JPH10274033A - Exhaust system for multi-cylinder engine - Google Patents

Abstract

(57) [Problem] To secure layout characteristics and support rigidity of a catalyst device directly mounted on a manifold while preventing exhaust interference and making exhaust resistance uniform. SOLUTION: Independent exhaust passage portions 5A and 5D of end cylinders are connected to an exhaust collecting portion 6 at a position close to a head connecting flange portion 7 in the center of the inside, and independent exhaust passage portions 5B and 5C of an intermediate cylinder are provided outside thereof. And is connected to the exhaust collecting part 6. The catalyzer connection flange 9 has a center C set within the width W of the independent intake passage 5C of the third cylinder and is slightly inclined outward toward the rear in the cylinder row direction with respect to the vertical direction. 8 is directly attached. Further, a bolt fastening portion 10I is provided at a position between the independent exhaust passage portions 5B and 5C on a substantially extended line of the axis L of the catalyst device 8, and a reinforcing rib 11 is extended below the bolt fastening portion 10I, and a caterer connecting flange portion is provided. A bolt fastening portion 10H is also provided on a substantially extended surface of the nine end surfaces, and a partition 12 is provided in the exhaust collecting portion 6 in a substantially cylinder row direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust device for a multi-cylinder engine in which a catalyst device for purifying exhaust gas is directly connected to a downstream end of an exhaust manifold.

[0002]

2. Description of the Related Art When a catalyst device for purifying exhaust gas is arranged in an exhaust system of an engine, the catalyst device is directly connected (directly attached) to a downstream end of an exhaust manifold to introduce a high-temperature exhaust gas to the catalyst. It has been conventional to accelerate the temperature rise and enhance the purification performance by the catalyst.

[0003] In a so-called FR vertical engine which is mounted on a front portion of a vehicle body with an output shaft directed in the vehicle front-rear direction and drives rear wheels, a transmission is usually connected to the rear end of the engine. The front end of the transmission overhangs laterally at the connection between the transmission and the transmission. Therefore, when the catalyst device is directly connected to the downstream end of the exhaust manifold, the catalyst device:
For example, as described in Japanese Patent Application Laid-Open No. 8-68316, it is common to arrange the exhaust manifold directly below the gathering portion of the exhaust manifold in the vertical direction. Further, there is a case where the catalyst device is largely extended to the side so as not to interfere with the transmission.

[0004]

SUMMARY OF THE INVENTION FR installed vertically
In a car, for example, when trying to correspond to both the left handle and the right handle, the steering device may come almost directly under the exhaust manifold, for example, such that the steering device comes almost directly under the exhaust manifold, and from there In the case where the steering column extends rearward and upward, when the catalyst device is directly connected to the downstream end of the exhaust manifold, it is necessary to prevent the catalyst device from interfering with the steering column. It is difficult to space the catalyst device in a vertical direction directly below the collection portion of the exhaust manifold while avoiding interference with the column. Also, in such a case where the steering device comes almost immediately below the exhaust manifold and the steering column extends rearward and upward from there, the catalyst device is extended to a side position that does not interfere with the steering column. In this case, the vibration characteristics of the power plant deteriorate, and the support rigidity of the catalyst device deteriorates.

Further, the exhaust manifold is required to prevent exhaust interference between cylinders and to make exhaust resistance of each cylinder uniform.

It is therefore an object to ensure the layout and support rigidity of the catalyst device directly mounted on the exhaust manifold while preventing exhaust interference between the cylinders and making the exhaust resistance of each cylinder uniform.

