JPS6343564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalytic exhaust system for an internal combustion engine in which a muffler is equipped with a catalyst for purifying exhaust gas.

Although it is widely used to install a catalyst in a muffler as an exhaust purification measure, this catalyst increases exhaust resistance and may reduce engine output. For this reason, it is conceivable to increase the size of the catalyst to reduce the exhaust resistance, but this would require a large amount of expensive catalyst, resulting in high costs.

Moreover, if the catalyst is made larger, the exhaust volume will be smaller than the catalyst capacity, so it will take more time for the catalyst to reach its activation temperature, especially during cold starts, resulting in improved purification efficiency. There are also problems such as a decrease in

The present invention was developed based on the above circumstances, and it is possible to downsize the catalyst without increasing exhaust resistance, and moreover, the catalyst reaches its activation temperature in a short time, reducing the exhaust gas. The purpose of the present invention is to provide a catalytic exhaust system for an internal combustion engine that improves purification efficiency.

That is, in order to achieve the above object, the present invention
A muffler is connected to the exhaust pipe of the engine, and the interior of the muffler is divided from the exhaust upstream side into an expansion chamber, a catalyst storage chamber in which a catalyst for exhaust purification is installed, and a muffling chamber by multiple partition walls. An auxiliary expansion chamber is connected to the adjacent expansion chamber, a downstream end of the exhaust pipe is introduced into the expansion chamber, and the downstream end opening of the exhaust pipe is provided to face the partition wall constituting the catalyst storage chamber. It is characterized by:

The present invention will be explained below based on a first embodiment shown in FIGS. 1 to 5.

Figure 1 shows a motorcycle, where 1 is a frame, 2
is a single-cylinder engine, 3 is a steering wheel, 4 is a driving wheel, 5
is a fuel tank, and 6 is a seat. An exhaust pipe 7 having a double pipe structure is connected to the exhaust hole of the engine 2, and a muffler 8 is connected to the downstream end of the exhaust pipe 7. And this muffler 8
As shown in FIG. 3, the interior is divided into three chambers, an expansion chamber 11, a catalyst storage chamber 10, and a muffling chamber 9, in order from the exhaust upstream side. That is, the expansion chamber 11, the storage chamber 10, and the silencing chamber 9 are separated by partition walls 12a, 12b,
12c, and the expansion chamber 11 and the catalyst storage chamber 10 are communicated with each other via a throttle passage 13a provided in the partition wall 12a. Further, the silencing chamber 9 and the catalyst storage chamber 10 are communicated with each other via a throttle passage 13b provided in the partition wall 12b and a plurality of communication holes 14, and the throttle passages 13a and 13b are provided facing each other. ing. A catalyst 15 for purifying exhaust gas is installed in the catalyst housing chamber 10. A tail pipe 17 having a large number of through holes 16 on its circumferential surface is inserted into the muffling chamber 9 . One end of this tail pipe 17 is opened into the catalyst storage chamber 10 and the other end is opened to the outside.
A sound absorbing material 18 made of, for example, fibrous glass fiber is adhered to the outer peripheral surface of.

By the way, in the middle of muffler 8, that is, catalyst 15
A sub-muffler 19 is connected to the upstream side of the exhaust gas so as to be located at the lower rear of the engine 2, and the inside of this sub-muffler 19 forms an auxiliary expansion chamber 20 having a relatively large capacity. This auxiliary expansion chamber 20
is for supplementing the capacity of the expansion chamber 11.
It communicates with the expansion chamber 11 via 1. Also,
An inner pipe 22 that is integrally connected to the downstream end of the exhaust pipe 7 is introduced into the expansion chamber 11, and the downstream end opening 22a of the inner pipe 22 faces the partition wall 12a that constitutes the catalyst storage chamber 10. It is provided.

According to this configuration, under normal operating conditions, the exhaust gas intermittently sent from the engine 2 through the exhaust pipe 7 and the inner pipe 22 first passes through the expansion chamber 11 as indicated by the arrow in FIG. and expands in this expansion chamber 11.

