WO2012090238A1

WO2012090238A1 - Exhaust device

Info

Publication number: WO2012090238A1
Application number: PCT/JP2010/007538
Authority: WO
Inventors: 仲矢高垣
Original assignee: トヨタ自動車株式会社
Priority date: 2010-12-27
Filing date: 2010-12-27
Publication date: 2012-07-05

Abstract

The present invention addresses the problem of providing an exhaust device which renders unnecessary the installation of a sub-muffler on a tailpipe and the installation of an exhaust passage opening/closing mechanism on the main muffler, and which is capable of reducing the particle velocity of exhaust sound of a specific frequency due to air column resonance occurring in an exhaust system, and reducing the weight and the manufacturing cost, by means of a simple construction. The exhaust device is equipped with an outlet pipe (33) having an exhaust passage (61c) that circulates exhaust gas from an inlet aperture end to an atmosphere aperture end (61b) which exhausts the exhaust gas into the atmosphere. In addition, the exhaust device has: a partition member (62) that divides the exhaust passage (61c) into a large passage (61f) and a small passage (61g); a connecting member (63) equipped with a connecting hole (63a) that connects the large passage (61f) and the exhaust passage (61c); a pivot shaft (64) attached to the wall part of outlet pipe (33); and a valving element (65) that is subjected to the flow of exhaust air and therefore swings around the pivot shaft (64) so as to change the flow volume of the exhaust gas passing through the connecting hole (63a).

Description

Exhaust system

The present invention relates to an exhaust device, and more particularly to an exhaust device that suppresses an increase in the particle velocity of exhaust sound due to air column resonance occurring in an exhaust pipe of an internal combustion engine.

Conventionally, an exhaust device 1 as shown in the upper part of FIG. 17 is known as this type of exhaust device.
The exhaust device 1 includes a front pipe 3 connected to the engine 2 and a catalytic converter 4 including

catalytic converters

4 a and 4 b provided on the front pipe 3. The exhaust device 1 includes a tail pipe 5 connected to the catalytic converter 4 b, a sub muffler 6 provided on the tail pipe 5, and a main muffler 7 connected to the tail pipe 5.

As shown in FIG. 18, the sub muffler 6 has an exhaust gas passage 8a that communicates with the exhaust gas passage 5a of the tail pipe 5, and a sub pipe 8 that is connected to the tail pipe 5, and a resonance chamber 6a that communicates with the exhaust gas passage 8a. And. As shown in the upper part of FIG. 17, the sub muffler 6 is disposed in the center portion of the tail pipe 5.

With this configuration, the antinode portion of the sound pressure level of the standing wave indicated by the arrow a in the sound pressure mode of the air column resonance generated in the tail pipe 5 is reduced by the Helmholtz resonance action of the resonance chamber 6a. It has become. In the sound pressure mode in the tail pipe 5, since both ends of the tail pipe 5 are open ends, as shown in the center part of FIG. 17, the sound pressure is lowest at both ends and the sound pressure is highest at the center part. Sound pressure mode of air column resonance. In the case of the particle velocity indicated by the solid line, it is opposite to the sound pressure mode, and the particle velocity is highest at both ends and lowest at the center.

When such air column resonance of exhaust sound occurs, if some measure for reducing the air column resonance such as the sub-muffler 6 is not taken, a muffled sound is generated in the passenger compartment, causing an unpleasant exhaust noise problem. It will end up.

As shown in FIG. 18, the main muffler 7 includes a main body 7a, an inlet pipe portion 5A of the tail pipe 5 inserted into the main body 7a, and an outlet pipe 7b. The main body 7a has an expansion chamber 7A and a resonance chamber 7B adjacent to the expansion chamber 7A.

The inlet pipe portion 5A passes through the expansion chamber 7A and the resonance chamber 7B and opens at the resonance chamber 7B. A plurality of small holes 5b are formed in the wall portion of the inlet pipe portion 5A located in the expansion chamber 7A, and the exhaust gas passage 5c in the inlet pipe portion 5A communicates with the expansion chamber 7A.

The outlet pipe 7b opens in the expansion chamber 7A and extends so as to penetrate the resonance chamber 7B and is opened in the atmosphere. In the main muffler 7, the resonance chamber 7B is generated between a connection portion 3a of the front pipe 3 with the engine 2 and an opening portion 7d on the atmosphere side of the outlet pipe 7b as shown in the lower part of FIG. The sound pressure level in the air column resonance mode of the exhaust system is reduced by the so-called Helmholtz resonance action.

In this exhaust system air column resonance mode, the connection portion 3a of the front pipe 3 to the engine 2 is closed by an unillustrated exhaust valve, and the opening portion 7d is an opening end. A sound pressure mode of air column resonance in which the sound pressure is lowest at the opening portion 7d and the middle portion of the exhaust system, and the sound pressure is highest at the central portion between the connecting portion 3a and the middle portion having the lowest sound pressure and the opening portion 7d. It has become. In the case of the particle velocity indicated by the solid line, the sound pressure mode is reversed, the particle velocity is highest in the opening portion 7d and the middle portion of the exhaust system, and the middle of the connecting portion 3a and the middle portion having the highest particle velocity and the opening portion 7d. Particle velocity is lowest in the part.

When such air column resonance of exhaust noise occurs, if any measures for reducing the air column resonance such as the resonance chamber 7B of the main muffler 7 are not taken, a booming noise is generated in the vehicle interior even in this case, which is uncomfortable. The problem of noise of the exhaust noise will occur.

Further, for exhaust sound having a frequency other than the specific frequency of the air column resonance of the exhaust diameter, a wide frequency is caused by the expansion effect when the exhaust gas flows into the expansion chamber 7A from the plurality of small holes 5b of the inlet pipe portion 5A. The sound pressure level is reduced over the band.

Therefore, in the exhaust device 1, the sound pressure level of the specific frequency generated in the tail pipe 5 is reduced by the sub muffler 6, and the sound pressure level of the specific frequency generated in the exhaust system is reduced by the resonance chamber 7B. That is, the sound pressure level in a wide frequency band other than the two specific frequencies is reduced.

