JP2012241545A - Exhaust device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable improvement of detection accuracy of A/F imbalance on the basis of an output of an A/F sensor in an exhaust device configured such that a turbine housing of a supercharger and a catalyst are installed in series in an exhaust gas flow direction in the middle of an exhaust passage of an engine, and a bypass passage for bypassing a turbine wheel of the supercharger is opened/closed by a waste gate valve.SOLUTION: The A/F sensor 40 is provided in a region between the turbine housing 24 and the catalyst 10 in the exhaust passage 9. A detection part of the A/F sensor 40 is set in such a manner that exhaust gas discharged from the bypass passage 27 directly hits on the detection part.

Description

  The present invention has a configuration in which a turbine housing and a catalyst of a supercharger are installed in series in the exhaust gas flow direction in the middle of an exhaust passage, and a bypass passage that bypasses the turbine wheel of the supercharger is opened and closed by a waste gate valve The present invention relates to an engine exhaust system.

  Conventionally, the turbocharger turbine housing and the catalyst are installed in series in the exhaust gas flow direction in the middle of the engine exhaust passage, and a bypass passage for bypassing the turbocharger turbine wheel is provided in the exhaust passage, A configuration is known in which a waste gate valve for adjusting the amount of exhaust gas bypass is provided in the bypass passage (see, for example, Patent Document 1).

The catalyst is installed downstream of the turbine housing in the exhaust gas flow direction. The region between the turbine housing and the catalyst in the exhaust passage is formed in an inverted L shape that extends in the horizontal direction and then bends approximately 90 degrees and extends downward in the vertical direction. An exhaust sensor such as an air-fuel ratio sensor (hereinafter referred to as an A / F sensor) or an O ₂ sensor is installed in an inverted L-shaped region in the exhaust passage.

JP 2008-208740 A

  In Patent Document 1, since exhaust gas that has passed through the turbine wheel hits an exhaust sensor that is installed in an inverted L-shaped region in the exhaust passage, the engine is sequentially (predetermined from each cylinder of the engine). The timing according to the combustion order of the exhaust gas) hits the exhaust sensor in a state where the exhaust gas to be discharged is mixed. That is, the exhaust gas sequentially discharged from each cylinder does not hit the exhaust sensor. For this reason, there is a concern that the accuracy in detecting an air-fuel ratio imbalance (referred to as A / F imbalance) between the cylinders based on the output of the exhaust sensor is concerned.

  By the way, since the exhaust gas is cooled in a state where the exhaust passage is cooled, such as in the initial cold start, the water vapor contained in the exhaust gas is condensed and easily becomes condensed water. If this condensed water is applied to the sensor element disposed on the front end side of the exhaust sensor, the sensor element may be damaged.

  For example, as shown in JP-A-9-222416, even if the sensor element is covered with a cover, an opening for introducing exhaust gas is provided on the side of the cover, Since the exhaust gas exhaust opening is provided on the end face of the cover, depending on the exhaust sensor mounting posture, condensed water may enter the sensor element from the end face opening.

  In view of such circumstances, the present invention provides a bypass passage in which a turbine housing and a catalyst of a supercharger are installed in series in the exhaust gas flow direction in the middle of an exhaust passage of an engine and bypass the turbine wheel of the supercharger In the exhaust system of an engine configured to be opened and closed by a waste gate valve, the object is to improve the detection accuracy of A / F imbalance based on the output of an exhaust sensor.

  Further, according to the present invention, a wastegate valve is a bypass passage in which a turbine housing and a catalyst of a supercharger are installed in series in an exhaust gas flow direction in the middle of an exhaust passage of an engine and bypass the turbine wheel of the supercharger. In an exhaust system of an engine configured to be opened and closed, it is possible to improve the detection accuracy of A / F imbalance based on the output of an exhaust sensor and to prevent damage to the sensor element of the exhaust sensor due to moisture. It is aimed.

  In the engine exhaust system according to the present invention, a turbocharger turbine housing and a catalyst are provided in series in the exhaust gas flow direction in the middle of an engine exhaust passage, and the turbocharger turbine wheel is bypassed in the exhaust passage. And a waste gate valve for adjusting the bypass amount of the exhaust gas from the bypass passage, and an exhaust sensor is provided in a region between the turbine housing and the catalyst in the exhaust passage. The exhaust sensor is provided with a detection portion that is set to a state in which exhaust gas discharged from the bypass passage directly hits.

