WO2016035155A1

WO2016035155A1 - Exhaust device for internal combustion engine

Info

Publication number: WO2016035155A1
Application number: PCT/JP2014/073134
Authority: WO
Inventors: 濱本　高行; 杉山　孝伸; 英弘藤田
Original assignee: 日産自動車株式会社
Priority date: 2014-09-03
Filing date: 2014-09-03
Publication date: 2016-03-10

Abstract

In an inline four cylinder internal combustion engine (1), exhaust ports for the second cylinder and third cylinder merge inside a cylinder head (3) and form a single opening serving as a collective exhaust port. An exhaust manifold (5) is provided with individual exhaust pipes (6, 7) for the first and fourth cylinders and a collective exhaust pipe (8), and the leading ends of these three exhaust pipes (6, 7, 8) are connected to a catalytic converter (11). The pair of individual exhaust pipes (6, 7) merge at an obtuse angle via a volume chamber (12), and an outlet pipe part (12a) is connected to a diffuser part (11a). The difference in flow velocity from the second and third cylinders is reduced as the flow velocity of the exhaust decreases due to expansion of the exhaust inside the volume chamber (12).

Description

Exhaust device for internal combustion engine

The present invention relates to an exhaust system for a multi-cylinder internal combustion engine, and in particular, a collective exhaust pipe through which exhaust from a plurality of cylinders flows and an individual exhaust pipe through which exhaust from individual cylinders flow independently are connected to a single catalytic converter. The present invention relates to an exhaust device for an internal combustion engine.

For example, Patent Document 1 discloses that in an in-line four-cylinder internal combustion engine, exhaust ports of cylinders # 2 and # 3 whose ignition order is not continuous are merged inside the cylinder head, while exhaust ports of cylinders # 1 and # 4 are left as they are. An exhaust device configured to open on the side of the cylinder head is disclosed. That is, the exhaust ports of the # 2 and # 3 cylinders are configured as one collective exhaust port, and the exhaust port of the # 1 cylinder and the exhaust port of the # 4 cylinder are configured as individual exhaust ports for each individual cylinder. Yes. The collective exhaust ports for the # 2 and # 3 cylinders are connected to the catalytic converter via one collective exhaust pipe, and the individual exhaust ports of the # 1 and # 4 cylinders are independent individual exhaust pipes. Is connected to the catalytic converter. In Patent Document 1, the end portions of these collective exhaust pipes and individual exhaust pipes are connected to the catalytic converter end portions so as to be basically parallel to the central axis of the catalytic converter.

In such a configuration in which the exhaust ports of some cylinders are merged inside the cylinder head, the temperature of the exhaust gas introduced into the catalytic converter via the collective exhaust pipe can be high during the cold start. This is advantageous in terms of early activity of the catalyst.

However, on the other hand, the flow rate of the exhaust gas introduced into the catalytic converter via the collective exhaust pipe is different from the flow rate of the exhaust gas introduced into the catalytic converter via the individual exhaust pipe. That is, the collective exhaust pipe where the exhaust ports of the # 2 and # 3 cylinders merge has a larger passage cross-sectional area than the individual exhaust pipe for each cylinder, and therefore has a relatively low flow velocity. On the other hand, the exhaust gas introduced from the individual exhaust pipes of the # 1 cylinder and the # 4 cylinder has a high flow velocity and high straightness.

Therefore, the ventilation resistance with respect to the exhaust of the # 1 and # 4 cylinders flowing through the individual exhaust pipes is relatively high, and becomes the rate-determining factor that determines the exhaust resistance of the entire internal combustion engine.

Also, for example, the exhaust flow from the individual exhaust pipe strongly collides with a part of the catalyst carrier configured as a monolith catalyst carrier, which is not preferable from the viewpoint of catalyst deterioration.

JP 2008-38838 A

The present invention relates to an exhaust system for an internal combustion engine in which a collective exhaust pipe through which exhaust from a plurality of cylinders flows and an individual exhaust pipe through which exhaust from individual cylinders flow independently are connected to a diffuser portion of a single catalytic converter. In
A plurality of individual exhaust pipes are joined in the immediate vicinity of the catalytic converter and then connected to the diffuser part.
A volume chamber is provided at the junction of the individual exhaust pipes.

