Exhaust apparatus for internal combustion engine

An exhaust apparatus for an internal combustion engine includes a first exhaust collecting section, a first exhaust passage, a first exhaust sensor, and a rib. The first exhaust passage is connected to the first exhaust collecting section and has a curved shape to change a flow direction of the exhaust gas from a direction in which the exhaust gas is ejected from each of first cylinders. The first exhaust passage includes an outer wall provided on a radially outer side of the curved shape. The rib is provided on the outer wall of the first exhaust passage and extends along a direction perpendicular to a direction in which the exhaust gas flows. The rib is positioned downstream from the first exhaust sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2011-256961, filed Nov. 25, 2011, entitled “Exhaust Apparatus For Internal Combustion Engine.” The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to an exhaust apparatus for an internal combustion engine.

2. Discussion of the Background

In a typical exhaust system for an internal combustion engine, an exhaust sensor for detecting the composition of exhaust gas ejected from a plurality of cylinders is arranged in a cone section through which the exhaust gas between an exhaust manifold in which the exhaust gases from the cylinders are collected and a close coupled catalytic converter immediately downstream of the engine.

The exhaust sensor protrudes in the cone section and is arranged in a location where all of exhaust flows from the cylinders uniformly comes into contact with the detecting section to detect the composition of all the exhaust gases from the cylinders (see Japanese Unexamined Patent Application Publication No. 2010-001869).

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an exhaust apparatus for an internal combustion engine includes a first exhaust collecting section, a first exhaust passage, a first exhaust sensor, and a rib. The first exhaust collecting section includes first exhaust ports extending from a plurality of first cylinders in the internal combustion engine. The first exhaust ports are combined to collect exhaust gas ejected from the plurality of first cylinders. The exhaust gas from the exhaust collecting section is to flow through the first exhaust passage. The first exhaust passage is connected to the first exhaust collecting section and has a curved shape to change a flow direction of the exhaust gas from a direction in which the exhaust gas is ejected from each of the first cylinders. The first exhaust passage includes an outer wall provided on a radially outer side of the curved shape. The first exhaust sensor is disposed on the outer wall of the first exhaust passage and includes a first detector configured to detect a constituent of the exhaust gas. The first detector protrudes from the outer wall of the first exhaust passage into an inside of the first exhaust passage. The rib is provided on the outer wall of the first exhaust passage and extending along a direction perpendicular to a direction in which the exhaust gas is to flow. The rib is positioned downstream from the first exhaust sensor.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1illustrates in general an internal combustion engine1according to the present embodiment. The internal combustion engine1illustrated inFIG. 1is a transverse V6 engine. The six cylinders are arranged such that three cylinders are positioned on the front side and the other three cylinders are positioned on the rear side in the vehicle, an FR bank (front bank)2is disposed on the front side in the vehicle, and an RR bank (rear bank)3is disposed on the rear side.

An intake air is introduced from an intake system communicating with the portion directly above the internal combustion engine1to the cylinders of both the banks2and3in an engine main body4. The intake air introduced from the intake passage into each cylinder is subjected to injection of a fuel supplied through a fuel injection valve, and they results in a mixed gas. The mixed gas burns in each cylinder, and this burning causes the piston to reciprocate and rotates the crankshaft. The exhaust gas after the burning in each cylinder is ejected to the exhaust system.

The exhaust system in the internal combustion engine is made up of two exhaust systems of one in the FR bank2and the other in the RR bank3for the engine main body4, and the two exhaust systems are combined downstream.

FIG. 2is a top view that illustrates the exhaust system in the FR bank2according to the present embodiment.

The exhaust system in the FR bank2includes exhaust ports21ato21f, an exhaust manifold22as an exhaust collecting section, a cone section23as an exhaust passage, a close coupled catalytic converter24immediately downstream of the engine, and an FR bank-side exhaust pipe25(seeFIG. 1).

As illustrated inFIG. 2, the exhaust ports21ato21fin the FR bank2extend in groups of two from the cylinders with the numbers4to6(hereinafter referred to as cylinders #4to #6) in the FR bank2toward the front of the vehicle.

