JP2009030445A - Exhaust system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust system capable of effectively preventing reduction in exhaust efficiency, by changing the flow passage cross-sectional area of exhaust gas stepwise to an exhaust flow rate of a low speed, a medium speed and high speed rotation area of an internal combustion engine. <P>SOLUTION: This exhaust system 1 has an exhaust introducing pipe 21 for introducing the exhaust gas from an engine, an expansion chamber 22 connected to a downstream end part of the exhaust introducing pipe 21, a main exhaust pipe 23 and an auxiliary exhaust pipe 24 connected to a downstream side wall of the expansion chamber 22, and an extension exhaust pipe 25 having a diameter smaller than the main exhaust pipe 23. The exhaust introducing pipe 21, the main exhaust pipe 23 and the auxiliary exhaust pipe 24 are inserted into the expansion chamber 22. The main exhaust pipe 23 is coaxially inserted into the exhaust introducing pipe 21 with a clearance, and the extension exhaust pipe 25 is coaxially inserted into the main exhaust pipe 23 with a clearance. A communicating port for exhausting the exhaust gas passing through the clearance with the extension exhaust pipe 25 to an external part, is formed in a downstream end part of the main exhaust pipe 23. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust device for an internal combustion engine.

In an internal combustion engine, if the exhaust gas flow velocity of the exhaust gas flowing in the exhaust pipe decreases, the exhaust efficiency decreases, and as a result, the torque decreases.
Therefore, it has a two-stage exhaust cross-sectional area and the exhaust cross-sectional area changes without using a control valve in accordance with the exhaust gas exhaust flow rate, thereby preventing the exhaust gas flow velocity from decreasing. That is, there is an exhaust device for an internal combustion engine that prevents a reduction in exhaust efficiency.
This exhaust system includes a main exhaust pipe for low and medium speeds having a cross-sectional area with respect to an exhaust gas flow rate of exhaust gas in a low and medium speed rotation region, and exhaust gas in excess of the exhaust flow rate of the low and medium speed rotation region. And a high-speed auxiliary exhaust pipe for exhausting. The exhaust gas is exhausted only from the main exhaust pipe at the exhaust flow rate in the low and medium speed rotation region, and the exhaust gas is exhausted from the main exhaust pipe and the auxiliary exhaust pipe at the exhaust flow rate in the high speed rotation region.

8 and 9 show the main part of the exhaust device of this conventional internal combustion engine.
As shown in FIGS. 8 and 9, this conventional exhaust system includes an exhaust introduction pipe 31 into which exhaust gas from the engine is introduced, an expansion chamber 32 connected to the downstream end of the exhaust introduction pipe 31, and an expansion. The main exhaust pipe 33 and the auxiliary exhaust pipe 34 connected to the downstream side wall of the chamber 32, and the upstream end of the main exhaust pipe 33 has a gap C 4 at the downstream end of the exhaust introduction pipe 31 inside the expansion chamber 32. Are inserted coaxially (see Patent Document 1).

Japanese Patent Laid-Open No. 2003-232212

The conventional exhaust system has a low-medium-speed channel cross-sectional area and a high-speed channel cross-sectional area, and the exhaust flow rates in the low-speed rotation range and the medium-speed rotation range of the internal combustion engine are the same. Since the cross-sectional area of the flow path is used, the cross-sectional area of the flow path is increased with respect to the exhaust flow rate in the low-speed rotation region, which causes a problem that the exhaust flow velocity and the exhaust efficiency in the low-speed rotation region are reduced.
Further, since the adjustment of the size of the flow path cross-sectional area is performed only by adjusting the size of the gap C4, if the exhaust efficiency in the low-speed rotation region is improved, the exhaust efficiency in the medium-high speed rotation region is deteriorated. There is a limit to preventing a reduction in exhaust efficiency from the low speed rotation range of the engine to the entire high speed rotation range.

  In view of such circumstances, the present invention has a three-stage exhaust passage cross-sectional area with respect to the exhaust flow rate in the low-speed, medium-speed, and high-speed rotation regions of an internal combustion engine, and exhaust gas exhaust without using a control valve. An object of the present invention is to provide an exhaust system for an internal combustion engine that can effectively prevent a reduction in exhaust efficiency by changing the cross-sectional area of the exhaust flow according to the flow rate.

