion 312 having a smaller diameter than the diameter of the upstream end opening 311a of the upstream cylindrical portion 311 of the guide 31 is the center of the substantially central portion of the casing 30 in the exhaust flow direction. It is eccentric to the upper side closer to the sensor element 41 of the oxygen concentration sensor 4 than Q. As a result, the exhaust from the upstream catalyst 21 is smoothly guided to the sensor element portion 41 by the guide 31, the oxygen concentration in the exhaust is accurately detected by the exhaust concentration sensor 4, and information from the oxygen concentration sensor 4 is detected. The internal combustion engine can be controlled smoothly based on the above.

  In addition, when the internal combustion engine is cold-started or the like, the condensed water produced by condensation when the exhaust from the upstream catalyst 21 is blown onto the cold guide 31 and comes into contact with the guide 31 is a cylindrical portion on the downstream side of the guide 31. The gas is discharged out of the guide 31 through the discharge holes 33 opened at the lower position upstream of the downstream end opening 312a of the 312. Further, the guide 31 is formed to have a thickness t2 (for example, 1.0 mm) that is thinner than a thickness t1 (for example, 1.5 mm) at the substantially central portion of the casing 30 in the exhaust flow direction between the two catalysts 21 and 22. Therefore, when the exhaust from the upstream side catalyst 21 is blown to the cold guide 31 at the time of cold start of the internal combustion engine or the like, the thickness t2 of the guide 31 is formed thin, so that the upstream side is heated quickly. When the exhaust from the catalyst 21 comes into contact with the guide 31, the amount of condensed water produced by condensation is small. Further, since each of the discharge holes 33 is opened upstream of the sensor element portion 41 of the oxygen concentration sensor 4 in the exhaust flow direction, dew condensation occurs when the exhaust from the upstream catalyst 21 contacts the guide 31. The condensed water produced in this manner is smoothly discharged from the discharge holes 33 that open upstream of the sensor element portion 41 of the oxygen concentration sensor 4 in the exhaust flow direction. This effectively prevents the condensed water from being guided by the guide 31 together with the exhaust and adhering to the sensor element portion 41 of the oxygen concentration sensor 4, and thermal stress due to boiling (expansion) of the condensed water is applied to the sensor element portion 41. Since it does not act, it is possible to effectively prevent a decrease in detection accuracy or failure of the oxygen concentration sensor 4.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  In this embodiment, in order to make it easy to connect the upstream end of the casing of the converter to the downstream end in which exhaust manifolds extending from the exhaust port of the automobile internal combustion engine having a plurality of cylinders are combined into one, the exhaust flow direction of the casing The central part is bent. In addition, the structure other than a casing is the same as that of the case of the said Example 1, The same code | symbol is attached | subjected about the same part and the detailed description is abbreviate | omitted.

  That is, in this embodiment, as shown in FIG. 3, the casing 50 of the converter 5 is provided at the upstream end of the exhaust passage 1. The casing 50 is divided into an upstream casing 501 and a downstream casing 502 at a substantially central portion in the exhaust flow direction, and the upstream end of the upstream casing 501 is connected to the downstream end of the exhaust manifold 11. The upstream casing 501 accommodates the upstream catalyst 21, while the downstream casing 502 accommodates the downstream catalyst 22, and these catalysts 21 and 22 serve as a tandem exhaust purification catalyst. . The downstream end of the upstream casing 501 and the upstream end of the downstream casing 502 are joined. In this case, the center Q1 of the upstream casing 501 is inclined upward with an inclination angle of approximately 35 ° with respect to the center Q2 of the substantially horizontal downstream casing 502.