The exhaust manifold22in the FR bank2combines the exhaust ports21ato21fon the front side of the vehicle and collects the exhaust gases from the cylinders #4to #6in the FR bank2.

As illustrated inFIG. 2, the exhaust manifold22combines the two exhaust ports21aand21bextending from the cylinder #4into a branch22a, the two exhaust ports21cand21dextending from the cylinder #5into a branch22b, and the two exhaust ports21eand21fextending from the cylinder #6into a branch22c. The exhaust manifold22combines the branches22a,22b, and22ccorresponding to the cylinders #4to #6in a downstream location and collects the exhaust gases in a collecting section22d.

The exhaust manifold22is connected to the cone section23in the FR bank2. The cone section23is curved so as to change its direction with respect to the direction in which the exhaust gases are ejected from the cylinders #4to #6and allows the exhaust gas from the exhaust manifold22to flow downstream.

As illustrated inFIG. 2, the cone section23is joined to the exhaust manifold22with a flange section23ain a surface contact manner.

A linear air-fuel ratio (LAF) sensor26is arranged in the cone section23(seeFIGS. 1,4, and6). The LAF sensor26outputs a current value proportional to an air-fuel ratio on the basis of, for example, the amount of oxygen ions passing through a zirconia solid electrolyte to an engine control unit (ECU) and detects a constituent of the exhaust gas.

The LAF sensor26is arranged in an extension line in the direction in which the exhaust gases are ejected from the cylinders #4to #6when viewed from a horizontal plane. That is, from the exhaust ports21ato21fof the cylinders #4to #6through the collecting section22dto a detecting section26a(seeFIG. 4) of the LAF sensor26are arranged in a line when viewed from a horizontal plane, and the exhaust gases flow toward the detecting section26aof the LAF sensor26in a straight-line manner.

The close coupled catalytic converter24in the FR bank2is a three-way catalytic converter that cleans the exhaust flowing from the cone section23of noxious substances by oxidation and reduction. The close coupled catalytic converter24may include one in which platinum, palladium, rhodium or the like is attached to the surface of a porous ceramic cylinder through which the exhaust passes using activated alumina as the base. The close coupled catalytic converter24is housed in a protective case made of a heat resisting steel plate.

The close coupled catalytic converter24is connected to the FR bank-side exhaust pipe25. The FR bank-side exhaust pipe25meets an RR bank-side exhaust pipe35extending in the rear of the vehicle described below in a downstream location and communicates with a collective exhaust pipe5.

FIG. 3is a top view of the exhaust system in the RR bank3.

The exhaust system in the RR bank3includes exhaust ports31ato31f, an exhaust manifold32as an exhaust collecting section, a cone section33as an exhaust passage, a close coupled catalytic converter34immediately downstream of the engine, and the RR bank-side exhaust pipe35(seeFIG. 1).

As illustrated inFIG. 3, the exhaust ports31ato31fin the RR bank3extend in groups of two from the cylinders with the numbers1to3(hereinafter referred to as cylinders #1to #3) in the RR bank3toward the rear of the vehicle.

The exhaust manifold32in the RR bank3combines the exhaust ports31ato31fon the rear side of the vehicle and collects the exhaust gases from the cylinders #1to #3in the RR bank3.

As illustrated inFIG. 3, the exhaust manifold32combines the two exhaust ports31aand31bextending from the cylinder #1into a branch32a, the two exhaust ports31cand31dextending from the cylinder #2into a branch32b, and the two exhaust ports31eand31fextending from the cylinder #3into a branch32c. The exhaust manifold32combines the branches32a,32b, and32ccorresponding to the cylinders #1to #3in a downstream location and collects the exhaust gases in a collecting section32d.

The exhaust manifold32is connected to the cone section33in the RR bank3. The cone section33is curved so as to change its direction with respect to the direction in which the exhaust gases are ejected from the cylinders #1to #3and allows the exhaust gas from the exhaust manifold32to flow downstream.

As illustrated inFIG. 3, the cone section33is joined to the exhaust manifold32with a flange section33ain a surface contact manner.

A LAF sensor36is arranged in the cone section33(seeFIGS. 1 and 5). The LAF sensor36outputs a current value proportional to an air-fuel ratio on the basis of, for example, the amount of oxygen ions passing through a zirconia solid electrolyte to the ECU and detects a constituent of the exhaust gas.