In such a configuration, the exhaust gas flowing through the individual exhaust pipes expands in the volume chamber and flows into the diffuser section with a reduced flow velocity. Therefore, the speed difference with the flow speed of the exhaust gas flowing through the collective exhaust pipe becomes small.

Therefore, the exhaust resistance of the entire internal combustion engine is reduced and the output can be improved. In addition, local exhaust collision with the catalyst carrier is suppressed, and early deterioration of the catalyst is suppressed.

The front view which shows 1st Example of the exhaust apparatus which concerns on this invention. The perspective view of 1st Example similarly. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is a cross-sectional view of a main part along the line BB in FIG. 2. The characteristic view which showed the ventilation resistance of 1st Example compared with the comparative example. The characteristic view which showed the uniformity per catalyst gas of 1st Example compared with the comparative example. The perspective view which shows 2nd Example of the exhaust apparatus which concerns on this invention.

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

FIGS. 1 and 2 show a first embodiment in which the present invention is applied to an in-line four-cylinder internal combustion engine 1. The internal combustion engine 1 includes a cylinder block 2 and a cylinder head 3, and an exhaust port (not shown) of each cylinder extends toward one side surface 3 a of the cylinder head 3. Here, the exhaust ports of the # 1 cylinder and the # 4 cylinder are opened to the side surface 3a of the cylinder head 3 as individual exhaust ports independently for each cylinder, and the exhaust ports of the # 2 cylinder and the # 3 cylinder are cylinders. They merge with each other inside the head 3 and open to the side surface 3a of the cylinder head 3 as one collective exhaust port. Note that the ignition timings of the # 2 and # 3 cylinders are separated by 360 ° CA, and no exhaust interference occurs.

As shown in FIG. 2, the exhaust manifold 5 attached to the side surface 3a of the cylinder head 3 is connected to the # 1 individual exhaust pipe 6 connected to the individual exhaust port of the # 1 cylinder and the individual exhaust port of the # 4 cylinder. # 4 individual exhaust pipe 7 and a collective exhaust pipe 8 connected to a central collective exhaust port, and the base ends of these three

exhaust pipes

6, 7, 8 are supported by a head mounting flange 9. Has been. The # 1 individual exhaust pipe 6 and the # 4 individual exhaust pipe 7 have a substantially circular cross-sectional shape, and the collective exhaust pipe 8 has an elongated oval cross-sectional shape extending in the cylinder row direction. Further, the passage cross-sectional area of the collective exhaust pipe 8 is set larger than the individual passage cross-sectional areas of the # 1 individual exhaust pipe 6 and the # 4 individual exhaust pipe 7.

The tips of # 1 individual exhaust pipe 6, # 4 individual exhaust pipe 7 and collective exhaust pipe 8 are connected to a diffuser portion 11a on the upstream side of a single catalytic converter 11, respectively. The catalytic converter 11 is a cylindrical monolithic catalyst carrier accommodated in a cylindrical metal case, and the diffuser portion 11a forms a space whose diameter gradually increases between the end face of the catalyst carrier. It has a substantially conical shape.

As shown in FIG. 1, the catalytic converter 11 is located on the side of the cylinder block 2, and the central axis L of the catalytic converter 11 is obliquely outward with respect to the vertical direction of the internal combustion engine 1 (the arrow y direction in FIG. 1). It is arranged in a posture that becomes slanted. Further, as shown in FIG. 2, in the cylinder row direction, the cylinder head 3 is disposed at a substantially central position (that is, to the side of the collective exhaust port of the # 2 and # 3 cylinders).

Accordingly, the collective exhaust pipe 8 linearly extends from the head mounting flange 9 along the direction orthogonal to the cylinder row direction, and is bent so that the tip portion is directed downward, and faces the upper side of the diffuser portion 11a. It is connected to a conical surface (in particular, a position close to the central axis L). As shown in FIG. 3, at the connection portion with the catalytic converter 11, the front end of the collective exhaust pipe 8 is opened in a substantially semicircular shape. Note that the collective exhaust pipe 8 is connected to the side closer to the internal combustion engine 1 with respect to the catalytic converter 11 positioned on the side of the internal combustion engine 1.

