JP5044631B2 - Exhaust device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust system for an internal combustion engine, and more particularly to an exhaust system for an internal combustion engine that suppresses exhaust noise caused by air column resonance in an exhaust pipe provided at the most downstream in the exhaust direction of exhaust gas.

  As an exhaust device for an internal combustion engine used in a vehicle such as an automobile, one as shown in FIG. 36 is known (for example, see Patent Document 1). In the exhaust device 4 shown in FIG. 36, exhaust gas exhausted from the engine 1 as an internal combustion engine to the exhaust manifold 2 is purified by the catalytic converter 3 and then introduced from the catalytic converter 3.

  The exhaust device 4 includes a front pipe 5 connected to the catalytic converter 3, a center pipe 6 connected to the front pipe 5, a main muffler 7 as a silencer connected to the center pipe 6, a tail pipe 8 connected to the main muffler 7, and a tail The sub muffler 9 is interposed in the pipe 8.

  The main muffler 7 is provided with an expansion chamber for expanding and silencing exhaust gas inside and a resonance chamber for silencing exhaust sound of a specific frequency by Helmholtz resonance. Specifically, the resonance frequency can be tuned to the low frequency side by increasing the volume of the resonance chamber or increasing the protruding length of the center pipe 6 protruding into the resonance chamber. On the other hand, the resonance frequency can be tuned to the high frequency side by reducing the volume of the resonance chamber or shortening the length of the protruding portion of the center pipe 6 protruding into the resonance chamber.

  When the air column resonance corresponding to the length of the tail pipe 8 is generated in the tail pipe 8 due to exhaust pulsation during operation of the engine 1, the sub muffler 9 reduces the sound pressure level of the air column resonance. Yes.

In general, in a pipe having an upstream opening end and a downstream opening end on the upstream side and downstream side of the exhaust gas in the exhaust direction, incident waves due to exhaust pulsation during engine operation are reflected at the upstream opening end and the downstream opening end of the pipe. Thus, it is known that air column resonance having a frequency that is a natural number multiple of the half wavelength is generated with air column resonance having a frequency with the pipe length of the half wavelength as a basic component.
For example, when the tail pipe 8 not provided with the sub-muffler 9 extends rearward from the main muffler 7, the wavelength λ 1 of the air column resonance of the fundamental vibration (primary component) is the tube length L of the tail pipe 8. Therefore, the wavelength λ2 of air column resonance of the secondary component is substantially 1 time of the tube length L.
Further, the wavelength λ3 of the air column resonance of the third-order component is 2/3 times the tube length L, and the upstream opening end and the downstream opening end in the tail pipe 8 become constant nodes of the sound pressure distribution of the standing wave. You can be there.

  The frequency fm (Hz) of air column resonance in the tail pipe 8 is expressed by the following formula (1).

fm = (c / 2L) · m (1)
Here, c represents the speed of sound (m / sec), L represents the length of the tail pipe (m), and m represents the order.
As is clear from the above equation (1), the longer the pipe length L of the tail pipe 8, the more the frequency fm shifts to a low frequency region where the engine speed (rpm) is lower.
Further, the frequency of the exhaust pulsation of the engine 1 increases as the rotational speed of the engine 1 increases, and the primary component and the second exhaust sound due to air column resonance corresponding to the rotational speed of the engine 1 are increased. It is known that the sound pressure level (dB) of the exhaust sound increases with the next component.

Therefore, for example, when a long tail pipe 8 having a pipe length of 1.5 m or more is used, air column resonance may occur in a normal rotation region where the engine speed Ne is low, and exhaust noise deteriorates. As a result, the driver feels uncomfortable.
For this reason, when the pipe length of the tail pipe 8 is long, it is a part of the antinode of the standing wave having a high sound pressure level and the antinodes of the primary and secondary components of the exhaust sound due to the air column resonance. By providing a sub-muffler 9 having a capacity smaller than that of the main muffler 7 at an optimal position, exhaust noise is suppressed in the normal rotation range of the engine 1 to prevent the driver from feeling uncomfortable. .

  On the other hand, by adjusting the resonance frequency of the resonance chamber of the main muffler 7 connected to the upstream opening end of the tail pipe 8 to the air column resonance frequency of the tail pipe 8, the air column resonance of the tail pipe 8 is performed in the resonance chamber of the main muffler 7. It is possible to mute the sound.

  That is, by increasing the volume of the resonance chamber or by increasing the length of the protruding portion of the center pipe 6 to tune the resonance frequency of the resonance chamber to the low frequency side, the tail pipe 8 It is conceivable to silence the air column resonance generated in the chamber in the resonance chamber in advance.

