JP2563904B2 - Engine exhaust system - Google Patents

Description

TECHNICAL FIELD The present invention relates to, for example, an exhaust system for an engine for a motorcycle.

[Prior art]

In the exhaust pipe connecting the engine and the silencer, conventionally, the downstream end connected to the silencer has a double pipe structure consisting of an outer pipe and an inner pipe, and a sound absorbing material such as glass wool is provided between the outer pipe and the inner pipe. Filled with is known.

By the way, the downstream end of the exhaust pipe is often bent in the middle in order to avoid a link connecting the rear arm and the shock absorber, a rear wheel, or the like. If the exhaust pipe (outer pipe) is bent like this, it becomes difficult to insert the inner pipe,
Conventionally, it has been practiced to divide the inner pipe into two parts, an upstream side and a downstream side with a bent portion as a boundary, and insert these divided inner pipes from both end openings of the outer pipe.

[Problems to be solved by the invention]

However, in this structure, a gap is formed between the insertion tip portions of the split inner pipe, and the exhaust gas leaking from the gap directly hits the outer pipe, so that the outer pipe is locally heated, causing a problem of discoloration.

In addition, the existence of the gap disturbs the flow of exhaust gas,
There are also problems such as generation of airflow noise and reduction of engine output.

The present invention has been made under such circumstances, and the first divided inner pipe and the second divided inner pipe can be accurately and easily aligned with each other, and the connecting portions of these divided inner pipes can be easily adjusted. An object of the present invention is to provide an exhaust system for an engine, which can prevent the sound absorbing material from entering and can reliably connect the divided inner pipes to each other without a gap.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention constitutes an outer shell of an exhaust pipe, and an outer pipe having both ends opened, an inner pipe inserted inside the outer pipe, and an outer peripheral surface of the inner pipe. It is assumed that the engine exhaust system has a sound absorbing material filled between the outer pipe and the outer pipe, and the outer pipe is bent midway in the axial direction.

And, the inner tube, with the bent portion of the outer tube as a boundary,
The first divided inner pipe located upstream of the bent portion and the second divided inner pipe located downstream of the bent portion are divided into the first divided inner pipe and the second divided inner pipe. The split inner pipe is inserted from both end openings of the outer pipe toward the bent portions, respectively, and a diameter of the split inner pipe is inserted into the insertion tip of one of the first and second split inner pipes. Is expanded toward the outer side in the direction to form a superposed portion that covers the insertion tip of the other split inner tube, and the insertion tip of the first and second split inner tubes and the outer tube In between, the first and second divided inner pipes are coaxially held with respect to the outer pipe, and a ring-shaped support tool that separates the sound absorbing material from the bent portion is arranged.

[Action]

According to this configuration, the overlapping portion of one of the divided inner tubes covers the insertion tip of the other divided inner tube from the radial outside,
It is butted against the insertion tip of this split inner tube. Moreover,
Since the first and second divided inner pipes are held coaxial with the outer pipe through the supporting members, respectively, when these divided inner pipes are inserted from both end openings of the outer pipe toward the bent portion,
The insertion tip of the split inner tube is accurately aligned without being displaced in the radial direction of the outer tube.

Therefore, no gap is created between the insertion tip portions of the first and second divided inner tubes, and the leakage of exhaust gas in the outer tube can be prevented. Therefore, the outer pipe is not directly exposed to the high temperature exhaust gas, and the flow of the exhaust gas inside the inner pipe can be kept smooth.

Further, since the sound absorbing material filled between the outer pipe and the inner pipe is isolated from the bent portion by the support, the sound absorbing material is inserted when the first and second divided inner pipes are inserted into the outer pipe. Is hard to stick out toward the bent part. Therefore, it is possible to prevent the sound absorbing material from entering the abutting portion of the insertion tip of the divided inner pipe, and the workability of connecting these divided inner pipes is not impaired.

Example of Invention

The present invention will be described below based on an embodiment shown in the drawings.

FIG. 4 is a side view showing the entire motorcycle, and a frame indicated by reference numeral 1 is equipped with, for example, a 4-cycle 4-cylinder engine 2. In each cylinder 3a-3d of engine 2,
Exhaust outlet pipes 4a to 4d are connected, and these exhaust outlet pipes 4a to 4d are connected.
The downstream end of the exhaust gas is directly under the crankcase 5 and is assembled into one via an exhaust assembly 6. The exhaust pipe 7 extending from the downstream end of the exhaust assembly 6 is bent to one side while avoiding the link 8 connecting the rear arm 20 and the shock absorber 21 and the rear wheel 9, and this bent portion 11 is bent. It is located approximately in the center.

A single silencer 10 is connected to the downstream end of the exhaust pipe 7.

As shown in FIG. 1, the exhaust pipe 7 has a double pipe structure including an outer pipe 12 which is an outer shell of the exhaust pipe 7 and an inner pipe 13 inserted inside the outer pipe 12. . And the inner pipe
A first divided inner pipe 13a located upstream of the bent portion 11 of the outer pipe 12 and a second divided inner pipe 13b located downstream of the bent portion 11 are separated from each other by the bent portion 11 of the outer pipe 12. It is divided into two parts. Each of the first and second divided inner tubes 13a and 13b is made of punching metal having a large number of through holes 18 and is formed in a straight tube shape. Such divided inner tubes 13a and 13b are inserted from the openings at both ends of the outer tube 12 toward the bent portion 11, and the insertion tips are located inside the bent portion 11. Further, a sound absorbing material 16 such as glass wool is mounted on the outer peripheral surfaces of the divided inner tubes 13a, 13b, and the sound absorbing material 16 is filled between the outer tube 12 and the divided inner tubes 13a, 13b. .