  In this configuration, the exhaust gas discharged from the bypass passage directly hits the detection portion of the exhaust sensor. That is, it can be said that the exhaust gas discharged sequentially from each cylinder of the engine (timing according to a predetermined combustion order) hits the detection portion of the exhaust sensor in a state where it is not mixed. Thereby, it becomes possible to improve the detection accuracy of the air-fuel ratio imbalance (A / F imbalance) between the cylinders of the engine based on the output of the exhaust sensor.

  Preferably, the exhaust gas discharged from the bypass passage is set to flow straight toward the inlet of the catalyst, and the detection portion of the exhaust sensor is disposed at a position corresponding to the flow of the straight exhaust gas.

  In this configuration, when the waste gate valve is open, the exhaust gas discharged from each cylinder of the engine sequentially (timing according to a predetermined combustion order) and passing through the bypass passage directly hits the detection part of the exhaust sensor. It becomes clear that This makes it possible to improve the detection accuracy of the A / F imbalance based on the output of the exhaust sensor. In addition, at that time, the exhaust gas turbulence is created by the presence of the exhaust sensor, so that the exhaust gas hits a wide area instead of hitting the local area at the catalyst inlet. As a result, the exhaust gas discharged from the bypass passage can be introduced from a wide area at the inlet of the catalyst while being kept at a relatively high temperature. It becomes possible.

  Preferably, the region between the turbine housing and the catalyst in the exhaust passage is shaped so as to go straight along the exhaust gas discharge direction from the turbine housing and then bend 90 degrees.

  Preferably, in the turbine housing, the exhaust gas is discharged from the bypass passage to the downstream side of the exhaust gas discharge port of the bypass passage and the exhaust gas discharge port from the turbine wheel and hits the detection portion of the exhaust sensor. A partition member for preventing the exhaust gas discharged from the turbine wheel from being mixed in the flow is provided.

  In this configuration, for example, when the waste gate valve is open, exhaust gas discharged from each cylinder of the engine sequentially (timing according to a predetermined combustion order) and passing through the bypass passage and exhaust gas discharged from the turbine wheel respectively. And become difficult to mix. Therefore, when the waste gate valve is open, exhaust gas discharged from each cylinder of the engine sequentially (timing according to a predetermined combustion order) and passing through the bypass passage is likely to directly hit the detection part of the exhaust sensor, Exhaust gas discharged from each cylinder of the engine sequentially (timing according to a predetermined combustion order) and mixed by the turbine wheel is less likely to hit the detection part of the exhaust sensor. Thereby, the above-mentioned operation and effect can be obtained remarkably.

  Preferably, when the waste gate valve is opened, the exhaust gas discharged from the turbine wheel is less likely to be mixed with the flow of exhaust gas discharged from the bypass passage and hitting a detection portion of the exhaust sensor. Arranged in a state.

  The waste gate valve is a plate-like member that is disposed on the discharge port side of the bypass passage so that the discharge port can be opened and closed. When the waste gate valve is opened, the waste gate valve travels straight from the bypass passage and is discharged. It is arranged between the gas and the exhaust gas discharged straight from the turbine wheel.

  In this configuration, for example, when the waste gate valve is open, the exhaust gas discharged from the bypass passage and the exhaust gas discharged from the turbine wheel are hardly mixed. Therefore, when the waste gate valve is open, exhaust gas discharged from each cylinder of the engine sequentially (timing according to a predetermined combustion order) and passing through the bypass passage is likely to directly hit the detection part of the exhaust sensor, The exhaust gas discharged from each cylinder of the engine sequentially (timing according to a predetermined combustion order) and mixed by the turbine wheel is less likely to hit the detection part of the exhaust sensor. As a result, the above-described functions and effects can be easily obtained.

  Preferably, the detection part of the exhaust sensor has a structure in which the sensor element is covered with a double wall composed of an inner cover and an outer cover, and the inner cover and the outer cover are provided with a side opening and an end opening, respectively. The detection portion of the exhaust sensor is in an installation state in which exhaust gas discharged from the bypass passage flows from the side opening and flows out from the end opening.

  In this configuration, even if the water vapor contained in the exhaust gas is condensed in a situation where the exhaust passage is cold, such as at the initial cold start of the engine, the exhaust gas containing the condensed water flows from the side opening of the exhaust sensor. Then, it collides with the inner cover and gas-liquid separation occurs. The gas-liquid separated condensed water goes from the facing space between the outer cover and the inner cover toward the end face opening, while the gas-liquid separated exhaust gas component enters from the side opening of the inner cover and hits the sensor element. become. Thereby, since the condensed water does not hit the sensor element, the sensor element is prevented from being damaged.