In this case, the downstream end opening 2 of the inner pipe 22
2a faces the partition wall 12a, which is the peripheral wall of the catalyst storage chamber 10, so the exhaust flow flowing into the expansion chamber 11 collides head-on with the partition wall 12a, and after this, a part of the exhaust gas is throttled. It flows into the catalyst storage chamber 10 through the passage 13a, and the rest flows into the auxiliary expansion chamber 20 through the through hole 21.

Then, the exhaust gas that has flowed into the auxiliary expansion chamber 20 is expanded again inside this chamber and temporarily stored. Therefore, the pulsation of the exhaust gas is regulated and the exhaust gas is sent substantially continuously into the catalyst storage chamber 10, and as a result, a large amount of exhaust gas is prevented from being sent into the catalyst storage chamber 10 at once. Therefore, the amount of exhaust gas that comes into contact with the catalyst 15 in the muffler 8 is apparently reduced, so the catalyst 15 can be made smaller without reducing the purification efficiency, and the number of expensive catalysts 15 can be reduced. In addition, as the catalyst 15 is made smaller, the muffler 8 can also be made smaller, which is particularly advantageous for motorcycles where the muffler 8 is an important element in appearance.

Moreover, by regulating the exhaust pulsation,
The exhaust gas when it comes into contact with the catalyst 15 becomes a substantially smooth steady flow, which reduces exhaust resistance.
A decrease in the output of the engine 2 can be prevented.

Further, since the downstream end opening 22a of the inner pipe 22 that guides the exhaust gas into the expansion chamber 11 faces the partition wall 12a that is the peripheral wall of the catalyst storage chamber 10, the high temperature and high pressure exhaust flow is directed from the front to the partition wall 12a. There will be a collision. For this reason, the catalyst storage chamber 10 and the catalyst 1
The rise in temperature of the catalyst 15 is promoted, and the rise time for the catalyst 15 to reach the activation starting temperature becomes faster. Therefore, the exhaust gas purification efficiency is improved, especially during a cold start.

Note that the exhaust gas purified by the catalyst 15 flows into the silencing chamber 9 through the throttle passage 13b and the communication hole 14, and then passes through the sound absorbing material 18 to the tail pipe 17.
During the process until the exhaust gas is discharged, the exhaust pressure and temperature are gradually lowered and the exhaust gas is muffled.

Furthermore, the present invention is not limited to the first embodiment described above, and second and third embodiments will be described below. Here, the same components as those in the first embodiment are given the same numbers, and the explanation thereof will be omitted.

That is, FIGS. 6 to 8 illustrate the second aspect of the present invention.
An example is shown, in which a silencing room 31 is separated by a partition wall 3.
2, the primary silencing chamber 33a and the secondary silencing chamber 3
3b, a primary silencing chamber 33a and a catalyst storage chamber 1.
0 through the exhaust passage 34, and the primary silencing chamber 33a and the secondary silencing chamber 33b are communicated with each other through throttle holes 35, 35, and one end of the tail pipe 17 is placed in the secondary silencing chamber 33b. It is opened.

Even with this configuration, a part of the exhaust gas from the engine 2 is primarily stored in the auxiliary expansion chamber 20, and the high-temperature, high-pressure exhaust gas that has flowed into the expansion chamber 11 collides head-on with the partition wall 12a. Therefore, the same effects as in the first embodiment described above can be obtained. Then, the purified exhaust gas flows into the primary silencing chamber 33a through the exhaust passage 34, as shown by the arrow in FIG. The pressure becomes high, and a part of the inflowing exhaust gas is sucked into the low-pressure secondary silencing chamber 33b through the sound absorbing material 18 and the throttle holes 35, 35, and is discharged to the outside through the tail pipe 17.

9 to 11 show a third embodiment of the present invention, in which the downstream end opening 22a of the inner tube 22 is extended toward the partition wall 12b, and a through hole 21 is formed in the side surface of the inner tube 22. An exhaust outlet hole 41 is provided so as to directly face the expansion chamber 11 and the silencing chamber 9, and the expansion chamber 11 and the silencing chamber 9 are communicated with each other through the exhaust passage 42. A catalyst 15 is installed here as a storage chamber 10.