In the conventional exhaust system 1, the cooperation of the sub muffler 6 and the main muffler 7 provided on the tail pipe 5 as described above causes the specific frequency of the different specific frequencies due to the air column resonance generated in the tail pipe 5 and the exhaust system. The mode of air column resonance is reduced by Helmholtz resonance.

In the case of the resonance chamber 7B of the sub muffler 6 and the main muffler 7 using the resonance action of the Helmholtz, the flow rate of the exhaust gas flowing through the sub muffler 6 and the main muffler 7 is small when the engine is decelerated or rotated at a low speed. Further, there is a problem that the Helmholtz resonance action in the resonance chamber 7B of the main muffler 7 does not work effectively. For this reason, particularly when the engine is decelerated or when the engine is running at a low speed, the noise due to the exhaust noise is not sufficiently reduced, and the reduction of the booming noise generated in the passenger compartment is insufficient.

In order to solve the problem of noise at the time of engine deceleration and low rotation, a silencer valve that opens and closes the exhaust pipe is provided, and the opening and closing of the silencer valve is controlled to suppress noise generation due to air column resonance. An exhaust device configured to do this is known (for example, see Patent Document 1).

In this exhaust system, a silencer valve is provided at the downstream opening end of the tail pipe, which is a node of the sound pressure of the standing wave of air column resonance, and this silencer valve is attached to the downstream opening end of the tail pipe. It consists of a valve case and a butterfly valve type valve body, and an orifice for restricting the passage cross-sectional area of the tail pipe is formed at the center of the valve body.

Further, the valve body is provided with a drive shaft, and this drive shaft is provided so as to extend in a direction orthogonal to the central axis in the extending direction of the tail pipe. The drive shaft is connected to an electromagnetic actuator via a drum and a wire, and the electromagnetic actuator is controlled to be turned on / off by a control unit. The control unit outputs a command signal for controlling the electromagnetic actuator to the electromagnetic actuator based on a detection signal of a throttle sensor that detects the opening of the throttle valve.

The control unit outputs an off signal to the electromagnetic actuator to keep the valve body open by the electromagnetic actuator. The control unit outputs an ON signal to the electromagnetic actuator based on detection information from the throttle sensor when the vehicle is decelerated, and causes the valve body to be closed by the electromagnetic actuator.

For this reason, it is possible to prevent the muffler valve from obstructing exhaust of exhaust gas during steady running or acceleration of the vehicle. Further, when the vehicle decelerates, exhaust gas passes only through the orifice, so that the particle motion of the standing wave of air column resonance where the exhaust gas particle velocity is maximum is given resistance to the particle motion, and the tail pipe It is possible to suppress an increase in sound pressure due to air column resonance.

Japanese Patent Laid-Open No. 3-03912

In the exhaust device described in Patent Document 1, it is possible to suppress an increase in sound pressure due to air column resonance of the tail pipe when the engine is decelerated or when the engine is running at a low speed.

However, in the exhaust device described in Patent Document 1, since it is necessary to control the opening and closing of the silencer valve by the control unit and the electromagnetic actuator, the structure and control of the exhaust device become complicated, and the weight and manufacturing cost of the exhaust device are complicated. There has been a problem that increases. In the exhaust device described in Patent Document 1, the noise increase is reduced by reducing the flow rate of the exhaust gas by the silencer valve and reducing the particle velocity of the standing wave of the air column resonance. There is a problem that a sufficient silencing effect cannot be obtained because the narrowing-down range is a structure.

The present invention has been made to solve the above-described conventional problems, and eliminates the need for installing a sub-muffler in the tail pipe and an opening / closing mechanism for an exhaust passage in the main muffler, and has a simple structure. It is an object of the present invention to provide an exhaust device capable of reducing the particle velocity of exhaust sound having a specific frequency due to air column resonance generated in the exhaust system, and reducing the weight and manufacturing cost.

In order to solve the above-described problems, an exhaust system according to the present invention is configured to allow the exhaust gas to flow from an introduction opening end that introduces exhaust gas of an internal combustion engine toward an exhaust opening end that exhausts the exhaust gas into the atmosphere. The exhaust device having an exhaust pipe having the exhaust pipe, wherein the exhaust passage is partitioned into a large passage having a large passage cross-sectional area and a small passage having a small passage cross-sectional area in a predetermined section along the flow direction of the exhaust gas. A partition member provided in the exhaust pipe, a communication member provided in the exhaust pipe located upstream in the exhaust direction of the section, and having a communication hole that connects the large passage and the exhaust passage; and the exhaust pipe By receiving only the swinging shaft attached to the wall portion of the wall and the exhaust flow flowing through the exhaust passage, the swinging shaft is swung around the swinging shaft so as to vary the flow rate of the exhaust gas flowing through the communication hole. Moving valve And having a, the.

With this configuration, the exhaust device according to the present invention eliminates the need for installing a sub-muffler in the tail pipe and installing an opening / closing mechanism for the exhaust passage in the main muffler, and by air column resonance generated in the exhaust system with a simple structure. The particle speed of the exhaust sound of a specific frequency is reduced, and the weight and manufacturing cost are reduced.

When the rotational speed of the internal combustion engine is relatively low, the valve body is in a closed state, and the exhaust gas is exhausted into the atmosphere through the small passage. The particle velocity is suppressed in the small passage. As a result, an increase in air column resonance excited in the exhaust pipe is suppressed.

In particular, since the small passage is formed in a predetermined section along the exhaust direction, the allowable range of the dimensional accuracy of the height of the small passage can be made relatively large, and the number of processing steps and assembly steps of the components are reduced. In addition, the yield of producing good products is increased. As a result, the manufacturing cost is reduced.

