JPH0650052B2 - Motorcycle exhaust system - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an exhaust device provided in a motorcycle.

[Prior Art] In an exhaust device of a motorcycle, an exhaust pipe connecting between an exhaust hole of an engine and a silencer is arranged at a position that is noticeable in appearance, and therefore its surface is plated with chrome, It has a beautiful metallic luster. However, the plating discolors due to direct heat transfer from the connection with the exhaust hole and heating by the high-temperature exhaust gas passing through the exhaust pipe, and loses its beautiful metallic luster.
Further, if the surface is polished to remove the discolored portion, the plating may be peeled off.

The conventional exhaust pipe has a double pipe structure in order to eliminate the cause of discoloration due to the exhaust gas, and measures are taken such as inserting a heat insulating material into the space sandwiched by the double pipe. However, even with such a double pipe structure, it is not possible to prevent discoloration in the vicinity of the exhaust hole connection portion due to direct heat transfer from the exhaust hole, and moreover, the double pipe structure causes an increase in weight. Along with this, there is a problem that the exhaust pipe structure is complicated. [Object of the Invention] An object of the present invention is to prevent the discoloration of the surface of the motorcycle in the vicinity of the exhaust hole connecting portion without increasing the weight. To provide a device.

[Structure of Invention]

In the exhaust system of the present invention to achieve the above object, the rear ends of the plurality of exhaust pipes respectively connected to the plurality of exhaust holes of the engine are connected to a silencer via a collecting pipe, and the plurality of exhaust pipes are connected to the outside of the vehicle body. In the motorcycle arranged so as to be exposed to the outside, the collecting pipe is housed in the expansion chamber of the silencer, and the exhaust pipe is formed as a smooth pipe having a single pipe structure made of stainless steel, and the entire silencer. Is disposed near the front of the vehicle so that its front end overlaps with the engine in a vertical region when viewed from the side.

〔Example〕

 The present invention will be described below with reference to the embodiments shown in the drawings.

In the motorcycle shown in FIG. 3, 1 is a body frame,
Reference numeral 2 is a 2-cylinder engine mounted on the vehicle body frame 1, and 3 is an exhaust device. The exhaust device 3 is connected to an exhaust hole of the engine 2 and an exhaust pipe 4 connected to a rear end of the exhaust pipe 4 and a front end thereof is below the engine 2 and is in a vertical region with the engine 2 in a side view. It is composed of a silencer 5 which is generally arranged toward the front so as to overlap. Reference numeral 13 is a front wheel, and 14 is a rear wheel.

As shown in FIGS. 1 and 2, the exhaust pipe 4 of the exhaust device 3 is formed of a smooth pipe having a single pipe structure and is made of stainless steel, and its surface is not particularly plated. Although stainless steel has a large coefficient of thermal expansion,
A band 15 is wound around the joint between the stainless steel exhaust pipe 4 and the muffler 5 and is fixed by tightening.
Is designed to suppress the thermal expansion of. The muffler 5 of the exhaust device 3 is composed of a first expansion chamber 6 and a second expansion chamber 7, and glass wool muffling materials 8 and 9 are attached to the inner walls of the muffler 5. The two exhaust pipes 4 and 4 are gathered in the collecting pipe 10 and communicate with the first expansion chamber 6, and the first expansion chamber 6 to the second
The expansion chamber 7 is connected by a communication pipe 11, and the second expansion chamber 7 is communicated with the outside air by a communication pipe 12.

The first expansion chamber 6 forms an outer shell in which, in addition to the box-shaped portion located below the engine 2, a convex portion that largely protrudes upward in the rear of the engine 2 is combined, and the first expansion chamber 6 has an extremely large capacity. It has become. On the other hand, the second expansion chamber 7 is arranged on the side of the vehicle body, and its capacity is relatively small because the capacity of the first expansion chamber 6 is large. Therefore, the rear end of the second expansion chamber 7 is located in the vicinity of the front end of the rear wheel 14, and is considerably forward as compared with the rear end position of the silencer of the conventional exhaust system. With such a configuration toward the front, the weight of the silencer 5 is concentrated on the center of gravity of the vehicle, which is advantageous for improving the steering stability of the vehicle.

According to the above-described exhaust device, since the exhaust pipe 4 is composed of only a single pipe, it can be made lighter than the exhaust pipe having the conventional double pipe structure. Even with such a single pipe structure, the exhaust hole has a thermal conductivity of less than about 1/4 that of ordinary steel and is made of stainless steel that is extremely strong against oxidation. The surface is not discolored not only by heating by direct heat transfer from the exhaust gas but also by heating by high temperature exhaust gas, and a beautiful metallic luster is always maintained over the entire exhaust pipe 4 from the exhaust hole connecting portion to the silencer. be able to. Even if a slight discoloration occurs, the original metallic luster can be easily reproduced by polishing the surface.

On the other hand, since the collecting pipe 10 connected to the rear end of the exhaust pipe 4 is housed in the atmosphere that is not easily oxidized in the first expansion chamber 6 of the silencer 5, expensive stainless steel is used as a measure against discoloration or corrosion. Need not be used.

〔The invention's effect〕

As described above, in the present invention, since the exhaust pipe connecting from the exhaust hole of the engine to the muffler is formed as the smooth pipe having the single pipe structure, the weight can be reduced, and the single pipe structure can be achieved. Since the exhaust pipe is made of stainless steel, which has low thermal conductivity and is resistant to oxidation, it does not cause heating due to direct heat transfer from the exhaust hole and surface discoloration due to heating of the exhaust gas, and noise is eliminated from the exhaust hole connection part. The entire exhaust pipe up to the vessel can be always kept in a beautiful metallic luster. Even if discoloration occurs, the original metallic luster can be easily restored by polishing the smooth surface. Moreover, since the collecting pipe is housed in the expansion chamber of the silencer, it is not necessary to use expensive stainless steel as a measure against discoloration or corrosion.

In addition, the front end of the muffler is located near the front of the vehicle, which overlaps with the engine in the vertical region when viewed from the side, so that the length of the exhaust pipe made of expensive stainless steel is shortened as much as possible. You can

Further, since the silencer is entirely arranged near the front of the vehicle body and the weight of the silencer is close to the body weight of the vehicle, the steering stability of the vehicle can be improved.

[Brief description of drawings]

FIG. 1 is a side view showing a partial cross section of an exhaust device having an exhaust pipe according to an embodiment of the present invention, FIG. 2 is a plan view showing the exhaust device in a partial cross section, and FIG. 3 is the exhaust device. FIG. 3 is a side view of the motorcycle provided with. 2 ... Engine, 3 ... Exhaust device, 4 ... Exhaust pipe, 8 ...
… Silencers, 6, 7 ... Expansion chambers, 10 ... Collecting pipes.

Claims (1)

[Claims] 1. A rear end of a plurality of exhaust pipes respectively connected to a plurality of exhaust holes of an engine is connected to a silencer via a collecting pipe, and the plurality of exhaust pipes are arranged to be exposed to the outside of the vehicle body. In the motorcycle, the collecting pipe is housed in the expansion chamber of the silencer, the exhaust pipe is formed as a smooth pipe having a single pipe structure made of stainless steel, and the entire silencer has a front end in a side view. The exhaust system for motorcycles is characterized in that it is arranged near the front of the vehicle so that it overlaps with the engine in the vertical direction.