JPH0114733Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exhaust system for an internal combustion engine having a so-called dual-type exhaust pipe.

[Prior Art] Conventionally, in multi-cylinder internal combustion engines with four or more cylinders, in order to effectively utilize exhaust pulsation and improve engine performance,
Two exhaust pipes are provided in which cylinders whose exhaust strokes do not overlap with each other are assembled, and these exhaust pipes are merged and connected to one exhaust pipe to constitute an exhaust system of an internal combustion engine. For example, in a 4-cylinder internal combustion engine where the ignition order is 1st cylinder → 3rd cylinder → 4th cylinder → 2nd cylinder, the exhaust pipe that brings together the 1st and 4th cylinders and the 2nd and 3rd cylinders are connected. The collected exhaust pipes are provided separately, and both of these exhaust pipes are joined to form one exhaust pipe.

[Problems to be Solved by the Invention] FIG. 3 shows pressure fluctuations at the fourth cylinder exhaust port of a four-cylinder internal combustion engine, with the crank angle plotted on the horizontal axis. During the exhaust stroke, the pronounced positive pressure waves are a result of the pressure increase that occurs during blowdown in each cylinder, and the cylinder numbers are shown next to the waveforms. What should be noted here is that the positive pressure wave due to the blowdown of the second cylinder is synchronized with the latter half of the exhaust stroke. When the positive pressure waves are synchronized in the latter half of the exhaust stroke, the exhausted burnt gas flows backward, increasing the amount of residual gas in the cylinder and thus leading to a decrease in volumetric efficiency. On the other hand, since the positive pressure wave due to the blowdown of the second cylinder propagates along the path indicated by the broken line in FIG. 5, the positive pressure wave of the second cylinder always synchronizes with the latter half of the exhaust stroke at low and medium speeds. That is, in the low to medium speed range, the positive pressure wave of the next ignition cylinder is synchronized with the latter half of the exhaust stroke, reducing engine performance.

Furthermore, in order to reduce exhaust interference between the second and first cylinders and improve engine performance, an expansion chamber is provided at the junction of the two exhaust pipes with a volume sufficient to attenuate pressure fluctuations in the exhaust gas. This expansion chamber is used to reduce the pressure in the latter half of the exhaust stroke (the shaded area in FIG. 3). However, in conventional exhaust systems, the pressure waves of the second cylinder's exhaust gas propagate to the fourth cylinder's exhaust port via the expansion chamber, especially in the low rotation speed range, causing a pressure rise in the latter half of the exhaust stroke, which reduces engine performance. This had the disadvantage of causing Such drawbacks also occur in the case of six-cylinder internal combustion engines.

An object of the present invention is to provide an exhaust system for an internal combustion engine that can improve engine performance by lowering the pressure in the latter half of the exhaust stroke and reducing pressure propagation to the next ignition cylinder.

[Means for Solving the Problems] The exhaust system for an internal combustion engine of the present invention has two exhaust pipes, a first exhaust pipe and a second exhaust pipe, each of which collects cylinders whose exhaust strokes do not overlap with each other. This is a so-called dual type exhaust system, and an expansion chamber having a volume sufficient to attenuate exhaust pressure fluctuations is provided at the junction of the first and second exhaust pipes. The interior of this expansion chamber is divided into an upstream chamber and a downstream chamber by a first baffle plate having a large number of holes, and the upstream chamber is further divided into an upstream chamber and a downstream chamber by a second baffle plate having a large number of holes. It is separated into first and second compartments corresponding to the first and second exhaust pipes.

[Function] By employing this configuration, the exhaust system for an internal combustion engine of the present invention functions as follows. That is, since the exhaust manifold has a dual type exhaust manifold in which cylinders whose exhaust strokes do not overlap with each other are assembled, exhaust pulsation can be effectively utilized. In addition, the exhaust gas that has flowed into the expansion chamber through the first and second exhaust pipes is sufficiently mixed by the second baffle plate with a large number of holes, and at the same time, the exhaust gas is Exhaust pulsation is sufficiently attenuated and absorbed by the volume. Furthermore, the first baffle plate can attenuate pressure fluctuations reflected from the catalyst, muffler, etc. downstream of the expansion chamber, making it possible to improve engine performance.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1, 2, and 4.

It is assumed that the ignition order of the four-cylinder internal combustion engine 1 is first cylinder → third cylinder → fourth cylinder → second cylinder.
The exhaust port 1a of the first cylinder and the exhaust port 1b of the fourth cylinder of the internal combustion engine 1 are collected by an exhaust manifold 2, and the exhaust manifold 2 is connected to the expansion chamber 4 via the first exhaust pipe 3. . On the other hand, the exhaust port 1c of the second cylinder and the exhaust port 1d of the third cylinder of the internal combustion engine 1 are collected by an exhaust manifold 5, and the exhaust manifold 5 is connected to the second exhaust pipe 6.
It is connected to the expansion chamber 4 via. The expansion chamber 4 has a volume sufficient to attenuate pressure fluctuations in the exhaust gas,
The first buttful plate 9 has a large number of holes inside.
The upstream chamber is separated into an upstream chamber and a downstream chamber 4c by a second baffle plate 8 having a large number of holes.
a and a second compartment 4b corresponding to the second exhaust pipe 6
separated into The downstream chamber 4c is a third compartment 4c.
After all, the interior of the expansion chamber 4 is divided into three compartments 4.
It is separated into a, 4b, and 4c. Among these compartments, the compartment 4a communicates with the first exhaust pipe 3, and the compartment 4b communicates with the second exhaust pipe 6. Furthermore, the compartment 4c is directly connected to the third exhaust pipe 7. The third exhaust pipe 7 is connected to a tail pipe (not shown) via a catalyst and a muffler (not shown).