Then, as shown in FIG. 1, a trumpet-shaped overlapping portion 17 expanded radially outward is provided at the insertion tip portion of the first divided inner pipe 13a located on the upstream side of the bent portion 11. Has been formed. The overlapping section 17 covers the insertion tip of the second split inner tube 13b so as to cover the insertion tip from the outside.
Therefore, the first and second divided inner tubes 13a and 13b are the outer tubes 1
The inside of 2 is integrally continuous along the axial direction.

The insertion tip portions of the first and second divided inner tubes 13a and 13b are coaxially held by the outer tube 12 via ring-shaped supporting members 19, respectively. The support 17 is, as shown in FIG.
It is located on both sides of the bent part 11 and has the above-mentioned split inner pipe.
The sound absorbing material 16 on the outer peripheral surfaces of 13a and 13b is separated from the bent portion 11.

According to this structure, the insertion tip of the first divided inner tube 13a is provided with the overlapping portion 17 that covers the insertion tip of the second divided inner tube 13b. Tube 13a, 13
When b is inserted from both end openings of the outer tube 12, the overlapping portion 17 is butted against the insertion tip so as to cover the insertion tip of the second divided inner tube 13b from the outside in the radial direction.

Moreover, since the insertion tip portions of the first and second divided inner pipes 13a and 13b are coaxially held by the outer pipe 12 via the support members 19, respectively, the first and second divided inner pipes 13a and 13b are retained. 13a, 13
The insertion tips of b are accurately aligned without being displaced from each other in the radial direction. Therefore, although the inner pipe 13 is divided into two in the axial direction, the first and second divided inner pipes 13a, 13
The insertion tip of b can be connected without a gap.

Therefore, the outer tube 12 is not directly exposed to exhaust gas, and discoloration does not occur. Moreover, the exhaust is a continuous inner pipe
Since it smoothly flows through the insides of 13a and 13b, it is possible to prevent the generation of airflow noise, and also the flow resistance of exhaust gas is small and there is no fear that the engine output will decrease.

Further, in the present embodiment, since the bent portion 11 is set at the substantially central portion of the exhaust pipe 7, the divided inner pipes 13a and 13b can be shared, and the number of types of parts is reduced, which contributes to cost reduction.

Further, according to the above configuration, the sound absorbing material 16 mounted on the outer peripheral surfaces of the first and second divided inner pipes 13a and 13b respectively supports the divided inner pipes 13a and 13b in the state of being inserted into the outer pipe 12. It is separated from the bent portion 11 by a tool 19. Therefore, when the first and second divided inner pipes 13a and 13b are inserted into the outer pipe 12, the sound absorbing material 16 is less likely to protrude toward the bent portion 11, and the sound absorbing material 16 is separated into the first and second divided pipes. Tube 13a, 13b
Can be prevented from entering the abutting portion of the insertion tip of the. Therefore, the workability of connecting the divided inner pipes 13a and 13b is not impaired, and the first and second divided inner pipes 13a and 13b can be accurately connected to each other.

The engine according to the present invention is not limited to four cylinders, and can be implemented with, for example, three cylinders, six cylinders, or a single cylinder.

〔The invention's effect〕

According to the present invention described in detail above, the insertion tip portions of the first and second divided inner pipes can be accurately connected without a gap, and the leakage of exhaust gas in the outer pipe can be prevented. Therefore,
The outer pipe is not directly exposed to high-temperature exhaust, discoloration of the outer pipe can be prevented, the flow of exhaust in the inner pipe becomes smooth, and the engine output is not adversely affected.
Moreover, the generation of air flow noise in the exhaust pipe can be reduced.

Furthermore, when the first and second split inner tubes are inserted into the outer tube, it is difficult for the sound absorbing material to protrude toward the bent portion, and the sound absorbing material is prevented from entering the abutting portion of the insertion tip of the split inner tube. it can. Therefore, there is an advantage that the workability of connecting the first and second divided inner pipes is not impaired, and the divided inner pipes can be surely connected.

[Brief description of drawings]

The drawings show one embodiment of the present invention. Fig. 1 is a sectional view of an exhaust pipe, Fig. 2 is a plan view of an exhaust system, Fig. 3 is a side view of the same, and Fig. 4 is a side view of a motorcycle. . 7 ... Exhaust pipe, 11 ... Bent portion, 12 ... Outer pipe, 13 ... Inner pipe, 13a, 13b ... First split inner pipe, Second split inner pipe, 16
...... Sound absorbing material, 17 …… Overlapping section, 19 …… Supporting equipment.

Claims (1)

(57) [Claims] 1. An outer pipe which constitutes an outer shell of an exhaust pipe and has both ends opened, an inner pipe inserted inside the outer pipe, and an outer pipe attached to an outer peripheral surface of the inner pipe. And a sound-absorbing material filled between the outer pipe and the outer pipe, which is bent in the middle of the axial direction. Divided into a first divided inner pipe located upstream of the bent portion and a second divided inner pipe located downstream of the bent portion, and these first divided inner pipe and second divided inner pipe Is inserted from both end openings of the outer pipe toward the bent portions, respectively, and at the insertion tip end of one of the first and second divided inner pipes, the radially outer side is formed. Is expanded toward the other inner divided pipe to form an overlapping portion that covers the insertion tip of the other divided inner tube, and Between the insertion tip of the second split inner tube and the outer tube, the first and second split inner tubes are held coaxially with the outer tube, and the sound absorbing material is provided at the bent portion. An exhaust system for an engine, characterized in that a ring-shaped support tool is arranged so as to be separated from the engine.