JP2598913B2 - Exhaust system for motorcycle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust system for a motorcycle equipped with an engine having front and rear cylinders, and more particularly, to a muffler provided on one side of a vehicle body. In which an exhaust chamber is provided on the lower surface side of the device.

(Prior Art) As the above-described exhaust device, there is a conventional one disclosed in Japanese Patent Application Laid-Open No. 60-93111.

According to this, an engine having front and rear cylinders is supported on the body of a motorcycle. Behind this engine,
A muffler is provided on one side of the vehicle body, and an exhaust chamber is provided on the vehicle body side of the muffler in the vehicle width direction. Both the muffler and the exhaust chamber are connected to each other, and the insides of these mufflers are mutually connected. They are in communication with each other.

On the other hand, a front exhaust pipe extends from the exhaust hole of the front cylinder and a rear exhaust pipe extends from the exhaust hole of the rear cylinder toward the rear of the vehicle body. The extension end of the front exhaust pipe once faces the front end of the muffler and then faces the exhaust chamber. The extension end of the rear exhaust pipe directly faces the exhaust chamber.

The exhaust from the front and rear cylinders passes through the exhaust pipes, flows into the exhaust chamber, and flows from the exhaust chamber into the mufflers through the through holes, so that the muffler is sufficiently silenced. It is designed to be exhausted.

(Problems to be Solved by the Invention) In the above-described conventional technology, the front and rear cylinders are separated from each other in the front and rear directions, so that the rear exhaust pipe tends to have a shorter pipe length than the front exhaust pipe. If the lengths of the exhaust pipes differ, the exhaust pulsation effects of the exhaust pipes differ from each other, causing variations in the performance of the cylinders, which hinders improvement in engine performance. It is not preferable because there is a risk of causing it.

Further, in the above-described conventional technology, the lower part of the exhaust chamber protrudes largely downward from the lowermost surface of each of the muffler and the extended end of the exhaust pipe. Of the exhaust pipe, and tends to move away from the exhaust pipe, so that the exhaust pipe may not be sufficiently cooled.

In addition, as described above, since the lower portion of the exhaust chamber protrudes greatly downward, the traveling wind is disturbed and the air resistance of the vehicle increases, which may increase the power loss.

(Purpose of the Invention) The present invention has been made in view of the above circumstances, and prevents engine performance from being varied in front and rear cylinder tubes, thereby improving engine performance, and It is an object of the present invention to sufficiently cool an exhaust pipe by traveling wind and reduce power loss by reducing air resistance of a vehicle.

(Structure of the Invention) A feature of the present invention for achieving the above object is to allow a vehicle body to support an engine having front and rear cylinders,
Behind the engine, a muffler is provided on one side of the vehicle body, an exhaust chamber is provided on the muffler so as to be arranged in the vehicle width direction, and the exhaust chamber is located on the lower surface side of the vehicle body. The respective interiors of the chamber are communicated with each other, and a front exhaust pipe is formed from an exhaust hole of the front cylinder,
In a motorcycle in which a rear exhaust pipe extends toward the rear of the vehicle body from an exhaust hole of the rear cylinder, a portion of a lower surface of the exhaust chamber, which is opposite to the muffler in a vehicle width direction, faces upward. The recessed portion is formed into a recess, and the extension end of the front exhaust pipe is connected to the muffler, while the extension end of the rear exhaust pipe is guided into the recess of the exhaust chamber, and a flat surface is formed in the recess. Fold forward to make it almost U-shaped when viewed as a bent part,
The bent end of the bent portion is connected to the muffler, and the lowermost surface of the lower surface of the exhaust chamber on the muffler side in the vehicle width direction, the muffler same as above, and the lowermost surfaces of the bent portion are set to substantially the same height. It is at the point where it was located.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

2 to 4, reference numeral 1 denotes a motorcycle, which is indicated by an arrow.
Fr indicates the front of the vehicle body. The motorcycle 1 has a so-called cradle-shaped body frame 2. A front wheel 4 is supported by a front fork 3 at a front portion of the body frame 2, while a rear arm 7 is pivotally supported at a rear portion of the body frame 2 by a pivot shaft 6 so that the rear arm 7 can swing up and down. The moving end supports the rear wheel 8.

An engine 9 is supported on the vehicle body frame 2. The engine 9 is a multi-cylinder engine having a front cylinder 10 and a rear cylinder 11, and is provided with one carburetor 12 which is also used for both cylinders 10, 11. These two cylinders 10, 11
Is connected to the crankcase 13 so as to form a V shape in a side view.