[0007]

According to a first aspect of the present invention, there is provided an exhaust system for a multi-cylinder engine, comprising: a plurality of independent exhaust passages communicating with exhaust ports of a plurality of cylinders arranged in series; An exhaust manifold having an exhaust collecting portion that joins the flowing exhaust gas on the downstream side is provided, and at the downstream end of the exhaust collecting portion, the axis is inclined with respect to the vertical direction as viewed from a horizontal direction orthogonal to the cylinder row direction. In an exhaust system for a multi-cylinder engine in which a catalyst device is directly connected in an arrangement, an independent exhaust passage portion communicating with an exhaust port of a cylinder located in the middle of the exhaust manifold in the cylinder array direction is located at an end in the cylinder array direction. Independent exhaust passages communicating with the exhaust ports of the cylinders are routed outward in a direction perpendicular to the cylinder row direction to communicate with the exhaust manifold, and the exhaust manifold of the exhaust manifold The center of the downstream end to which the catalyst device is connected is within the width of the vertical extension line of the independent intake passage communicating with the intake port of the cylinder located in the middle when viewed from the horizontal direction orthogonal to the cylinder row direction. It is configured to be located.

In the exhaust device for a multi-cylinder engine, an independent exhaust passage communicating with an exhaust port of a cylinder located in the middle of the exhaust manifold in the cylinder row direction is connected to an exhaust port of a cylinder located at an end in the cylinder row direction. The independent exhaust passage communicating with the cylinders is routed outward in the direction perpendicular to the cylinder row direction and communicates with the exhaust collecting section, thereby reducing the difference in the passage length of the independent exhaust passage for each cylinder and reducing exhaust resistance. For example, in a four-cylinder engine, when the ignition order is the first cylinder-third cylinder-fourth cylinder-second cylinder, first, the ignition is performed at an intermediate position. The independent exhaust passages corresponding to the second and third cylinders whose order is not continuous, and the independent exhaust passages corresponding to the first cylinder and the fourth cylinder which are located at the end positions and are also not continuous in the ignition order,
It is possible to prevent exhaust interference between the cylinders, for example, by merging them at the downstream side and finally merging them at the exhaust collecting part. Further, in this exhaust device, the catalyst device is directly connected to the downstream end of the exhaust collecting portion in such a manner that the axis is inclined with respect to the vertical direction, and furthermore, the exhaust manifold of the exhaust manifold connecting the catalyst device is connected. The center of the downstream end of the portion is located within the width of the vertical extension line of the independent intake passage portion communicating with the intake port of the intermediate cylinder as viewed from the horizontal direction orthogonal to the cylinder row direction. This makes it possible to dispose the catalyst device directly mounted on the exhaust manifold in a space directly in front of the connection between the engine and the transmission on the side of the engine so as to avoid interference with the steering column and the like. The independent exhaust passage is routed outward, and the catalyst device can be firmly supported by the highly rigid portion of the structure that covers the independent exhaust passage for the cylinder at the end position. Therefore, it is possible to secure the layout and support rigidity of the catalyst device directly mounted on the exhaust manifold while preventing exhaust interference between the cylinders and making the exhaust resistance of each cylinder uniform.

According to a second aspect of the present invention, in the exhaust system for a multi-cylinder engine according to the first aspect, when there are a plurality of cylinders located in the middle in the cylinder row direction, the exhaust manifold is exhausted. The center of the downstream end of the collecting portion is independent from the plurality of cylinders located in the middle when viewed from a direction orthogonal to the cylinder row direction, and communicates with the intake port of the cylinder on the side where the catalyst device is inclined in the cylinder row direction. The intake passage is located within the width of the vertical extension line. By doing so, the length of the exhaust path from the mounting position of the exhaust manifold to the engine body to the downstream end of the exhaust collecting section is short and compact, and the exhaust gas of high temperature accelerates the rise of the catalyst temperature. The effect of the device can be further enhanced, and the distance between the position where the exhaust manifold is attached to the engine body and the position where the catalyst device is connected can be shortened to increase the support rigidity of the catalyst device.