  The engine exhaust system according to the present invention includes a bypass passage in which a turbine housing and a catalyst of the supercharger are installed in series in the exhaust gas flow direction in the middle of the exhaust passage of the engine and bypass the turbine wheel of the supercharger. In the configuration that is opened and closed by the waste gate valve, it becomes possible to improve the detection accuracy of the A / F imbalance based on the output of the exhaust sensor.

  The engine exhaust system according to the present invention is a bypass in which a turbine housing and a catalyst of a supercharger are installed in series in an exhaust gas flow direction in the middle of an exhaust passage of the engine and bypass the turbine wheel of the turbocharger. In the configuration in which the passage is opened and closed by the waste gate valve, it is possible to improve the detection accuracy of the A / F imbalance based on the output of the exhaust sensor, and avoid damage to the sensor element of the exhaust sensor due to moisture. It becomes possible.

It is a figure showing the schematic structure of one embodiment of the exhaust system of the engine concerning the present invention. FIG. 2 is an enlarged view of a region between a turbine housing and a catalyst in FIG. 1, showing a state where a waste gate valve is opened. It is the figure which looked at the turbine housing from the A direction of FIG. It is the figure which looked at the area | region between a turbine housing and a catalyst from the B direction of FIG. 2 and FIG. It is explanatory drawing for demonstrating the installation attitude | position of an A / F sensor in FIG. It is sectional drawing which shows schematic structure of the detection part of the A / F sensor of FIG. FIG. 4 is a view corresponding to FIG. 3, showing another embodiment of the engine exhaust device according to the present invention. FIG. 8 is a diagram corresponding to FIG. 4 in the embodiment of FIG. 7.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  1 to 6 show an embodiment of the present invention. The engine 1 exemplified in this embodiment has, for example, in-line four cylinders, but the number of cylinders and the engine type are not particularly limited.

  A cylinder head (not shown) of the engine 1 includes an intake manifold 2 for distributing and supplying intake air to each cylinder, and exhaust manifolds 3A and 3B for collecting exhaust gas discharged from each cylinder. It is attached.

  An intake pipe 4 for taking in air from the atmosphere is connected to the intake manifold 2. An air cleaner 5 is attached to the inlet of the intake pipe 4. The intake manifold 2 and the intake pipe 4 constitute an intake passage.

  A throttle valve 6 for adjusting the intake air amount of the engine 1 is provided upstream of the intake manifold 2 in the intake flow direction. Although not shown, the throttle valve 6 is operated by a throttle motor and an electronic control unit (ECU).

  The first exhaust manifold 3A is connected to the exhaust ports of, for example, the first and fourth cylinders of the engine 1, and the second exhaust manifold 3B is connected to each of the second and third cylinders of the engine 1, for example. It is connected to the exhaust port. Each of the exhaust manifolds 3A and 3B has a shape in which the upstream side is bifurcated and gathers on the downstream side to form one, that is, a 2-in-1 shape.

  A turbocharger 20 as a supercharger is attached to the downstream side of the two exhaust manifolds 3A and 3B via a first relay exhaust pipe 8. The first relay exhaust pipe 8 has a passage divided into two inside, and the downstream sides of the two exhaust manifolds 3A and 3B are individually connected to the upstream side of the passages. The downstream side of each passage is connected in communication with a turbine housing 24 described below. The turbocharger 20 adopting such a configuration is called a so-called “twin scroll type turbocharger”.

  The turbocharger 20 supercharges intake air using exhaust pressure and supplies it to the engine 1, and includes a turbine wheel 21, a compressor impeller 22, and the like.

  The basic operation of the turbocharger 20 is that the turbine wheel 21 is rotated by the energy of exhaust gas discharged from the engine 1 to the exhaust manifolds 3A and 3B, and the compressor impeller 22 is rotated integrally therewith. The air sucked into the intake pipe 4 is supercharged and forcibly sent into the combustion chamber of each cylinder of the engine 1. The air supercharged by the compressor impeller 22 is cooled by the intercooler 7. The intercooler 7 is installed downstream of the compressor impeller 22 in the intake pipe 4 in the intake air flow direction.

