JP5494068B2 - Engine exhaust system - Google Patents

Description

  The present invention relates to an exhaust gas purification unit that is disposed in an exhaust passage of an engine and purifies the exhaust gas, an exhaust pipe that forms the exhaust passage, and an exhaust sensor that detects the properties of the exhaust gas that has passed through the exhaust gas purification unit. And belongs to a technical field related to an engine exhaust system.

  As an exhaust device for this type of engine, the exhaust pipe connected to the exhaust downstream side of the exhaust purification section is composed of an outer pipe and an inner pipe so that the detection part of the exhaust sensor faces the inner pipe. Those are known (for example, see Patent Documents 1 and 2). In this device, the exhaust gas after passing through the exhaust gas purification unit branches into a central part flow passing through the inner pipe and an outer peripheral part flow passing between the inner pipe and the outer pipe and is discharged to the exhaust downstream side. . As a result, the condensed water adhering to the tube wall when the engine is cold rides on the outer peripheral portion and passes between the inner tube and the outer tube, so that the detection unit of the exhaust sensor detects the condensed water in the exhaust gas. It is possible to suppress flooding.

JP-A-8-254522 JP 2007-224877 A

  As described above, in each of the above-mentioned patent documents, the detection unit of the exhaust sensor has a structure that is difficult to be wetted by the condensed water in the exhaust gas. A reduction in accuracy can be prevented.

  However, in these exhaust devices, the exhaust flow branches into a central portion flow and an outer peripheral portion flow, and only the central portion flow passes around the detection portion of the exhaust sensor. There is a problem that the exhaust properties (for example, oxygen concentration, etc.) cannot be accurately detected.

  The present invention has been made in view of such a point, and an object of the present invention is to provide an exhaust purification unit that is disposed in an exhaust passage of an engine and purifies the exhaust, and an exhaust pipe that forms the exhaust passage. And an exhaust sensor for an engine having an exhaust sensor for detecting the exhaust property after passing through the exhaust purification unit, the exhaust sensor is used to control the exhaust property of the entire exhaust flow by devising the configuration. An object of the present invention is to prevent the exhaust sensor from being damaged or the detection accuracy of the exhaust sensor from being damaged by the detection part of the exhaust sensor being covered with the condensed water scattered together with the exhaust while detecting with high accuracy.

  In order to achieve the above object, according to the present invention, an inner pipe is provided in an exhaust pipe connected to the exhaust purification section, and an end of the inner pipe on the exhaust downstream side is connected to a pipe wall of the exhaust pipe. Between the pipe and the exhaust pipe, an annular space is formed in which the exhaust downstream side is closed and the exhaust upstream side is open.

  Specifically, in the first aspect of the present invention, an exhaust purification unit that is disposed in the exhaust passage of the engine and purifies the exhaust, an exhaust pipe that forms the exhaust passage, and after passing through the exhaust purification unit An exhaust system for an engine provided with an exhaust sensor for detecting the nature of the exhaust is intended.

In the exhaust pipe connected to the exhaust downstream side end of the exhaust purification unit, an inner pipe extending along the exhaust pipe is provided, and the inner pipe has an end on the exhaust downstream side of the exhaust pipe. By connecting to the pipe wall of the exhaust pipe, an annular space is formed between the exhaust pipe and the exhaust downstream side is closed and the exhaust upstream side is open, and all of the exhaust flow that has passed through the exhaust purification unit The exhaust sensor is disposed so that its detection part faces the inner pipe and is connected to the exhaust downstream side end of the exhaust purification part in the exhaust pipe. The downstream portion is a downstream cone portion that is reduced in diameter toward the exhaust downstream side, and a part of the exhaust gas that has passed through the exhaust gas purification portion is returned to the intake air as EGR gas in the downstream cone portion. as the EGR outlet of is provided That.