According to a third aspect of the present invention, in the exhaust system for a multi-cylinder engine according to the first aspect of the present invention, when there are a plurality of cylinders located at an intermediate position in the cylinder row direction, the cylinders of the exhaust manifold may be changed. When viewed from a horizontal direction perpendicular to the row direction, the catalyst device is sandwiched between two independent exhaust passages adjacent to each other and substantially on the extension of the axis of the catalyst device and communicating with the exhaust ports of a plurality of cylinders located in the middle. The bolted portion for coupling to the engine body is provided at the position. In this way, by fastening the exhaust manifold to the engine body at a position very close to the axis of the catalyst device, the rigidity of the manifold supporting the catalyst device can be increased, and the support rigidity of the catalyst device can be increased. In particular, it is possible to suppress the vibration in the horizontal direction orthogonal to the cylinder row direction.

According to a fourth aspect of the present invention, in the exhaust system for a multi-cylinder engine according to the first aspect of the present invention, when the exhaust manifold is viewed from a horizontal direction orthogonal to the cylinder row direction in the exhaust manifold, A bolt fastening portion for connecting to the engine body is provided at a position on a substantially extended surface of the end surface of the downstream end. In this way, the exhaust manifold can be bolted to the engine body at a position very close to the extension of the end face connecting the catalyst device, whereby the vertical swing of the catalyst device can be suppressed.

According to a fifth aspect of the present invention, in the exhaust system for a multi-cylinder engine according to the third aspect of the present invention, the reinforcement extends below the bolt fastening portion of the exhaust manifold to near the downstream end of the exhaust collecting portion. The rib is extended. By providing such reinforcing ribs, the support rigidity of the catalyst device can be further increased, and the effect of suppressing the run-out in the horizontal direction orthogonal to the cylinder row direction can be enhanced.

According to a sixth aspect of the present invention, in the exhaust system for a multi-cylinder engine according to the fifth aspect of the present invention, the exhaust device is connected to a reinforcing rib below the bolted portion.
The connecting position between the passage wall of the independent exhaust passage portion located on one side in the cylinder row direction and the passage wall of the independent exhaust passage portion located on the other side in the cylinder row direction extends outward in a direction orthogonal to the cylinder row direction. A connecting wall is provided, and the thickness of the connecting wall in the cylinder row direction is set to an independent exhaust passage communicating with an exhaust port of a cylinder located in the middle of the cylinder row direction, and exhaust of a cylinder positioned at an end in the cylinder row direction. The thickness in the direction perpendicular to the wall surface of the wall separating the independent exhaust passage portion communicating with the port is larger than the thickness. By providing such a connecting wall, it is possible to further increase the support rigidity of the catalyst device and to suppress the run-out in the horizontal direction orthogonal to the cylinder row direction.

According to a seventh aspect of the present invention, in the exhaust system for a multi-cylinder engine according to the first aspect of the present invention, an exhaust port of the cylinder located at an intermediate position in the cylinder row direction is provided at an exhaust collecting portion of the exhaust manifold. A partition is provided in a substantially cylinder row direction that separates a portion corresponding to an independent exhaust passage portion communicating with a portion corresponding to an independent exhaust passage portion communicating with an exhaust port of a cylinder located at an end in the cylinder row direction. is there. By providing such a partition, it is possible to increase the manifold stiffness of a portion near the catalyst device connection position and increase the support stiffness of the catalyst device.

An exhaust system for a multi-cylinder engine according to an eighth aspect of the invention applies the configuration according to the second aspect to a case where the engine is a four-cylinder engine. The configuration according to claim 2 can be applied to a four-cylinder engine as described above. In this case, the difference in the passage length of the independent exhaust passage for each cylinder can be reduced to achieve uniform exhaust resistance. And, for example, the ignition sequence is
In the case of the third cylinder-the fourth cylinder-the second cylinder, the independent exhaust passages corresponding to the second cylinder and the third cylinder which are also at the intermediate position and whose ignition order is not continuous, The independent exhaust passages corresponding to the first cylinder and the fourth cylinder, which are located at positions and whose ignition order is not continuous, are respectively joined on the downstream side, and finally they are joined at the exhaust collecting section. It is possible to prevent exhaust interference between them.
Also, a catalyst device directly attached to the exhaust manifold can be arranged in a space directly in front of the engine and the connection between the engine and the transmission to avoid interference with the steering column, etc., and the cylinder at the intermediate position Independent exhaust passages are routed outwards to cover the independent exhaust passages for the cylinders at the end positions, so that the catalyst device can be firmly supported by the highly rigid part, and the exhaust manifold can be attached to the engine body The length of the exhaust path from the exhaust to the downstream end of the exhaust assembly is short and compact. Thus, the support rigidity of the catalyst device can be increased.