The present invention relates to an exhaust introduction pipe into which exhaust gas from an engine is introduced, an expansion chamber connected to a downstream end portion of the exhaust introduction pipe, a main exhaust pipe and an auxiliary exhaust connected to a downstream side wall of the expansion chamber An exhaust system for an internal combustion engine in which an upstream end of the main exhaust pipe is inserted coaxially with a gap at a downstream end of the exhaust introduction pipe inside the expansion chamber,
An extended exhaust pipe having a smaller diameter than the main exhaust pipe is inserted coaxially with a gap at the downstream end of the main exhaust pipe, and the extended exhaust pipe is inserted into the downstream end of the main exhaust pipe. A communication port for exhausting the exhaust gas passing through the gap with the pipe to the outside is formed.

According to the present invention, the exhaust gas introduction pipe, the main exhaust pipe, and the extended exhaust pipe having different flow path cross-sectional areas are arranged coaxially in order of increasing area from upstream to downstream. Depending on the flow rate, the exhaust gas in the exhaust introduction pipe is exhausted from three places: the extension exhaust pipe, the communication port at the downstream end of the main exhaust pipe, and the auxiliary exhaust pipe through the gap between the exhaust introduction pipe and the main exhaust pipe .
Normally, according to the flow velocity distribution in the exhaust pipe, the maximum flow velocity is at the center of the pipe, and the parabola is zero on the pipe wall. Specifically, since friction is generated between the exhaust gas and the pipe wall, when the exhaust gas flow rate is small with respect to the cross-sectional area of the exhaust pipe, most of the exhaust gas flows through the center of the pipe, A small amount of exhaust gas flows at a low speed on the inner wall side of the pipe. If the exhaust flow rate of the exhaust pipe increases, the exhaust flow velocity at the center of the pipe increases, and the exhaust gas flows in an increased amount and speed on the inner wall side of the pipe.

  Therefore, when the exhaust gas flow rate is small, most of the exhaust gas in the exhaust pipe is exhausted from the extended exhaust pipe via the main exhaust pipe, and when the exhaust gas flow rate is increased, the exhaust gas in the exhaust pipe is increased. Is exhausted from the communication port at the downstream end of the extension exhaust pipe and the main exhaust pipe. When the exhaust gas flow rate is large, the exhaust gas in the exhaust introduction pipe is connected to the extended exhaust pipe, the communication port at the downstream end of the main exhaust pipe, and the auxiliary exhaust pipe via the gap between the exhaust introduction pipe and the main exhaust pipe. Exhausted from.

In this way, the flow passage cross-sectional area of the exhaust gas changes in three stages according to the exhaust gas flow rate of the exhaust gas.
Further, since the size of the flow passage cross-sectional area of the exhaust can be adjusted by adjusting the size of the gap between the exhaust introduction pipe and the main exhaust pipe and the gap between the main exhaust pipe and the extended exhaust pipe, The cross-sectional area can be adjusted more finely. That is, since the exhaust efficiency can be adjusted more finely, it is possible to effectively prevent a reduction in exhaust efficiency from the low speed rotation area to the entire high speed rotation area of the internal combustion engine.

The present invention also provides an exhaust introduction pipe into which exhaust gas from the engine is introduced, an extension chamber connected to the downstream end of the exhaust introduction pipe, a main exhaust pipe connected to the downstream side wall of the extension chamber, and An exhaust system for an internal combustion engine, comprising: an auxiliary exhaust pipe, wherein an upstream end portion of the main exhaust pipe is inserted coaxially with a gap at a downstream end portion of the exhaust introduction pipe inside the expansion chamber ,
An extended exhaust pipe having a smaller diameter than the main exhaust pipe is inserted coaxially with a gap at the downstream end of the main exhaust pipe, and the extended exhaust pipe is inserted into the downstream end of the main exhaust pipe. A communication port for exhausting the exhaust gas passing through the gap with the pipe to the outside is formed, and the second extension exhaust pipe having a smaller diameter than the extension exhaust pipe has a gap at the downstream end of the extension exhaust pipe. And a communication port for exhausting the exhaust gas passing through the gap with the second extension exhaust pipe to the outside is formed in the downstream portion of the extension exhaust pipe. To do.

