JPH0347993Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an exhaust system for a motorcycle equipped with a two-stroke engine when viewed from the side.

(Background Art) It is common practice to cover the lower part of the engine of a motorcycle with a front lower cowl having a U-shaped cross section, and in this case, the front lower cowl may also cover the exhaust pipe.

By the way, when the engine is a two-stroke engine, the chamber provided in the middle of the exhaust pipe has a large diameter, so a notch in the front and rear direction is formed on the bottom of the front lower cowl, and a part of the chamber is exposed to this notch. That's what I do.

However, when the notch is formed in the front lower cowl in this manner, the front lower cowl is divided into left and right parts, which may cause vibration.

(Purpose of the invention) Therefore, an object of the present invention is to provide an exhaust system for a motorcycle in which there is no need to provide a notch in the front lower cowl, thereby preventing the front lower cowl from vibrating.

(Structure of the invention) The present invention is an exhaust system for a motorcycle equipped with a two-stroke engine in which a cylinder protruding forward is offset to either the left or right side of the vehicle body, and the exhaust pipe connected to the lower surface of the cylinder is connected to the exhaust pipe connected to the lower surface of the cylinder. A cross-section that covers the lower part of the engine, consisting of a front exhaust pipe whose diameter gradually increases from the joining part, a large-diameter chamber that connects to the front exhaust pipe, and a rear exhaust pipe that connects to this chamber and gradually becomes smaller in diameter. The present invention is characterized in that the front exhaust pipe is covered with a U-shaped front lower cowl, and the chamber is disposed behind the front lower cowl.

(Embodiments) Hereinafter, preferred embodiments that further embody the present invention will be described in detail with reference to the drawings.

First, in order to clarify the present invention, the overall schematic structure of a motorcycle equipped with an exhaust system according to the present invention will be explained with reference to FIG. The figure is a side view of the motorcycle. The motorcycle designated by reference numeral 40 has a front fork 45 supported by a head tube 44 which is the front part of a body frame 41.
Furthermore, at the lower end of this front fork 45, the front wheel 4
6, and a handle 47 is attached to the upper end. On the other hand, the front end of a rear fork 49 extending rearward is pivotally attached to the curved rear end of a main pipe 48 extending rearward from the head tube 44, and the rear wheel 50 is supported at this rear end. In addition, rear fork 49
A shock absorber 51 is interposed between the intermediate portion of the vehicle body frame 41 and the vehicle body frame 41 . On the other hand, a fuel tank 52 is mounted on the upper part of the main pipe 48, and a seat 53 is further attached behind this. Further, an engine unit 55 is mounted on the down tube blower 54 which is an intermediate portion of the vehicle body frame 41.
The exhaust device 1 according to the present invention is coupled to the exhaust device 1 according to the present invention. on the other hand,
A front lower cowl 56 is provided on both sides near the engine unit 55 to cover it, and a front cowl 57 is provided above the front lower cowl 56.
Attached. The front cowl 57 extends to the front of the front fork 49, and a screen 58 is attached to the upper end of the cowl 57 to improve wind characteristics. Also, front lower cowl 5
6 is a lower cowl upper part 56a that covers the engine unit 55 and a lower cowl lower part 56b that covers the exhaust system 1.
Consisting of This front lower cowl 56 has a cross section of U.
form a letter shape.

Next, the exhaust system 1 according to the present invention will be specifically explained with reference to FIGS. 1 to 3. FIG. 1 is a plan view clearly showing the same exhaust system, FIG. 2 is a side view of the same, and FIG. 3 is a front view of the same.

The engine unit 55 is a two-stroke engine having a front cylinder 2 and a rear cylinder 3, and is V-shaped when viewed from the side, with the cylinders 2 and 3 offset from each other in the left and right directions, as shown in FIG. Therefore, the front cylinder 2 protrudes forward substantially horizontally, and the exhaust port of the front cylinder 2 opens downward. The exhaust device 1 according to the present invention is connected in communication with this exhaust port, and the exhaust device 1 is effectively disposed using a dead space on the bottom surface of the engine 55.