The conventional exhaust system has a structure in which there is no passage corresponding to a small passage, and an opening having a small cross-sectional area is simply formed. In this case, in order to increase the suppression of the particle speed of the exhaust sound, it is necessary to reduce the height of the small opening to about several millimeters and to form it with high accuracy. In the exhaust device according to the present invention, since the small passage is formed in a predetermined section along the exhaust direction, the necessity of forming with such high accuracy is eliminated.

When the rotational speed of the internal combustion engine is relatively high, the valve body is opened by the flow of exhaust gas, and the exhaust gas flows into the large passage through the communication hole and is exhausted into the atmosphere from the exhaust opening end. The As a result, the back pressure of the exhaust gas does not increase and the load on the internal combustion engine does not increase.

Further, the exhaust system according to the present invention has a sound pressure of the exhaust sound of the primary component and the secondary component having different specific frequencies due to the air column resonance generated in the exhaust system and the exhaust pipe which are particularly problematic in comparison with the conventional exhaust system. And reduced. As a result, the problem of noise such as a booming noise generated in the vehicle interior due to air column resonance of the exhaust device is solved. Since a control device and a sub-muffler for controlling a mechanism for reducing the sound pressure at the specific frequency are not required, the weight and manufacturing cost are reduced.

The exhaust device according to the present invention is preferably configured such that the partition member is provided in the exhaust pipe so that the exhaust direction downstream side of the section becomes the exhaust opening end.

With this configuration, in the exhaust device according to the present invention, the partition member is provided in the exhaust pipe so that the downstream side in the exhaust direction of the section is the exhaust opening end, so that the particles in the standing wave of air column resonance excited in the exhaust pipe This particle velocity can be reduced in the largest velocity range.

In the exhaust device according to the present invention, preferably, the length of the section in the flow direction of the exhaust gas is a downstream side that opens from an upstream opening end that opens to the upstream side of the exhaust pipe to a downstream side of the exhaust pipe. The length is approximately 1/4 of the length to the opening end.

With this configuration, the exhaust apparatus according to the present invention has an exhaust opening end on the downstream side in the exhaust direction of the section and an exhaust opening from an upstream opening end in which the length of the exhaust gas in the section opens on the upstream side of the exhaust pipe. Since it is formed with approximately ¼ of the length to the downstream opening end that opens to the downstream side of the tube, this particle has the largest particle velocity in the standing wave of air column resonance excited in the exhaust pipe. Speed can be reduced.

The exhaust device according to the present invention preferably includes a pressing member that presses the valve body against the communication member so as to close the communication hole when the flow rate of the exhaust gas flowing through the exhaust passage is relatively small. To do.

With this configuration, in the exhaust device according to the present invention, since the valve body presses the communication member by the pressing member, the communication hole of the connection member is reliably closed by the valve body. In particular, when the internal combustion engine with a small exhaust gas flow rate is rotated at a low speed, the communication hole is stably closed without being affected by the environment such as vibration of surrounding components.

According to the present invention, it is not necessary to install a sub-muffler in the tail pipe or an exhaust passage opening / closing mechanism in the main muffler, and an exhaust sound of a specific frequency due to air column resonance generated in the exhaust system with a simple structure. It is possible to provide an exhaust device that can reduce the particle velocity and reduce the weight and manufacturing cost.

It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a perspective view which shows the structure of an exhaust system. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a perspective view of the muffler which shows a part of muffler in cross section. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a side view of the muffler seen from the upstream. FIG. 4 is a view showing an embodiment of an exhaust device according to the present invention, and is a cross-sectional view of a muffler showing a cross section AA of FIG. 3. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a schematic diagram which shows the structure of the Helmholtz resonator which has a resonance pipe. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a perspective view of an outlet pipe. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a front view of the outlet pipe seen from the downstream of the flow direction of exhaust gas. FIG. 8 is a view showing an embodiment of the exhaust device according to the present invention, and is a cross-sectional view of the outlet pipe showing a BB cross section of FIG. 7. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a schematic diagram which shows the state of the particle velocity in the standing wave of the air column resonance of an outlet pipe. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a schematic diagram which shows the time passage of the particle velocity in the standing wave of air column resonance, and the state of a vibration. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a schematic diagram explaining opening end reflection and closing end reflection in the standing wave of air column resonance. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is sectional drawing which shows the flow state of the exhaust gas in a muffler at the time of low engine rotation. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is sectional drawing which shows the flow state of the exhaust gas in an outlet pipe at the time of low engine rotation. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is sectional drawing which shows the flow state of the exhaust gas in an outlet pipe at the time of high engine rotation. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a graph which shows the relationship between an engine speed and a sound pressure level. It is a figure which shows embodiment of the exhaust apparatus which concerns on this invention, and is a front view of the outlet pipe which has another structure seen from the downstream of the flow direction of exhaust gas. It is a figure which shows the exhaust system provided with the conventional exhaust apparatus, The upper part of a figure is a longitudinal cross-sectional view of the muffler which connected the sub muffler and the tail pipe, and the outlet pipe, and the center part of a figure generate | occur | produces in a tail pipe The mode of air column resonance is shown, and the lower part of the figure shows the mode of air column resonance generated in the exhaust system from the closed end of the front pipe to the open end of the outlet pipe. It is a figure which shows the exhaust system provided with the conventional exhaust apparatus, and is a longitudinal cross-sectional view of a sub muffler and a muffler.

1 to 15 are views showing an embodiment of an exhaust device according to the present invention, and the configuration of the exhaust device 20 according to the embodiment will be described with reference to the drawings.

As shown in FIG. 1, the exhaust device 20 according to the embodiment is connected to an engine 10 as an in-line four-cylinder internal combustion engine, and is configured to purify exhaust gas discharged from the engine 10 and discharge it to the atmosphere. Has been. The exhaust device 20 further reduces the particle velocity of standing waves in the air column resonance generated inside. That is, the increase in the sound pressure of the exhaust sound generated by the air column resonance is suppressed.