According to the present invention, the exhaust introduction pipe, the main exhaust pipe, the extension exhaust pipe, and the second extension exhaust pipe having different flow path cross-sectional areas are arranged coaxially in order of increasing area from upstream to downstream. Therefore, according to the exhaust gas flow rate, the exhaust gas in the exhaust introduction pipe is connected to the second extension exhaust pipe, the communication port at the downstream end of the extension exhaust pipe, the communication port at the downstream end of the main exhaust pipe, and the exhaust introduction pipe And exhaust from four places of the auxiliary exhaust pipe via the gap between the main exhaust pipe and the main exhaust pipe.
Normally, according to the flow velocity distribution in the exhaust pipe, the maximum flow velocity is at the center of the pipe, and the parabola is zero on the pipe wall. Specifically, since friction is generated between the exhaust gas and the pipe wall, when the exhaust gas flow rate is small with respect to the cross-sectional area of the exhaust pipe, most of the exhaust gas flows through the center of the pipe, A small amount of exhaust gas flows at a low speed on the inner wall side of the pipe. If the exhaust flow rate of the exhaust pipe increases, the exhaust flow velocity at the center of the pipe increases, and the exhaust gas flows in an increased amount and speed on the inner wall side of the pipe.

Therefore, when the exhaust gas exhaust flow rate is small, most of the exhaust gas in the exhaust introduction pipe is exhausted from the second extended exhaust pipe via the main exhaust pipe and the extended exhaust pipe, and when the exhaust gas exhaust flow rate is increased, The exhaust gas in the exhaust introduction pipe is exhausted from the communication port at the downstream end of the second extension exhaust pipe and the extension exhaust pipe.
When the exhaust gas flow rate is further increased, the exhaust gas in the exhaust introduction pipe is connected to the second extension exhaust pipe, the extension exhaust pipe, the communication port at the downstream end of the extension exhaust pipe, and the downstream end of the main exhaust pipe. When the exhaust gas is exhausted and the exhaust gas flow rate is large, the exhaust gas in the exhaust introduction pipe is connected to the second extension exhaust pipe, the extension exhaust pipe, the communication port at the downstream end of the extension exhaust pipe, and the main exhaust. Exhaust gas is exhausted from the communication port at the downstream end of the pipe and the auxiliary exhaust pipe via the gap between the exhaust introduction pipe and the main exhaust pipe.

As described above, the flow passage cross-sectional area of the exhaust gas changes in four stages according to the exhaust gas flow rate of the exhaust gas.
In addition, the adjustment of the size of the flow passage cross-sectional area of the exhaust gas is adjusted by three gaps: a gap between the exhaust introduction pipe and the main exhaust pipe, a main exhaust pipe and the extended exhaust pipe, and a gap between the extended exhaust pipe and the second extended exhaust pipe. Therefore, the flow passage cross-sectional area can be adjusted more finely. That is, since the exhaust efficiency can be adjusted more finely, power loss and residual gas in the cylinder during the exhaust process from the low speed rotation range to the entire high speed rotation range of the internal combustion engine are reduced. The charging efficiency is improved, and the heat storage in the internal combustion engine is also reduced due to these factors, which contributes to low fuel consumption in combination with effects such as reduction of heat loss.

  As described above, according to the present invention, the flow passage cross-sectional area of the exhaust gas can be changed in three stages in accordance with the exhaust flow rate of the internal combustion engine without using a control valve, thereby finely adjusting the exhaust efficiency. Therefore, it is possible to effectively prevent a reduction in exhaust efficiency from the low speed rotation range to the high speed rotation range of the internal combustion engine as compared with the conventional exhaust system. Furthermore, prevention of the exhaust efficiency from being lowered leads to an improvement in fuel consumption of the internal combustion engine.