First, the front exhaust pipe 4 is connected to the exhaust port, and the front exhaust pipe 4 has a front part 4a that curves from the joint part and extends a predetermined length forward, and a substantially horizontal plane from the end of the front part 4a. It is formed from an intermediate portion 4b that is curved and folded back toward the rear cylinder 3 inside, and a rear portion 4c that extends rearward from the end of the intermediate portion 4b. Also,
The rear portion 4c is formed to have a diameter that gradually increases toward the rear, and a chamber 5 is integrally connected to the rear end of the rear portion 4c, and the chamber 5 is disposed at the rear of the front lower cowl 56. A rear exhaust pipe 6 is integrally and continuously formed at the rear end of the chamber 5, and the rear exhaust pipe 6 is formed so that its diameter gradually becomes smaller toward the rear, and a silencer 7 is connected to the rear end of the chamber 5. . As a result, the rear end opening of the silencer 7 communicates with the atmosphere, and communicates with the exhaust port of the front cylinder 2 via the silencer 7, the rear exhaust pipe 6, the chamber 5, and the front exhaust pipe 4.

What should be noted here is that the front exhaust pipe 4 extending from the front cylinder 2 is not simply extended rearward, but rather the length of the exhaust pipe is substantially lengthened, so that it is first extended forward from the joining part of the front cylinder 2. At the same time, it is turned back using the offset of each cylinder 2 and 3, and then extended to the rear. As a result, in a two-stroke engine equipped with offset front and rear cylinders, the exhaust system 1 can be laid out compactly by effectively utilizing the dead space at the bottom of the engine unit 55, and the necessary and sufficient exhaust pipe length can be obtained. . In particular, as shown in FIG. 3, it can be compactly stored inside the lower part of the front lower cowl 56, which tapers inward toward the bottom.

Note that heat radiation holes 59 for radiating heat from the exhaust device 1 are provided at appropriate locations in the lower cowl lower portion 56b. 5 and 6 show cross-sectional views of the heat dissipation hole taken along line AA and line BB in FIG. 1, respectively. As is clear from FIGS. 5 and 5, the heat dissipation hole 59 forms a bulge 60 that gradually penetrates a part of the side surface (approximately rectangular shape) of the lower cowl lower part 56b from the outside to the inside toward the front. This bulge 6
A heat dissipation hole 59 is formed by opening the front surface of the lower cowl, and has a function of dissipating heat inside the lower cowl lower part 56b to the outside through the heat dissipation hole 59 by suction action based on the running wind.

Further, the reference numeral 61 indicates an exhaust device connected to the rear part of the rear cylinder 3 that projects approximately vertically upward, 62 is a front exhaust pipe whose middle part is curved upward, 63 is a chamber, 64 is a rear exhaust pipe, and 65 is a front exhaust pipe whose middle part is curved upward. It's a silencer.

In the embodiment, the front cylinder 2 was applied to a case where the front cylinder 2 was provided substantially horizontally toward the front, but the present invention can be similarly applied to a case where the front cylinder 2 is inclined upwardly toward the front, for example.

(Effects of the invention) As described above, in the exhaust system for a motorcycle according to the invention, since the chamber is arranged behind the front lower cowl, a sufficient diameter of the chamber can be ensured, which can contribute to improving the output of the two-stroke engine. Further, even if the diameter of the chamber is increased, it does not interfere with the front lower cowl, so there is no need to form a cutout in the front lower cowl as in the conventional case, and the strength of the front lower cowl can be improved and the vibration resistance can be improved.

[Brief explanation of the drawing]

Figure 1 is a plan view clearly showing the exhaust system according to the present invention, Figure 2 is a side view of the same, Figure 3 is a front view of the same, and Figure 4 is a front view of the same.
The figure is a side view of a motorcycle equipped with the exhaust system according to the present invention, and FIGS. 5 and 6 are cross-sectional views of the heat dissipation hole taken along line A-A and line B-B in FIG. In the drawing, 1 is an exhaust system, 2 is a front cylinder, 3 is a rear cylinder, 4 is a front exhaust pipe, and 55 is an engine unit.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In an exhaust system for a motorcycle equipped with a two-stroke engine in which a cylinder protruding forward is offset to either the left or right side of the vehicle body, an exhaust pipe connected to the lower surface of the cylinder. consists of a front exhaust pipe that gradually becomes larger in diameter from the connecting part, a large-diameter chamber that is connected to this front exhaust pipe, and a rear exhaust pipe that is connected to this chamber and gradually becomes smaller in diameter, and An exhaust system for a motorcycle, characterized in that the front exhaust pipe is covered with a front lower cowl having a U-shaped cross section, and the chamber is disposed behind the front lower cowl. (2) The exhaust system for a motorcycle according to claim 1, wherein the chamber is arranged closer to the center of the vehicle body than the offset cylinder.