  According to this configuration, the end of the inner pipe on the exhaust downstream side is connected to the pipe wall of the exhaust pipe, so that the exhaust downstream side is closed between the inner pipe and the exhaust pipe and the exhaust upstream An annular space having an open side is formed. Therefore, when the engine is started, the outer peripheral part flow that passes through the outer peripheral part of the exhaust purification part and flows into the annular space along the pipe wall of the exhaust pipe is blocked by the closed part of the annular space and flows backward. After flowing from the downstream side toward the upstream side along the outer peripheral surface of the pipe, it collides with the central part flow near the upstream opening of the inner pipe and flows into the inner pipe in a form dragged by the central part flow. It will be. Because of this collision, the condensed water contained in the outer peripheral flow is subdivided, so that even if condensed water collides with the detection part of the exhaust sensor, the exhaust sensor may be damaged or its detection accuracy may be reduced. Nor.

  Further, as described above, the outer peripheral part flow after passing through the exhaust purification part flows into the annular space and flows backward, and then collides with the central part flow and is guided into the inner pipe together with the central part flow. All the exhaust flow after passing through the exhaust purification section can be circulated in the inner pipe. Since the detection part of the exhaust sensor faces in the inner pipe, the exhaust sensor can accurately detect the properties of the entire exhaust flow including the central part flow and the outer peripheral part flow.

Further, in an engine employing EGR control, which has been developed in recent years in order to reduce NOx and the like in the exhaust, the exhaust sensor detection unit prevents the EGR cooler from being clogged with soot and the like, while the EGR cooler detects the condensate Therefore, it is possible to prevent the detection accuracy from being lowered due to water.

That is, in this type of engine, an EGR cooler for cooling the EGR gas is disposed in the middle of the EGR pipe for circulating the exhaust gas to the intake air. For this reason, if the exhaust gas discharged from the engine is recirculated to the intake air without being purified, soot or the like in the exhaust gas is clogged in the heat exchange passage of the EGR cooler, resulting in variations in the EGR amount or the required EGR amount. There is a problem that it cannot be secured sufficiently.

On the other hand, in the present invention, the exhaust cone portion located on the exhaust downstream side of the exhaust purification section is provided with the EGR outlet, so that the exhaust after the soot and the like are removed by the exhaust purification section is EGR. Can be removed from the tube. Thereby, it is possible to prevent the EGR cooler provided in the EGR pipe from being clogged with soot.

By the way, the EGR pipe is preferably unitized with the manifold and the exhaust purification unit from the viewpoint of improving the assemblability, and for this purpose, the EGR pipe is connected to a portion of the exhaust pipe near the downstream side of the exhaust purification section. There is a need. Since an exhaust sensor is usually provided in this portion, the EGR outlet for connecting the EGR pipe is located in the vicinity of the exhaust sensor, resulting in the following problems.

That is, as described above, since the EGR cooler is disposed in the EGR pipe, the exhaust gas condensed by the EGR cooler when the engine is cold flows into the exhaust pipe from the EGR outlet through the EGR pipe. . Since a take-out space for forming the take-out port is required around the EGR take-out port, the inflowing condensed water accumulates in the take-out space. Assuming that the engine is started in this state, the exhaust discharged from the engine flows into the exhaust passage at once, and the accumulated condensed water is scattered, and the detection part of the exhaust sensor is caused by the scattered large condensed water. As a result, the exhaust sensor is damaged or the detection accuracy of the exhaust sensor is lowered.

On the other hand, in the present invention, as described above, an inner pipe is provided in the exhaust pipe connected to the exhaust downstream side of the exhaust purification section (in the downstream cone section), and between the inner pipe and the exhaust pipe. By forming an annular space in which the exhaust downstream side is closed, the condensed water accumulated in the annular space (extraction space) is caused to collide with the central part flow by the outer peripheral part flow that flows back into the space and then flows backward. Can be subdivided. Therefore, it is possible to prevent the condensed water accumulated in the space from colliding with the detection unit of the exhaust sensor with large particles, and it is possible to prevent the exhaust sensor from being damaged and the detection accuracy from being lowered.