The LAF sensor36is arranged in an extension line in the direction in which the exhaust gases are ejected from the cylinders #1to #3when viewed from a horizontal plane. That is, from the exhaust ports31ato31fof the cylinders #1to #3through the collecting section32dto a detecting section36a(seeFIG. 5) of the LAF sensor36are arranged in a line when viewed from a horizontal plane, and the exhaust gases flow toward the detecting section36aof the LAF sensor36in a straight-line manner.

The close coupled catalytic converter34in the RR bank3is a three-way catalytic converter that cleans the exhaust flowing from the cone section33of noxious substances by oxidation and reduction. The close coupled catalytic converter34may include one in which platinum, palladium, rhodium or the like is attached to the surface of a porous ceramic cylinder through which the exhaust passes using activated alumina as the base. The close coupled catalytic converter34is housed in a protective case made of a heat resisting steel plate.

The close coupled catalytic converter34is connected to the RR bank-side exhaust pipe35. The RR bank-side exhaust pipe35meets the FR bank-side exhaust pipe25extending from the front of the vehicle in a downstream location and communicates with the collective exhaust pipe5.

As illustrated inFIG. 1, the collective exhaust pipe5is connected to an underfloor catalytic converter6in a downstream location. The catalyst of the same kind as in the close coupled catalytic converters24and34can be used in the close coupled catalytic converter6.

The cone section23in the FR bank2is described below with reference toFIG. 4.FIG. 4is a cross-sectional view that illustrates the cone section23and the LAF sensor26in the FR bank2.

The cone section23in the FR bank2is joined to the exhaust manifold22with the flange section23ain a surface contact manner, is curved so as to change its direction downward inFIG. 4with respect to the direction in which the exhaust gases are ejected from the cylinders #4to #6(horizontal direction inFIG. 4), and allows the exhaust gases to flow into the close coupled catalytic converter24. The cone section23has a flared skirt shape that gradually increases its diameter downstream from the curve because the downstream close coupled catalytic converter24has a large diameter.

The LAF sensor26is arranged in the cone section23in the FR bank2along an extension line in the direction in which the exhaust gases are ejected from the cylinders #4to #6when viewed from a horizontal plane. Because the cone section23is curved and changes the direction of the exhaust flow, the LAF sensor26is disposed on an outer wall23bof the cone section23remote from the exhaust manifold22, and the detecting section26afor detecting a constituent of the exhaust gases protrudes inside the cone section23in a location where the downwardly turning exhaust gases from the cylinders #4to #6come into direct contact with the detecting section26a.

Because the outer wall23bof the cone section23is a curved surface, the LAF sensor26is fixed to the cone section23with a support23dhaving an L shape in cross section, the support23denabling the LAF sensor26to be inserted from the above.

In the cone section23in the FR bank2, a rib23cextending on the outer wall23bin a straight line in the direction perpendicular to the direction of the exhaust flow (in a horizontal direction inFIG. 4) and positioned downstream from the LAF sensor26is disposed.

The cone section33in the RR bank3is described below with reference toFIG. 5.FIG. 5is a cross-sectional view that illustrates the cone section33and the LAF sensor36in the RR bank3.

The cone section33in the RR bank3is joined to the exhaust manifold32with the flange section33ain a surface contact manner, is curved so as to change its direction downward inFIG. 5with respect to the direction in which the exhaust gases are ejected from the cylinders #1to #3(horizontal direction inFIG. 5), and allows the exhaust gases to flow into the close coupled catalytic converter34. The cone section33has a flared skirt shape that gradually increases its diameter downstream from the curve because the downstream close coupled catalytic converter34has a large diameter.

The LAF sensor36is arranged in the cone section33in the RR bank3along an extension line in the direction in which the exhaust gases are ejected from the cylinders #1to #3when viewed from a horizontal plane. Because the cone section33is curved and changes the direction of the exhaust flow, the LAF sensor36is disposed on an outer wall33bof the cone section33remote from the exhaust manifold32, and the detecting section36afor detecting a constituent of the exhaust gases protrudes inside the cone section33in a location where the downwardly turning exhaust gases from the cylinders #1to #3come into direct contact with the detecting section36a.