  The turbine wheel 21 is rotatably provided in the turbine housing 24. The downstream side of the first relay exhaust pipe 8 (in the middle of the exhaust passage) downstream of the two exhaust manifolds 3A and 3B is connected to the exhaust introduction port of the turbine housing 24.

  The compressor impeller 22 is provided in a compressor housing 25 installed in the middle of the intake pipe 4. The compressor impeller 22 is attached to a turbine shaft 23 that is integral with the turbine wheel 21. Thereby, the turbine wheel 21 and the compressor impeller 22 rotate integrally.

  A second relay exhaust pipe 9 for discharging exhaust gas to the atmosphere is connected to the downstream side of the turbine housing 24. This second relay exhaust pipe 9 is a part called “elbow”, and goes straight along the discharge direction of exhaust gas discharged from a discharge port 26 on the turbine wheel 21 side described below, and then bends approximately 90 degrees. It is formed in an inverted L shape that extends substantially downward in the vertical direction.

  A catalyst 10 for purifying exhaust gas is provided on the downward portion of the second relay exhaust pipe 9. Since the diameter of the catalyst 10 is set larger than the diameter of the downward portion of the second relay exhaust pipe 9, the downward portion of the second relay exhaust pipe 9 has a cone shape that gradually increases in diameter toward the catalyst 10. It is said that. The two exhaust manifolds 3A and 3B and the first and second relay exhaust pipes 8 and 9 constitute a part of the exhaust passage.

  The turbocharger 20 of this embodiment is provided with a bypass passage 27, a waste gate valve (WGV) 28, and the like.

  The bypass passage 27 is provided in the turbine housing 24 so as to guide the exhaust gas discharged from the engine 1 to the catalyst 10 by bypassing the turbine wheel 21. That is, the bypass passage 27 is installed so as to short-circuit the inlet side and the outlet side in the turbine housing 24. As shown in FIGS. 2 and 3, the exhaust port of the bypass passage 27 is provided next to the exhaust gas exhaust port 26 that rotationally drives the turbine wheel 21 in the turbine housing 24.

  The waste gate valve 28 is installed on the discharge port side of the bypass passage 27 so as to be openable and closable, and adjusts the opening amount of the bypass passage 27 to adjust the exhaust gas bypass amount. By adjusting the exhaust gas bypass amount, for example, the supercharging pressure can be controlled, and the catalyst 10 can be activated quickly after the engine 1 is cold started.

  The waste gate valve 28 is formed, for example, as a circular and plate-like member, and a predetermined outer peripheral position thereof is attached to the support shaft 29 so as to rotate together. Although not shown in the figure, a drive source is connected to the support shaft 29 via a power transmission mechanism, and the driving force generated by the drive source is converted into rotational power for rotating the support shaft 29 by the power transmission mechanism. Then, by transmitting the rotational power to the support shaft 29, the waste gate valve 28 that is integrally rotated with the support shaft 29 is opened and closed.

  The waste gate valve 28, the support shaft 29, the power transmission mechanism and the driving source constitute a waste gate valve unit. The drive source can be, for example, a motor, a vacuum regulating valve, or the like. The power transmission mechanism can be, for example, a link mechanism or a gear mechanism.

As shown in FIGS. 2 to 6, an A / F sensor 40 as an exhaust sensor is provided in a region between the turbine housing 24 and the catalyst 10 in the second relay exhaust pipe 9. This exhaust sensor may be an O ₂ sensor in addition to the A / F sensor 40.

  The A / F sensor 40 is attached such that a detection portion (arrangement portion of the sensor element 41) on the tip side protrudes into the region in the second relay exhaust pipe 9. The structure and attachment state of the detection part on the tip side of the A / F sensor 40 will be described in detail below.

  For example, as shown in FIG. 6, the detection portion on the front end side of the A / F sensor 40 has a structure in which the sensor element 41 is covered with a double wall composed of an inner cover 42 and an outer cover 43.

  The sensor element 41 includes a rod-shaped solid electrolyte portion that contacts exhaust gas, and the rod-shaped sensor element 41 is held in a state of penetrating the body 44.

  The side openings 45 and 46 are provided on the side surfaces of both covers 42 and 43 at positions shifted so as not to overlap each other in the direction orthogonal to the tip protruding direction. Furthermore, end face openings 47 and 48 are provided at the tip end faces of both covers 42 and 43. The distance from the side openings 45, 46 to the end openings 47, 48 is set as long as possible.