  According to a second aspect of the present invention, in the first aspect of the present invention, the exhaust sensor has a detection portion in the inner tube within a range from the intermediate portion in the longitudinal direction of the inner tube to the exhaust downstream end. It shall be arranged so as to face.

  According to this structure, the detection part of an exhaust sensor can be located as far as possible from the upstream edge part (namely, upstream opening) of an inner side pipe | tube. Thereby, the condensed water subdivided by the collision between the central flow and the outer peripheral flow of the exhaust flow is sufficiently dispersed until it reaches the detection part of the exhaust sensor on the exhaust flow. As a result, the amount of water covered by the detection unit can be reduced.

According to a third aspect of the present invention, in the first aspect of the invention, the engine body is mounted horizontally in the engine room of the front portion of the vehicle, and the exhaust passage extends from the rear side surface of the engine main body to the downstream cone portion. Within the range to the exhaust downstream side end, it extends so that its height decreases toward the rear of the vehicle, and is formed so that its height is the lowest at the lower surface of the downstream cone It is assumed that

  According to this configuration, the exhaust passage is located at the lowest position at the lower end portion of the downstream cone portion, so that condensed water easily accumulates in this portion. The present invention is particularly useful for an engine having such a structure.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the EGR pipe further includes an EGR pipe having one end connected to the intake passage of the engine and the other end connected to the EGR outlet. It is assumed that the height decreases from the connecting portion with the passage toward the EGR outlet.

  According to this configuration, the passage height of the EGR pipe becomes lower from the connection portion between the EGR pipe and the intake pipe toward the EGR outlet, and therefore, the EGR pipe is condensed on the heat exchange surface of the EGR cooler when cold. Condensed water finally flows to the EGR outlet and tends to accumulate in the vicinity of the EGR outlet. The present invention is particularly useful for an engine having such a structure.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the exhaust pipe downstream end of the inner pipe is partially exposed to the outside of the exhaust pipe. It is assumed that a flexible joint is provided at the exposed portion at the exhaust downstream side end of the inner pipe.

  According to this configuration, the downstream end portion of the inner pipe is disposed so that a part thereof is exposed to the outside of the exhaust pipe, and the flexible joint is provided on the exposed portion. The structure can be made compact and simple.

As described above, according to the engine exhaust device of the present invention, the inner pipe is provided in the exhaust pipe connected to the exhaust purification section, and the end of the inner pipe on the exhaust downstream side is connected to the pipe wall of the exhaust pipe. A portion between the inner pipe and the exhaust pipe that forms an annular space that is closed on the exhaust downstream side and open on the upstream side of the exhaust, and connected to the exhaust downstream end of the exhaust purification unit in the exhaust pipe As a downstream cone portion whose diameter decreases toward the exhaust downstream side, an EGR outlet for returning a part of the exhaust gas after passing through the exhaust gas purification portion to the intake air as EGR gas is provided in the downstream cone portion. As a result, the exhaust sensor can detect the exhaust properties of the entire exhaust flow with high accuracy, and the exhaust sensor can be damaged by being covered with condensed water splashed with the exhaust or its detection accuracy can be reduced. Prevent It is possible. Moreover, it is possible to prevent the EGR cooler from being clogged with soot and the like, and to prevent the condensed water accumulated in the space from colliding with the detection part of the exhaust sensor in the form of large particles. It is possible to prevent the damage and the deterioration of detection accuracy.

It is the figure seen from the vehicle left side which shows the exhaust apparatus of the engine which concerns on embodiment of this invention. It is the perspective view seen from the diagonal right side of the vehicle rear side which shows the internal structure of an exhaust apparatus. It is a longitudinal cross-sectional view of an exhaust apparatus. It is the perspective view seen from the diagonal right side of the vehicle rear side which shows the internal structure of an exhaust apparatus.