Hereinafter, an embodiment (first embodiment) of the present invention will be described with reference to the drawings. FIG. 1 is a partially broken plan view showing the main part of the exhaust device according to the present embodiment, and FIG. 2 is an enlarged view of the main part of FIG. 3 is a cross-sectional view taken along line AA in FIG.
In FIG. 1, the exhaust device 1 of the present embodiment includes a silencer 10 that removes noise components of exhaust gas, and an exhaust unit 20 that exhausts exhaust gas.
The silencer 10 includes a cylindrical silencer chamber 11 closed at both ends, a silencer tube 12 inserted into the silencer chamber 11, and four conical partition plates 13 attached to the silencer tube 12. .
The silencing chamber 11 has an insertion hole at the center of the wall surfaces at both ends of the internal combustion engine on the upstream side and the atmospheric side on the downstream side, and the silencing tube 12 is inserted into the insertion hole, and the silencing chamber 11 and the silencing tube 12 are coaxial. It is arranged in a heart shape. The muffler tube 12 is fixed in a state where there is no gap with the insertion hole, and is further fixed with a stopper (not shown).

The muffler tube 12 has an exhaust introduction port 14, a porous tube 15 having a large number of small holes drilled along the circumference and accommodated in the muffler chamber 11, and an exhaust discharge port 16.
The porous cylinder 15 has three types of small holes having different diameters in order to remove low-frequency, medium-frequency, and high-frequency sound waves that are noise components of exhaust gas. The perforated tube 15 includes a large hole tube portion 15a having a small hole with a large diameter, a medium hole tube portion 15b having a small hole with a medium diameter, and a small hole tube portion having a small hole with a small diameter. 15c, and small holes are arranged in descending order of diameter from upstream to downstream.

The four partition plates 13 are made of cone-shaped members having a small diameter that is the same as the outer diameter of the muffler tube 12 and a large diameter that is the same dimension as the inner diameter of the muffler chamber 11. The sound deadening tube 12 is mounted on the outer peripheral surface in a direction extending in the downstream direction and at a predetermined interval in the axial direction.
If it demonstrates in detail, the 1st partition plate 13 will be arrange | positioned in the position close | similar to the upstream side wall surface of the muffling chamber 11, and is mounted | worn with the outer peripheral surface of the large hole cylinder part 15a. Further, the upstream end of the second partition plate 13 is attached to the outer peripheral surface of the downstream end portion of the large hole cylinder portion 15a, and the upstream end of the third partition plate 13 is the downstream end of the middle hole cylinder portion 15b. It is attached to the outer peripheral surface of the part. Further, the upstream end of the fourth partition plate 13 is attached to the outer peripheral surface of the downstream end portion of the small hole cylinder portion 15c, and the fourth partition plate 13 is disposed at a position close to the downstream side wall surface. Has been.

At this time, the partition plates 13 adjacent to each other are arranged in the axial direction so as not to overlap in the radially outward direction.
Further, at this time, the expansion chamber 11a, the expansion chamber 11b, and the expansion chamber 11c for attenuating the sound wave that is the noise component of the exhaust gas are formed in the noise reduction chamber 11 by the noise reduction tube 12 and the four partition plates 13. Yes.
The expansion chamber 11a is composed of an annular space formed by the muffler chamber 11, the exhaust introduction port 14, the large-hole cylindrical portion 15a, the first partition plate 13, and the second partition plate 13. Exhaust gas and sound waves that have passed through the small hole of the hole cylinder portion 15a are expanded. The expanded exhaust gas and sound waves are diffused in the downstream direction in the expansion chamber 11a while reducing the flow velocity, and further, the expansion formed by the inner peripheral surface of the muffler chamber 11 and the second partition plate 13 is performed. It is contained in the acute-angled space of the chamber 11a. At this time, the sound wave is attenuated and a silencing effect is obtained.

  The expansion chamber 11b is composed of an annular space formed by the sound deadening chamber 11, the large hole cylinder portion 15a, the large hole cylinder portion 15b, the second partition plate 13, and the third partition plate 13. Exhaust gas and sound waves that have passed through the small hole of the large hole cylinder portion 15b are expanded. The expanded exhaust gas and sound waves are diffused in the downstream direction in the expansion chamber 11b while reducing the flow velocity, and further, the expansion formed by the inner peripheral surface of the silencer chamber 11 and the third partition plate 13 is performed. It is contained in the acute angle space of the chamber 11b. At this time, the sound wave is attenuated and a silencing effect is obtained.