  Since the detection portion of the A / F sensor 40 has a double wall structure, even if condensed water in the exhaust gas enters the space between the outer cover 43 and the inner cover 42 from the side opening 46 of the outer cover 43. The condensed water hits the side surface of the inner cover 42 and comes to the front end side from the facing space, so that the condensed water does not enter the side opening 45 of the inner cover 42. Thus, the outer periphery of the sensor element 41 of the A / F sensor 40 has a gas-liquid separation structure.

  The exhaust gas from which the condensed water is separated in this way enters the facing space between the inner cover 43 and the sensor element 41 from the side opening 45 of the inner cover 42 and flows along the longitudinal direction of the sensor element 41. Then, it comes into contact with the outer peripheral surface of the sensor element 41. The condensed water that has entered the facing space between the outer cover 43 and the inner cover 42 is discharged to the outside from the end face opening 46 of the outer cover 43.

  By the way, the above-described A / F sensor 40 is arranged so that the detection portion thereof is located on an extension line in the exhaust gas discharge direction. In particular, in this embodiment, as shown by the thick line in FIG. 2, the exhaust gas discharged from the discharge port of the bypass passage 27 is set to flow straight in the discharge direction, and this exhaust gas is the catalyst 10. It is set so as to flow in a straight line toward the entrance. Therefore, the detection portion of the A / F sensor 40 is disposed at a position that directly contacts the flow of the straight exhaust gas discharged from the bypass passage 27.

  Further, in the turbine housing 24, a partition member 31 is provided in a region from the position where the inner wall portion 24 a where the outlet 26 on the turbine wheel 21 side and the outlet of the bypass passage 27 are provided to the radially outward flange 24 b. Is provided.

  The partition member 31 is provided between the discharge port 26 on the turbine wheel 21 side and the discharge port of the bypass passage 27 arranged at positions adjacent to each other in the region. That is, the partition member 31 makes it difficult to mix the exhaust gas discharged from the bypass passage 27 and the exhaust gas discharged from the discharge port 26 on the turbine wheel 21 side, for example, when the waste gate valve 28 is opened. It is provided for.

  In this embodiment, the posture of the detection portion of the A / F sensor 40 is specified as follows, and will be described.

  As shown by the alternate long and short dash line in FIG. 5, the central axis 51 of the A / F sensor 40 is defined with respect to a straight line 53 extending in a direction orthogonal to a straight line 52 along the flow of exhaust gas discharged straight from the bypass passage 27. It can be set to be parallel. The straight line 52 is a center line when the flow of exhaust gas is viewed from directly above. Further, the straight line 53 is substantially parallel to the horizontal direction.

  In addition, the central axis 51 of the A / F sensor 40 can be set to be inclined by a predetermined angle (see θ in FIG. 5) with respect to the straight line 53. Here, the angle θ refers to the exhaust gas from the position of the straight line 53 at the tip of the A / F sensor 40 from a position where the central axis 51 coincides with the straight line 53 and a proper position of the body 44 of the A / F sensor 40 as a fulcrum. The angle formed by the central axis 51 with respect to the straight line 53 when the A / F sensor 40 is tilted so as to be shifted downstream in the flow direction.

  When the mounting posture of the A / F sensor 40 is specified in this way, it is possible to prevent the exhaust gas discharged from the bypass passage 27 from flowing from the end surface openings 47 and 48 of the A / F sensor 40. It becomes possible to make the height as high as possible, which is advantageous in preventing the sensor element 41 from being damaged by water. In particular, when the mounting posture of the A / F sensor 40 is set to be inclined by a predetermined angle θ as in the latter case, the exhaust gas discharged from the bypass passage 27 is opened to the side surface of the outer cover 43 of the A / F sensor 40. It becomes easy to flow diagonally downward from 46 toward the tip side.

  In the embodiment having such a configuration, the following operations and effects can be obtained.

  First, when the waste gate valve 28 is opened, since the partition member 31 is provided, the exhaust gas discharged from the bypass passage 27 and the exhaust gas discharged from the discharge port 26 on the turbine wheel 21 side are mixed. It becomes difficult. Therefore, for example, as shown in FIG. 2, the exhaust gas discharged sequentially from each cylinder of the engine 1 (timing according to a predetermined combustion order) and passing through the bypass passage 27 is detected by each detection portion (sensor element) of the A / F sensor 40. The exhaust gas that is discharged sequentially from each cylinder of the engine 1 (timing according to a predetermined combustion order) and mixed by the turbine wheel 21 is detected by the A / F sensor 40. It becomes difficult to hit directly.

