JPS6230283B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an exhaust system for a motorcycle.

Generally, the exhaust system of a motorcycle is an important element of its appearance, so the outer surfaces of its exhaust pipe and muffler are chrome plated.

However, since this exhaust pipe is heated by engine exhaust gas, when the exhaust gas temperature is high, the surface of the exhaust pipe becomes discolored and the appearance is impaired. As a measure to prevent this discoloration of the exhaust pipe, conventionally, as seen in Japanese Utility Model Application Publication No. 110523/1983, a gap is created between the inside of the exhaust pipe and the inner surface of the exhaust pipe. It is known that the insertion and exhaust pipes have a double pipe structure.

On the other hand, in multi-cylinder engines for motorcycles, for example, as seen in Japanese Utility Model Publication No. 33-10007,
BACKGROUND ART Engine performance has been improved by connecting intermediate portions of a plurality of exhaust pipes connected to each cylinder with each other through a connecting pipe.

By the way, when connecting exhaust pipes using such a connecting pipe, if the exhaust pipe has a double pipe structure as described above, it is structurally extremely difficult to connect the connecting pipe directly to the inner pipe. . For this reason, conventionally, the connecting pipe is connected to the outer exhaust pipe, and a through hole is provided in the inner pipe corresponding to the connecting position of the connecting pipe.

However, according to this conventional configuration, high-temperature exhaust gas flowing inside the inner pipe flows into the gap between the exhaust pipe and the inner pipe through the through hole, and the exhaust pipe is heated by this exhaust gas, and the exhaust pipe is heated. There is a problem when the surface becomes discolored.

The present invention has been made based on the above circumstances, and its object is to provide an exhaust system for a motorcycle that can prevent exhaust gas from flowing into the gap and reliably prevent discoloration on the surface of the exhaust pipe. It's about getting.

That is, in the present invention, when a plurality of exhaust pipes having a double pipe structure are communicated with each other through a connecting pipe, the exhaust pipe and the inner pipe are brought into close contact with each other at the connecting part of the connecting pipe, and the connecting pipe is A blocking portion for closing the gap between the exhaust pipe and the inner pipe is formed at the connecting portion, and a through hole communicating with the connecting pipe is formed in the peripheral wall of the blocking portion.

The first embodiment of the present invention will be described below with reference to FIGS. 1 to 5.
This will be explained based on the diagram.

The body of the motorcycle shown by reference numeral 1 in Fig. 1 includes:
A multi-cylinder engine 2, for example a two-cylinder engine, is installed. One end of exhaust pipes 3, 3 is connected to the exhaust port of each cylinder of the engine 2, and the other ends of these exhaust pipes 3, 3 are connected to mufflers 4, 4.
A connecting pipe 5 is branched and connected to the middle part of these exhaust pipes 3, 3 near the mufflers 4, 4, and this connecting pipe 5 passes through the lower part of the vehicle body 1 to connect the left and right exhaust pipes 3, 3.
are connected.

Inside each exhaust pipe 3, 3, there is a first inner pipe 6 from the end on the engine 2 side to the connecting part of the connecting pipe 5, and from this connecting part to the end on the muffler 4, 4 side. The second inner pipe 7 is located in the part of the exhaust pipe 3, respectively.
It is inserted with a predetermined gap 8 between it and the inner surface. Upstream end of first inner tube 6 and second inner tube 7
The downstream end of the first inner pipe 6 and the upstream end of the second inner pipe 7 are spot welded to the inner surface of the exhaust pipe 3, and the downstream end of the first inner pipe 6 and the upstream end of the second inner pipe 7 are connected to the exhaust pipe 3 and the connecting pipe. In front of the connecting portion with 5, they are fitted together without any gaps and are spot welded. The fitting portions 9 of the inner tubes 6 and 7 are brought into close contact with the inner surface of the exhaust pipe 3 by reducing the diameter of the exhaust pipe 3 covering the outside thereof. In addition, the second inner pipe 7
is enlarged in diameter on the downstream side of the fitting part 9, and this enlarged diameter part 10 is continuous with the fitting part 9 and is in close contact with the inner surface of the exhaust pipe 3. Therefore, the fitting portion 9 and the enlarged diameter portion 10 constitute a blocking portion 15 that closes the gap 8 in the middle. and,
Peripheral wall 1 of the part where this enlarged diameter portion 10 and the exhaust pipe 3 are in close contact with each other
Through holes 11, 11 are formed in 5a so as to face each other, and the end of the connecting pipe 5 is welded to the opening periphery of the through holes 11, 11.

The connecting tube 5 of this embodiment is divided into left and right connecting tube halves 5a and 5b at the center, and the end of one connecting tube half 5a connects to the other connecting tube half through a gasket 12. It is fitted onto the outer periphery of the end portion of 5b and is tightened and held by a metal tightening band 13. In this case, the connecting pipe 5 has a single layer structure, but as is clear from FIG.
3 are connected to each other, and therefore, it cannot become an external appearance element, so even if the surface becomes discolored, there is no problem. In addition, since the connecting pipe 5 is horizontally suspended perpendicular to the direction of travel, it is easily exposed to the traveling wind, so that the surface temperature is kept relatively low and the surface is less likely to discolor.