The expansion chamber 11c includes an annular space formed by the sound deadening chamber 11, the large hole cylinder portion 15b, the large hole cylinder portion 15c, the third partition plate 13, and the fourth partition plate 13. Exhaust gas and sound waves that have passed through the small hole of the large hole cylinder portion 15c are expanded. The expanded exhaust gas and sound waves are diffused in the downstream direction in the expansion chamber 11c while reducing the flow velocity, and further, the expansion formed by the inner peripheral surface of the silencer chamber 11 and the fourth partition plate 13 is performed. It is contained in the acute-angled space of the chamber 11c. At this time, the sound wave is attenuated and a silencing effect is obtained.
In this way, low frequency, medium frequency, and high frequency sound waves, which are noise components of the exhaust gas of the internal combustion engine, are removed.

Next, the exhaust part 20 is demonstrated, referring FIG. 2 and FIG.
As shown in FIG. 2, the exhaust section 20 is connected to an exhaust introduction pipe 21 connected to the muffler pipe 12, an expansion chamber 22 connected to the downstream end of the exhaust introduction pipe 21, and a downstream side wall of the expansion chamber 22. The main exhaust pipe 23 and the auxiliary exhaust pipe 24, and the extended exhaust pipe 25 having a smaller diameter than the main exhaust pipe 23 are provided.
The expansion chamber 22 has one insertion hole on the upstream side and two insertion holes at the same height position on the downstream atmosphere side.
The main exhaust pipe 23 has an upstream pipe portion 23a having a smaller diameter than the exhaust introduction pipe 21, and a downstream pipe portion 23b fitted to the outer peripheral surface on the downstream side of the upstream pipe portion 23a.

An exhaust introduction pipe 21 is inserted into the insertion hole on the upstream side of the expansion chamber 22, and an upstream pipe portion 23 a of the main exhaust pipe 23 and an auxiliary exhaust pipe 24 are inserted into the two insertion holes on the downstream side.
The downstream end portion of the exhaust introduction pipe 21 is arranged at a position closer to the upstream side from the middle in the expansion chamber 22, and the upstream pipe portion 23a has a gap C1 at the end portion of the exhaust introduction pipe 21 and is coaxial. It is inserted in a shape. The upstream end portion of the upstream pipe portion 23 a is disposed near the position of the upstream wall of the expansion chamber 22. The auxiliary exhaust pipe 24 has an upstream end portion disposed at a position closer to the downstream side from the middle in the expansion chamber 22 and projects the downstream end portion to the atmosphere side.
In this case, the exhaust introduction pipe 21, the upstream pipe portion 23 a, and the auxiliary exhaust pipe 24 are fixed in a state where there is no gap with each insertion hole of the expansion chamber 22. It is fixed with a stopper that comes into contact with the outer edge of the insertion hole.

In the downstream pipe portion 23b of the main exhaust pipe 23, an extended exhaust pipe 25 is inserted coaxially with a gap C2 and fixed with a stopper (not shown). At this time, in the downstream pipe portion 23b, the end faces of the upstream pipe portion 23a and the extended exhaust pipe 25 facing each other are arranged at a predetermined interval.
In this case, since the extended exhaust pipe 25 is inserted with the gap C2 into the downstream pipe portion 23b having a diameter larger than that of the upstream pipe portion 23a of the main exhaust pipe 23, the downstream pipe portion 23b having an enlarged diameter is not provided. Compared with the case where the extended exhaust pipe 25 is inserted into the main exhaust pipe 23 with a gap, the flow passage cross-sectional area of the extended exhaust pipe 25 can be increased. Therefore, regardless of the thickness of the tube wall of the extended exhaust pipe 25, the flow path cross-sectional area of the extended exhaust pipe 25 can be made closer to the flow path cross-sectional area of the upstream end portion of the main exhaust pipe 23. The cross-sectional area and the size of the gap can be adjusted.
As a result, the exhaust efficiency can be adjusted more finely.

