JPH0552116A - Exhaust device for internal combustion engine - Google Patents

Abstract

PURPOSE:To make performance compatibility between exhaust purification and power in an internal combustion engine. CONSTITUTION:A first exhaust manifold 15A is connected to an exhaust valve 12A of an each cylinder in an engine 11 and a second exhaust manifold 15B is connected to the other exhaust valve 12B. A preliminary exhaust purification catalyst 16A, 16B is installed in each collective portion 14A, 14B, and a main exhaust purification catalyst 18 is installed in an exhaust pipe downstream. A control valve 19 installed in a branching path 13A connected to #2, 3 cylinder in the first exhaust manifold 15A and a control valve 19 installed in a branching path 13B connected to #1, 4 cylinder in the second exhaust manifold 15B are half opened in a low speed region and fully opened in a high speed region by so controlling. Accordingly, exhaust passes through one of preliminary exhaust purification catalysts 16A, 16B and the main exhaust purification catalyst 18, thereby enhancing the conversion efficiency, and in the low speed region the influence by exhaust interference is evaded, thereby improving in fuel consumption. In the high speed region, due to increase in path area, high power can be ensured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system for an internal combustion engine, and more particularly to a technique for improving exhaust purification performance while ensuring engine output performance.

[0002]

2. Description of the Related Art As a conventional exhaust device having an exhaust purification catalyst for an internal combustion engine, there is, for example, one shown in FIG. 6 (see Japanese Utility Model Laid-Open No. 61-122335). That is,
Each cylinder of the engine has two exhaust valves, and is provided with a first exhaust manifold 1 and a second exhaust manifold 2 that are connected corresponding to these exhaust valves. The first exhaust purification catalyst 3 is interposed between the second exhaust purification catalyst 4 and the exhaust pipe 3 formed by collecting the first exhaust manifold 1 and the second exhaust manifold 2 on the downstream side. Is installed.

Further, a control valve 5 which is closed in the low speed region of the engine is provided upstream of the second exhaust manifold 2. As a result, since the control valve 5 is closed in the low engine speed range, all the exhaust gas from each cylinder passes through the first exhaust gas purification catalyst 3, so that the first exhaust gas purification catalyst 3 can be brought to the activation temperature early. Also, the exhaust temperature can be effectively exhibited by maintaining the activation temperature even during idle operation.

Further, in the engine high speed range, the exhaust resistance can be reduced by opening the control valve 5, and the exhaust gas passes through the second exhaust gas purification catalyst 4 to obtain a normal exhaust gas purification action.

[0005]

However, in such a conventional exhaust system, since the control valve 5 is provided in the upstream portion of the second exhaust manifold 2, the second exhaust manifold is closed when the control valve 5 is closed. Since the exhaust gas hardly flows downstream of the control valve 5 of No. 2, it is kept at a low temperature. For this reason, most of the exhaust gas discharged to the second exhaust manifold 2 at the beginning of opening of the control valve 5 is cooled on the downstream side of the control valve 5 of the second exhaust manifold 2, so that the second exhaust gas purification is performed. Since the conversion efficiency of the catalyst 4 is poor and the catalyst 4 does not pass through the first exhaust gas purification catalyst 3, the conversion efficiency of the catalyst cannot be effectively utilized and the conversion efficiency of the entire system deteriorates.

When the control valve 5 is closed (low speed range), the first
Since the exhausts of the cylinders whose combustion strokes are continuous on the upstream side of the exhaust purification catalyst 3 communicate with each other through the short branch passage portion, the output is largely reduced due to the exhaust interference. Lengthening the branch passage of each cylinder on the upstream side of the first exhaust gas purification catalyst 3 is difficult because of a large layout restriction, and also causes an increase in weight.

The present invention has been made to solve the above-mentioned conventional problems. The internal combustion engine which solves the above problems is improved by improving the shape of the exhaust passage, the arrangement of the exhaust purification catalyst, and the passage area control mechanism. An object is to provide an exhaust system for an engine.