  In other words, the exhaust gas discharged sequentially from each cylinder of the engine 1 (at a timing corresponding to a predetermined combustion order) is likely to hit the detection portion of the A / F sensor 40, respectively. Therefore, it becomes possible to improve the detection accuracy of A / F imbalance based on the output of the A / F sensor 40.

  Further, although the exhaust gas discharged from the bypass passage 27 is linearly directed to a predetermined angle range on the outer diameter side at the inlet of the catalyst 10, the exhaust gas discharged from the bypass passage 27 is temporarily A / F. Since it hits the detection part of the sensor 40, a turbulent flow of exhaust gas is created by the A / F sensor 40. As a result, the exhaust gas hits a wide area instead of hitting the local area at the inlet of the catalyst 10. In other words, the exhaust gas discharged from the bypass passage 27 can be introduced from a wide area at the inlet of the catalyst 10 while being kept at a relatively high temperature. It becomes possible to make it.

  Further, when water vapor contained in the exhaust gas is condensed in a state where the exhaust passage (exhaust manifolds 3A, 3B, first and second relay exhaust pipes 8, 9) is cooled, for example, at the initial cold start of the engine 1, etc. The exhaust gas containing the condensed water directly hits the detection portion of the A / F sensor 40. However, the exhaust gas containing the condensed water enters from the side opening 46 of the outer cover 43 so that it does not flow from the end face openings 47 and 48 of the two covers 42 and 43. Then, the exhaust gas containing condensed water entering from the side opening 46 of the outer cover 43 collides with the inner cover 42 and is separated into gas and liquid. The gas-liquid separated condensed water is directed from the facing space between the outer cover 43 and the inner cover 42 toward the end surface opening 48 and discharged to the outside from the end surface opening 48, while the gas-liquid separation is performed. The exhaust gas component enters from the side opening 45 of the inner cover 42 and comes into contact with the sensor element 41 and is discharged to the outside through the end surface openings 47 and 48. In this way, it can be avoided that the condensed water flows from the end face openings 47 and 48 of the two covers 42 and 43 and hits the sensor element 41, so that the sensor element 41 can be prevented from being damaged by being covered with water. become.

  In particular, in this embodiment, by specifying the mounting posture of the A / F sensor 40 as shown in FIG. 5, the exhaust gas is allowed to flow obliquely downward from the side opening 46 of the outer cover 43, so that the exhaust gas and It is devised so that the condensed water can easily flow to the tip of the detection portion of the A / F sensor 40. Thereby, the exhaust gas from which the condensed water has been separated can easily flow from the facing space between the inner cover 42 and the sensor element 41 toward the tip along the longitudinal direction of the sensor element 41. On the other hand, it becomes possible to make the condensed water separated from the exhaust gas easily flow from the facing space of the two covers 42 and 43 toward the end face opening 48 at the front end, and smoothly and efficiently from the end face opening 48 to the outside. It becomes possible to discharge.

  When the waste gate valve 28 is closed, for example, as shown in FIG. 4, all exhaust gas discharged from the engine 1 is introduced toward the turbine wheel 21. Is exhausted from the exhaust port 26 on the turbine wheel 21 side to the second relay exhaust pipe 9. In this case, the exhaust gas discharged from the discharge port 26 on the turbine wheel 21 side is introduced from a wide area at the inlet of the catalyst 10 while spreading.

  As described above, in the embodiment to which the present invention is applied, the exhaust gas discharged from the bypass passage 27 is made difficult to mix the exhaust gas discharged from the discharge port 26 on the turbine wheel 21 side and is discharged from the bypass passage 27. The exhaust gas is devised so as to make it easy to directly hit the detection portion of the A / F sensor 40 (the portion where the sensor element 41 is disposed). As a result, the exhaust gas discharged sequentially from each cylinder of the engine 1 (at a timing corresponding to a predetermined combustion order) and passing through the bypass passage 27 can easily hit the detection portion of the A / F sensor 40. The exhaust gas discharged from each cylinder sequentially (timing according to a predetermined combustion order) and mixed in the turbine wheel 21 is less likely to hit the detection portion of the A / F sensor 40, so that the A based on the output of the A / F sensor 40 / F imbalance detection accuracy can be improved.