Further, the downstream pipe portion 23b includes a communication port 23c composed of a plurality of small holes drilled along the circumference of the downstream end portion, and an annular member 23d that closes the downstream side in the axial direction of the gap C2. .
The annular member 23d is fitted to the outer peripheral surface of the extended exhaust pipe 25 and is in contact with the downstream end face of the downstream pipe portion 23b. As a result, the exhaust gas in the gap C2 in which the outlet on the downstream side in the axial direction is blocked is exhausted from the communication port 23c. By passing the exhaust gas through the communication port 23c, sound waves that are noise components of the exhaust gas are removed, and a silencing effect is obtained.
In this case, the extended exhaust pipe 25 has a flow passage cross-sectional area corresponding to the exhaust flow rate in the low speed rotation region, and the main exhaust pipe 23 has a flow passage cross sectional area corresponding to the exhaust flow rate in the medium speed rotation region. is doing. In addition, the auxiliary exhaust pipe 24 has a flow path cross-sectional area corresponding to the exhaust flow rate in excess of the exhaust flow rate in the medium speed rotation range in the high speed rotation range.

Next, the operation of the exhaust device 1 for the internal combustion engine of the present embodiment will be described in detail with reference to FIGS. 4 to 6.
FIG. 4 is an explanatory diagram showing an exhaust path in the low speed rotation region, and FIG. 5 is an explanatory diagram showing an exhaust route in the medium speed rotation region. FIG. 6 is an explanatory diagram showing an exhaust path in a high speed rotation region.
As shown in FIG. 4, in the low-speed rotation region where the exhaust flow rate is small, most of the exhaust gas in the exhaust introduction pipe 21 flows through the center of the pipe and is exhausted from the extended exhaust pipe 25 through the main exhaust pipe 23. .

In this case, the exhaust gas or the outside air in the expansion chamber 22 moves to the main exhaust pipe 23 through the gap C1 due to the pressure drop in the main exhaust pipe 23 at a predetermined exhaust flow velocity. Occurs. For this reason, outside air flows into the expansion chamber 22 from the auxiliary exhaust pipe 24, and further, this outside air flows into the main exhaust pipe 23 through the gap C <b> 1. This outside air cools the inside of the expansion chamber 22 and the main exhaust pipe 23, thereby obtaining a silencing effect.
Further, at a predetermined exhaust flow rate, due to the pressure drop in the extended exhaust pipe 25, the outside air flows into the C2 from the communication port 23c, and further, the introduced outside air flows into the extended exhaust pipe 25. With this outside air, the inside of the extended exhaust pipe 25 is cooled, and a silencing effect is obtained.

  As shown in FIG. 5, in the middle speed rotation region where the exhaust flow rate is increased, in the exhaust introduction pipe 21, most of the exhaust gas flows through the center of the pipe, and the exhaust gas in the exhaust introduction pipe 21 flows into the main exhaust pipe 23. . In the main exhaust pipe 23, the amount and speed of exhaust gas increase both in the central portion of the pipe and on the inner wall side of the pipe, so that the exhaust gas in the central portion of the pipe goes straight and flows to the extended exhaust pipe 25, and the exhaust gas on the inner wall side of the pipe It flows to C2. Finally, the exhaust gas is exhausted from the extended exhaust pipe 25 and the communication port 23c via the gap C2.

  In this case, the exhaust gas or the outside air in the expansion chamber 22 moves to the main exhaust pipe 23 through the gap C1 due to the pressure drop in the main exhaust pipe 23 at a predetermined exhaust flow velocity. Will occur. For this reason, outside air flows into the expansion chamber 22 from the auxiliary exhaust pipe 24, and further, this outside air flows into the main exhaust pipe 23 through the gap C <b> 1. This outside air cools the inside of the expansion chamber 22 and the main exhaust pipe 23, thereby obtaining a silencing effect.