According to a ninth aspect of the present invention, there is provided an exhaust system for a multi-cylinder engine, wherein the configuration according to the first or eighth aspect is applied to a vertically mounted engine mounted with the cylinder row direction oriented in the vehicle front-rear direction. It is. The invention is thus advantageously applied to a vertical engine.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an external view of an engine exhaust manifold and a catalyst device as an example of this embodiment viewed from above the engine, FIG. 2 is an external view of the engine viewed from the side, and FIG. FIG. 4 is a sectional view taken along line AA of FIG. 2, and FIG. 5 is a sectional view taken along line BB of FIG. 2 (sectional view taken along line B'-B 'of FIG. 4).

This example is applied to an in-line four-cylinder engine. In the figure, reference numeral 1 denotes an engine body, and 2 denotes
This is a transmission connected to the rear end of the engine. The engine body 1 includes first to fourth four cylinders in a tandem arrangement. The exhaust manifold 4 is connected to one side surface of the cylinder head 3 that forms the upper part of the engine body 1.

The exhaust manifold 4 has four independent exhaust passages 5A, 5B, 5C, 5D communicating with exhaust ports (not shown) of the first to fourth cylinders of the engine body 1, and the independent exhaust passages. An exhaust collecting section 6 that joins exhaust gases flowing through the sections 5A, 5B, 5C, and 5D on the downstream side, and at the upstream end of each independent exhaust passage section 5A, 5B, 5C, 5D, the independent exhaust passage section 5A, 5B, 5C, and 5D are connected to each other to form a head connecting flange portion 7 for bolting to the cylinder head 3 by bolting, and at the downstream end of the exhaust collecting portion 6, the axial center is in the cylinder row direction with respect to the vertical direction. On the rear side (the right side in FIG. 1) (right side in FIG. 1), a cater connection flange portion 9 to which the catalyst device 8 is directly connected is disposed integrally with the catalyst device 8 in a slightly inclined outward direction. . 1 and 2, reference numerals 4A, 4B, 4C, and 4D denote upstream openings of the four independent exhaust passages 5A, 5B, 5C, and 5D, respectively, and the opening 4A communicates with the exhaust port of the first cylinder. The opening 4B communicates with the exhaust port of the second cylinder, the opening 4C communicates with the exhaust port of the third cylinder, and the opening 4D
Connects to the exhaust port of the cylinder.

The independent exhaust passages 5A and 5D communicating with the respective exhaust ports of the first cylinder and the fourth cylinder located at the end of the exhaust manifold 4 in the cylinder row direction are curved from the portion of the head connecting flange 7. Then, it extends inward in the cylinder row direction, merges at a first junction 5AD substantially at the center in the cylinder row direction, and the exhaust junction 6 is located at a position where the first junction 5AD is close to the head connecting flange 7. Connected to In addition, the independent exhaust passages 5B and 5C communicating with the exhaust ports of the second cylinder and the third cylinder located in the middle in the cylinder row direction are provided substantially at the center of the cylinder row direction from the head connection flange 7 and substantially in the cylinder row direction. It extends outward in the direction orthogonal to and surrounds the independent exhaust passages 5A, 5D on the end cylinder side, and extends outside the first junction 5AD of the independent exhaust passages 5A, 5D on the end cylinder side. At the second merging portion 5BC adjacent to the exhaust gas collecting portion 6. The second merging portion 5BC is connected to the exhaust collecting portion 6.