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

  1 to 4 show an exhaust system 1 for an engine according to an embodiment of the present invention. This exhaust system 1 is for removing harmful substances such as soot discharged from an engine body 2.

  The exhaust device 1 is arranged on an exhaust manifold 3 connected to the engine body 2, an exhaust purification unit (exhaust purification unit) 4 connected to the exhaust manifold 3, and an exhaust upstream side and a downstream side of the exhaust purification unit 4. And an exhaust sensor 5 for detecting the exhaust properties (oxygen concentration in the present embodiment) and an EGR device 6 (only the EGR pipe 7 is shown in FIG. 1) for circulating a part of the exhaust into the intake air. I have. A detection signal of the exhaust sensor 5 is transmitted to an engine ECU (not shown), and the ECU controls the fuel injection amount and the EGR amount of the engine body 2 based on the detection signal.

  The engine body 2 is a multi-cylinder diesel engine in which a plurality of cylinders are arranged in series, and is arranged horizontally in the engine room so that the crankshaft extends in the vehicle width direction. The engine body 2 is not limited to a diesel engine, and may be, for example, a normal gasoline engine equipped with a spark plug.

  The engine body 2 is disposed such that its upper end portion is inclined (slant) toward the vehicle rear side with respect to the lower end portion (see FIG. 1). Exhaust ports (not shown) communicating with the respective cylinders are formed side by side in the vehicle width direction on the surface 2a on the vehicle rear side of the engine body 2. In the following description, “upstream side” and “downstream side” mean the exhaust upstream side and the exhaust downstream side, respectively.

  The exhaust manifold 3 includes branch pipes 3a (only the branch pipe 3a located on the leftmost side in the vehicle width direction is shown in FIG. 1) connected to the exhaust ports, and downstream ends of the branch pipes 3a. And a gathering unit 3b that gathers.

  The exhaust purification unit 4 has a cylindrical filter housing 9 that holds a filter 8 (see FIGS. 2 and 3) inside. The filter 8 is a porous ceramic diesel particulate filter (hereinafter referred to as DPF), for example, a known structure shown in Patent Document 1 (Japanese Patent Laid-Open No. 2007-224877) may be employed. it can. The upstream end portion of the filter housing 9 is connected to the collective portion 3 b of the exhaust manifold 3 via the upstream cone pipe 10. The downstream end of the filter housing 9 is connected to the downstream cone pipe 11, and the downstream end of the downstream cone pipe is further connected to the exhaust pipe 13 (see FIG. 3) via the flexible joint 12. Only connected). The exhaust purification unit 4, the upstream cone pipe 10, and the downstream cone pipe 11 are unitized in consideration of the ease of assembly to the engine body 2.

  The upstream cone pipe 10 has a diameter that increases toward the downstream side, and is connected to the upstream end of the filter housing 9. The upstream cone pipe 10 is formed by welding two sheet metal forming members that are divided into upper and lower halves.

  Similarly to the upstream cone pipe 10, the downstream cone pipe 11 is formed by two upper and lower half sheet metal forming members. An inner pipe 15 extending along the pipe 11 is provided in the downstream cone pipe 11. The inner diameter of the upper half of the downstream cone pipe 11 is kept substantially constant toward the downstream side, whereas the lower half of the downstream cone pipe 11 has an inner diameter as it goes downstream. Decrease (see FIG. 3). In other words, the downstream cone pipe 11 is formed in a cone shape whose diameter is reduced toward the downstream side.

  The exhaust passage formed by the exhaust manifold 3, the upstream cone pipe 10, the filter housing 9, and the downstream cone pipe 11 is inclined such that the height of the exhaust passage decreases toward the rear of the vehicle (see FIG. 3). And in the range L (refer FIG. 1) from the vehicle rear side surface 2a of the said engine main body 2 to the downstream end part of the said downstream cone pipe 11, this channel | path height is in the lower surface part 16 of the downstream cone pipe 11. The lowest. Further, the lower surface portion 16 of the downstream cone pipe 11 is substantially horizontal because the engine body 2 as a whole is slanted (inclined) toward the vehicle rear side.