  Further, the upstream casing 501 and the downstream casing 502 are formed such that the upstream and downstream ends thereof are smaller in diameter than the housing portions of the upstream and downstream catalysts 21 and 22 by spinning. The oxygen concentration sensor 4 is provided at the downstream end of the upstream casing 501 located between the upstream catalyst 21 and the downstream catalyst 22 (upstream from the connection with the downstream casing 502). Yes. The oxygen concentration sensor 4 is attached to the upper end position of the downstream end portion of the upstream casing 501 as an exhaust passage portion between the two catalysts 21 and 22, and the sensor element portion 41 penetrates the downstream end portion of the upstream casing 501. Then, it protrudes toward the center Q1 of the downstream end of the upstream casing 501. In this case, the tip of the sensor element portion 41 is located above the center Q1 of the downstream end portion of the upstream casing 501 between the two catalysts 21 and 22. Further, the center P of the downstream end opening 312a of the downstream cylindrical portion 312 in the guide 31 is eccentric to the upper side closer to the sensor element portion 41 of the oxygen concentration sensor 4 than the center Q1 of the downstream end portion of the upstream casing 501. Yes. In addition, shaping | molding of the upstream casing 501 and the downstream casing 502 (upper / lower end part) is not limited to spinning processing, You may shape | mold by press work.

  A guide 31 is provided immediately downstream of the upstream catalyst 21 in the upstream casing 501. The guide 31 is inclined substantially parallel to the center Q 1 of the upstream casing 501, and the condensed water produced by condensation when the exhaust from the upstream catalyst 21 comes into contact with the guide 31 is the upstream cylindrical portion 311. And it is easy to be led near the lower end of the taper portion 313. In this case, the downstream end portion of the upstream casing 501 between the catalysts 21 and 22 is formed to have a thickness t1 (for example, 1.5 mm) thicker than the thickness t2 (for example, 1.0 mm) of the guide 31.

  Therefore, in the second embodiment, the flow of exhaust from the upstream catalyst 21 is caused to flow downstream of the upstream casing 501 between the upstream and downstream catalysts 21 and 22 by the guide 31 immediately downstream of the upstream catalyst 21. It is guided with respect to the sensor element portion 41 of the oxygen concentration sensor 4 positioned above the center Q1 of the end portion. At this time, the center P1 of the downstream end 312a of the downstream cylindrical portion 312 having a smaller diameter than the diameter of the upstream end opening 311a of the upstream cylindrical portion 311 of the guide 31 is the center Q1 of the downstream end of the upstream casing 501. Further, the oxygen concentration sensor 4 is eccentric toward the upper side that is closer to the sensor element portion 41 of the oxygen concentration sensor 4. As a result, the exhaust from the upstream catalyst 21 is smoothly guided to the sensor element portion 41 by the guide 31, the oxygen concentration in the exhaust is accurately detected by the exhaust concentration sensor 4, and information from the oxygen concentration sensor 4 is detected. The internal combustion engine can be controlled smoothly based on the above.

  In addition, the condensed water that is condensed when exhaust gas from the upstream catalyst 21 is blown to the cold guide 31 and contacts the guide 31 when the internal combustion engine is cold-started is the lower end of the upstream cylindrical portion 311 and the tapered portion 313. It is smoothly guided to the vicinity of the portion, and is discharged out of the guide 31 through the discharge holes 33 that open to the lower position upstream of the downstream end opening 312 a of the downstream cylindrical portion 312 of the guide 31. Thus, the condensate production reduction effect by the thin guide 31 and the smooth drainage effect of the condensate by the discharge holes 33 opened upstream of the sensor element part 41 in the exhaust flow direction are considered. Thus, the condensed water is effectively prevented from being guided by the guide 31 together with the exhaust and adhering to the sensor element portion 41 of the oxygen concentration sensor 4, and thermal stress due to boiling (expansion) of the condensed water is applied to the sensor element portion 41. Since it does not act, it is possible to effectively prevent a decrease in detection accuracy or failure of the oxygen concentration sensor 4.

  Next, a third embodiment of the present invention will be described with reference to FIGS.

  In this embodiment, the mounting position of the air concentration sensor and the opening position of the discharge hole are changed. The rest of the configuration except for the air concentration sensor and the exhaust hole is the same as in the case of the first embodiment, and the same parts are denoted by the same reference numerals and detailed description thereof is omitted.

