JPS62165525A - Exhaust muffler for motorcycle - Google Patents

Abstract

PURPOSE:To divide the recessed portions into the left side and the right side to make their size smaller, and restrict a bad influence from these recessed portions to the output, by furnishing a recessed portion where a motive power transmitting member comes in at one of a pair of exhaust pipes, while a recessed portion where a pivot bolt and a nut comes in at the other side exhaust pipe. CONSTITUTION:At the inside of the expansion 21c in the left side exhaust pipe 21, is furnished a recessed portion 35 to avoid the interference with a chain 17. And at the front side of the recessed portion 35, is arranged a recessed portion 35a, extended from the recessed portion 35, to avoid the interference with the head of a pivot bolt 15. On the other hand, at the inside of the expansion 22c in the right side exhaust pipe 22, is furnished a recessed portion 36 to avoid the interference with the tip of the pivot bolt 15 and the nut 16 to gear with the tip. Furthermore, inside the expansions 21b and 22b, recessed portions 37 and 38 are furnished to avoid the interference with a pivot bolt 13 and the nut 14 respectively. Since the recessed portions 35 and 36 are divided to furnish at the exhaust pipes 21 and 22 in such a way, the section forms of the expansion chambers 31 and 32 can be made symmetric and the recessed portions 35 and 36 can be made smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust silencing device for a motorcycle equipped with a two-stroke engine.

[Conventional technology]

In a motorcycle equipped with a two-stroke engine with multiple cylinders, the exhaust pipe extending from each cylinder is placed separately on both sides of the vehicle body, and an expansion chamber is provided in the middle of the exhaust pipe. In addition, by reducing the pressure of the expansion chamber, the outlet of the expansion chamber is constricted to reflect pressure waves at the constricted portion and push the air-fuel mixture back into the cylinder, thereby increasing the filling efficiency.

Incidentally, the volume of the expansion chamber is important for maintaining the output of the engine, and it is necessary to increase the volume of the expansion chamber by increasing the outer diameter of the expansion portion of the exhaust pipe. for that,
The chain wheel that drives the rear wheels, the tip of the pivot bolt and the nut that connects the link to the cushion unit of the link type suspension may interfere with the exhaust pipe located on the left side of the vehicle, There is a recess inside the left exhaust pipe where the chain and bolt tips can be seen.

[Problem that the invention seeks to solve]

However, in this type of conventional exhaust silencer,
The recess in the left exhaust pipe had to be made larger in order to expose the chain and pivot bolt. As a result, the concave portion reflected pressure waves in front of the throttle portion, which had a significant effect on the output of the cylinder to which the left exhaust pipe was connected.

Therefore, there was a problem that the engine output could not always be maintained.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an exhaust silencing device for a motorcycle that can maintain engine output. The exhaust silencer according to the present invention provides a concave portion facing the power transmission member that drives the rear wheels inside the expanded portion of one of the pair of exhaust pipes disposed on both sides of the rear arm, and A concave portion is provided inside the expanded portion of the tube, which passes through the link and cushion unit pivotally attached to the rear arm in the vehicle width direction, and faces the tip and nut of the pivot bolt that pivotally attaches these members.

[Operation] In the present invention, the cross-sectional shapes of the expansion chambers of the left and right exhaust pipes are made close to symmetrical, and the recesses are made small, thereby reducing the influence of the recesses on the output of each cylinder.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view showing an exhaust muffling device for a motorcycle according to the present invention, FIG. 2 is a side view of the same, FIG. 3 is a side view showing a part of the right exhaust pipe as seen from the inside, and FIG. is a side view showing a motorcycle equipped with an exhaust system, and FIG. 5 is a side view of a motorcycle equipped with an exhaust system.
-V line cut L: In the figure, the symbol 1 in FIG. 4 indicates a motorcycle. Reference numeral 2 designates a two-stroke, two-cylinder engine housed in a space formed below a fuel tank 3 of a motorcycle 1. The engine 2 is supported by a frame 4 so that the crankshaft extends in the width direction of the vehicle and the cylinders are tilted forward. ing.

Reference numeral 5 designates a rear arm pivotably mounted up and down on a pivot shaft 6 that is horizontally suspended on a pivot 4a at the rear of the frame, and a rear wheel shaft 8 that rotatably supports a rear wheel 7 at its rear end. is suspended horizontally. 10 is a cushion unit that constitutes a link type suspension that swingably supports the rear arm 5;
The upper end of this cushion unit 10 is pivotally attached to the rear upper side of the frame 4, and the lower end is connected to the rear arm 5 via a link which will be described later. 11 is a pair of left and right first links whose rear ends correspond to the front side of the rear wheel 7 of the rear arm 5; 12 is a plate-shaped second link whose rear end is interposed between the first links 11; , the front end is pivotally connected to the rear lower side of the frame 4 by a pivot bolt 13 and a nut 14. These members are the front end of the first link 11,
They are pivotally connected to each other by a pivot bolt 15 that passes through the rear end of the second link 12 and the lower end of the cushion unit 10 in the vehicle width direction from the left side to the right side of the vehicle body. This pivot bolt 15 has a relatively thin head, and the tip protruding to the right of the first link 11 is provided with a knurled hole 1-16.
are screwed together. Therefore, the first pivot bolt 15
The size of the lateral protruding portion of the link is larger on the right side than on the left side. Reference numeral 17 denotes a chain as a power transmission member for driving the rear wheel 7, and the chain is passed between a sprocket 18 provided on the left side of the rear wheel 7 and a driving sprocket 19 of the engine 2.