Because the outer wall33bof the cone section33has an upper surface, the LAF sensor36is inserted from the above and fixed with a support33d.

Because the cone section33in the RR bank3on the rear side of the vehicle has empty space and the layout has ample room, the distance L2between the detecting section36aof the LAF sensor36and the outer wall33bwith which the exhaust gas having passed through the detecting section36acollides in the cone section33in the RR bank on the rear side of the vehicle is increased.

That is, the distance L2for the cone section33in the RR bank3on the rear side of the vehicle is longer than the distance L1(seeFIG. 4) between the detecting section26aof the LAF sensor26and the outer wall23bwith which the exhaust gas having passed through the detecting section26acollides in the cone section23in the FR bank2on the front side of the vehicle. That is, the relation L2>L1is established. Thus, in the cone section33, where the distance L2is set, the momentum of the exhaust gas colliding with the outer wall33bis weakened, and the stress occurring in the collision is reduced.

The cone section33in the RR bank3does not include an outer wall that has a rib, unlike the cone section23in the FR bank2including the outer wall having the rib23c. The outer wall33bof the cone section33in the RR bank3with which the exhaust gas having passed through the detecting section36aof the LAF sensor36collides has a large rounded shape33c. In the cone section33, which includes the outer wall33bwith the large rounded shape33c, the momentum of the exhaust gas colliding with the outer wall33bis weakened, and the stress occurring in the collision is reduced.

In contrast to the cone section33in the RR bank3, in which the longer distance L2is set and the outer wall33bhas the large rounded shape33c, the cone section23in the FR bank2has the shorter distance L1between the detecting section26aof the LAF sensor26and the outer wall23bwith which the exhaust gas having passed through the detecting section26acollides and has a great momentum of the exhaust gas colliding with the outer wall23b.

In addition, the exhaust gases ejected from the cylinders #4to #6collide with the outer wall23bin different locations.FIGS. 6A to 6Cillustrate exhaust flows from the exhaust ports21ato21fof the cylinders #4to #6into the cone section23in the FR bank according to the present embodiment. The locations where the exhaust gases flowing toward the detecting section26aof the LAF sensor26in a straight-line manner collide with the outer wall23bdiffer among the cylinders #4to #6in the location perpendicular to the direction of the exhaust flow, as illustrated in the regions indicated by the broken lines inFIGS. 6A to 6C. The locations of the collisions of the exhaust flow with the outer wall23bin the height direction do not differ among the cylinders #4to #6, as illustrated in the arrows indicating the exhaust flows. Accordingly, the locations of the collisions of the exhaust gases from the cylinders #4to #6with the outer wall23bare arranged in a line perpendicular to the direction of the exhaust flow.

In the present embodiment, the rib23cextending on the outer wall23bof the cone section23in the FR bank2in the locations of the collisions of the exhaust gases from the cylinders #4to #6in the direction perpendicular to the direction of the exhaust flow (horizontal direction inFIGS. 6A to 6C) in a straight line and positioned downstream from the LAF sensor26is disposed.

FIGS. 7A and 7Billustrate the cone section23in the FR bank2according to the above-described present embodiment,FIG. 7Ais a cross-sectional view thereof, andFIG. 7Bis a frontal view thereof.

The single rib23cis formed such that the outer wall23bwith which the exhaust gas having passed through the detecting section26aof the LAF sensor26collides with protrudes outward, as illustrated inFIG. 7A, and the rib23cextends over the wide outer wall23bin a straight line in the direction perpendicular to the direction of the exhaust flow (horizontal direction inFIGS. 7A and 7B), as illustrated inFIG. 7B.

The shape of the external protrusion of the rib23con the outer wall23bis set at an arc shape having a predetermined radius of curvature at which the optimum balance between increasing the stiffness of the outer wall23band not interfering with the exhaust flow inside the cone section23is achieved.