According to the first embodiment of the present invention, the inner pipes 6 and 7 are inserted into the exhaust pipe 3, and a gap 8 is formed between the inner pipes 6 and 7 and the exhaust pipe 3. Therefore, the heat of the exhaust gas is insulated by the gap 8 and is difficult to be transmitted to the exhaust pipe 3.

At the connecting portion between the exhaust pipe 3 and the connecting pipe 5, the ends of the inner pipes 6 and 7 form a blocking part 15 that closely contacts the inner surface of the exhaust pipe 3 to close the gap 8. Since the peripheral wall 15a of the exhaust pipe 15 is provided with through holes 11, 11 connected to the connecting pipe 5, even though the exhaust pipes 3, 3 are communicated with each other through the connecting pipe 5,
The exhaust gas flowing through the inner pipes 6 and 7 does not flow into the gap 8. Therefore, the exhaust pipe 3 does not need to come into direct contact with high-temperature exhaust gas, and discoloration of the surface of the exhaust pipe 3 can be reliably prevented.

Moreover, since the blocking part 15 is constructed by overlapping the inner pipes 6, 7 and the exhaust pipe 3 and bringing them into close contact with each other, there is no need for any other special member to fill the gap 8. It does not require an increase in the number of points, has a simple structure, is easy to assemble, and has the advantage of being inexpensive.

Note that at the joint between the exhaust pipe 3 and the connecting pipe 5, the enlarged diameter part 10 of the inner pipe 7 is in close contact with the inner surface of the exhaust pipe 3; , the heat conduction to the exhaust pipe 3 is relatively small, and the portion where the enlarged diameter portion 10 and the exhaust pipe 3 are in close contact is localized, so the heat transferred to the exhaust pipe 3 is transferred to other parts. Therefore, the temperature of this area does not rise to the extent that the surface becomes discolored.

Note that the present invention is not limited to the first embodiment described above, and for example, FIG. 6 shows a second embodiment of the present invention.

In this second embodiment, the downstream end of the first inner pipe 6' is extended rearward beyond the connecting part of the connecting pipe 5, and is brought into close contact with the inner surface of the enlarged diameter part 10 of the second inner pipe 7'. , the blocking portion 15' that closes the gap 8 has a triple wall structure.

According to this second embodiment, since the blocking part 15' has a triple wall structure, it becomes more difficult for the heat of the exhaust gas to be transferred to the outermost exhaust pipe 3, and even when the exhaust temperature is high, the exhaust pipe 3 Prevents surface discoloration.

Note that this second embodiment has the same configuration as the first embodiment except for the points mentioned above, so the sixth embodiment has the same structure as the first embodiment.
In the drawings, the same components as in the first embodiment are given the same numbers, and their explanations will be omitted.

According to the present invention described in detail above, since the gap is closed at the blocking portion, even if a through hole connected to the connecting pipe is provided in the blocking portion, the exhaust gas flowing inside the inner pipe will not flow into the gap. Therefore, the exhaust pipe does not come into direct contact with high-temperature exhaust gas, and discoloration of the exhaust pipe surface can be reliably prevented.

Moreover, since the shutoff part is constructed by overlapping the inner pipe and the exhaust pipe and bringing them into close contact with each other, there is no need for any special other members to fill the gap, and therefore there is no need for an increase in the number of parts. It has the advantage of having a simple structure, being easy to assemble, and being available at a low cost.

[Brief explanation of the drawing]

1 to 5 show a first embodiment of the present invention, FIG. 1 is a side view of the entire motorcycle, FIG. 2 is a perspective view of the entire exhaust system, and FIG. 3 is a partially sectional view. A side view, FIG. 4 is a longitudinal sectional view of the main part, and FIG. 5 is a sectional view taken along line V-V in FIG. 1. Also, the 6th
The figure is a longitudinal sectional view of the main part of the second embodiment of the present invention. 2...Engine, 3...Exhaust pipe, 4...Muffler, 5...Connecting pipe, 6, 6', 7, 7'...Inner pipe (first inner pipe, second inner pipe), 8 ...Gap, 11...
...through hole, 15, 15'...blocking part, 15a...peripheral wall.

Claims (1)

[Scope of Claims] 1. A plurality of exhaust pipes provided for each cylinder of a multi-cylinder engine, one end communicating with the exhaust port of the cylinder and the other end communicating with a muffler, and an intermediate portion of these exhaust pipes connected to each other. A connecting pipe for communication, and an inner pipe inserted into the inside of the exhaust pipe with a gap between the inner surface of the exhaust pipe, and the exhaust pipe and the inner pipe are connected at a connecting part of the connecting pipe. forming a blocking part that closes a gap between the exhaust pipe and the inner pipe at the connecting part of the connecting pipe by bringing them into close contact with each other;
An exhaust system for a motorcycle, characterized in that a through hole connected to the connecting pipe is formed in the peripheral wall of the blocking portion.