Then, air is sucked into the carburetor 12 from the air cleaner 12a, and the air-fuel mixture is sent from the carburetor 12 to the engine 9, whereby the engine 9 operates. Thus, the engine 9 drives the rear wheel 8 so that the motorcycle 1 runs.

In addition, 14 is a handle, 15 is a fuel tank, 16 is a seat, and 17 is a shock absorber.

2, 5 and 6, an exhaust device 20 is provided for the engine 9. The exhaust device 20 has an upper muffler 21 and a lower muffler 22 which are positioned above and below, which have substantially the same shape and the same size as each other. 2
It is located on the right side, which is one side of the rear.

In the vehicle width direction, a sheet metal exhaust chamber 23 is provided on the vehicle body side with respect to the mufflers 21 and 22, and the exhaust chamber 23 is located on the lower surface side of the rear part of the vehicle body frame 2. A portion of the lower surface of the exhaust chamber 23 opposite to the lower muffler 22 in the vehicle width direction is recessed upward, and this is a recess 24.

On the other hand, a front exhaust pipe 25 extends from the exhaust hole of the front cylinder 10 toward the rear of the vehicle body, and a rear exhaust pipe 26 extends from the exhaust hole of the rear cylinder 11 toward the rear of the vehicle body. .

The front ends of the mufflers 21 and 22, the exhaust chamber 23, and the insides of the extended ends of the exhaust pipes 25 and 26 communicate with each other, and the exhaust from each of the cylinders 10 and 11 is Exhaust pipe 2
From 5, 26, the gas passes through the exhaust chamber 23 and the mufflers 21, 22, and is discharged to the rear of the vehicle body.

Referring to FIG. 2 to FIG. 6, the two mufflers 21, 22
Are supported by the body frame 2 as follows.

That is, the right end of the pivot 6 supports the front and rear halfway portions of the bracket plate 28. The front end of the bracket plate 28 is screwed to the vehicle body frame 2 by a first bolt 29,
Thus, the bracket plate 28 is fixed to the vehicle body frame 2. The second end of the bracket plate 28
The upper muffler 21 is screwed with a bolt 30.

Reference numeral 31 denotes a connecting pipe, and the upper end of the connecting pipe 31 is connected to the rear cylinder 11.
And a lower end of the connecting pipe 31 is connected to a front end of the upper muffler 21.
Further, the upper muffler 21 and the lower muffler 22 are connected to each other by a communication cylinder 32.
2 is supported on the vehicle body frame 2 side by a bracket plate 28, a connecting pipe 31, a communicating cylinder 32 and the like. 33 is a rear footrest.

The connecting pipe 31 functions as a dummy exhaust pipe in a side view, and has a shape as if it is an exhaust pipe that guides exhaust from the exhaust hole of the rear cylinder 11 toward the upper muffler 21. I have. In this case, the connecting pipe 31, the vehicle body frame 2, and the lower muffler 22 cover the rear exhaust pipe 26 from the side of the vehicle body, and thereafter the exhaust pipe 26 is not visible in a side view. For this reason, the function of the connection pipe 31 as a dummy exhaust pipe is further promoted.

The configuration of the exhaust device 20 will be described in more detail with reference to FIG. 1 and FIGS. 5 to 11.

First, the connecting pipe 31 will be described with reference to FIG. 1 and FIGS. 5 to 9. As shown in FIG.
The front end opening of 31 is closed by a plug material 34, and this front end is screwed to the vehicle body frame 2 by a third bolt 35.

On the other hand, as shown in FIG.
, And a band cylinder 37 protrudes forward from the cover plate 36. A slit 38 extending in the axial direction is formed at the protruding end of the band cylinder 37,
At 37, a fastening screw 39 for fastening portions sandwiching the slit 38 is provided. And this band cylinder 37
The rear end of the connection tube 31 is fitted into the band tube 37 by screwing the fastening screw 39 in this state.

However, in the above case, when the rear end of the connection pipe 31 is to move in the axial direction due to thermal deformation or the like due to the driving of the engine 9, the rear end of the connection pipe 31 slides in the band cylinder 37 in the axial direction. Thus, the thermal deformation is absorbed (arrow A in FIG. 8).

In addition, a cover body 40 that covers the cover plate 36 and the band cylinder body 37 is provided, which is a conical cylinder body and protrudes from the front end of the upper muffler 21. A notch 41 is formed in the cover body 40 as a screw operation space for the fastening screw 39.

In FIGS. 1, 10 and 11, the upper muffler
21 is a front and rear chamber 43,44 formed by a partition plate therein.
A pipe 46 connecting the front chamber 43 and the rear chamber 44, a hole 47 connecting the rear chamber 44 and the intermediate chamber 45, and an upper muffler
A pipe 48 is provided for communication with the rear outside of the pipe 21.