The engine 10 includes an engine main body 11 serving as a drive source for the vehicle, and an exhaust manifold 12 that distributes exhaust gas discharged from the engine main body 11. The engine 10 is not limited to the in-line 4 cylinders, and may be configured by in-line 3 cylinders or in-line 5 cylinders or more, and is configured by a V-type engine having 3 or more cylinders in each bank divided into left and right. May be.

The exhaust manifold 12 includes four

exhaust branch pipes

12a, 12b, 12c, and 12d connected to exhaust ports communicating with the first to fourth cylinders of the engine body 11, and

exhaust branch pipes

12a, 12b, 12c, The exhaust collecting pipe 12e collects the downstream side of 12d. The exhaust gas exhausted from each cylinder of the engine 10 is introduced into the exhaust collecting pipe 12e through the

exhaust branch pipes

12a, 12b, 12c, and 12d.

The exhaust device 20 includes a catalytic converter 21 including

catalytic converters

21a and 21b, a front pipe 23 connected to the catalytic converter 21a via a universal joint 22, and an exhaust pipe connected to the catalytic converter 21b via a universal joint 24. The tail pipe 25 and a muffler 30 as a silencer connected to the tail pipe 25 are provided. The exhaust device 20 is installed on the downstream side of the engine 10 so as to be elastically suspended below the floor of the vehicle. The upstream side indicates the upstream side in the exhaust direction of the exhaust gas discharged from the engine 10, and the downstream side indicates the downstream side in the exhaust direction of the exhaust gas.

The

catalytic converters

21a and 21b are each formed by attaching a catalyst such as platinum or palladium to a honeycomb base material or a granular activated alumina support, and have a main body case for storing them. The catalytic converter 21a connected to the downstream end of the exhaust collecting pipe 12e at the upstream end and the catalytic converter 21b connected to the tail pipe 25 at the downstream end respectively reduce NOx in the exhaust gas exhausted from the exhaust collecting pipe 12e. And CO and HC are oxidized.

The universal joint 22 is composed of a spherical joint such as a ball joint, and allows relative displacement between the catalytic converter 21 a and the front pipe 23. Similarly to the universal joint 22, the universal joint 24 is formed of a spherical joint such as a ball joint, and allows relative displacement between the catalytic converter 21 b and the tail pipe 25.

The front pipe 23 is formed in a cylindrical shape, and has an exhaust passage 23b through which exhaust gas discharged from the catalytic converter 21a is introduced from the introduction opening end 23a and flows to the catalytic converter 21b.

As shown in FIG. 1, the tail pipe 25 is also formed in a cylindrical shape like the front pipe 23, and has an upstream opening end through which exhaust gas discharged from the exhaust passage 25a and the catalytic converter 21b flows into the exhaust passage 25a. 25b and the downstream opening end 25c which discharges | emits exhaust gas. The downstream opening end 25 c is formed in the inlet pipe portion 25 </ b> A of the tail pipe 25 inserted into the muffler 30.

As shown in FIGS. 2 to 4, the muffler 30 includes a muffler body 31, a separator 32, an inlet pipe portion 25A constituting a part of the tail pipe 25, and an outlet pipe 33 as an exhaust pipe. Has been. The exhaust gas flowing into the muffler main body 31 from the inlet pipe portion 25A is discharged from the outlet pipe 33, and the exhaust sound is muted in the muffler main body 31.

The muffler body 31 includes an outer shell 41 formed in a cylindrical shape, an end plate 42 that closes both ends of the outer shell 41 to define an internal space, and an end plate 43. The

end plates

42 and 43 are respectively fixed to the outer shell 41 by fixing means such as caulking so that the exhaust gas does not leak from the internal space to the outside.

A separator 32 is interposed between the end plate 42 and the end plate 43. The separator 32 partitions the internal space in the muffler main body 31 into an expansion chamber 30A located on the upstream side in the exhaust direction and a resonance chamber 30B located on the downstream side in the exhaust direction of the expansion chamber 30A.

2 to 4, the end plate 42 is formed with an insertion hole 42a, and the separator 32 is formed with

insertion holes

32a and 32b. An inlet pipe portion 25A is inserted through these

insertion holes

42a and 32a. Further, through holes 43a are formed in the end plate 43, and the outlet pipe 33 is inserted through these through

holes

32b and 43a.

As shown in FIGS. 2 and 4, the inlet pipe portion 25A has a plurality of communication holes 25d that allow the exhaust passage 25a and the expansion chamber 30A to communicate with each other. Exhaust gas flows into the expansion chamber 30A from the communication hole 25d. Further, exhaust gas flows from the downstream opening end 25c of the inlet pipe portion 25A into the resonance chamber 30B.

Here, the expansion chamber generally has a relatively large cross-sectional area (mm ²⁾ with respect to the cross-sectional area of the exhaust passage in the inlet pipe in the muffler (mm ^2), provided with a predetermined volume (mm ³⁾ It consists of hollows.
In the expansion chamber, when the exhaust gas flows into the expansion chamber from the exhaust passage, the volume of the exhaust gas is rapidly expanded, the pressure fluctuation due to the exhaust pulsation is weakened, and the sound pressure level (dB) of the exhaust sound is reduced. Thus, the so-called expansion effect is obtained in which the frequency is reduced over a wide frequency band.

The resonance chamber is a cavity having a predetermined volume (mm ³ ) so as to resonate an exhaust sound having a specific frequency (Hz) using the so-called Helmholtz resonance principle. As schematically shown in FIG. 5, the resonance chamber is connected to a resonance pipe p having a so-called neck portion having an introduction passage b, and is formed in the resonance member so as to communicate with the introduction passage b. Inside, the exhaust sound of a specific frequency resonates.

The specific frequency is f (Hz), the sectional area of the resonance pipe p is S (mm ² ), the length of the resonance pipe p, that is, the distance of the introduction passage b is L (mm), and the volume of the cavity h is V ( mm ³ ), and c is the speed of sound in air (m / s), the specific frequency f is known to be represented by the following formula (1).