Reference numeral 20 denotes an exhaust silencer equipped on the motorcycle 1, which is composed of a pair of exhaust pipes 21, 22 arranged on both sides of the rear arm 5, and a silencer 23, 24 connected to the rear ends of these exhaust pipes. has been done. The exhaust pipes 21 and 22 extend downward from the front side of the engine 2 and extend rearward from the bottom side of the engine 2.

After that, the rear arm 5 extends upwardly below the pivot portion 4a of the frame 4 and extends to both sides of the vehicle body.
It is formed to cross diagonally from the bottom. Also,
The exhaust pipes 21 and 22 are straight pipe sections 2 connected to the engine 2.
1a, 22a, and a tapered expanded portion 21b that gradually increases the cross-sectional area of the exhaust passage toward the downstream side.
, 22b, bulging portions 21c and 22c extending across the rear arm 5 from below, and a constriction portion 21d that is formed in a tapered shape that becomes smaller toward the downstream side and reflects pressure waves generated by the jetting of combustion gas. 22d. The expanded portions 21b, 22b, the bulged portions 21c, 22c
, the throttle portions 21d and 22d form an expansion portion, and expansion chambers 31 and 32 are formed in the middle of the exhaust passage.

35, as shown in FIG. 5, is a recess provided inside the bulging portion 21C of the left exhaust pipe 21 at a portion that interferes with the chain 17, and avoids the interference by facing the chain 17. be.

A recess 35a extends from the front side of the recess 35 so that the head of the pivot bolt 15 is exposed to avoid interference with the head of the pivot bolt 15. Reference numeral 36 is provided inside the bulging portion 22c of the right exhaust pipe 22 at a portion that interferes with the tip of the pivot bolt 15, and the nut 16 and the exhaust pipe 22 are screwed together with this tip and the tip. Avoiding interference with. 37 and 38 are concave portions provided inside the expanded portions 21b and 22b to avoid interference between the expanded portions and the pivot bolts 13 and nuts 1-14 that pivotally connect the second link 12 to the frame side.

In the exhaust silencer for a motorcycle configured as described above, a recess 35 is provided in the left exhaust pipe 21 to avoid interference with the chain 17, and a recess 36 is provided in the right exhaust pipe 21 to avoid interference with the tip of the pivot bolt 15. Since it is provided in the exhaust pipe 22,
The shape of each recess 35, 36 can be made smaller compared to the conventional one. Moreover, the cross-sectional shapes of the left and right expansion chambers 31 and 32 are respectively recessed on the inside, so that they can be approximated to be symmetrical with respect to a vertical line that bisects the vehicle body into left and right halves.

Therefore, it is possible to suppress the pressure waves generated when exhaust gas is ejected from the engine 2 from being reflected by the recesses 35 and 36 compared to the conventional case. Moreover, the pressure waves can be reflected in the same way in the left and right exhaust pipes 21 and 22. As a result, the influence of the recesses 35 and 36 on the output of each cylinder of the engine 2 can be reduced.

〔Effect of the invention〕

As explained above, according to the present invention, of the pair of exhaust pipes disposed on both sides of the rear arm, a recessed part facing the power transmission member that drives the rear wheels is provided inside the expansion part of one of the exhaust pipes, and the other A recess is provided inside the expansion part of the exhaust pipe of the exhaust pipe, so that the tip and nut of the pivot bolt that passes through the link and the cushion unit pivotally attached to the rear arm and the rear arm in the vehicle width direction and faces the nut. The cross-sectional shapes of the expansion chambers of the left and right exhaust pipes can be brought closer to being symmetrical, and the recessed portions can be made smaller.

Therefore, it is possible to suppress the reflection of pressure waves by the recessed portions, thereby reducing the influence of the recessed portions on the output of each cylinder, and thus the output of the engine can be maintained.

[Brief Description of the Drawings] Fig. 1 is a plan view showing the exhaust silencer for a motorcycle according to the present invention, Fig. 2 is a side view of the same, and Fig. 3 shows a part of the right exhaust pipe as seen from the inside. 4 is a side view showing a motorcycle equipped with an exhaust system, and FIG. 5 is a sectional view taken along the line V-V in FIG. 1. 5... Rear arm, 10... Cushion unit, 15... Tu support bolt, 16... Nut,
17...Chain, 21.22...Exhaust pipe, 3
1.32...expansion chamber, 35.36...recess.

Claims (1)

[Claims] In a motorcycle in which a pair of exhaust pipes is provided on both sides of a rear arm that is swingably supported by a cushion unit connected via a link, and an expansion section that forms an expansion chamber is provided in the exhaust pipe, one A concave portion facing the power transmission member for driving the rear wheels is provided inside the expanded portion of one exhaust pipe, and a link and a cushion unit pivotally connected to the rear arm are provided inside the expanded portion of the other exhaust pipe, and a recessed portion is provided in the vehicle width direction. An exhaust silencer for a motorcycle, which has a concave portion facing the tip and nut of a pivot bolt for pivotally connecting these members.