  As shown in FIG. 6, in the high-speed rotation region where the exhaust gas flow rate is large, in the exhaust introduction pipe 21 and the main exhaust pipe 23, the amount and speed of exhaust gas increase both in the central part of the pipe and the inner wall side. In the exhaust introduction pipe 21, the exhaust gas at the center of the pipe goes straight and flows to the main exhaust pipe 23, the exhaust gas on the inner wall side flows into the gap C 1, and the exhaust gas that has flowed into the gap C 1 passes through the expansion chamber 22. Then, it flows into the auxiliary exhaust pipe 24. Further, in the main exhaust pipe 23, the exhaust gas in the central portion of the pipe advances straight as it is and flows into the extended exhaust pipe 25, and the exhaust gas on the inner wall side of the pipe flows into the gap C2. Finally, the exhaust gas is exhausted from the extended exhaust pipe 25, the communication port 23c via the gap C2, and the auxiliary exhaust pipe 24 via the gap C1.

  According to the exhaust apparatus 1 of the present embodiment having the above-described configuration, the extended exhaust pipe 25 having a flow path cross-sectional area corresponding to the exhaust flow rate in the low-speed rotation region, and the flow path cross-sectional area corresponding to the exhaust flow rate in the medium-speed rotation range. And an auxiliary exhaust pipe 24 having a channel cross-sectional area corresponding to the exhaust flow rate in excess of the exhaust flow rate in the medium speed rotation range in the high speed rotation range, Since the exhaust introduction pipe 21, the main exhaust pipe 23, and the extended exhaust pipe 25 are arranged coaxially, the control valve is not used for the exhaust flow rate in the low, medium, and high speed rotation regions. The cross-sectional area of the exhaust passage can be changed in three stages.

Further, since the size of the cross-sectional area of the flow path is adjusted by adjusting the sizes of the two gaps C1 and C2, in the case of the conventional example (FIG. 8) in which the adjustment is performed with only one of the gaps C4. In comparison, the flow path cross-sectional area can be adjusted more finely. That is, since the exhaust efficiency can be adjusted more finely, it is possible to effectively prevent a decrease in exhaust efficiency from the low speed rotation area to the entire high speed rotation area of the internal combustion engine.
Moreover, since the flow passage cross-sectional area of the exhaust gas changes in three stages according to the exhaust flow rate without using a control valve, there is no need for special control parts for changing the flow passage cross-sectional area, and the material cost can be reduced. At the same time, since there are no movable parts, there is no failure due to this, and the manufacturing work is facilitated.

FIG. 7: has shown the expanded plane sectional view which shows the principal part of the exhaust apparatus which concerns on 2nd Embodiment of this invention.
In the present embodiment, the exhaust part 20 has a second extended exhaust pipe 26 having a smaller diameter than the extended exhaust pipe 25. The extended exhaust pipe 25 has an extended upstream pipe portion 25a having a smaller diameter than the main exhaust pipe 23, and an extended downstream pipe portion 25b fitted to the outer peripheral surface of the downstream end portion of the extended upstream pipe portion 25a. Yes.
In this case, the extended upstream pipe portion 25a is inserted coaxially into the downstream pipe portion 23b of the main exhaust pipe 23 with a gap C2, and is fixed by a stopper (not shown). A second extended exhaust pipe 26 is inserted coaxially into the extended downstream pipe portion 25b with a gap C3, and is fixed with a stopper (not shown). At this time, in the extended downstream pipe portion 25b, the end surfaces of the extended upstream pipe portion 25a and the second extended exhaust pipe 26 facing each other are arranged at a predetermined interval.

The extended downstream pipe portion 25b includes a communication port 25c composed of a plurality of small holes drilled along the circumference of the downstream end portion, and an annular member 25d that closes the downstream side in the axial direction of the gap C3. Yes.
The annular member 25d is fitted to the outer peripheral surface of the second extended exhaust pipe 26 and is in contact with the downstream end face of the downstream pipe portion 25b. As a result, the exhaust gas in the gap C3 in which the outlet on the downstream side in the axial direction is blocked is exhausted from the communication port 25c. By passing the exhaust gas through the communication port 25c, the sound wave that is a noise component of the exhaust gas is removed, and a silencing effect is obtained.
Further, in the present embodiment, the exhaust gas in the exhaust introduction pipe 21 corresponds to the exhaust flow rate of the internal combustion engine, the second extended exhaust pipe 26, the communication port 25c via the gap C3, the communication port 23c via the gap C2, The air is exhausted from the auxiliary exhaust pipe 24 via the gap C1.