In this case, if the frequency (Hz) of the exhaust sound propagating from the introduction passage b to the cavity h coincides with f, the exhaust sound resonates in the cavity h. When resonance occurs in the cavity h, air vibrates vigorously in the branch passage b of the resonance pipe p, and vibration energy is converted into heat energy and attenuated due to friction with the inner wall of the resonance pipe p. As a result, the resonant exhaust noise is reduced.

The specific frequency f is a frequency that substantially matches the frequency of the air column resonance that occurs in the exhaust system of the embodiment when the engine speed Ne (rpm) is relatively low, and in the exhaust system mode shown in the lower part of FIG. The sound pressure of the air column resonance is set to be reduced by Helmholtz resonance in the muffler 30.

6 to 8, the outlet pipe 33 includes a circular pipe portion 51 having a circular outer periphery and a square pipe portion 52 having a rectangular outer periphery. The circular pipe portion 51 is configured by a circular pipe connected to the square pipe portion 52. The circular pipe portion 51 includes an expansion chamber opening end 51a that opens in the expansion chamber 30A, a communication opening end 51b that opens to communicate with the rectangular pipe portion 52, and an expansion chamber opening end 51a and a communication opening end 51b. And an exhaust passage 51c through which the exhaust gas flows.

The rectangular pipe portion 52 includes a rectangular pipe main body 61, a partition member 62, a communication member 63, a swing shaft 64, and a valve body 65.

The square pipe body 61 has a connection end 61a as an upstream opening end connected to the circular pipe portion 51 and an atmosphere opening end 61b that opens to the atmosphere as an exhaust opening end, and the connection end 61a and the atmosphere opening end 61b. And an exhaust passage 61c through which the exhaust gas flows. The connecting end 61 a has a wall portion 61 d and a through hole 61 e formed so as to penetrate the wall portion 61 d, and the exhaust gas in the exhaust passage 51 c penetrates from the communication opening end 51 b of the circular pipe portion 51. It flows into the exhaust passage 61c through the hole 61e.

The partition member 62 is formed of a plate material, and is attached to the inside of the rectangular pipe body 61 so as to partition the exhaust passage 61c into a large passage 61f having a large passage sectional area and a small passage 61g having a small passage sectional area. Small passage 61g partitioned by the partition member 62, as shown in FIG. 8, the length from the inlet 62a to the outlet 62b is formed in _{L 1,} the lower surface of the bottom surface 61t and the partition member 62 of the square pipe body 61 62c length up are formed by L _2.

The length _{L 1} is the expansion chamber opening end 51a of the outlet pipe 33 shown in FIG. 4, and the length between the atmosphere opening end 61b and _L, L 1 = (1/4) are formed by L Yes. Further, as shown in FIG. 9, the length L ₁ is substantially the same as the length La of the high-particle velocity region of the standing wave of the air column resonance generated in the exhaust passage 61c of the outlet pipe 33. ing. This length La is ８ of the wavelength λ of the standing wave when a standing wave due to air column resonance is formed in the outlet pipe 33. In this region, the particle velocity is high. For this reason, it is more preferable that the small passage described above is provided in the region indicated by the length La so that the particle velocity can be reduced.

In FIG. 9, a curve indicated by a substantially parabolic curve a represents the magnitude of the particle velocity in the standing wave of the air column resonance of the exhaust pipe whose both ends are open ends. The particle velocity is a minimum of zero and maximum at both ends. Moreover, the direction of the white arrow represents the direction of particle velocity, and represents that open end reflection occurs at the open ends of both ends.

It is known that the particle velocity at each position in the exhaust pipe is oscillating so that the gas in the exhaust pipe enters and exits as shown in FIG. 10, and FIG. The minimum portion is shown as a curve and an arrow.

Hereinafter, the open end reflection and the closed end reflected wave in the outlet pipe 33 will be described with reference to FIG. For example, a case where an incident wave G due to exhaust pulsation during operation of the engine 10 is incident on the outlet pipe 33 and the wavelength of the incident wave G is an incident wave G having the tube length L of the outlet pipe 33 as a half wavelength will be described. .

As shown in FIG. 11, the incident wave G is the air opening end 61b of the small passage 61g of the outlet pipe 33, both the transmitted wave G ₁ is being transmitted to the air, the expansion chamber opening end 51a from the atmosphere opening end 61b A reflected wave R ₁ (open end reflected wave) indicated by a solid line is reflected. Further, the incident wave G is towards the expansion chamber opening end 51a in the valve body 65 in the closed position reflected waves indicated by a broken line (closed end reflection wave) R ₂ is reflected.

The reflected wave R ₁ is an open end reflected wave having the same phase as the incident wave G, and the reflected wave R ₂ is a closed end reflected wave having a phase difference of 180 degrees with respect to the incident wave G. In FIG. 11, the reflected wave R ₁ has the same phase as the incident wave G, and therefore the incident wave G and the reflected wave R ₁ overlap. However, for convenience of explanation, the reflected wave R _{1 is changed} to the incident wave G. The reflected wave R ₂ corresponding to this is also drawn with the horizontal line of phase 0 as the center.

Thus, since the reflected wave R ₁ is in phase with the incident wave G, when the frequency of the incident wave G becomes the air column resonance frequency of the outlet pipe 33, mutual interference occurs between the incident wave G and the reflected wave R _1. The sound pressure level of the exhaust sound is increased.

On the other hand, since the reflected wave R ₂ is 180 degrees out of phase with the reflected wave R ₁ and the incident wave G, they cancel each other and the sound pressure level of the exhaust sound is reduced. For example, as shown in FIG. 15, when the frequency of the incident wave G due to the exhaust pulsation becomes the primary component f ₁ of the air column resonance frequency of the outlet pipe 33, the interference due to the reflected wave R ₁ that is the open end reflected wave alone is As indicated by the broken line, the sound pressure level increases (becomes maximal). In contrast, due to the presence of interference due to the reflected wave R ₂ is a closed end reflected wave, as shown by the solid line, increase in the sound pressure level due to air column resonance is suppressed, greatly sound pressure level of exhaust sound Reduced to

Similarly, when the frequency of the incident wave G due to the exhaust pulsation becomes the secondary component f ₂ of the air column resonance frequency of the outlet pipe 33, the sound due to the interference of the reflected wave R ₁ that is the open end reflected wave an increase in the pressure level, is suppressed by the interference of the reflected wave R ₂ is a closed end reflection wave, the sound pressure level of exhaust noise can be greatly reduced.