[0008]

For this reason, the present invention is directed to an exhaust system for an internal combustion engine having two exhaust valves per cylinder, and a branch passage portion connected to one exhaust valve of each cylinder and the branch passages. A first exhaust manifold composed of a collecting portion formed by collecting the downstream side of the section, a branch passage section connected to the other exhaust valve of each cylinder, and a downstream side of these branch passage sections. And a second exhaust manifold including a collecting portion, and a preliminary exhaust purification catalyst is provided in each of the collecting portions of the first exhaust manifold and the second exhaust manifold. A cylinder in which a main exhaust gas purification catalyst is interposed in an exhaust pipe formed by collecting the downstream side of the second exhaust manifold, and the combustion stroke order is not continuous in the branch passage portion of the first exhaust manifold. Of the two cylinder groups, and a branch passage portion connected to one of the two cylinder groups, and a branch passage portion of the second exhaust manifold, the other of the two cylinder groups. A control valve for partially opening and closing the passage area of the branch passage portion connected to each of the branch passage portions, and a control means for controlling the opening and closing of the control valve according to the engine operating state detected by the operating state detecting means. , Are provided.

[0009]

In the operating region where the control valve is closed, the exhaust gas discharged to the first exhaust manifold mainly flows out through the branch passage portion connected to the other cylinder group of the two cylinder groups, and the downstream thereof. The exhaust gas is discharged via the auxiliary exhaust purification catalyst on the side and the main exhaust purification catalyst on the further downstream side. Also, the second
The exhaust gas discharged to the exhaust manifold mainly flows out of the branch passage portion connected to one of the two cylinder groups, and the preliminary exhaust purification catalyst on the downstream side and the downstream exhaust purification catalyst on the downstream side. It is discharged via the main exhaust purification catalyst. In this way, all the exhaust gas is exhausted via the preliminary exhaust gas purification catalyst and the main exhaust gas purification catalyst, so both the preliminary exhaust gas purification catalyst and the main exhaust gas purification catalyst can be warmed to the activation temperature early to ensure good conversion efficiency. it can. Further, since the exhaust gas from the cylinder in which the combustion process is continuous is mainly divided and discharged into the branch passage portion of the first exhaust manifold and the branch passage portion of the second exhaust manifold, and is communicated with the downstream exhaust pipe. The effect of exhaust interference can be reduced.

In the operating range in which the control valve is open, the exhaust gas from each cylinder is evenly discharged to the two branch passage portions in the first and second exhaust manifolds, and passes through the preliminary exhaust gas purification catalyst and the main exhaust gas purification catalyst. Is discharged. Therefore, the area of the branch passage portion is increased, the passage resistance is reduced, high output can be secured, and good conversion efficiency can be secured through the two exhaust purification catalysts.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1 showing the configuration of the first embodiment, an internal combustion engine 11 has two exhaust valves 12A and 12B per cylinder, and a branch passage portion 13A connected to one exhaust valve 12A of each cylinder is downstream. The first exhaust manifold 15A is formed by the branch passage portions 13A and the gathering portion 14A that are gathered on the side. Similarly, the branch passage portions 13B connected to the other exhaust valve 12B of each cylinder are gathered on the downstream side, and each branch passage portion 13B and the gathering portion 14B form a second exhaust manifold 15B.

Collecting portion of the first exhaust manifold 15A
Preliminary exhaust purification catalysts 16A and 16B are provided in the 14A and the collecting portion 14B of the second exhaust manifold 15B, respectively. Further, a main exhaust purification catalyst 18 is interposed in an exhaust pipe 17 formed by collecting the downstream sides of the first exhaust manifold 15A and the second exhaust manifold 15B. Furthermore,
In each branch passage portion 13A of the first exhaust manifold 15A,
One of the two cylinder groups consisting of cylinders whose combustion stroke order is not continuous (for example, in the present embodiment, in a four-cylinder engine having an ignition order of # 1 → # 3 → # 4 → # 2, # 1 The branch passage portion 13A connected to the cylinder and the # 4 cylinder and each branch passage portion 13B of the second exhaust manifold 15B, and the other cylinder group of the two cylinder groups (in this embodiment, Control valves 19 for opening and closing the passages are respectively provided in branch passage portions 13B connected to the # 2 cylinder and the # 3 cylinder, and a common rotary shaft 20 of these control valves 19 is connected to an actuator 21. .. The actuator 21 is driven by a control signal from the control device 22. The actuator 21 and the control device 22 constitute a control means.

