JPH0579333A - Exhaust device of engine - Google Patents

Abstract

PURPOSE:To vary the length of an exhaust pipe in a small device by attaching a case on the way of the exhaust pipe, providing an expansion part and a rotational changeover valve on the case, providing a partitioning member on the rotational changeover valve, and transferring the partitioning member to the expansion part by the turning movement of the rotational changeover valve. CONSTITUTION:An exhaust pipe length varying device 17 is mounted on the way of an exhaust pipe 16c. A case 21 and a rotational changeover valve 22 rotatably mounted on the side plate 21a of the case 21 are provided in the exhaust pipe length varying device 17. The rotational changeover valve 22 is formed of a rotational shaft 23 rotatably supported by the side plate 21a of the case 21, and a partitioning wall 26 erected on a bottom plate 25. An expansion part 21b is formed on the bottom part of the case 21, and when the rotary shaft 23 is rotated, the bottom plate 25 and the partitioning wall 26 enter the expansion part 21b, and thereby an exhaust confluent part 27 in which exhaust gas from the exhaust pipe 16c forms confluence is formed. Consequently, the length of the exhaust pipe can be varied in a small device 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust system capable of varying an exhaust pipe length according to the engine speed.

[0002]

2. Description of the Related Art Generally, in a 4-cycle engine,
Because the exhaust pipe length is set so that the frequency of the pulsating reflected wave of the exhaust gas is synchronized with the high engine speed, the frequency of the pulsating reflected wave becomes incompatible on the low engine speed side, resulting in a drop in output. There's a problem. Therefore, it has been proposed to lengthen the exhaust pipe length on the low rotation speed side and shorten it on the high rotation speed side. For example, in Japanese Unexamined Patent Publication No. 63-285218, a chamber is installed between a plurality of exhaust pipes and a muffler, and an exhaust pipe extension and an exhaust collecting portion are provided in the chamber to exhaust the exhaust gas according to the number of revolutions. It is arranged to switch to the exhaust pipe extension or the exhaust collecting part.

[0003]

However, in the above-mentioned conventional apparatus, the exhaust collecting section must be provided separately from the exhaust pipe, which causes a problem that the apparatus becomes large in size.
In particular, it was difficult to apply it to motorcycles.

The present invention solves the above problems, and an object of the present invention is to provide an exhaust system for an engine in which the exhaust pipe length can be made variable with a small device.

[0005]

To this end, an engine exhaust system according to the present invention includes a case 21 mounted in the middle of a plurality of exhaust pipes 16a to 16d, a bulged portion 21b formed in the case 21, and a case. 21, a rotation switching valve 22 rotatably mounted on the rotation switching valve 21, and a passage 2 provided in the rotation switching valve 22 and communicating with the exhaust pipes 16a to 16d independently of each other.
Partitioning members 25 and 26 capable of forming 6a to 26d, and the partitioning member 25 and 26 by the rotation of the rotation switching valve 22.
26 is moved to the bulging portion 21b. It should be noted that the numbers added to the above configuration are for comparison with the drawings, and the configuration of the present invention is not limited thereby.

[0006]

In the present invention, when the engine speed is low,
Exhaust gas flowing into the exhaust pipe length variable device from each exhaust pipe flows along independent passages and then enters the muffler,
Exhaust pulsation is reflected in the muffler, so the length of the exhaust pipe becomes long, and the exhaust pipe length variable device is switched so that the exhaust gas that flows in from each exhaust pipe merges in the exhaust merging section at high engine speeds. Since the pulsation is reflected in the exhaust merging portion, the length of the exhaust pipe is shortened, and the frequency of the reflected wave and the engine speed are synchronized.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall side view of a motorcycle to which the present invention is applied, FIG. 2 is a partial cross-sectional view of an exhaust pipe length varying device according to the present invention, and FIG. 3 is a view taken along the line XX of FIG. FIG.

In FIG. 1, a motorcycle 1 has a body frame such as a head pipe 2, a main frame 3, a seat rail 5 and a rear arm bracket 6, and a front fork 7 is rotatably supported on the head pipe 2. A front wheel 9 is attached to the lower part of the front wheel 9. An engine 10 is mounted and fixed between the main frame 3 and the rear arm bracket 6, and a fuel tank 11 is arranged above the main frame 3. One end of a rear arm 12 is swingably supported by the rear arm bracket 6, and a rear wheel 13 is rotatably attached to the other end of the rear arm 12 and supported by a seat rail 5 via a rear shock 15. Has been done. Exhaust pipe 16 of engine 10
Are connected to the two mufflers 19 via the exhaust pipe length varying device 17 according to the present invention.

The exhaust pipe length varying device 17 according to the present invention will be described with reference to FIGS. 2 and 3. In the present embodiment, the exhaust pipe 16 of the engine 10 includes four exhaust pipes 16a to 16d, but the exhaust pipe 16 is not limited to this and is determined according to the number of cylinders.