On the other hand, the lower muffler 22 is similar to the upper muffler 21,
It has rear chambers 50, 51 and an intermediate chamber 52, and is provided with a pipe 53 connecting the rear chamber 51 and the intermediate chamber 52, and a pipe 54 connecting the intermediate chamber 52 to the outside of the rear of the lower muffler 22.

The extension end of the front exhaust pipe 25 is fitted into the front end of the lower muffler 22 and connected thereto. On the other hand, the right end of the exhaust chamber 23 is joined to the left outer surface of the lower muffler 22,
The front chamber 50 communicates with the exhaust chamber 23 through a front through hole 56, and the rear chamber 51 of the upper and lower muffler 22 communicates with the exhaust chamber 23 through a pair of upper and lower rear through holes 57.

Further, the exhaust chamber 23 is provided with the communication cylinder 32 and the through hole.
The communication cylinder 32 is further connected to the front chamber of the upper muffler 21.
43 is communicated with another through hole 59.

Next, the flow of exhaust gas will be described with reference to FIGS. 1, 10, and 11, and the exhaust gas from the front exhaust pipe 25 first enters the front chamber 50 of the lower muffler 22 as shown by the arrow B in the figure. And then into the exhaust chamber 23 through the front through hole 56. A part of the exhaust gas in the exhaust chamber 23 is indicated by an arrow C in FIG.
As shown in the figure, the front chamber 43 of the upper muffler 21 passes through the through holes 58 and 59.
After flowing into the upper muffler 21 as shown by an arrow D in the figure, and is discharged. On the other hand, the other part of the exhaust gas in the exhaust chamber 23 flows into the rear chamber 51 of the lower muffler 22 through the rear through hole 57 as shown by the arrow E in the figure, and then flows downward as shown by the arrow F in the figure. It flows through the muffler 22 and is discharged. During this time, the energy of the sound wave in the exhaust gas is attenuated, and the exhaust noise is reduced.

On the other hand, the extension end of the rear exhaust pipe 26 is guided into the recess 24 below the exhaust chamber 23 having a relatively large area in a plan view, and becomes substantially U-shaped in a plan view in the recess 24. As described above, and this is a bent portion 60.

The bent end 60a of the bent portion 60 is further bent toward the right side of the vehicle body, and the bent end 60a is fitted into a connecting pipe 61 protruding from the left side surface of the lower muffler 22 and fastened by a band 62. . Further, an arc-shaped extension tube 63 is attached to the bent end 60a, and an end of the extension tube 63 passes through the front through hole 56 and faces the inside of the exhaust chamber 23.

Therefore, the exhaust gas from the rear exhaust pipe 26 flows into the exhaust chamber 23 through the extension pipe 63 as shown by an arrow G in the figure, and thereafter, the exhaust air from the upper muffler 21 and the exhaust gas from the front exhaust pipe 25 similarly. It is discharged through the lower muffler 22. In particular, in FIG. 11, the lower surface of the exhaust chamber 23 on the lower muffler 22 side in the vehicle width direction, the upper and lower mufflers 22, and the lowermost surfaces of the bent portions 60 have substantially the same height as each other. It is located in.

As described above, the extension end of the rear exhaust pipe 26 is located below the vehicle body frame 2 and is prevented from being externally covered by the exhaust chamber 23. The operation of connecting the end to the lower muffler 22 may be complicated. However, in this embodiment, the extending end is substantially U
The bent portion 60 is shaped like a letter, and it is relatively easy to elastically deform such a shape. For this reason,
When the extended end is connected to the lower muffler 22, it is easy to appropriately elastically deform the bent portion 60 to position the extended end at a predetermined position.Therefore, the rear exhaust pipe 26, the lower muffler 22, Can be easily connected. Moreover,
Since there is a space below the bent portion 60 before reaching the traveling road surface, this space can be used as a work space, and the work is facilitated from this point as well.

(Effects of the Invention) According to the present invention, an engine having front and rear cylinders is supported on a vehicle body, and a muffler is provided on one side of the vehicle body behind the engine so that the muffler is arranged in the vehicle width direction. And the exhaust chamber is located on the lower surface side of the vehicle body, the muffler and the interior of the exhaust chamber are communicated with each other, and a front exhaust pipe is passed through an exhaust hole of the front cylinder to the rear cylinder. In a motorcycle in which rear exhaust pipes are respectively extended toward the rear of the vehicle body from exhaust holes, a portion of the lower surface of the exhaust chamber opposite to the muffler in the vehicle width direction is recessed upward. This is a recess, and the extension end of the front exhaust pipe is connected to the muffler, while the extension end of the rear exhaust pipe is guided into the recess of the exhaust chamber. So that And bent portions so bent toward the front,
The bent end of the bent portion is connected to the muffler, and the following effects are produced.