  Moreover, when the exhaust passage (exhaust manifolds 3A and 3B, first and second relay exhaust pipes 8 and 9) is cold as in the cold start of the engine 1, water vapor contained in the exhaust gas becomes condensed water. Although it is easy, even if the water vapor contained in the exhaust gas becomes condensed water in such a situation, the condensed water is not applied to the sensor element 41 of the A / F sensor 40. It becomes possible to avoid damage to the sensor 40.

  By the way, in the case of this embodiment, the waste gate valve 28 is half-opened in the initial stage of the cold start, and the exhaust passage (exhaust manifolds 3A, 3B, first, second) is in the middle of warming up. When the temperature of the relay exhaust pipes 8 and 9) rises to some extent and the water vapor contained in the exhaust gas hardly becomes condensed water, the waste gate valve 28 can be controlled to be fully opened. In order to control the opening degree of the waste gate valve 28 in the initial stage of the cold start and the situation in which the water vapor contained in the exhaust gas is unlikely to become condensed water during the warm-up stage, for example, the exhaust gas It can be done based on temperature. For example, when the temperature of the exhaust gas discharged from the engine 1 exceeds a predetermined threshold value, it can be determined that the water vapor contained in the exhaust gas is unlikely to become condensed water during the warm-up stage. The temperature of the exhaust gas discharged from the engine 1 is, for example, an actually measured value or a predicted value (a calculated value using parameters such as engine speed and intake air amount as parameters). The threshold value is appropriately set by various experiments and simulations, and is set lower than the warm-up completion temperature, for example.

  When the waste gate valve 28 is in a half-open state as described above, exhaust gas discharged from each cylinder of the engine 1 sequentially (timing according to a predetermined combustion order) and passing through the bypass passage 27 is half-open. The waste gate valve 28 is installed so that the exhaust gas containing the condensed water does not directly collide with the sensor element 41 of the A / F sensor 40 by colliding with the waste gate valve 28 in the state. It is preferable to manage.

  In this way, the condensed water is supplied to the sensor element 41 of the A / F sensor 40 in the initial cold start stage where the condensed water is likely to be generated due to the synergistic action with the setting of the mounting posture of the A / F sensor 40 as described above. Since it is possible to further increase the possibility of making it difficult to apply, it is further advantageous in avoiding damage to the sensor element 41 of the A / F sensor 40 due to moisture.

  Further, when the waste gate valve 28 is fully opened during the warming-up stage when the condensed water is less likely to be generated as described above, the bypass passage 27 is discharged sequentially from each cylinder of the engine 1 (at a timing corresponding to a predetermined combustion order). It becomes possible to directly apply the exhaust gas passing through each to the detection part of the A / F sensor 40. Thereby, it becomes possible to improve the detection accuracy of A / F imbalance based on the output of the A / F sensor 40.

  In this way, by controlling the opening degree of the waste gate valve 28 when the engine 1 is cold-started, the sensor element 41 of the A / F sensor 40 can be prevented from being damaged by water and the output of the A / F sensor 40 can be prevented. It is possible to increase as much as possible the possibility of achieving an improvement in the detection accuracy of A / F imbalance based on the above.

  In addition, this invention is not limited only to the said embodiment, It can change suitably in the range equivalent to the claim and the said range.

  (1) The engine 1 to which the exhaust device described in the above embodiment is applied may be either a diesel engine or a gasoline engine. In the case of a diesel engine, the catalyst 10 is, for example, a diesel particulate filter (DPF), and in the case of a gasoline engine, the catalyst 10 is, for example, a three-way catalyst.

  (2) FIGS. 7 and 8 show another embodiment of the present invention. In this embodiment, the partition member 31 as shown in FIG. 3 is not provided. Instead, when the waste gate valve 28 is opened (fully opened), the waste gate valve 28 is It is devised to play the role of the partition member 31.

  That is, as shown in FIG. 7 and FIG. 8, when the waste gate valve 28 is opened approximately 90 degrees from the fully closed state (when fully opened), it is discharged from the bypass passage 27 and is detected by the A / F sensor 40. The exhaust gas discharged from the exhaust port 26 on the turbine wheel 21 side is made difficult to mix with the flow of exhaust gas toward the vehicle.

  Specifically, when the support shaft 29 of the waste gate valve 28 is disposed between the bypass passage 27 and the discharge port 26 on the turbine wheel 21 side, and the waste gate valve 28 is fully opened, a circular and plate-like shape is obtained. A waste gate valve 28 made of a member is disposed between the exhaust gas that is discharged straight from the bypass passage 27 and the exhaust gas that is discharged straight from the discharge port 26 on the turbine wheel 21 side, and both the exhaust gases. The posture is almost parallel to the discharge direction.