  That is, in the present embodiment, as shown in FIGS. 4 and 5, the air concentration sensor 6 is located on the upper side of the central portion of the casing 30 in the exhaust flow direction between the catalysts 21 and 22 (the upper left side in FIG. 4). At a position) is attached to a recessed portion 34 that is recessed inwardly toward the center Q from the obliquely upward direction, and passes through the recessed portion 34 and protrudes toward the center Q of the approximately central portion of the casing 30 in the exhaust flow direction. It has an element part 61. In this case, the tip of the sensor element portion 61 is positioned above the center Q of the substantially central portion (exhaust passage portion) of the casing 30 in the exhaust flow direction between the catalysts 21 and 22.

  The center P of the downstream end opening 312a of the cylindrical portion 312 on the downstream side of the guide 31 is on the oblique upper side that is closer to the sensor element portion 61 of the oxygen concentration sensor 6 than the center Q of the substantially central portion of the casing 30 in the exhaust flow direction. It is eccentric to the side (in the diagonally upper left side in FIG. 4). Further, the discharge holes 35, 35,... Opened to the lower position upstream of the downstream end opening 312a of the downstream cylindrical portion 312 of the guide 31 are substantially central portions in the exhaust flow direction of the casing 30 between the catalysts 21, 22. The lower position of the guide 31 that is point-symmetric with respect to the sensor element portion 61 of the oxygen concentration sensor 6 with respect to the center Q of the oxygen concentration sensor 6, that is, the mounting position with respect to the recess 34 of the oxygen concentration sensor 6 (upper left side position in FIG. On the other hand, it is formed so as to be biased toward the lower other side portion (lower right side portion in FIG. 4) of the taper portion 313 farthest from the sensor element portion 61 in the opposite direction.

  Therefore, in the third embodiment, the flow of exhaust from the upstream catalyst 21 is caused to flow downstream of the upstream casing 501 between the upstream and downstream catalysts 21 and 22 by the guide 31 immediately downstream of the upstream catalyst 21. It is guided with respect to the sensor element portion 61 of the oxygen concentration sensor 6 located above the center Q of the end portion. At this time, the center P of the downstream end opening 312a of the downstream cylindrical portion 312 of the guide 31 is closer to the sensor element 61 of the oxygen concentration sensor 6 than the center Q of the substantially central portion of the casing 30 in the exhaust flow direction. It is decentered toward the side (in the oblique upper left side in FIG. 4). Thus, the exhaust from the upstream catalyst 21 is smoothly guided to the sensor element unit 61 by the guide 31, the oxygen concentration in the exhaust is accurately detected by the exhaust concentration sensor 6, and information from the oxygen concentration sensor 6 is detected. The internal combustion engine can be controlled smoothly based on the above.

  Moreover, the condensed water condensed when the exhaust gas from the upstream catalyst 21 is blown to the cold guide 31 and contacts the guide 31 when the internal combustion engine is cold-started is the lower end of the upstream cylindrical portion 311 and the tapered portion 313. It is smoothly guided to the vicinity of the portion, and is discharged out of the guide 31 through the discharge holes 35 that open to the lower position upstream of the downstream end opening 312 a of the downstream cylindrical portion 312 of the guide 31. At this time, each discharge hole 35 is located at a lower position of the guide 31 that is symmetric with respect to the sensor element portion 61 of the oxygen concentration sensor 6 with respect to the center Q of the substantially central portion of the exhaust flow direction of the casing 30 between the two catalysts 21 and 22. In other words, the attachment position of the oxygen concentration sensor 6 to the recess 34 of the sensor element portion 61 is formed so as to be biased toward the lower other side portion of the tapered portion 313 that is farthest in the opposite direction from the sensor element portion 61 with respect to the center Q. Therefore, the condensed water is smoothly discharged from the other side of the lower portion of the tapered portion 313 of the guide 31 that is farthest from the sensor element portion 61 of the oxygen concentration sensor 6. Thus, combined with the effect of reducing the amount of condensed water produced by the thin guide 31 and the effect of smoothly discharging the condensed water by the discharge holes 35 opened upstream of the sensor element 61 in the exhaust flow direction. Thus, the condensed water is effectively prevented from being guided together with the exhaust gas by the guide 31 and adhering to the sensor element portion 61 of the oxygen concentration sensor 6, and thermal stress due to boiling (expansion) of the condensed water acts on the sensor element portion 61. Therefore, it is possible to effectively prevent a decrease in detection accuracy or failure of the oxygen concentration sensor 6.