  However, since the throttle valve is closed when the vehicle decelerates, only the exhaust flow in which the amount of gas exhausted from the engine 1 to the exhaust device 4 is rapidly reduced becomes only the air pressure introduced into the resonance chamber. For this reason, an air amount sufficient to perform Helmholtz resonance cannot be obtained in the resonance chamber, and it becomes difficult to suppress air column resonance of the tail pipe 8. In particular, when the vehicle is decelerating in a high rotation speed range, the engine 1 rapidly decreases in rotational speed. Therefore, a primary component of exhaust sound due to air column resonance enters the normal rotation speed area of the engine 1, and the vehicle interior is reduced at a low speed. A squeaky sound may be generated, which causes discomfort to the driver.

  An exhaust device that includes a pair of valves that open and close an exhaust pipe is known as a means for suppressing such exhaust noise during deceleration or low speed (for example, see Patent Document 2).

The exhaust device includes a pair of rotating plates that are rotatably provided in a cylindrical housing as a tail pipe, a pair of arms connected to these rotating plates, and a pair of these arms. Both ends are connected to each other, and include an arm that rotates a pair of rotating plates in conjunction with each other, and a spring that connects one arm and the cylindrical housing.
In this exhaust device, the pair of rotating plates are urged by the spring so as to be in a position to substantially close the exhaust passage in the cylindrical housing. With this configuration, when the engine rotates at a low speed, the exhaust gas is discharged through the gap between the inner wall of the cylindrical housing and the rotating plate, and the engine exhaust noise is reduced. On the other hand, when the engine rotates at a high speed, the flow rate of the exhaust gas increases, and the pair of rotating plates rotate in conjunction with the elastic force of the spring to open the exhaust passage. Are discharged without resistance.

JP 2006-46121 A JP 2001-342827 A

  However, in such a conventional exhaust system of the engine 1, in the configuration in which the air column resonance of the tail pipe 8 is reduced by the resonance chamber of the main muffler 7, the volume of the resonance chamber needs to be increased. There is a problem that the main muffler 7 is enlarged. Further, as the main muffler 7 is increased in size, the weight of the exhaust device increases, and the manufacturing cost of the exhaust device increases.

Further, in the exhaust device having a pair of rotating plates in the cylindrical housing, the exhaust gas is discharged through a gap in which the cross-sectional area of the exhaust passage between the inner wall of the cylindrical housing and the rotating plate is narrowed. Therefore, the exhaust noise in the wide frequency range of the engine is reduced to some extent.
However, since the air column resonance of the cylindrical housing is not taken into consideration, it is insufficient to reduce the sound pressure level of the exhaust sound increased by the air column resonance generated at a specific frequency.
In addition, since the pair of rotating plates are urged by the spring so as to be in a position that substantially closes the exhaust passage in the cylindrical housing, when the engine rotates at high speed, it resists the elastic force of the spring. There was a problem that the rotating plate had to be rotated, and the back pressure increased and an extra load was applied to the engine.
In addition, since the pair of rotation plates are configured to rotate in conjunction with each other, the pair of arms connected to the rotation plates, the arm that rotates the pair of rotation plates in conjunction with each other, and a spring are used. However, there has been a problem that the manufacturing cost of the exhaust device increases.

  The present invention has been made in order to solve the above-described conventional problems. The sound pressure level is reduced by the tail column air column resonance with a simple configuration while reducing the increase in weight and the increase in manufacturing cost. It is an object of the present invention to provide an exhaust device for an internal combustion engine that can reliably suppress the increase.

  In order to solve the above problems, an exhaust system for an internal combustion engine according to the present invention is (1) provided on the downstream side in the exhaust direction of the internal combustion engine, and has a downstream opening end that exhausts the exhaust gas of the internal combustion engine into the atmosphere. An exhaust system having an exhaust pipe having an upstream open end for introducing the exhaust gas on the upstream side in the exhaust direction and having a first swing shaft attached to an upper portion of the exhaust pipe A first valve body that swings about the first swing shaft so as to vary the size of the passage cross-sectional area of the exhaust pipe by receiving only the exhaust flow flowing in the exhaust pipe. An exhaust gas flow having a valve and a second swing shaft attached to an upper portion of the exhaust pipe so as to be separated from the first swing shaft in the extending direction of the exhaust pipe, and flowing in the exhaust pipe By receiving only A second valve having a second valve body that swings about the second swing shaft so as to vary the size of the passage cross-sectional area of the exhaust pipe, and when the exhaust flow is received The swinging cycle of the first valve is different from the swinging cycle of the second valve.

  In this exhaust device, the first valve and the second valve are arranged so as to be separated from each other in the extending direction of the exhaust pipe, and the swing cycle of the first valve and the swing cycle of the second valve are made different. Therefore, when the exhaust gas discharged according to the rotational speed of the internal combustion engine is introduced into the exhaust pipe from the upstream opening end, the first valve and the second valve do not swing at the same cycle. As a result, the first valve and the second valve suppress the swinging of each other, and the flutter excited by either one of the valves is suppressed by the other valve, and an abnormal noise caused by the fluttering is suppressed. Is suppressed.