An exhaust pipe length varying device 17 is attached in the middle of the exhaust pipes 16a to 16d. Exhaust pipe length variable device 17
Is a case 21 fixed to the exhaust pipes 16a to 16d,
A rotation switching valve 22 is rotatably mounted on the side plate 21a of the case 21. The rotation switching valve 22 includes a rotation shaft 23 rotatably supported by a side plate 21 a of the case 21.
And a bottom plate 25 formed integrally with the rotary shaft 23 and the bottom plate 2
It consists of 5 partition walls 26 that are integrally erected from 5,
The exhaust pipe 1 is formed by a partition member composed of the bottom plate 25 and the partition wall 26.
6a to 16d, the passages 26a to which they respectively communicate independently
26d can be formed. A pulley 24 around which a wire 24a is wound is attached to one end of the rotary shaft 23, and the rotary shaft 23 is rotated by driving the wire 24a by an electric motor (not shown).

As shown in FIG. 3, a bulging portion 21b is formed at the bottom of the case 21, and when the rotary shaft 23 rotates in the direction of the arrow in the figure, the bottom plate 25 and the partition wall 26 bulge as shown by the dotted line in the figure. The exhaust pipe 16a-
It is configured to form an exhaust merging portion 27 where the exhaust from 16d merges. When the rotary shaft 23 rotates in the direction opposite to the arrow shown in the figure, the bottom plate 25 and the partition wall 26 are switched to the positions shown by the solid lines in the figure, and the partition wall 26 and the bottom plate 25 are moved.
The passages 26a to 26d partitioned by are configured to communicate with the exhaust pipes 16a to 16d independently. The cross-sectional area of the exhaust merging portion 27 (the one-dot chain line hatching portion in FIG. 3) is set to be 1.5 times or more the cross-sectional area of each of the exhaust pipes 16a to 16d.

The operation of the present invention having the above structure will be described. When the engine 10 rotates at a low speed, the rotary shaft 23 of the rotation switching valve 22 rotates in the direction opposite to the arrow shown in the drawing, the partition members 25 and 26 are switched to the positions shown by the solid lines in the drawing, and the partition walls 26 and the bottom plate 25 partition the partition members 25 and 26. Passages 26a-2
6d communicates with the exhaust pipes 16a to 16d independently, and the exhaust gas flowing in from the exhaust pipes 16a to 16d independently flows along the passages 26a to 26d, and then the two exhaust pipes of FIG. It joins the pipe and flows into the two mufflers 19. The pulsation of the exhaust gas is reflected by the expansion section in the muffler 19, and this reflected wave advances toward the exhaust valve of the engine. As a result, since the length of the exhaust pipe becomes long, it is possible to reduce the frequency of the reflected wave and synchronize it with the engine speed, and it is possible to prevent the output from decreasing when the engine speed is low.

When the engine 10 rotates at high speed, the rotary shaft 23
Is rotated in the direction of the arrow in the drawing, and the partition members 25 and 26 are bulged 2
The exhaust gas flowing from the exhaust pipes 16a to 16d merges in the exhaust merging portion 27 to move to the exhaust pipe 16 again.
It branches into a to 16d and flows to the two mufflers 19 in FIG. Exhaust pulsation is reflected in the exhaust merging portion 27, and this reflected wave advances toward the exhaust valve of the engine. As a result, since the exhaust pipe length is shortened, it is possible to increase the frequency of the reflected wave and synchronize it with the engine speed, thereby improving fuel efficiency and output characteristics.

FIG. 4 shows the relationship between engine speed and torque. The dotted line A is a characteristic curve when the exhaust pipe length is increased,
A chain line B is a characteristic curve when the exhaust pipe length is shortened. Therefore, if the rotation switching valve 22 is started to open at the rotation speed R1 and the rotation switching valve 22 is completely opened at the rotation speed R3, it is possible to perform control with the advantages of both characteristic curves as shown by the diagonal lines in the figure. .. The rotation switching valve 22 may be opened and closed at the rotation speed R2 at the intersection of the characteristic curves A and B.

[0015]

As is apparent from the above description, according to the present invention, a case mounted in the middle of a plurality of exhaust pipes, a bulge portion formed in the case, and a rotatable case. A rotation switching valve to be mounted, and a partitioning member provided in the rotation switching valve and capable of forming a passage that communicates with each of the exhaust pipes independently of each other. The partitioning member is provided by the rotation of the rotation switching valve. Since it is configured to be moved to the bulging portion, the exhaust pipe length can be made variable with a small device. Further, since such an exhaust pipe length varying device is mounted in the middle of the exhaust pipe, the waveform of the reflected wave can be set to an optimum one by changing the shape of the case.

[Brief description of drawings]

FIG. 1 is an overall side view of a motorcycle to which the present invention is applied.

FIG. 2 is a partial sectional view of an exhaust pipe length varying device according to the present invention.

3 is a sectional view taken along line XX of FIG. 2 and viewed in the direction of the arrow.

FIG. 4 is a diagram showing a control method according to the present invention, showing a relationship between engine speed and torque.

[Explanation of symbols]

16a to 16d ... Exhaust pipe, 21 ... Case, 21b ... Bulging portion 22 ... Rotation switching valve, 25, 26 ... Partition member, 26a
~ 26d ... passage

Claims (1)

[Claims] 1. A case mounted in the middle of a plurality of exhaust pipes, a bulge portion formed in the case, a rotation switching valve rotatably mounted in the case, and a rotation switching valve provided in the rotation switching valve. And an partitioning member capable of forming a passage that communicates with each of the exhaust pipes independently of each other, and the partitioning member is moved to the bulging portion by rotation of the rotation switching valve. Exhaust system.