JPS6242110Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to the structure of an intake pipe connected to feed a mixture to an engine as a fuel supply path for a motorcycle or the like.

(Prior art and its problems) Conventionally, as described in, for example, Japanese Patent Application Laid-Open No. 57-26017, an engine equipped with auxiliary equipment such as a carburetor behind the body frame of a motorcycle,
It is known to have a suspended power unit that is integrated with a rear wheel drive system that transmits the output of the engine. In this case, the intake pipe that connects the carburetor and the engine needs to be curved due to the layout with other equipment, and generally its cross-sectional shape is often circular.

However, such a simple circular shape was created with a focus only on ventilation resistance, and there are concerns about mounting space in the limited car body or changes in engine output due to stagnation of airflow at curved parts. Since no consideration was given to this, there was a problem in that it did not suit the actual situation, especially when applied to motorcycles.

(Means for Solving the Problems) This invention was made to solve the problems of the prior art, and it combines an engine equipped with auxiliary equipment such as a carburetor, and a drive system that transmits the output of the engine. In a motorcycle or the like in which an integrally formed power unit is suspended on a frame, at least the curved portion of the intake passage communicating with the carburetor and the engine is formed to have an oval cross section that is flattened in a predetermined direction of the vehicle body; The outer circumferential side and the inner circumferential side of the curved part are respectively located in the long diameter direction of the oval shape, and the carburetor is connected to one end of the curved part in the flow path extension direction. The purpose of the present invention is to provide a fuel supply path structure for a motorcycle, etc., which can accommodate limited installation space and prevent a decrease in output when the engine rotates at high speed.

(Function) The curved part of the intake passage is a flat oval shape, so even when installation space is limited, a predetermined flow pressure cross-sectional area can be secured, while the curvature of the outer and inner circumferences Since the airflow speeds differ significantly, the speed difference in the airflow in the intake passage increases accordingly, stirring the airflow and supplying fuel with a uniform concentration. Since the flow path extension direction of the curved portion of the intake passage coincides with the flow path extension direction, smooth flow of air within the intake passage can be ensured.

(Embodiment) Fig. 3 shows a case where the power unit 1 according to the present invention is applied to a scooter type motorcycle, and the front part of the power unit 1 is connected to the center of the frame 2 via a link (not shown). The rear part thereof is suspended via a rear suspension 3 to the rear part of the frame 2, which is below the seat 4. The power unit 1 is formed by integrally forming an engine 6 equipped with auxiliary equipment such as a carburetor 5, and a rear wheel 7 as a drive system for transmitting the output of the engine 6. The air-fuel mixture is sent to the engine 6 via the intake pipe 8.

FIG. 1 shows details of the power unit 1, and the crankshaft 9 of the engine 6 is connected to the automatic transmission mechanism 1.
On the other hand, the cylinder chamber 12 of the engine 6 communicates with the downstream side of an intake pipe 14 as an intake passage through a reed valve 13. A flange 15 is provided at the upstream end of the carburetor 6, and the carburetor 6 is attached to this flange 15. The intake pipe 14 rises substantially upward from the connecting portion with the cylinder chamber 12 and is curved toward the rear of the rear vehicle body (toward the near side in FIG. 1).

FIG. 2 shows the cross-sectional shape of the intake pipe 14 near the curved part, which is an oval shape that is flattened in the left-right direction of the vehicle body, and the outer and inner circumferential sides of the intake pipe 14 are located in the long diameter direction of the oval. ing. As shown in the figure, in this embodiment, the direction of the intake pipe 14 is inclined at a predetermined angle with respect to the vertical direction (vertical direction in the figure).

Therefore, the air-fuel mixture flows down from the carburetor 6 toward the crank chamber 12 along the intake pipe 14 and is supplied to the cylinder chamber 12, but in this case, the cross-sectional shape of the vicinity of the curved part of the intake pipe 14 is oval. Therefore, the difference in curvature between the inner circumferential side and the outer circumferential side becomes large, and the difference in flux between the airflows on both sides of the inside becomes large, so that the concentration of the air-fuel mixture becomes more uniform. Furthermore, since the direction of the flow of the mixture from the carburetor 6 and the direction of extension of the pipe of the intake pipe 14, especially the direction of extension of the flow path at the curved portion, are the same, the flow of the mixture is always smooth, and the flow of the mixture is always smooth. Fuel can be supplied according to the situation.

(Effects of the invention) As described above, according to this invention, a motorcycle, etc., in which a power unit that integrally forms an engine equipped with auxiliary equipment such as a carburetor and a drive system that transmits the output of the engine is suspended on a frame. In,
The cross section of at least a curved portion of the intake passage communicating the carburetor and the engine is formed to be an oval shape flat in a predetermined direction of the vehicle body;
The outer circumferential side and the inner circumferential side of the curved portion are respectively located in the long diameter direction of the oval shape, and the carburetor is connected to one end of the curved portion in the flow path extension direction, so that the power unit Even if there are restrictions on the internal layout, it is possible to maintain a specified cross-sectional area of the flow path (for example, if the cross-sectional shape is circular, if the space is narrowed, the flow path cross-sectional area will be small. ) The intake pipe can be installed. In addition, since the cross section of the curved part is an ellipse that is flat in a predetermined direction, it is possible to deal with the case where the installation space is restricted in the predetermined direction. Since the difference in curvature is large, the air-fuel mixture can be sufficiently stirred in the intake passage without causing fluctuations in engine output. Furthermore, since the carburetor is arranged so that the flow direction of the air-fuel mixture from the carburetor matches the flow path extension direction of the curved portion of the intake passage, the difference in curvature of the curved portion causes the engine to run at high speed. Can deal with fuel supply at times.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing details of the main parts of the power unit according to this invention, Figure 2 is a sectional view taken along line A-A in Figure 1, and Figure 3 shows the power unit suspended at the rear of a motorcycle. FIG. 1...Power unit, 2...Frame, 5...
Carburetor, 6...engine, 14...intake pipe.

Claims (1)

[Scope of utility model registration request] In a motorcycle or the like in which a power unit that integrally forms an engine equipped with auxiliary equipment such as a carburetor and a drive system that transmits the output of the engine is suspended on a frame, at least a curvature in an intake passage that communicates between the carburetor and the engine. The carburetor is formed so that its cross section is an oval shape flattened in a predetermined direction of the vehicle body, and the outer circumferential side and the inner circumferential side of the curved portion are located in the major diameter direction of the oval shape, respectively. A fuel supply path structure for a motorcycle or the like, characterized in that the curved portion is connected to one end in the flow path extension direction.