An EGR outlet 17 is formed in a portion slightly above the lower surface portion 16 of the downstream cone pipe 11, and for attaching the downstream exhaust sensor 5 further above the EGR outlet 17. A sensor mounting hole 18 (see FIG. 3) is formed. An EGR pipe 7 constituting a part of the EGR device 6 is connected to the EGR outlet 17. The end of the EGR pipe 7 opposite to the side connected to the outlet 17 is connected to an intake pipe (not shown). In the middle of the EGR pipe 7, although not shown, EGR cooler for cooling the EGR gas passing through the EGR pipe 7 is provided. The EGR pipe 7 is formed such that its passage height decreases from the connection portion with the intake passage toward the EGR outlet 17.

  The inner tube 15 is formed of a cylindrical integrally molded product having an inner diameter that is substantially constant along the axial direction thereof. The inner pipe 15 is joined to the downstream cone pipe 11 by welding in a state in which the outer circumferential side surface of the downstream end is in close contact with the inner circumferential surface of the downstream cone pipe 11. The inner pipe 15 is formed so as to curve inward in the radial direction of the downstream cone pipe (that is, on the side away from the upper half of the downstream cone pipe 11) as it goes upstream. Thus, an annular space 30 is formed between the inner pipe 15 and the downstream cone pipe 11, which is closed on the downstream side and opened on the upstream side. It can be said that the annular space 30 is a bag-like space opened to the upstream side. The annular space 30 is formed over the entire circumference along the outer circumferential surface so as to surround the inner tube 15.

The exhaust sensor 5 is an oxygen concentration sensor (O ₂ sensor) using zirconia ceramic. The exhaust sensor 5 includes a main body portion 5a having a male screw portion 5c for attachment, a rod-shaped detection portion 5b connected to the main body portion 5a, and a protective tube 20 surrounding the outer periphery of the detection portion 5b. . The protective tube 20 is for protecting the detection element from being directly exposed to an exhaust flow or condensed water, and a plurality of exhaust intake ports 20 a are formed on the surface of the protective tube 20.

  A nut 19 is welded to the outer peripheral surface of the downstream cone pipe 11 coaxially with the sensor mounting hole 18, and the exhaust sensor 5 is engaged with the nut 19 by screwing a male screw portion 5 c into the downstream cone pipe. 11 is attached. An insertion hole 21 is formed in the inner pipe 15 coaxially with the sensor mounting hole 18 of the downstream cone pipe 11, and the exhaust sensor 5 has a detection unit 5 b in a state of being attached to the downstream cone pipe 11. It arrange | positions so that it may face in the inner side pipe | tube 15 from the insertion hole 21. FIG. In the attached state, the tip of the detection unit 5 b is located on the axis of the inner tube 15. Moreover, the detection part 5b of the exhaust sensor 5 is located considerably downstream from the upstream end of the inner pipe. That is, the detection part 5 b of the exhaust sensor 5 is located in the middle part of the inner pipe 15 in the length direction. Note that the detection part 5 b of the exhaust sensor 5 may be located at the downstream end of the inner pipe 15.

  The downstream end of the inner pipe 15 is located on the downstream side of the downstream end of the downstream cone pipe 11, so that the downstream end of the inner pipe 15 is positioned outside the downstream cone pipe 11. A mounting surface 22 that is exposed to the surface is formed. A flange member 23 constituting a flexible joint 12 (see, for example, JP-A-2002-89259) and a spherical projecting member 26 are attached to the attachment surface 22.