  In addition, this invention is not limited to said each Example, The other various modifications are included. For example, in each of the above-described embodiments, the oxygen concentration sensors 4 and 6 are described as an example of the sensor for detecting the components in the exhaust gas. However, the present invention is not limited to the oxygen concentration sensor, but a NOx sensor, an HC sensor, a CO sensor, etc. Needless to say, the present invention can be effectively applied to sensors that detect components in various exhaust gases.

  Further, in each of the above embodiments, the thickness t2 (for example, 1.0 mm) of the guide 31 is thinner than the thickness t1 (for example, 1.5 mm) at the substantially central portion of the casing 30 in the exhaust flow direction between the two catalysts 21 and 22. However, the wall thickness t2 of the guide is not limited to 1.0 mm, and the production of condensed water can be further suppressed by further reducing the thickness.

It is a vertical side view of the casing of the converter showing a schematic configuration when the exhaust passage structure according to the first embodiment of the present invention is applied to an internal combustion engine for an automobile. It is a longitudinal side view of the casing of the converter in the vicinity of the upstream catalyst. It is a vertical side view of the casing of the converter which shows schematic structure at the time of applying the exhaust passage structure which concerns on Example 2 of this invention to the internal combustion engine for motor vehicles. It is a vertical rear view of the casing of the converter in the vicinity of the oxygen concentration sensor when the exhaust passage structure according to Embodiment 3 of the present invention is applied to an automobile internal combustion engine. It is the vertical side view of the casing of the converter similarly cut | disconnected in the AA line of FIG.

Explanation of symbols

1 Exhaust passage 21 Upstream catalyst (Upstream catalyst)
22 Downstream catalyst (downstream catalyst)
31 Guide 311a Upstream end opening of the upstream cylindrical portion of the guide (upstream end opening of the guide)
312a Downstream end opening of downstream cylindrical portion of guide (downstream end opening of guide)
33, 35 Exhaust hole 4 Oxygen concentration sensor (sensor)
41 sensor element part 6 oxygen concentration sensor (sensor)
61 Center of the downstream end opening of the downstream cylindrical portion of the sensor element part P (center of the downstream end opening of the guide)
Q Center of the center of the exhaust flow direction of the casing (center of the exhaust passage)
Q1 Center of the upstream casing (center of the exhaust passage)
t1 Thickness of the casing in the center of the exhaust flow direction (thickness of the exhaust passage)
t2 Guide wall thickness

Claims (4)

In the exhaust passage structure of an internal combustion engine in which a catalyst is connected to each of the upstream and downstream sides of the exhaust passage in the exhaust flow direction, and a sensor for detecting a component in the exhaust is provided between the two catalysts.
The sensor element portion of the sensor is located above the center of the exhaust passage portion between the two catalysts, and the exhaust flow is guided to the sensor element portion of the sensor immediately downstream of the upstream catalyst. A guide having a substantially cylindrical shape is formed, and the diameter of the downstream end opening is smaller than the diameter of the upstream end opening.
The center of the downstream end opening of the guide is decentered closer to the sensor element portion of the sensor than the center of the exhaust passage portion between the two catalysts,
The lower position of the guide is provided with a discharge hole that discharges condensed water in the exhaust that is in contact with the guide to the outside of the guide on the upstream side of the downstream end opening of the guide. An exhaust passage structure for an internal combustion engine. The exhaust passage structure for an internal combustion engine according to claim 1,
An exhaust passage structure for an internal combustion engine, wherein the guide is formed to be thinner than a thickness of an exhaust passage portion between the two catalysts. The exhaust passage structure for an internal combustion engine according to claim 1 or 2,
An internal combustion engine characterized in that an exhaust hole that opens at a lower position of the guide is formed at a site that is point-symmetric with respect to the sensor element portion of the sensor with respect to the center of the exhaust passage portion between the two catalysts. Exhaust passage structure. The exhaust passage structure for an internal combustion engine according to any one of claims 1 to 3,
The exhaust passage structure of an internal combustion engine, wherein the exhaust hole is opened upstream of the sensor element portion of the sensor in the exhaust flow direction.

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