The control device 22 serves as an engine operating state detecting means, and an engine rotation speed signal detected by the rotation speed sensor 23 and an engine load signal (or engine control signal) such as a throttle valve opening detected by the load sensor 24. (The fuel injection amount obtained in step 1 may be used), and the control valve 19 is opened and closed via the actuator 21 in accordance with the engine operating state obtained based on these signals. Is becoming Specifically, control is performed so that the control valve 19 is closed when the engine is started and in the low speed / low load range, and is fully opened in the high speed / high load range. The control valve 19 is
As shown in Fig. 2, the passage area is partially blocked even when closed,
The opening degree is controlled so that a certain amount of exhaust gas is circulated.

Next, the operation will be described. The control valve 19 is closed when the engine is started and in the low speed / low load range, and most of the exhaust gas from each cylinder is located in the branch passage portion 13A on the side where the control valve 19 is not interposed.
(# 1, 4 cylinders), 13B (# 2, 3 cylinders)
Exhaust gas from the cylinders whose combustion stroke order is not continuous passes through the preliminary exhaust gas purification catalysts 16A and 16B, respectively, and has long collecting portions 14A and 14B.
After passing through B, merge at the exhaust pipe 17. Therefore,
Most of the exhaust from the cylinders with continuous combustion strokes merges after passing through a long exhaust passage, so it is possible to avoid the influence of exhaust interference peculiar to the low speed range, suppress the decrease in output and extend fuel efficiency. Can be held at

Further, most of the exhaust gas reaches the preliminary exhaust gas purification catalysts 16A and 16B through only one branch passage portion 13A or 13B in which the control valve 19 is not interposed, so that the branch passage portion 13 is provided.
The amount of cooling in A and 13B is reduced, and the preliminary exhaust purification catalyst 16
The inlet temperatures of A and 16B can be maintained at a high temperature and good conversion efficiency can be secured. Further, since the control valve 19 partially blocks the passage area as described above, a small amount of exhaust gas is always provided in the branch passage portion 13A (# 2, 3) in which the control valve 19 is interposed.
Cylinder), 13B (# 1, 4 cylinders), and the downstream side portion of the control valve 19 is also warmed by this, so the control valve
Cooling of the downstream portion of the exhaust control valve 19 at the beginning of opening 19 can be suppressed, and good conversion efficiency of the catalyst can be ensured.

In the high speed / high load region of the engine, the control valve 19 is fully opened, and the exhaust gas from each cylinder has two branch passage portions 13A,
It is uniformly discharged to 13B, and the passage area also increases in response to the increase in the exhaust flow rate, so that the increase in passage resistance can be suppressed and a high output can be secured. Further, as in the case where the control valve 19 is closed, all the exhaust gas passes through one of the auxiliary exhaust gas purification catalysts 16A and 16B and the main exhaust gas purification catalyst 18, so sufficient conversion efficiency is secured even if the exhaust gas flow rate increases. it can.

Further, since the control valve 19 is fully opened, the first
Exhaust manifold 15A and second exhaust manifold 15
Exhaust gases exhausted from all the cylinders at the collecting sections 14A and 14B of B are merged at a uniform rate. Figure 3
A second embodiment will be described.

In this embodiment, the first exhaust manifold 15
One of two sets of cylinder groups (# 1, 4) and (# 2, 3), which are composed of cylinders whose combustion stroke order of A is not continuous, for example, the cylinder group
The branch passage portion 13A connected to (# 2, 3) is a branch passage portion connected to the other cylinder group (# 1, 4).
13A is formed on the upstream side of the mutual collecting portion, and the control valve 19 is provided on the upstream collecting portion.