Because the stiffness of the outer wall23bin the location of collision of an exhaust gas is increased by the rib23c, the stress occurring when the exhaust gases from the cylinders #4to #6collide in different locations in the direction perpendicular to the direction of the exhaust flow (horizontal direction in the drawings) can be reduced by the use of the rib23c. Because the rib23cis disposed such that the outer wall23bprotrudes outward, the rib23cis not an obstacle to the exhaust flow inside the cone section23. In addition, because only the single rib23cis disposed, an increase in interference with the exhaust flow inside the cone section23that would be caused by multiple ribs does not occur.

The inventors conducted a test for checking the advantageous effect of reducing a stress by the use of the rib23c.FIG. 8illustrates results of a CAE test for a stress in the cone section23in the FR bank2according to the present embodiment and for that in a cone section231that does not include the rib23caccording to a comparative example.FIG. 9illustrates in graphs the results of the CAE test for the stress in the cone section23in the FR bank2according to the present embodiment and for that in the cone section231not including the rib23caccording to the comparative example.

Conditions of the test: An exhaust gas was ejected from the cylinder #4, and the stress occurring in the outer wall of the cone section23in the FR bank2and that of the cone section231at that time were measured.

Results: As illustrated inFIG. 8, a stress occurred in the left portion in the outer wall illustrated inFIGS. 8A and 8Bin each of the cone section23in the FR bank2according to the present embodiment and the cone section231including no rib23c. The results are based on ejection of the exhaust gas from the cylinder #4; if an exhaust gas is ejected from the cylinder #5or #6, a stress occurs in a central portion or a right portion in the outer wall illustrated inFIGS. 8A and 8Bin the same height location.

The location where the stress occurred in the cone section23in the FR bank2according to the present embodiment was in the rib23cand its vicinity.

As illustrated inFIG. 9, in the cone section23in the FR bank2according to the present embodiment, the occurring stress was below a target value. In contrast, in the cone section231including no rib23caccording to the comparative example, the occurring stress exceeded the target value. Thus, the advantageous effect of reducing the stress by the use of the rib23cwas confirmed. The target value is set such that the stress occurring in the cone section33, in which no noise occur, in the RR bank3, is used as the reference.

With the internal combustion engine according to the present embodiment, the following advantageous effects can be provided.

(1) The rib23cextends on the outer wall23bin the direction perpendicular to the direction of the exhaust flow, and the stiffness of the outer wall23bis increased. Thus, a stress occurring when the exhaust gases ejected from the cylinders #4to #6and having passed through the detecting section26aof the LAF sensor26collide with the outer wall23bof the cone section23in different locations in the direction perpendicular to the direction of the exhaust flow can be reduced by the use of the rib23c, and noise resulting from the stress can be reduced, and the silencing can be improved.

Unlike in the present embodiment, arrangement of a rib extending along the direction of the exhaust flow can be another approach. However, the arrangement of the rib extending along the direction of the exhaust flow is not efficient because the exhaust gases from the cylinders collide with the outer wall of the cone section in different locations in the direction perpendicular to the direction of the exhaust flow and the locations of the collisions are arranged in a line perpendicular to the direction of the exhaust flow.

(2) Because the rib23cis disposed in a location where the exhaust gas having passed through the detecting section26aof the LAF sensor26collides with the outer wall and the stiffness of the outer wall23bin that location of the collision is increased, a stress occurring when the exhaust gases collide in different locations in the direction perpendicular to the direction of the exhaust flow can be reduced by the use of the rib23c, noise resulting from the stress can be reduced, and the silencing can be improved.

Because the rib23cis formed such that the outer wall23bprotrudes outward, the rib23cis not an obstacle to the exhaust flow inside the cone section23and does not interfere with the exhaust flow, and the exhaust flow is not blocked.

Because only the single rib23cis disposed, an increase in interference with the exhaust flow inside the cone section including the rib that would be caused by multiple ribs does not occur.

(3) Because the exhaust gases flow toward the detecting sections26aand36aof the LAF sensors26and36in a straight-line manner, the exhaust gases from the cylinders can flow in the detecting sections26aand36awith reliability, and uniform detection among the cylinders can be achieved.