The two independent exhaust passages 5A and 5D at the end in the cylinder row direction are substantially symmetrical with each other and have substantially equal passage resistance.
The two independent exhaust passage portions 5B and 5C on the intermediate side in the cylinder row direction are also substantially symmetrical with each other and have substantially the same passage resistance. And
As described above, the independent exhaust passage portions 5A and 5D on the end cylinder side and the independent exhaust passage portions 5B and 5C on the intermediate cylinder side are separated from the independent exhaust passage portions 5A and 5D on the end cylinder side by the flange portion 7 for connecting the head. The curved portion extends inward in the cylinder row direction, merges at a first merging portion 5AD substantially at the center in the cylinder row direction, and is connected to the exhaust collecting portion 6. On the other hand, the independent exhaust passage portion 5 on the intermediate cylinder side.
B, 5C are routed outside each of the independent exhaust passages 5A, 5D on the end cylinder side, merge at the second merging section 5BC, and connect to the exhaust collecting section 6. The independent exhaust passage portions 5A and 5D on the end cylinder side and the independent exhaust passage portions 5B and 5C on the intermediate cylinder side have no difference in exhaust resistance. Further, the exhaust manifold 4 has an engine ignition sequence of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder, and the end cylinders (the first cylinder and the fourth cylinder) in which the ignition sequence is not continuous. The independent exhaust passage portions 5A and 5D of the cylinders first merge at the first junction portion 5AD, and the independent exhaust passage portions 5B and 5C of the intermediate cylinders (the second cylinder and the third cylinder) whose ignition order is not continuous first. Merge at the second merging section 5BC,
Since the two merging portions 5AD and 5BC finally merge at the exhaust collecting portion 6, exhaust interference is less likely to occur.

The catalyst device 8 is arranged such that its axis is inclined slightly outward toward the rear in the cylinder row direction with respect to the vertical direction. Bolt is fastened. The center (point C in FIG. 2) of the catalyst connecting flange 9 of the exhaust manifold 4 to which the catalyst device 8 is connected is such that the catalyst device 8 is positioned in the cylinder row direction when viewed from a direction orthogonal to the cylinder row direction. The intermediate cylinder on the inclined side, that is, the independent intake passage portion 5 on the third cylinder side
It is set to be located inside the width of the vertical extension line of C (width W in FIG. 2).

The engine body 1 is mounted on the head connecting flange portion 7 of the exhaust manifold 4 at a total of nine positions including a vertical position at both ends in the cylinder row direction, a horizontal symmetric position at an intermediate position and a vertical position, and a central one position. Fastening part 10 for connecting to
A, 10B, 10C, 10D, 10E, 10F, 10
G, 10H and 10I are provided. When viewed from a horizontal direction (a direction perpendicular to the drawing in FIG. 2) orthogonal to the cylinder row direction, the center bolt fastening portion 10I is substantially on the extension line of the axis L of the catalyst device 8, and It is provided at a position between the two independent exhaust passages 5B and 5C of the intermediate cylinder (the second cylinder and the third cylinder). The presence of the bolt fastening portion 10I at this position suppresses, in particular, horizontal runout perpendicular to the cylinder row direction. Further, the bolt fastening portion 10H on the lower right side of the intermediate position is a cater-connecting flange portion at the downstream end of the exhaust collecting portion 6 when viewed from a horizontal direction (a direction perpendicular to the drawing in FIG. 2) orthogonal to the cylinder row direction. 9 is located on a substantially extended surface of the end surface. The presence of the bolt fastening portion 10H at this position particularly suppresses the vertical swing of the catalyst device.