That is, the front cylinder extends forward from the rear cylinder from the rear cylinder, and reaches the exhaust chamber provided behind the engine.If the rear exhaust pipe is provided, the front cylinder is located forward of the rear cylinder. Therefore, the length of the rear exhaust pipe tends to be shorter than that of the front exhaust pipe, and when the lengths of the exhaust pipes differ from each other, the exhaust pulsation effects of the respective exhaust pipes are mutually reduced. Variations occur in the performance of each cylinder due to differences and the like, which may hinder improvement in engine performance, which is not preferable.

Therefore, in the present invention, as described above, the extending end of the rear exhaust pipe is guided into the recess of the exhaust chamber,
In the recess, the sheet is bent forward so as to be substantially U-shaped in plan view to form a bent portion, and a bent end of the bent portion is connected to the muffler.

That is, the extension length of the rear exhaust pipe, which tends to be short, is extended by bending the extended end of the rear exhaust pipe into a substantially U-shape, whereby the length of each of the front exhaust pipe and the rear exhaust pipe is reduced. I make them equal.

Therefore, it is possible to prevent a variation in performance between the front and rear cylinders due to a difference between the lengths of the front and rear exhaust pipes, thereby improving the engine performance.

In addition, the bent portion is guided into a recess formed on the side opposite to the muffler, so that the bent portion and the muffler are prevented from approaching each other.

For this reason, when connecting the bent end of the bent portion to the muffler, it is avoided that the bent end is bent with a small radius of curvature and connected to the muffler, and a certain large radius of curvature can be secured.

Therefore, since the flow of the exhaust gas from the bent portion toward the muffler is made smooth and the pressure loss is suppressed small, desired engine performance can be obtained.

Further, in the present invention, the lowermost portion of the lower surface of the exhaust chamber on the muffler side in the vehicle width direction, the muffler, and the lowermost surfaces of the bent portions are located at substantially the same height.

For this reason, the traveling wind passing from the bent portion, which is the extension end of the rear exhaust pipe, to the traveling road surface is prevented from being pushed down by the lower portion of the exhaust chamber as in the related art, The bent portion is sufficiently cooled by sufficiently contacting the traveling wind.

Further, as described above, since the lowermost surfaces are substantially flush with each other, the air resistance to the traveling wind can be reduced, and the power loss can be reduced.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a partial plan sectional view of an exhaust system, FIG. 2 is a right side view of the entire motorcycle, FIG.
FIG. 4 is a partially enlarged view of FIG. 2, FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3, FIG. 5 is a left side view of the exhaust device, FIG. 7 is a sectional view taken along the line VII-VII of FIG. 1, FIG. 8 is a sectional view taken along the line VIII-VIII of FIG.
FIG. 10 is a sectional view taken on line IX-IX of FIG. 7, FIG. 10 is a rear plan sectional view of the lower muffler, and FIG. 11 is a sectional view taken on line XI-XI of FIG. 1 ... motorcycle, 2 ... body frame, 9 ... engine, 10 ... front cylinder, 11 ... rear cylinder, 20 ... exhaust system, 21
… Upper muffler, 22… Lower muffler (muffler), 23… Exhaust chamber, 24… recess, 25… Front exhaust pipe, 22… Rear exhaust pipe, 60… Bending part, 60a… Bending end.

Claims (1)

(57) [Claims] An engine having front and rear cylinders is supported on a vehicle body, a muffler is provided on one side of the vehicle body behind the engine, and an exhaust chamber is provided on the muffler so as to be arranged in the vehicle width direction. The exhaust chamber is located on the lower surface side of the vehicle body, the muffler and the inside of the exhaust chamber are communicated with each other, a front exhaust pipe is provided from an exhaust hole of the front cylinder, and a rear exhaust pipe is provided from an exhaust hole of the rear cylinder. In the motorcycle which is respectively extended toward the rear of the vehicle body, of the lower surface of the exhaust chamber, a portion opposite to the muffler in the vehicle width direction is recessed upward, and this is defined as a recess, The extension end of the front exhaust pipe is connected to the muffler, and the extension end of the rear exhaust pipe is guided into the recess of the exhaust chamber. Bend towards The bent end of the bent portion is connected to the muffler, and the lower surface of the lower surface of the exhaust chamber on the muffler side in the vehicle width direction, the lower muffler, and the lowermost surface of the bent portion The exhaust device for a motorcycle, characterized in that the exhaust devices are located at substantially the same height as each other.