The locations of collisions of the exhaust gases having flowed in a straight-line manner toward the detecting section26aof the LAF sensor26on the outer wall23bare arranged in a line perpendicular to the direction of the exhaust flow. Thus, a stress occurring when the exhaust gases ejected from the cylinders #4to #6and having passed through the detecting section26aof the LAF sensor26collide with the outer wall23bof the cone section23in different locations on a line in the direction perpendicular to the direction of the exhaust flow can be reduced by the use of the rib23c, noise resulting from the stress can be reduced, and the silencing can be improved.

(4) In the FR bank2on the front side of the vehicle, a stress occurring when the exhaust gases ejected from the cylinders #4to #6and having passed through the detecting section26aof the LAF sensor26collide with the outer wall23bof the cone section23in different locations in the direction perpendicular to the direction of the exhaust flow can be reduced by the use of the rib23c, and noise resulting from the stress can be reduced, and the silencing can be improved.

In the RR bank3on the rear side of the vehicle, because empty space is present and the layout has ample room, the distance between the detecting section36aof the LAF sensor36and the outer wall33bwith which the exhaust gas collides in the cone section33can be increased, and the outer wall33bcan have the large rounded shape33cby which the exhaust gas having passed through the LAF sensor36can be prevented from strongly colliding with the outer wall. Thus, the silencing can be improved.

Accordingly, the silencing can be optimally improved on the front and rear sides of the vehicle.

(5) Because the RR bank3on the rear side of the vehicle has empty space and the layout has ample room, the distance L2between the detecting section36aof the LAF sensor36and the outer wall33bwith which the exhaust gas having passed through the detecting section36acollides in the cone section33in the RR bank3on the rear side of the vehicle can be increased. Thus, the exhaust gas having passed through the LAF sensor36does not strongly collide with the outer wall33b, the occurrence of noise can be suppressed, and the silencing can be improved. The rib is not required to be disposed on the outer wall33bof the cone section33.

The present application is not limited to the above-described embodiment. Various modifications and improvements within the scope of the present application are also included in the present application.

In the present embodiment, a LAF sensor is used as an exhaust sensor. Alternatively, an oxygen sensor that detects the concentration of oxygen in gas may also be used.

(A) An exhaust apparatus for an internal combustion according to an aspect of the embodiment includes an exhaust collecting section (e.g., exhaust manifold22) in which exhaust ports (e.g., exhaust ports21ato21f) extending from a plurality of cylinders in the internal combustion engine (e.g., internal combustion engine1) are combined and exhaust gases ejected from the plurality of cylinders are collected, an exhaust passage (e.g., cone section23) connected to the exhaust collecting section, being curved so as to change its direction with respect to a direction in which the exhaust gas is ejected from each of the cylinders, and allowing the exhaust gas from the exhaust collecting section to flow downstream, an exhaust sensor (e.g., LAF sensor26) disposed on an outer wall (e.g., outer wall23b) remote from the exhaust collecting section in the exhaust passage and including a detecting section (e.g., detecting section26a) that protrudes in the exhaust passage and that detects a constituent of the exhaust gas, and a rib (e.g., rib23c) extending on the outer wall of the exhaust passage in a direction perpendicular to a direction in which the exhaust gas flows and positioned downstream from the exhaust sensor.

With the exhaust apparatus according to the aspect (A) of the embodiment, because the rib extends on the outer wall in the direction perpendicular to the direction of the exhaust flow and the stiffness of the outer wall is increased, a stress occurring when the exhaust gases ejected from the cylinders and having passed through the detecting section of the exhaust sensor collide with the outer wall of the exhaust passage in different locations in the direction perpendicular to the direction of the exhaust flow can be reduced by the use of the rib, and noise resulting from the stress can be reduced, and the silencing can be improved.

Unlike in the exhaust apparatus described in the aspect (A) of the embodiment, arrangement of a rib extending along the direction of the exhaust flow can be another approach. However, the arrangement of the rib extending along the direction of the exhaust flow is not efficient because the exhaust gases from the cylinders collide with the outer wall of the exhaust passage in different locations in the direction perpendicular to the direction of the exhaust flow and the locations of the collisions are arranged in a line perpendicular to the direction of the exhaust flow.

(B) In the exhaust apparatus for the internal combustion engine described in the aspect (A) of the embodiment, the rib of the embodiment may be a single rib formed such that the outer wall in a location where the exhaust gas having passed through the detecting section of the exhaust sensor collides with the outer wall protrudes outward.