  In this case, as shown in FIGS. 7 and 8, when the waste gate valve 28 is fully opened, the waste gate valve 28 functions as a partition member 31 as shown in FIG. The exhaust gas discharged from each cylinder 1 (at a timing corresponding to a predetermined combustion order) and passing through the bypass passage 27 is likely to directly hit the detection part of the A / F sensor 40, and sequentially from each cylinder of the engine 1. (Timing according to a predetermined combustion order) The exhaust gas discharged and mixed in the turbine wheel 21 is less likely to hit the detection portion of the A / F sensor 40. Thereby, the operation | movement and effect which are not inferior compared with the said embodiment come to be acquired.

  The present invention provides an exhaust gas having a configuration in which a turbine housing and a catalyst of a supercharger are installed in series in an exhaust gas flow direction in the middle of an exhaust passage of an engine, and a bypass passage that bypasses the turbine housing is opened and closed by a waste gate valve. It can be suitably used for an apparatus.

1 engine
2 Intake manifold 3A First exhaust manifold (part of exhaust passage)
3B 2nd exhaust manifold (part of exhaust passage)
4 Intake pipe
8 First relay exhaust pipe (part of exhaust passage)
9 Second relay exhaust pipe (part of exhaust passage)
DESCRIPTION OF SYMBOLS 20 Turbocharger 21 Turbine wheel 24 Turbine housing 26 Turbine wheel side discharge port 27 Bypass passage 28 Waste gate valve 31 Partition member 40 A / F sensor 41 Sensor element 42 Inner cover 43 Outer cover 45 Side opening of inner cover 46 Outer cover Side opening 47 Inner cover end face opening 48 Outer cover end face opening

Claims (7)

A turbocharger turbine housing and a catalyst are provided in series in the exhaust gas flow direction in the middle of the exhaust passage of the engine.
A bypass passage for bypassing the turbine wheel of the supercharger is provided in the exhaust passage, and a waste gate valve for adjusting a bypass amount of exhaust gas from the bypass passage is provided,
An exhaust sensor is provided in a region between the turbine housing and the catalyst in the exhaust passage;
An exhaust system for an engine according to claim 1, wherein a detection portion of the exhaust sensor is set to a state in which exhaust gas discharged from the bypass passage directly hits. The engine exhaust system according to claim 1,
The exhaust gas discharged from the bypass passage is set to flow straight toward the inlet of the catalyst,
An exhaust system for an engine, wherein a detection portion of the exhaust sensor is disposed at a position corresponding to the flow of the exhaust gas going straight. The exhaust system for an engine according to claim 1 or 2,
The region between the turbine housing and the catalyst in the exhaust passage is shaped so as to go straight along the exhaust gas discharge direction from the turbine housing and then bend 90 degrees. The engine exhaust system. The engine exhaust system according to any one of claims 1 to 3,
In the turbine housing, on the downstream side of the exhaust gas exhaust port of the bypass passage and the exhaust gas exhaust port from the turbine wheel, the flow of exhaust gas from the bypass passage until it hits the detection part of the exhaust sensor, An exhaust system for an engine, characterized in that a partition member for making it difficult to mix exhaust gas discharged from the turbine wheel is provided. The engine exhaust system according to any one of claims 1 to 3,
The waste gate valve is arranged in a state in which it is difficult to mix the exhaust gas discharged from the turbine wheel with the flow of exhaust gas discharged from the bypass passage until it hits the detection part of the exhaust sensor when opened. An exhaust system for an engine. The engine exhaust system according to claim 5,
The waste gate valve is a plate-like member that is disposed on the discharge port side of the bypass passage so that the discharge port can be opened and closed. When the waste gate valve is opened, the waste gate valve travels straight from the bypass passage and is discharged. An exhaust system for an engine, wherein the exhaust system is disposed between a gas and exhaust gas discharged straight from the turbine wheel. The exhaust system for an engine according to any one of claims 1 to 6,
The detection part of the exhaust sensor has a structure in which the sensor element is covered with a double wall composed of an inner cover and an outer cover, and the inner cover and the outer cover are provided with side openings and end openings, respectively.
The engine exhaust system is characterized in that the detection part of the exhaust sensor is in an installed state in which exhaust gas discharged from the bypass passage flows in from the side opening and flows out from the end opening.

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