Further, when the first valve is arranged close to the opening at the downstream opening end, the first valve is configured to change the size of the passage cross-sectional area of the exhaust pipe, so that air column resonance is generated in the exhaust pipe. When this occurs, in response to the flow pressure of the exhaust flow rate according to the operating state of the internal combustion engine, the first valve swings and the passage cross-sectional area of the exhaust pipe is narrowed to a predetermined size. As described above, when the rotation speed of the internal combustion engine in which air column resonance occurs, the first valve can reduce the opening ratio of the exhaust pipe by restricting the passage sectional area of the exhaust pipe to a predetermined passage sectional area.
If the aperture ratio of the exhaust pipe is lowered in this way, an incident wave due to exhaust pulsation during operation of the internal combustion engine enters the exhaust pipe, and the frequency of the incident wave matches the air column resonance frequency of the exhaust pipe. Sometimes, the reflected wave reflected from the opening of the exhaust pipe whose passage cross-sectional area is reduced is reflected from the opening in the same phase with respect to the incident wave (reflection at the opening end), and 180% with respect to the incident wave. Can be distributed to the reflected wave (closed end reflection) reflected from the valve bodies having different degrees of phase.

For this reason, it is possible to suppress an increase in sound pressure level due to air column resonance of the exhaust pipe due to interference between the reflected wave due to the opening end reflection and the reflection due to the closed end reflection.
In addition, when the internal combustion engine is rotating at a high speed when the exhaust flow rate of the internal combustion engine is increased, the valve cross-sectional area of the exhaust passage can be increased by swinging the valve body by the pressure of the exhaust flow, so that the back pressure of the exhaust flow increases. Therefore, it is possible to prevent the exhaust performance from deteriorating.

In addition, when the throttle valve is closed and the vehicle is decelerated when the internal combustion engine is rotating at high speed, the exhaust flow rate of the internal combustion engine is abruptly reduced. In this case, the first valve is moved from the swinging position during acceleration. By quickly swinging upstream in the exhaust direction, the passage cross-sectional area of the exhaust pipe is narrowed down to a predetermined passage cross-sectional area.
For this reason, the opening ratio of the exhaust pipe can be quickly reduced, and the reflected wave of the closed end reflection is made to interfere with the reflected wave of the open end reflection reflected from the opening, and the sound pressure level is increased by the air column resonance of the exhaust pipe. It is possible to reliably suppress the increase.
The predetermined passage sectional area has two passage sectional areas at the time of acceleration and deceleration, and the passage sectional area is set to a passage sectional area capable of suppressing air column resonance at the time of acceleration and deceleration.

  In this way, the exhaust pipe is provided with the first valve, and the second valve is arranged so as to be separated from the first valve in the direction in which the exhaust pipe extends, and the first valve is operated during the air column resonance. By receiving an exhaust flow having a flow rate corresponding to the state and changing the passage cross-sectional area of the exhaust pipe to a predetermined passage cross-sectional area, occurrence of flapping of the first valve can be suppressed, and by the air column resonance of the exhaust pipe An increase in the sound pressure level can be suppressed.

This not only works when the first valve is arranged in the vicinity of the opening at the downstream opening end as described above, but also when the first valve is arranged in another configuration.
That is, in the second case where the second valve is disposed close to the opening at the downstream opening end and the first valve is disposed so as to be separated from the second valve in the extending direction of the exhaust pipe, In the third case where one valve is arranged close to the opening at the upstream opening end and the second valve is arranged so as to be separated from the first valve in the extending direction of the exhaust pipe, the second valve is In the fourth case where the first valve is disposed in the vicinity of the opening at the upstream opening end and is disposed so as to be separated from the second valve in the extending direction of the exhaust pipe, the first and third are When combined, when the second and fourth are combined, air column resonance is suppressed and the first valve is suppressed as in the case where the first valve is arranged close to the opening at the downstream opening end. And the occurrence of flapping of the second valve is suppressed, There is suppressed.

  The first valve includes a first swing shaft attached to an upper portion of the exhaust pipe, and a first valve body swinging about the first swing shaft, and the second valve is formed of the exhaust pipe. Since it is composed of a second swing shaft attached to the upper portion and a second valve body swinging around the second swing shaft, it is simple while reducing an increase in weight and an increase in manufacturing cost. With the configuration, it is possible to reliably suppress an increase in sound pressure level due to air column resonance of the exhaust pipe.

  In the exhaust system for an internal combustion engine according to the above (1), (2) the first valve and the second valve so that the second valve is located upstream of the first valve in the exhaust direction of the exhaust flow. A valve is provided on the downstream opening end side, and the first length from the axis of the first swing shaft of the first valve to the center of mass of the first valve body is set to the second swing of the second valve. It was longer than the second length from the axis of the shaft to the center of mass of the second valve element.