  The flange member 23 is made of a substantially rhombic plate material having a circular hole 23 a at the center, and is welded to the downstream cone pipe 11 in a state where the circular hole 23 a is externally fitted to the mounting surface 22. Two bolts 27 that support the flange member 24 (see FIG. 3), which is a mating component connected via the flexible joint 12, are provided on the seating surface (one side surface in the thickness direction) of the flange member 23. It is erected at a position facing each other across the. The spherical projecting member 26 is formed in an annular shape, and the surface thereof is formed in a spherical shape that fits into a concave spherical portion 24 a formed in the mating flange member 24. The spherical protruding member 26 is welded to both the flange member 23 and the inner tube 15 in a state where the inner peripheral surface thereof is fitted to the mounting surface 22 and the base end surface thereof is in contact with the seating surface 23b of the flange member 23. Has been.

In the engine exhaust system configured as described above, the exhaust passage height is the lowest in the lower surface portion 16 of the downstream cone pipe 11, and the lower surface portion 16 extends in the horizontal direction. Condensed water condensed by touching the wall surface of the exhaust pipe at a short time tends to accumulate in the take-out space 30a (see FIGS. 2 and 3) down the pipe wall surface and having the lower surface portion 16 as a bottom surface. This extraction space 30 a constitutes a part of the annular space 30. An EGR outlet 17 to which the EGR pipe 7 is connected communicates with the extraction space 30a, and the EGR pipe 7 is formed such that its height decreases toward the EGR outlet. For this reason, the condensed water condensed by the EGR cooler has a structure in which it easily falls in the EGR pipe 7 and accumulates in the extraction space 30a.

  Therefore, when the condensed water accumulated in the take-out space 30a scatters at the start of the engine due to the momentum of the exhaust flow, a large amount of condensed water collides with the detection portion 5b of the exhaust sensor 5, and the exhaust sensor 5 is damaged or detected. There is a problem that accuracy is lowered.

  On the other hand, in the above embodiment, the inner pipe 15 is provided in the downstream cone pipe 11, and the downstream end of the inner pipe 15 is connected to the pipe wall of the cone pipe 11, thereby An annular space 30 that is closed on the downstream side and opened on the upstream side is formed between 15 and the downstream cone pipe 11. Thus, by utilizing the convection effect of the exhaust in the annular space 30, it is possible to subdivide the condensed water accumulated in the take-out space 30a even if it is scattered by the force of the exhaust.

  That is, as shown in FIG. 3, the outer peripheral part flow that has passed through the outer peripheral part of the exhaust purification unit 4 flows from the upstream side toward the downstream side along the tube wall in the downstream side cone pipe 11. Since the downstream side of the annular space 30 is blocked on the downstream side of the annular space 30, the outer peripheral part flow that flows into the annular space 30 loses its destination at the downstream end, and flows backward along the outer peripheral surface of the inner pipe 15. It flows toward the upstream side. Thus, the condensed water that has reached the vicinity of the upstream opening 15 a of the inner pipe 15 collides with the central part flow that has passed through the central part of the exhaust purification unit 4. The outer peripheral part flow contains a lot of condensed water adhering to the tube wall and the condensate accumulated in the space. The condensed water is subdivided by the collision between the outer peripheral part flow and the central part flow. It flows into the inner tube while being dragged by the central flow.

Therefore, even if condensed water collides with the detection part of the exhaust sensor 5, the particle size is small, so the exhaust sensor 5 is not damaged or the detection accuracy is not lowered. In the above embodiment, the exhaust sensor 5 Since the detection unit is located considerably downstream of the upstream opening 15a (upstream end) of the inner pipe 15, the condensed water subdivided in the vicinity of the upstream opening 15a is detected by the exhaust sensor 5. It will be sufficiently dispersed before reaching the part. Thereby, the amount of moisture in the detection part of the exhaust sensor 5 can be reduced, and as a result, a decrease in detection accuracy due to the moisture of the exhaust sensor 5 can be prevented more reliably.
(Other embodiments)
The configuration of the present invention is not limited to the above embodiment, but includes various other configurations. That is, in the above-described embodiment, the exhaust sensor 5 is an O ₂ sensor that detects the oxygen concentration as the exhaust property, but is not limited to this. For example, the exhaust sensor 5 is a temperature that detects the exhaust temperature as the exhaust property. It may be a sensor.