Further, the # 1 individual exhaust pipe 6 and the # 4 individual exhaust pipe 7 positioned before and after the cylinder row direction are curvedly extended in the cylinder row direction so as to be substantially symmetric in a plan view, and the tip portion is directed downward. And is connected to a conical surface facing the upper side of the diffuser portion 11a (particularly, a portion closer to the outer periphery relatively away from the central axis L). More specifically, the # 1 individual exhaust pipe 6 and the # 4 individual exhaust pipe 7 merge so as to form an obtuse angle with each other via a volume chamber 12 having a substantially Y shape in the immediate vicinity of the catalytic converter 11, and the volume chamber An outlet pipe portion 12a serving as an outlet of 12 is connected to the diffuser portion 11a. As shown in FIG. 3, the distal end of the outlet pipe portion 12 a opens as a substantially semicircular inlet 12 b that is symmetrical to the end of the collective exhaust pipe 8.

The volume chamber 12 gradually changes in cross-sectional shape from the upper part where the pair of

individual exhaust pipes

6, 7 having a substantially circular cross section merge at an obtuse angle to the lower inlet 12 b, but the pair of

individual exhaust pipes

6, 7 In the upper part where it merged, it has a cross-sectional area larger than the sum of the passage cross-sectional areas of a pair of

individual exhaust pipes

6 and 7. As shown in FIG. 4, the cross-sectional area is slightly reduced between the inlet pipe 12b at the lower end of the outlet pipe portion 12a. In addition, the cross-sectional area may be the minimum immediately before the introduction port 12b, or the introduction port 12b may be the minimum cross-sectional area.

As is clear from FIG. 3, the opening area of the outlet pipe part 12a that finally flows into the diffuser part 11a is equal to the opening area of the front end of the collective exhaust pipe 8. That is, the exhaust passages of the # 2 and # 3 cylinders and the exhaust passages of the # 1 and # 4 cylinders are opened with an equal opening area with respect to the diffuser portion 11a. As is clear from FIG. 4, the outlet pipe portion 12a serving as the outlet of the volume chamber 12 and the distal end portion of the collective exhaust pipe 8 are joined at an acute angle in the diffuser portion 11a.

In the above configuration, the exhaust gas discharged from the # 1 cylinder and the # 4 cylinder flows through the

individual exhaust pipes

6 and 7 at a relatively high speed, but expands in the volume chamber 12, so that the flow velocity decreases. Then, once the expanded gas flow flows toward the inlet 12b, the gas is contracted and rectified effectively. Therefore, the flow of the gas flowing from the inlet 12b to the diffuser part 11a has a reduced flow velocity and is rectified. Accordingly, the difference in speed from the exhaust flow of the # 2 and # 3 cylinders flowing out from the collective exhaust pipe 8 is reduced, and the exhaust resistance of the # 1 and # 4 cylinders that controls the exhaust resistance of the internal combustion engine 1 as a whole is reduced. . Note that the ignition timings of the # 1 cylinder and the # 4 cylinder are 360 ° CA apart, and no exhaust interference occurs.

FIG. 5 shows the exhaust ventilation resistance of each cylinder in the same manner as in the above-described embodiment (a), with the tip of the # 1 individual exhaust pipe and the # 4 individual exhaust pipe parallel to the collective exhaust pipe 8 without having the volume chamber 12. It is the characteristic view shown by contrast with the comparative example (b) individually connected to the diffuser part 11a. As shown in the drawing, in the comparative example (b) that does not include the volume chamber 12, the ventilation resistance of the # 1 and # 4 cylinders is larger than that of the # 2 and # 3 cylinders. In a), the ventilation resistance of the # 1 and # 4 cylinders is greatly reduced, and the exhaust resistance of the internal combustion engine 1 as a whole is reduced. In the above embodiment, since the flow disturbance in the diffuser portion 11a is reduced, the airflow resistance is also reduced for the # 2 and # 3 cylinders.