The action will be explained below.

The exhaust gas discharged from the exhaust ports 1a and 1b is
It flows into the exhaust manifold 2 and into the expansion chamber 4 through the first exhaust pipe 3. Here, since the first cylinder and the fourth cylinder of the engine 1 are cylinders whose exhaust strokes do not overlap, there is no exhaust interference between the first cylinder and the second cylinder, and the exhaust pulsation can be used effectively. I can do it. Further, the exhaust gas discharged from the exhaust ports 1c and 1d flows into the exhaust manifold 5 and the second
The air flows into the expansion chamber 4 through the exhaust pipe 6. Here, since the second cylinder and the third cylinder are cylinders whose exhaust strokes do not overlap, no exhaust interference occurs between these two cylinders, and the exhaust pulsation can be effectively utilized as described above.

The exhaust gas flowing out from the first and second exhaust pipes 3 and 6 is discharged into the first and second compartments 4a and 4 of the expansion chamber 4, respectively.
b, is sufficiently mixed by the second buffle plate 8, and at the same time expands to the volume of the expansion chamber 4, effectively damping exhaust pulsation. Further, the mixing of the exhaust gas flowing into the first and second compartments 4a and 4b is further promoted by the first buffle plate 9. And the crank angle of engine 1 is 360
In the second half of the exhaust stroke of the second cylinder, the exhaust pulsation of the exhaust from the exhaust port 1c cannot be transmitted to the next ignition cylinder, the first cylinder, without passing through the second bump-full plate 8. . However, since the pressure of the exhaust port 1c in the latter half of the exhaust stroke is sufficiently reduced by the expansion chamber 4, and the second buff-full plate 8 attenuates the exhaust pulsation, the interference of the exhaust to the exhaust port 1a is extremely low. It will be minor. Also,
The first baffle plate 9 attenuates pressure fluctuations reflected from the catalyst, muffler, etc. downstream of the expansion chamber 4, thereby improving engine performance.

Figure 4 shows the volumetric efficiency (ETA = fresh air volume/displacement volume) with respect to the engine speed. In the figure, 10 indicates the characteristics of the conventional engine, and 11 indicates the characteristics of the exhaust system of the present invention. Indicates the characteristics of institutions that have As is clear from Figure 4, when the exhaust system of the present invention is used, the ETA is
Since the value has increased, the engine performance will improve by this amount.

[Effects of the invention] As explained above, according to the exhaust system for an internal combustion engine of the present invention, an expansion chamber is provided at the confluence of the first and second exhaust pipes that bring together cylinders whose exhaust strokes do not overlap with each other. , the inside of the expansion chamber is divided into an upstream chamber and a downstream chamber by a first buttful plate, and the upstream chamber is divided into a second chamber.
Since the baffle plate separates the first compartment corresponding to the first exhaust pipe and the second compartment corresponding to the second exhaust pipe, the exhaust pulsation is prevented by the second buffle plate and the expansion chamber volume. The first buffer plate can attenuate pressure fluctuations reflected from the catalyst, muffler, etc. downstream of the expansion chamber, and engine performance can be improved.

[Brief explanation of the drawing]

Fig. 1 is a front view of essential parts of the exhaust system for an internal combustion engine of the present invention, Fig. 2 is an enlarged perspective view of the expansion chamber portion, Fig. 3 is a diagram showing exhaust pressure fluctuations of a four-cylinder internal combustion engine, and Fig. 4 is a diagram showing exhaust pressure fluctuations of a four-cylinder internal combustion engine.
The figure shows the relationship between the engine speed and ETA, and FIG. 5 is a diagram showing the transmission path of the positive pressure plate to the fourth cylinder due to blowdown of the second cylinder, for example. 1...4-cylinder internal combustion engine, 1a, 1b, 1c, 1
d... Exhaust port, 2, 5... Exhaust manifold, 3... First exhaust pipe, 4... Expansion chamber, 4a...
...First compartment, 4b...Second compartment, 4c...
...Downstream chamber (third compartment), 6...Second exhaust pipe, 7...Third exhaust pipe, 8...Second buttful plate, 9...First buttfull plate.

Claims (1)

[Scope of utility model registration request] It has two exhaust pipes, a first exhaust pipe and a second exhaust pipe, each of which collects cylinders whose exhaust strokes do not overlap with each other, and the first and second exhaust pipes are merged to form one exhaust pipe. In the exhaust system for a multi-cylinder internal combustion engine having four or more cylinders connected to a third exhaust pipe, an expansion chamber having a volume sufficient to attenuate exhaust pressure fluctuations is provided at the confluence of the first and second exhaust pipes. The interior of the expansion chamber is separated into an upstream chamber and a downstream chamber by a first baffle plate having a large number of holes, and the upstream chamber is separated by a second baffle plate having a large number of holes. The exhaust system for an internal combustion engine is further characterized in that the exhaust system is further separated into first and second compartments corresponding to the first and second exhaust pipes, respectively.