  In the above embodiment, the exhaust purification unit 4 is configured to hold the DPF inside, but is not limited thereto, and may be, for example, a unit that holds the three-way catalyst inside.

Moreover, in the said embodiment, although the example which applied the exhaust apparatus 1 of this invention to the diesel engine was shown, you may make it apply not only to a diesel engine but to a gasoline engine etc., for example .

The present invention relates to an exhaust gas purification unit that is disposed in an exhaust passage of an engine and purifies the exhaust gas, an exhaust pipe that forms the exhaust passage, and an exhaust sensor that detects the properties of the exhaust gas that has passed through the exhaust gas purification unit. e Bei bets useful part of the exhaust gas to the exhaust system of an engine provided with an EGR device for returning to the intake as EGR gas.

1 Engine exhaust system 2 Engine body 4 Exhaust purification unit (exhaust purification unit)
5 Exhaust sensor 5b detector
7 EGR pipe 11 Downstream cone pipe (downstream cone section)
12 Flexible joint 15 Inner tube 16 Lower surface 17 EGR outlet 30 Annular space

Claims (5)

An exhaust purification unit disposed in the exhaust passage of the engine for purifying the exhaust, an exhaust pipe forming the exhaust passage, and an exhaust sensor for detecting the properties of the exhaust after passing through the exhaust purification unit. Engine exhaust system,
In the exhaust pipe connected to the exhaust downstream end of the exhaust purification section, an inner pipe extending along the exhaust pipe is provided,
The inner pipe is connected to the exhaust pipe at its end on the exhaust downstream side, thereby forming an annular space between the exhaust pipe and the exhaust downstream side that is closed and the exhaust upstream side is open. And is configured to circulate all of the exhaust flow that has passed through the exhaust purification unit in the inner pipe,
The exhaust sensor is disposed such that the detection portion faces the inner pipe ,
The portion connected to the exhaust downstream side end of the exhaust purification unit in the exhaust pipe is a downstream cone portion that decreases in diameter toward the exhaust downstream side,
2. An exhaust system for an engine according to claim 1, wherein an EGR outlet for returning a part of the exhaust gas after passing through the exhaust gas purification unit to intake air as EGR gas is provided in the downstream cone portion . The engine exhaust device according to claim 1,
In the engine, the exhaust sensor is disposed so as to face the inner pipe in a range from the lengthwise intermediate portion of the inner pipe to the exhaust downstream end. Exhaust system. The engine exhaust device according to claim 1 ,
The engine body is mounted horizontally in the engine room at the front of the vehicle,
The exhaust passage extends in a range from the vehicle rear side of the engine main body to the exhaust downstream end of the downstream cone portion so that the height thereof decreases toward the vehicle rear side. An exhaust system for an engine, characterized in that the lower surface portion of the downstream cone portion is formed to have the lowest height. The engine exhaust device according to claim 1 ,
An EGR pipe having one end connected to the intake passage of the engine and the other end connected to the EGR outlet;
The exhaust system for an engine according to claim 1, wherein the EGR pipe is formed such that a height thereof decreases from a connection portion with the intake passage toward the EGR outlet. The engine exhaust system according to any one of claims 1 to 4 ,
The exhaust pipe downstream end of the inner pipe is connected to the pipe wall of the exhaust pipe in a state where a part thereof is exposed to the outside of the exhaust pipe,
An exhaust system for an engine, wherein a flexible joint is provided at the exposed portion at the exhaust downstream end of the inner pipe.

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