FIG. 6 is a characteristic diagram showing the uniformity per gas at the end face of the catalyst carrier in comparison with Example (a) and Comparative Example (b). As shown in the figure, in the comparative example (b), the flow rate of the

individual exhaust pipes

6 and 7 is high, so that the gas contact at the end face of the catalyst carrier becomes uneven. On the other hand, the uniformity per gas improves by equalizing the flow rate through the volume chamber 12 as in the above embodiment.

Further, in the first embodiment, the tip of the collective exhaust pipe 8 of the # 2 and # 3 cylinders is connected to the side closer to the internal combustion engine 1 with respect to the catalytic converter 11 located on the side of the internal combustion engine 1. The tip ends of the pair of

individual exhaust pipes

6, 7 are connected to the opposite side of the catalytic converter 11 from the internal combustion engine 1 through the upper side of the collective exhaust pipe 8. That is, the collective exhaust pipe 8 is laid out inside the

individual exhaust pipes

6 and 7. Therefore, it is difficult for heat to escape from the collective exhaust pipe 8, which is more advantageous in terms of early activation of the catalyst during cold start.

Next, FIG. 7 shows a second embodiment of the present invention. In this embodiment, the collective exhaust pipes 8 for the # 2 and # 3 cylinders are laid out so as to go outward through the volume chambers 12 of the

individual exhaust pipes

6 and 7.

That is, with respect to the catalytic converter 11 located on the side of the internal combustion engine 1, the volume chamber 12 and the outlet pipe portion 12a of the

individual exhaust pipes

6 and 7 are connected to the diffuser portion 11a closer to the internal combustion engine 1, Conversely, the pipe 8 is connected to the side away from the internal combustion engine 1. Each connecting portion has a semicircular shape as in the above-described embodiment.

In such a configuration, the amount of heat released from the collective exhaust pipe 8 is larger than that in the first embodiment, and it is possible to suppress an excessive rise in the exhaust temperature of the # 2 and # 3 cylinders during a high load. Therefore, it is suitable for an internal combustion engine in which a high load range is frequently used.

Claims

In an exhaust system of an internal combustion engine in which a collective exhaust pipe through which exhaust from a plurality of cylinders flows and an individual exhaust pipe through which exhaust from individual cylinders flow independently are connected to a diffuser portion of a single catalytic converter,
A plurality of individual exhaust pipes are joined in the immediate vicinity of the catalytic converter and then connected to the diffuser part.
An exhaust system for an internal combustion engine, comprising a volume chamber at a junction of the individual exhaust pipes.
The internal combustion engine is an in-line four-cylinder internal combustion engine, and the exhaust ports of # 2 cylinder and # 3 cylinder merge inside the cylinder head to form one collective exhaust port, and the collective exhaust pipe is connected to the collective exhaust port And
2. An exhaust system for an internal combustion engine according to claim 1, wherein the exhaust ports of # 1 cylinder and # 4 cylinder are respectively connected to individual exhaust pipes.
The exhaust system for an internal combustion engine according to claim 1 or 2, wherein the volume chamber has a cross-sectional area larger than a sum of passage cross-sectional areas of a plurality of individual exhaust pipes.
The exhaust system for an internal combustion engine according to claim 3, wherein a cross-sectional area of the volume chamber is reduced with respect to an introduction port opened to the diffuser.
5. The exhaust system for an internal combustion engine according to claim 1, wherein the pair of individual exhaust pipes merge so as to form an obtuse angle with each other in the volume chamber.
The collective exhaust pipe is connected to a position closer to the internal combustion engine with respect to the catalytic converter located on the side of the internal combustion engine, and the volume chamber is connected to the outside of the connection portion of the collective exhaust pipe. 6. An exhaust system for an internal combustion engine according to any one of 1 to 5.
6. The catalytic converter located on the side of the internal combustion engine, the volume chamber is connected to a position closer to the internal combustion engine, and the collective exhaust pipe is connected to the outside of the volume chamber. An exhaust system for an internal combustion engine according to any one of the above.