Here, in the above description, when the small passage 61g at the atmospheric opening end 61b is made considerably smaller than the opening area of the exhaust passage 61c, for example, by 1/3 or less, the sound pressure level due to air column resonance is most suppressed. . Further, as shown in FIG. 8, has a small passage 61g of the length of the length L ₁ of the section along the flow direction of exhaust gas, as described above, the length L _1, the exhaust passage 61c of the outlet pipe 33 In the region where the particle velocity of the standing wave of the air column resonance generated in the region is almost the same as the length La shown in FIG. 9, the particle velocity is suppressed in the section of the region where the particle velocity is high. Become.

The communication member 63 is formed of a plate material, and is attached to the inside of the rectangular pipe main body 61 so as to be located upstream of the partition member 62 in the exhaust direction. The communication member 63 includes a communication hole 63a that connects the large passage 61f and the exhaust passage 51c, and the exhaust gas in the exhaust passage 61c flows into the large passage 61f through the communication hole 63a. It has become.

The rocking shaft 64 is made of a cylindrical bar and has one end 64a and the other end 64b. The one end portion 64 a and the other end portion 64 b are directly attached to a wall portion 61 h adjacent to the communication member 63 of the rectangular pipe body 61 so as to be swingable. In addition, the structure by which the one end part 64a and the other end part 64b are attached to the wall part 61h of the square pipe main body 61 via bearings, such as an oil-impregnated bearing, so that the rocking | fluctuation shaft 64 may rock | fluctuate more smoothly.

The valve body 65 is formed of a plate material and includes a main body 65a and a swinging portion 65b. The main body 65 a is formed in a size that can close the communication hole 63 a of the communication member 63. The oscillating portion 65 b is attached to the oscillating shaft 64. The swinging portion 65 b may be supported by the swinging shaft 64 so as to swing freely, or may be fixed to the swinging shaft 64.

The valve body 65 is configured to vary the flow rate of the exhaust gas flowing through the communication hole 63a by receiving only the exhaust flow flowing through the exhaust passage 61c. When the exhaust gas does not flow in the exhaust passage 61c and when the flow rate of the exhaust gas is small, the valve body 65 is in a state of closing the communication hole 63a. The valve body 65 is configured such that the degree of opening increases as the flow rate of the exhaust gas in the exhaust passage 61c increases, and the amount of exhaust gas passing through the communication hole 63a increases as the degree of opening increases. .

Specifically, the exhaust system described above includes the exhaust manifold 12, the catalytic converter 21a, the front pipe 23, the catalytic converter 21b, the tail pipe 25, the muffler 30, the outlet from the position of the closed exhaust valve in the engine 10 shown in FIG. This refers to the entire path of exhaust gas flowing through the pipe 33. The air column resonance generated in the exhaust system is excited between the closed end of the closed exhaust valve and the atmospheric opening end 61b of the square pipe portion 52 of the outlet pipe 33 that opens to the atmosphere, and the mode shown in the lower part of FIG. It becomes.

Next, the operation and action of the exhaust device 20 will be described.

First, when the engine 10 on the upstream side of the exhaust device 20 shown in FIG. 1 is started, the exhaust gas exhausted from each cylinder of the engine 10 is introduced from the exhaust manifold 12 to the catalytic converter 21, and the catalytic converter 21 performs NOx. Exhaust gas purification such as reduction of CO and oxidation of CO and HC is performed. The purified exhaust gas is introduced into the inlet pipe portion 25A through the tail pipe 25.

A part of the exhaust gas introduced into the inlet pipe portion 25A flows into the expansion chamber 30A from the exhaust passage 25a through the communication hole 25d as indicated by an arrow in FIG. At this time, the sound pressure level (dB) of the exhaust sound is reduced over a wide frequency band due to the above-described expansion effect. The exhaust gas in the expansion chamber 30A is exhausted from the expansion chamber opening end 51a of the outlet pipe 33 through the exhaust passage 51c to the atmosphere from the atmosphere opening end 61b.

Further, the exhaust gas in the exhaust passage 25a flows into the resonance chamber 30B from the downstream opening end 25c. When the frequency of the exhaust sound of the inflowing exhaust gas matches the set specific frequency, Helmholtz resonance is excited in the resonance chamber 30B, and the sound pressure of air column resonance generated in the exhaust system is reduced.

When the engine rotational speed Ne (rpm) is relatively low, as shown in FIG. 13, the valve body 65 is closed by its own weight, and the exhaust gas flowing through the exhaust passage 51c flows from the inlet 62a. It flows into the small passage 61g and is exhausted into the atmosphere from the outlet 62b.

Further, as described above, the incident wave of the exhaust sound propagating in the exhaust passage 51c is reflected at the closed end by the valve body 65 in the closed state, and proceeds in the upstream direction of the exhaust gas. Simultaneously with this closed end reflection, the incident wave of the exhaust sound is reflected at the opening end at the inlet 62a of the small passage 61g and proceeds in the upstream direction of the exhaust gas. Since the reflected waves of the closed-end reflection and the open-end reflection are different in phase by 180 degrees as described above, they cancel each other and the sound pressure level of the exhaust sound is reduced.

And since the particle velocity of the exhaust sound traveling in the small passage 61g is suppressed in the small passage 61g, an increase in air column resonance is suppressed. As described above, the outlet pipe 33 reduces the sound pressure level (dB) of the primary components f ₁ and f ₂ of the specific frequency that are particularly problematic as shown in FIG.