Further, the second exhaust manifold 15B has
Branch passage connected to the other cylinder group (# 1, 4)
The 13B mutual collecting portion is formed on the upstream side of the branch passage portion 13B mutual collecting portion connected to the one cylinder group (# 2, 3), and the control valve 19 is interposed in the upstream collecting portion. To do. Other configurations are the same as those in the first embodiment, and are controlled in the same manner. With this configuration, the number of control valves 19 can be reduced to two.

4 and 5 show a modification of the control valve. The control valve 29 shown in FIG. 4 has an outer diameter sufficiently smaller than the passage inner diameter of the branch passage portion in which the control valve 29 is interposed, and the control valve 29 is arranged with respect to the passage center axis of the branch passage portion. A small amount of exhaust gas is circulated through the annular gap outside the control valve 29 when the valve is fully closed to be orthogonal to each other.

The control valve 39 shown in FIG. 5 has a circular hole at the center.
39a is formed, and when the control valve 39 is fully closed so that the control valve 39 is orthogonal to the passage central axis of the branch passage portion, the hole 39a is formed.
A small amount of exhaust gas is circulated through the.

[0022]

As described above, according to the present invention, all the exhaust gas passes through the preliminary exhaust gas purification catalyst and the main exhaust gas purification catalyst in the entire operation region, and the control valve partially covers the passage area even when the control valve is closed. By shutting off the exhaust gas and flowing a small amount of exhaust gas to warm the passage, cooling of the exhaust gas on the downstream side of the control valve is suppressed from the beginning of the control valve opening, so high conversion of the catalyst is achieved in all operating conditions. Efficiency can be obtained and exhaust gas purification performance can be maintained well.

Further, by closing the control valve in an operating region where exhaust interference becomes a problem, most of the exhaust merges after passing through a long exhaust passage, so that the influence of exhaust interference can be avoided and the output reduction can be suppressed. In an operating region where fuel consumption can be improved and exhaust interference does not pose a problem, the control valve can be fully opened to increase the passage area to secure high output.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a first embodiment of the present invention.

FIG. 2 is a sectional view showing the structure and operation of a control valve used in the above embodiment.

FIG. 3 is a sectional view showing a configuration of a second embodiment of the present invention.

FIG. 4 is a longitudinal sectional view and a lateral sectional view showing another modification of the control valve.

FIG. 5 is a longitudinal sectional view and a lateral sectional view showing still another modification of the control valve.

FIG. 6 is a sectional view showing a configuration of a conventional example.

[Explanation of symbols]

 11 Internal combustion engine 12A, 12B Exhaust valve 13A, 13B Branch passage section 14A, 14B Collecting section 15A First exhaust manifold 15B Second exhaust manifold 16A, 16B Preliminary exhaust purification catalyst 17 Exhaust pipe 18 Main exhaust purification catalyst 19,29, 39 Control valve 21 Actuator 22 Controller 23 Rotation speed sensor 24 Load sensor

Claims (1)

[Claims] 1. An exhaust system for an internal combustion engine having two exhaust valves per cylinder, wherein a branch passage portion connected to one exhaust valve of each cylinder and a downstream side of these branch passage portions are formed together. A second exhaust manifold including a first exhaust manifold including a collecting portion, a branch passage portion connected to the other exhaust valve of each cylinder, and a collecting portion formed by gathering the downstream sides of these branch passage portions. And a pre-exhaust gas purification catalyst is provided in each of the collecting portions of the first exhaust manifold and the second exhaust manifold, and a downstream side of the first exhaust manifold and the second exhaust manifold is provided. A main exhaust gas purification catalyst is interposed in the exhaust pipes formed by assembling, and in the branch passage portion of the first exhaust manifold, one of two cylinder groups consisting of cylinders whose combustion strokes are not continuous on the other hand A branch passage connected to the cylinder groups,
In the branch passage portion of the second exhaust manifold, the
A control valve that opens and closes a branch passage portion that partially connects the branch passage portion connected to the other cylinder group of the group of cylinders, and an engine that detects the control valve by operating state detection means. An exhaust device for an internal combustion engine, comprising: a control unit that controls opening / closing according to an operating state.