In the exhaust manifold 4, the bolt fastening portion 10I provided at a position between the two independent exhaust passage portions 5B and 5C on the intermediate cylinder side on a substantially extended line of the axis L of the catalyst device 8 is provided. Is extended downward, and a reinforcing rib 11 is provided which reaches the position of the caterer connecting flange 9 at the lower end of the exhaust gas collecting part 6. The connection position between the passage walls of the independent exhaust passage portions 5A and 5B located on one side in the cylinder row direction and the passage walls of the independent exhaust passage portions 5C and 5D located on the other side in the cylinder row direction is defined as the cylinder row direction. A portion that extends outward in the direction perpendicular to and forms a connecting wall is below the bolt fastening portion 10I, is connected to the reinforcing rib 11, and has a thickness of the connecting wall portion in the cylinder row direction (see FIG. 5). T) is a thickness in a direction orthogonal to a wall surface of a wall separating the independent exhaust passage portions 5B and 5C on the intermediate cylinder side and the independent exhaust passage portions 5A and 5D on the end cylinder side (see FIGS. 4 and 5). t). Thereby, the support rigidity of the catalyst device 8 is further increased.

The exhaust manifold 6 of the exhaust manifold 4
, A portion 6a corresponding to the first merging portion 5AD where the independent exhaust passage portions 5A and 5D on the end cylinder side merge with the second exhaust passage portions 5B and 5C on the intermediate cylinder side. A partition wall 12 is provided substantially in the cylinder row direction so as to separate the portion 6b corresponding to the junction 5BC. By providing such a partition 12, the manifold rigidity of a portion near the cater connection position is increased, and the support rigidity of the catalyst device 8 is increased.

An exhaust pipe 13 is connected to the downstream side of the catalyst device 8 by a flange.

Although the above embodiment is directed to a four-cylinder engine, the present invention can be applied to a multi-cylinder engine other than the four-cylinder engine.

In the above-described embodiment, the independent exhaust passages on the end cylinder side are first joined together, the independent exhaust passages on the intermediate cylinder side are also joined together, and finally all are assembled at the exhaust collecting section. However, an embodiment is also possible in which the independent exhaust passages on the end cylinder side and the independent exhaust passages on the intermediate cylinder side are merged at the same time at the exhaust collecting portion.

[0030]

According to the present invention, it is possible to prevent the interference of exhaust gas between cylinders and to make the exhaust resistance of each cylinder uniform, and to secure the layout and support rigidity of the catalyst device directly mounted on the exhaust manifold. it can.

[Brief description of the drawings]

FIG. 1 is an external view of a connection structure between an exhaust manifold and a catalyst device of an engine according to an example of an embodiment, as viewed from above the engine.

FIG. 2 is an external view of a connection structure between the exhaust manifold and a catalyst device as viewed from an engine side.

FIG. 3 is an external view of a connection structure between the exhaust manifold and the catalyst device as viewed from the rear of the engine.

FIG. 4 is a sectional view taken along line AA of FIG. 2;

FIG. 5 is a sectional view taken along line BB of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 2 Transmission 3 Cylinder head 4 Exhaust manifold 5A, 5B, 5C, 5D Independent exhaust passage part 6 Exhaust gathering part 7 Head connecting flange part 8 Catalyst device 9 Cata connecting flange part 10A-10I Bolt fastening part 11 Reinforcing rib 12 partition

Claims (9)