In this configuration, a part of the exhaust from the engine 2 is transferred to the exhaust outlet 4 as shown by the arrow in FIG.
Since the exhaust gas flows into the auxiliary expansion chamber 20 through the silencing chamber 1 and the conduction hole 21 and is primarily stored, the exhaust gas almost continuously flows into the exhaust passage 42 and first flows into the primary silencing chamber 3.
3a. Therefore, the pressure in the silencing chamber 33a is higher than that in the catalyst storage chamber 10, so this exhaust gas flows into the catalyst storage chamber 10 through the throttle holes 35, 35, contacts the catalyst 15, and is discharged to the outside through the tail pipe 17. Ru.

Therefore, according to this third embodiment, the catalyst 1
Since the amount of exhaust gas that comes into contact with 5 is reduced, the above first
The same effects as in the embodiment can be obtained, and the inner tube 2
The temperature rise in the catalyst storage chamber 10 is promoted by the amount that the downstream end opening 22a of the catalyst storage chamber 10 is closer to the partition wall 12b.
There are advantages such as a shorter activation time of the catalyst 15.

Note that the catalytic exhaust system according to the present invention is not specified for use in motorcycles, but can be similarly applied to other vehicles such as tricycles.

According to the present invention described above, the exhaust gas from the engine is expanded in the auxiliary expansion chamber and is primarily stored, so that the pulsation of this exhaust gas is regulated and it is sent substantially continuously to the catalyst. Therefore, the amount of exhaust gas that comes into contact with the catalyst in the muffler is reduced, so the catalyst can be made smaller without reducing purification efficiency, and less expensive catalysts are needed. At the same time, since the exhaust gas becomes a substantially smooth steady flow when it comes into contact with the catalyst, exhaust resistance is reduced and a decrease in engine output can be prevented.

In addition, the high-temperature, high-pressure exhaust flow introduced into the expansion chamber collides head-on with the partition wall that forms the peripheral wall of the catalyst storage chamber, which accelerates the temperature rise of the catalyst storage chamber and the catalyst, bringing the catalyst to the activation starting temperature. The rise time to reach is faster. Therefore, there is an advantage that the exhaust gas purification efficiency is improved, especially during a cold start.

[Brief explanation of the drawing]

Figures 1 to 5 show a first embodiment of the present invention, with Figure 1 being a side view of the motorcycle, Figure 2 being a plan view of the exhaust system, Figure 3 being a sectional view of the muffler, and Figure 4 being a side view of the motorcycle. is a sectional view taken along the line - in Fig. 3, and Fig. 5 is a sectional view taken along the - line in Fig. 3.
6 to 8 show a second embodiment of the present invention, FIG. 6 is a sectional view of the muffler, and FIG. 7 is a sectional view taken along the line in FIG. 6. , FIG. 8 is a sectional view taken along the line - in FIG. 6, FIGS. 9 to 11 show a third embodiment of the present invention, FIG. 9 is a sectional view of the muffler, and FIG.
Figure 11 is a cross-sectional view along the line in Figure 9.
It is a sectional view along the XI-XI line. 2...Engine (single-cylinder engine), 7...Exhaust pipe,
8...Muffler, 9, 31...Muffling chamber, 10...Catalyst storage chamber, 12a, 12b, 12c...Partition wall, 15...Catalyst, 20...Auxiliary expansion chamber, 22...Inner pipe, 22a...Downstream end opening.

Claims (1)

[Claims] 1. A muffler is connected to the exhaust pipe of the engine, and the interior of the muffler is divided from the exhaust upstream side into an expansion chamber, a catalyst storage chamber in which a catalyst for exhaust purification is installed, and a muffling chamber by a plurality of partition walls. Connecting the auxiliary expansion chamber to the expansion chamber adjacent to the
Introducing the downstream end of the exhaust pipe into this expansion chamber,
A catalytic exhaust system for an internal combustion engine, characterized in that a downstream end opening of the exhaust pipe is provided opposite to a partition wall constituting the catalyst storage chamber.