When the engine speed Ne (rpm) is relatively high, as shown in FIG. 14, the valve body 65 is opened by the exhaust gas flowing through the exhaust passage 51c, passes through the communication hole 63a, and enters the large passage 61f. And is exhausted into the atmosphere from the atmosphere opening end 61b. Similarly to when the engine speed Ne is relatively low, the exhaust gas flowing in the exhaust passage 51c flows into the small passage 61g from the inlet 62a and is exhausted into the atmosphere from the outlet 62b.

Therefore, when the engine speed Ne (rpm) is relatively high, the valve body 65 opens, so that the back pressure of the exhaust gas does not increase and the load on the engine 10 does not increase.

Next, effects of the exhaust device 20 according to the embodiment will be described.

Since the exhaust device 20 is configured as described above, the following effects can be obtained.

That is, the exhaust device 20 includes the muffler 30, and the muffler 30 includes an outlet pipe 33 having an exhaust passage 61c. The exhaust passage 61c is divided into a large passage 61f having a large passage sectional area and a small passage 61g having a small passage sectional area. A partition member 62 for partitioning, a communication member 63 having a communication hole 63a for communicating the large passage 61f and the exhaust passage 61c, a swinging shaft 64 attached to the wall portion 61h of the outlet pipe 33, and a communication hole 63a. And a valve body 65 that swings about a swing shaft 64 so as to vary the flow rate of the exhaust gas flowing through the exhaust gas.

Formed with the outlet 62b of the small passage 61g is positioned in the atmosphere opening end 61b of the outlet pipe 33, the length _{L 1} of the small passage 61g is, in the

exhaust passage

51c, 1/4 of the length L of the 61c of the outlet pipe 33 Has been.

As a result, in the exhaust device 20, it is not necessary to install a sub-muffler in the tail pipe or an exhaust passage opening / closing mechanism in the main muffler, and at a specific frequency due to air column resonance generated in the exhaust system with a simple structure. The particle speed of the exhaust sound can be reduced, and the weight and manufacturing cost can be reduced.

The sound pressure of the exhaust sound propagating from the engine 10 can be reduced in the expansion chamber 30A of the muffler 30 over a wide frequency band other than the specific frequencies f ₁ and f ₂ described above. effective.

That is, in the expansion chamber 30A, when exhaust gas flows into the expansion chamber 30A through the communication hole 25d of the inlet pipe portion 25A, the sound pressure is reduced over a wide frequency band due to the expansion effect. The effect that it can do is acquired.

In the resonance chamber 30B, when the exhaust gas flows into the resonance chamber 30B through the downstream opening end 25c of the inlet pipe portion 25A, if the frequency of the exhaust sound matches the specific frequency, the Helmholtz resonance occurs in the resonance chamber 30B. Can be excited, and the sound pressure level at the air column resonance peak of the exhaust system can be reduced.

When the engine speed Ne is relatively low, the valve body 65 is closed, and the exhaust gas is exhausted into the atmosphere through the small passage 61g. Therefore, the exhaust gas traveling in the small passage 61g is exhausted. The sound particle velocity can be significantly suppressed in the small passage 61g. As a result, an increase in air column resonance excited in the outlet pipe 33 is remarkably suppressed.

In particular, since a small passage 61g is formed in a length L ₁ along the exhaust direction, it is possible to relatively increase the height tolerance of dimensional accuracy of L ₂ of the small passage 61g, processing steps or assembling steps Can be reduced, and the yield of producing good products can be increased, and as a result, the manufacturing cost can be reduced.

The conventional exhaust device has a structure in which there is no passage corresponding to the small passage 61g, and an opening having a small cross-sectional area is simply formed. In this case, in order to increase the suppression of the particle speed of the exhaust sound, it is necessary to reduce the height of the small opening to about several millimeters and to form it with high accuracy. The exhaust device 20 according to the embodiment has an effect that the necessity of forming with such high accuracy is eliminated.

When the engine speed Ne is relatively high, the valve body 65 is opened due to the flow of exhaust gas, and the exhaust gas flows into the large passage 61f through the communication hole 63a, and enters the atmosphere from the atmospheric opening end 61b. Exhausted. As a result, the back pressure of the exhaust gas does not increase, and the effect that the load on the engine 10 does not increase is obtained.

Further, in the exhaust device 20, as shown in FIG. 15, the exhaust sound of the primary component f ₁ and the secondary component f _{2 having} different specific frequencies due to air column resonance generated in the exhaust system and the tail pipe 25 which are particularly problematic. Sound pressure can be significantly reduced compared to conventional exhaust systems. As a result, it is possible to obtain an effect that noise problems such as a booming noise generated in the passenger compartment due to air column resonance of the exhaust device are solved. In addition, since a control device and a sub-muffler for controlling a mechanism for reducing the sound pressure at the specific frequency are not required, an effect that the weight and manufacturing cost can be significantly reduced is obtained.

In addition, in the exhaust apparatus 20 of embodiment, the case where the outlet pipe 33 was comprised with the square pipe part 52 by which the outer periphery was formed in the square was demonstrated.

However, in the exhaust device of the present invention, the outlet pipe may be configured with a shape and structure other than the rectangular pipe portion 52 of the embodiment. For example, as shown in FIG. 16, the outlet pipe 70 is configured by a pipe portion 72 whose upper part of the outer periphery is square and whose lower part is semicircular, and the valve body 65 is pressed against the communication member 63. Also good.

The pipe portion 72 includes a pipe body 81, a partition member 82, a communication member 83, the swing shaft 64 of the embodiment, a valve body 85, and a pressing member 86, and the rectangular pipe portion 52 of the embodiment. It is constituted similarly.

The pipe body 81 has an upper part formed in a square shape and a lower part formed in a semicircular shape, and the other structure is the same as that of the square pipe part 52. The partition member 82 is formed of a semicircular plate material, and is attached to the inside of the pipe body 81 so as to partition the exhaust passage into a large passage 81f having a large passage sectional area and a small passage 81g having a small passage sectional area. .