[Claims] An exhaust manifold having a plurality of independent exhaust passages communicating with exhaust ports of a plurality of cylinders arranged in series, and an exhaust manifold for joining exhaust gas flowing through the independent exhaust passages downstream is provided. An exhaust system for a multi-cylinder engine, wherein a catalyst device is directly connected to a downstream end of the exhaust collecting portion in an arrangement in which an axis is inclined with respect to a vertical direction as viewed from a horizontal direction orthogonal to a cylinder row direction, The independent exhaust passage communicating with the exhaust port of the cylinder located in the middle of the cylinder row of the exhaust manifold is connected to the independent exhaust passage communicating with the exhaust port of the cylinder located at the end in the cylinder row direction. The exhaust manifold is routed outwardly in a direction perpendicular to the exhaust manifold and communicates with the exhaust manifold. The exhaust of a multi-cylinder engine, wherein the exhaust is arranged within a width of a vertical extension line of an independent intake passage portion communicating with an intake port of the intermediate cylinder as viewed from a horizontal direction orthogonal to the vertical direction. apparatus. 2. A plurality of cylinders located at an intermediate position in the cylinder row direction, wherein the exhaust manifold is arranged such that a center of a downstream end of the exhaust collecting portion is located at the intermediate position when viewed from a direction orthogonal to the cylinder row direction. 2. The multi-cylinder engine according to claim 1, wherein the catalyst device is positioned within a width of a vertical extension line of an independent intake passage portion communicating with an intake port of a cylinder on a side where the catalyst device is inclined in the cylinder row direction among the plurality of cylinders. 3. Exhaust system. 3. A plurality of cylinders positioned at an intermediate position in the cylinder row direction, and the exhaust manifold is substantially on an extension of an axis of the catalyst device when viewed from a horizontal direction orthogonal to the cylinder row direction, and The multi-cylinder according to claim 1, further comprising a bolt fastening portion for connecting to an engine body at a position sandwiched between two adjacent independent exhaust passage portions communicating with the exhaust ports of the plurality of intermediate cylinders. Engine exhaust system. 4. The exhaust manifold is connected to an engine body at a position on a substantially extended surface of an end face at a downstream end of the exhaust collecting section when viewed from a horizontal direction orthogonal to a cylinder row direction. The exhaust device for a multi-cylinder engine according to claim 1, further comprising a portion. 5. The exhaust device for a multi-cylinder engine according to claim 3, wherein the exhaust manifold has a reinforcing rib extending below the bolt fastening portion and extending to near a downstream end of the exhaust collecting portion. 6. The exhaust manifold is connected to the reinforcing rib below the bolt fastening portion, and has a passage wall of an independent exhaust passage located on one side in the cylinder row direction and the other side in the cylinder row direction. A connecting wall extending outward in a direction perpendicular to the cylinder row direction at a connection position with the passage wall of the independent exhaust passage portion located at a thickness of the connection wall in the cylinder row direction. The thickness in the direction orthogonal to the wall surface of the wall separating the independent exhaust passage portion communicating with the exhaust port of the cylinder located in the middle and the independent exhaust passage portion communicating with the exhaust port of the cylinder located at the end in the cylinder row direction is determined. The exhaust device for a multi-cylinder engine according to claim 5, which is large. 7. The exhaust manifold includes a portion corresponding to an independent exhaust passage communicating with an exhaust port of a cylinder located at an intermediate position in the cylinder row direction, and a portion corresponding to an end portion in the cylinder row direction. 2. The exhaust device for a multi-cylinder engine according to claim 1, further comprising a partition in a direction substantially parallel to the row of cylinders separating a portion corresponding to an independent exhaust passage portion communicating with an exhaust port of a located cylinder. 8. An exhaust manifold having four independent exhaust passages communicating with exhaust ports of four cylinders arranged in series, and an exhaust manifold for joining exhaust gas flowing through the independent exhaust passages on the downstream side. The catalyst device is directly connected to the downstream end of the exhaust collecting portion in an arrangement in which the axis is inclined with respect to the vertical direction as viewed from a horizontal direction orthogonal to the cylinder row direction and inclined to one side in the cylinder row direction. In the exhaust system for a multi-cylinder engine, an independent exhaust passage communicating with an exhaust port of a cylinder located in the middle of the exhaust manifold in the cylinder row direction is communicated with an exhaust port of a cylinder located at an end in the cylinder row direction. The independent exhaust passage portion is routed outward in a direction perpendicular to the direction of cylinder rows to communicate with the exhaust collecting portion, and the exhaust manifold of the exhaust manifold is connected to a catalyst device by a catalyst device. The center of the downstream end to be connected communicates with the intake port of the cylinder on the side where the catalyst device is inclined in the cylinder row direction among the cylinders located in the middle as viewed from a horizontal direction orthogonal to the cylinder row direction. An exhaust system for a multi-cylinder engine, wherein the exhaust system is located within a width of a vertical extension line of the independent intake passage portion. 9. The exhaust device for a multi-cylinder engine according to claim 1, wherein the engine is a vertically mounted engine mounted with the cylinder row direction facing the vehicle front-rear direction.