With the exhaust apparatus according to the aspect (B) of the embodiment, because the rib is disposed in a location where the exhaust gas having passed through the detecting section of the exhaust sensor collides with the outer wall and the stiffness of the outer wall in that location of the collision is increased, a stress occurring when the exhaust gases collide in different locations in the direction perpendicular to the direction of the exhaust flow can be reduced by the use of the rib, noise resulting from the stress can be reduced, and the silencing can be improved.

Because the rib of the embodiment is formed such that the outer wall protrudes outward, the rib is not an obstacle to the exhaust flow inside the exhaust passage and does not block the exhaust flow.

Because only the single rib is disposed, an increase that would be caused by multiple ribs in interference with the exhaust flow inside the exhaust passage on which the ribs are disposed does not occur, and the exhaust flow is not blocked thereby.

(C) In the exhaust apparatus for the internal combustion engine described in the aspect (A) or (B) of the embodiment, the exhaust gases of the embodiment may flow from the exhaust ports extending from the plurality of cylinders toward the detecting section of the exhaust sensor in a straight-line manner.

With the exhaust apparatus according to the aspect (C), because the exhaust gases flow toward the detecting section of the exhaust sensor in a straight-line manner, the exhaust gases from the cylinders can flow in the detecting section with reliability, and uniform detection among the cylinders can be achieved.

The locations of the collisions of the exhaust gases having flowed in a straight-line manner toward the detecting section of the exhaust sensor on the outer wall are arranged in a line perpendicular to the direction of the exhaust flow. Thus, a stress occurring when the exhaust gases ejected from the cylinders and having passed through the detecting section of the exhaust sensor collide with the outer wall of the exhaust passage in different locations on a line in the direction perpendicular to the direction of the exhaust flow can be reduced by the use of the rib, noise resulting from the stress can be reduced, and the silencing can be improved.

(D) In the exhaust apparatus for the internal combustion engine described in any one of the aspects (A) to (C) of the embodiment, the internal combustion engine may be a transverse V engine, the exhaust passage in a front bank (e.g., FR bank2) on a front side of the vehicle may include the outer wall on which the rib is disposed, and the exhaust passage in a rear bank (e.g., RR bank3) on a rear side of the vehicle may not include the outer wall on which the rib is disposed.

With the exhaust apparatus according to the aspect (D) of the embodiment, in the front bank on the front side of the vehicle, a stress occurring when the exhaust gases ejected from the cylinders and having passed through the detecting section of the exhaust sensor collide with the outer wall of the exhaust passage in different locations in the direction perpendicular to the direction of the exhaust flow can be reduced by the use of the rib, and noise resulting from the stress can be reduced, and the silencing can be improved.

In the rear bank on the rear side of the vehicle of the embodiment, because empty space is present and the layout has ample room, the distance between the detecting section of the exhaust sensor and the outer wall with which the exhaust gas in the exhaust passage collides can be increased, and the outer wall can have the large rounded shape by which the exhaust gas having passed through the exhaust sensor can be prevented from strongly colliding with the outer wall, and the silencing can be improved.

Accordingly, the silencing can be optimally improved on the front and rear sides of the vehicle.

(E) In the exhaust apparatus for the internal combustion engine described in the aspect (D) of the embodiment, a distance (e.g., distance L1) between the detecting section of the exhaust sensor and the outer wall with which the exhaust gas having passed through the detecting section collides in the exhaust passage in the front bank on the front side of the vehicle may be longer than that (e.g., distance L2) in the rear bank on the rear side of the vehicle.

With the exhaust apparatus according to the aspect (E) of the embodiment, because the rear bank on the rear side of the vehicle has empty space and the layout has ample room, the distance between the detecting section of the exhaust sensor and the outer wall with which the exhaust gas having passed through the detecting section collides in the exhaust passage in the rear bank on the rear side of the vehicle can be increased. Thus, the exhaust gas having passed through the exhaust sensor does not strongly collide with the outer wall, the occurrence of noise can be suppressed, and the silencing can be improved. The rib is not required to be disposed on the outer wall of the exhaust passage.