That is, the exhaust system 1 in the first embodiment has a three-stage exhaust passage cross-sectional area corresponding to the exhaust flow rate from the low-speed rotation range to the high-speed rotation range of the internal combustion engine. Has a four-stage exhaust cross-sectional area with respect to the exhaust flow rate from the low speed rotation range to the high speed rotation range of the internal combustion engine.
Further, since the size of the flow path cross-sectional area is adjusted by adjusting the sizes of the three gaps of the gap C1, the gap C2, and the gap C3, the flow path cross-sectional area can be adjusted more finely. That is, since the exhaust efficiency can be adjusted more finely, it is possible to more effectively prevent the exhaust efficiency from decreasing from the low speed rotation range to the high speed rotation range of the internal combustion engine.
The other points are not different from those of the first embodiment, and detailed description thereof is omitted.

The present invention is not limited to the above embodiment.
The present invention can be implemented in various modes without departing from the gist of the present invention.

It is a partially broken top view which shows the principal part of the exhaust apparatus which concerns on 1st Embodiment. It is a principal part enlarged view of FIG. It is the sectional view on the AA line of FIG. It is explanatory drawing which shows the exhaust path of a low speed rotation area. It is explanatory drawing which shows the exhaust path of a medium speed rotation area. It is explanatory drawing which shows the exhaust path of a high speed rotation area. It is an expanded plane sectional view which shows the principal part of the exhaust apparatus which concerns on 2nd Embodiment. It is a plane sectional view showing the important section of the conventional exhaust device. It is the BB sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust device 10 Silencer part 11 Silencer room 12 Silencer pipe 13 Partition plate 15 Porous cylinder 20 Exhaust part 21 Exhaust introduction pipe 22 Expansion chamber 23 Main exhaust pipe 23a Upstream pipe part 23b Downstream pipe part 23c Communication port 23d Annular member 24 Auxiliary exhaust pipe 25 extended exhaust pipe 25a extended upstream pipe section 25b downstream pipe section 25c communication port 25d annular member 26 second extended exhaust pipe

Claims (2)

An exhaust introduction pipe for introducing exhaust gas from the engine, an expansion chamber connected to the downstream end of the exhaust introduction pipe, and a main exhaust pipe and an auxiliary exhaust pipe connected to the downstream side wall of the expansion chamber In the exhaust system of the internal combustion engine, the upstream end of the main exhaust pipe is inserted coaxially with a gap in the downstream end of the exhaust introduction pipe inside the expansion chamber.
An extended exhaust pipe having a smaller diameter than the main exhaust pipe is inserted coaxially with a gap at the downstream end of the main exhaust pipe, and the extended exhaust pipe is inserted into the downstream end of the main exhaust pipe. An exhaust system for an internal combustion engine, characterized in that a communication port for exhausting exhaust gas passing through a gap with a pipe to the outside is formed. An exhaust introduction pipe for introducing exhaust gas from the engine, an expansion chamber connected to the downstream end of the exhaust introduction pipe, and a main exhaust pipe and an auxiliary exhaust pipe connected to the downstream side wall of the expansion chamber In the exhaust system of the internal combustion engine, the upstream end of the main exhaust pipe is inserted coaxially with a gap in the downstream end of the exhaust introduction pipe inside the expansion chamber.
An extended exhaust pipe having a smaller diameter than the main exhaust pipe is inserted coaxially with a gap at the downstream end of the main exhaust pipe, and the extended exhaust pipe is inserted into the downstream end of the main exhaust pipe. A communication port for exhausting the exhaust gas passing through the gap with the pipe to the outside is formed, and the second extension exhaust pipe having a smaller diameter than the extension exhaust pipe has a gap at the downstream end of the extension exhaust pipe. And a communication port for exhausting the exhaust gas passing through the gap with the second extension exhaust pipe to the outside is formed in the downstream portion of the extension exhaust pipe. An exhaust device for an internal combustion engine.

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