The communication member 83 is formed of a plate material having a rectangular upper part and a semicircular lower part, and is attached to the inside of the pipe body 81 so as to be located upstream of the partition member 82 in the exhaust direction. The communication member 83 includes a communication hole 83a through which exhaust gas flows into the large passage 81f. The exhaust gas in the exhaust passage flows into the large passage 81f through the communication hole 83a. .

The valve body 85 is formed of a plate material having a square upper part and a semicircular lower part, and the other structure is configured in the same manner as the valve body 65 of the embodiment.

The pressing member 86 is composed of, for example, a coil spring provided at the other end portion 64 b of the swing shaft 64, and is configured to press the valve body 85 against the communication member 83. Further, as another structure of the pressing member 86, a weight may be provided at the lower portion of the valve body 65, and the valve body 85 may be pressed against the communication member 83 by this weight.

With this configuration, the same effect as the outlet pipe 33 of the embodiment can be obtained in the outlet pipe 70. In other words, installation of a sub-muffler on the tail pipe and installation of an exhaust passage opening / closing mechanism on the main muffler are not required, and the particle velocity of exhaust sound with a specific frequency due to air column resonance generated in the exhaust system is reduced with a simple structure. It is possible to reduce the weight and manufacturing cost. The communication hole 83a of the communication member 83 can be reliably closed by the valve body 65, and the valve body 65 can be stably maintained closed when the flow rate of the exhaust gas is small.

As shown in FIGS. 2 and 4, in the exhaust device 20 of the embodiment, the partition member 62 of the rectangular pipe portion 52 of the outlet pipe 33 is configured such that the end portion thereof is positioned at the atmospheric opening end 61 b. explained.

However, in the exhaust device of the present invention, the end of the partition member that partitions the exhaust passage into the large passage and the small passage may be positioned at the other opening end. That is, it can be configured such that the end of the partition member is arranged at a position where the particle velocity in the standing wave of air column resonance generated in the exhaust system becomes high.

For example, you may comprise so that the edge part of a partition member may be located in the expansion chamber opening end 51a opened to the expansion chamber 30A of the outlet pipe 33 shown in FIG. 4 which concerns on embodiment. Moreover, you may comprise so that the edge part of a partition member may be located in the upstream opening end 25b of the tail pipe 25 shown in FIG. 1 which concerns on embodiment.

In the exhaust system 20 of the embodiment, the length of the small passage 61g of the inlet 62a partitioned by the partition member 62 to an outlet 62b formed in _{L 1,} the expansion chamber opening end 51a of the outlet pipe 33, air The case where L ₁ = (1/4) L has been described, where L is the length between the open end 61b.

However, in the exhaust system of the present invention, it may be formed the length L ₁ (1/4) the length of the non-L. For example, the standing of the columnar resonance generated in the exhaust system, the outlet pipe, and the tail pipe in a predetermined range, such as L ₁ = (1/2) L to L ₁ = (1/10) L. The length L ₁ may be selected as appropriate depending on the range of particle velocities in the wave.

As described above, the exhaust device according to the present invention eliminates the need for installing a sub-muffler in the tail pipe and installing an opening / closing mechanism for the exhaust passage in the main muffler, and has an air column generated in the exhaust system with a simple structure. Since the particle velocity of the exhaust sound having a specific frequency due to resonance can be reduced, and the weight and manufacturing cost can be reduced, the exhaust device is useful in general.

10 Engine (Internal combustion engine)
20 exhaust device 23a introduction opening end 23b exhaust passage 25 tail pipe (exhaust pipe)
25A Inlet pipe section (exhaust pipe)
25a Exhaust passage 25b Upstream opening end 25c Downstream opening end 30 Muffler

30A Expansion chamber

30B Resonance chamber

33, 70 Outlet pipe (exhaust pipe)
51 circular pipe portion 51a expansion chamber opening end 51b

communication opening end

51c, 61c exhaust passage 52 rectangular pipe portion 61 rectangular pipe body 61b atmospheric opening end (exhaust opening end)
61f, 81f

Large passage

61g, 81g

Small passage

62, 82

Partition member

63, 83 Communication member 64

Oscillating shaft

65, 85 Valve body 72 Pipe portion 81 Pipe body 86 Press member L ₁ Length (section)

Claims

An exhaust system comprising an exhaust pipe having an exhaust passage for circulating the exhaust gas from an introduction opening end for introducing exhaust gas of an internal combustion engine toward an exhaust opening end for exhausting the exhaust gas into the atmosphere,
A partition member provided in the exhaust pipe so as to partition the exhaust passage into a large passage having a large passage sectional area and a small passage having a small passage sectional area in a predetermined section along the flow direction of the exhaust gas;
A communication member provided in the exhaust pipe located on the upstream side of the section in the exhaust direction, and having a communication hole for communicating the large passage and the exhaust passage;
A swing shaft attached to the wall of the exhaust pipe;
A valve body that swings about the swing shaft so as to vary the flow rate of the exhaust gas that flows through the communication hole by receiving only the exhaust flow that flows through the exhaust passage;
An exhaust system for an internal combustion engine, comprising:
The exhaust system for an internal combustion engine according to claim 1, wherein the partition member is provided in the exhaust pipe so that a downstream side in the exhaust direction of the section becomes the exhaust opening end.
The length of the section in the flow direction of the exhaust gas is approximately ¼ of the length from the upstream opening end that opens to the upstream side of the exhaust pipe to the downstream opening end that opens to the downstream side of the exhaust pipe. The exhaust device for an internal combustion engine according to claim 1 or 2, wherein the exhaust device is an internal combustion engine.
2. The internal combustion engine according to claim 1, further comprising a pressing member that presses the valve body against the communication member so as to close the communication hole when the flow rate of the exhaust gas flowing through the exhaust passage is relatively small. Engine exhaust system.