  In this exhaust device, since the first valve and the second valve are arranged so that the second valve is located upstream of the first valve in the exhaust direction of the exhaust flow, the air generated in the exhaust pipe by the first valve. Column resonance is suppressed, and flapping excited by the first valve by the second valve is suppressed. Further, since the first length of the first valve is longer than the second length of the second valve, the oscillation period of the first valve, that is, the time for the first valve to make one reciprocal movement to the left and right is set to the second. The swing period of the valve can be made longer, and the swing period of the first valve and the swing period of the second valve can be made different with a simple configuration. As a result, the fluttering excited by the first valve with a simple configuration is suppressed, and the generation of noise due to the fluttering is suppressed.

  In the exhaust system for an internal combustion engine according to (1) above, (3) the first valve and the second valve are positioned such that the second valve is located upstream of the first valve in the exhaust direction of the exhaust flow. A valve is provided on the downstream opening end side, and the first length from the axis of the first swing shaft of the first valve to the center of mass of the first valve body is set to the second swing of the second valve. It was shorter than the second length from the axis of the shaft to the center of mass of the second valve body.

  In this exhaust device, since the first valve and the second valve are arranged so that the second valve is located upstream of the first valve in the exhaust direction of the exhaust flow, the air generated in the exhaust pipe by the first valve. Column resonance is suppressed, and flapping excited by the first valve by the second valve is suppressed. In addition, since the first length of the first valve is shorter than the second length of the second valve, the swing period of the first valve can be shorter than the swing period of the second valve. The swing cycle of the first valve and the swing cycle of the second valve can be made different with a simple configuration. As a result, the fluttering excited by the first valve with a simple configuration is suppressed, and the generation of noise due to the fluttering is suppressed.

  In the exhaust system for an internal combustion engine according to the above (1), (4) the portion of the exhaust pipe in which the valve having the longer one of the first length and the second length is accommodated is the shorter one The diameter of the exhaust pipe was larger than that of the exhaust pipe in which the valve was accommodated.

  In this exhaust device, the part of the exhaust pipe in which the longer one of the first length and the second length is accommodated is expanded in diameter than the part of the exhaust pipe in which the shorter valve is accommodated. Therefore, the aperture ratio of the opening defined between the lower end portion of the longer valve of the first length and the second length and the inner wall surface portion of the exhaust pipe can be lowered to an appropriate value. . Further, the flow velocity of the exhaust gas flowing through the expanded exhaust pipe portion can be made relatively slower than the flow velocity of the exhaust gas flowing through the exhaust pipe portion where the diameter is not expanded, and the first length and the second length. The flow pressure over the longer valve can be varied. When the flow pressures are different from each other, the rotational sensitivity of the rotation of each valve to the flow of exhaust gas changes, and fluttering excited by the valve is suppressed, and generation of abnormal noise due to flapping is suppressed. As a result, it is possible to reliably suppress an increase in sound pressure level due to air column resonance in the exhaust pipe.

  In the exhaust system for an internal combustion engine according to the above (1), (5) a length from an axial center of the first swing shaft of the first valve to a lower end portion of the first valve body, The length from the axial center of the second swing shaft to the lower end of the second valve body was varied.

  In this exhaust device, the length from the axial center of the first swing shaft to the lower end portion of the first valve body is different from the length from the axial center of the second swing shaft to the lower end portion of the second valve body. Since the first valve and the second valve are configured, the swing cycle of the first valve and the swing cycle of the second valve can be made different with a simple configuration. As a result, the fluttering excited by the first valve and the second valve is suppressed with a simple configuration, and the generation of noise due to the fluttering is suppressed.

  In the exhaust system for an internal combustion engine according to (1) above, (6) a first weight is disposed at a lower end portion of the first valve body, and a second weight is disposed at a lower end portion of the second valve body, The weight of the first weight was different from the weight of the second weight.

Since the exhaust device is configured to make the weight of the first weight different from the weight of the second weight, the outer shapes of the first valve body and the second valve body can be formed in the same shape. The swing cycle of the first valve and the swing cycle of the second valve can be made different with a simple configuration.
When the weight of the first weight and the weight of the second weight are different, the rotational sensitivity to the flow pressure applied to the first valve and the second valve changes, and the fluttering excited by the first valve and the second valve is suppressed. Generation of abnormal noise is suppressed.
In addition, due to the difference in rotational sensitivity, there is a difference in response between the valves, and even when the exhaust gas flow pressure fluctuates, the sudden change in exhaust sound due to the opening and closing operation of each valve due to pressure fluctuations is eliminated. The
As a result, the fluttering excited by the first valve and the second valve is suppressed with a simple configuration, and the generation of noise due to the fluttering is reliably suppressed.

  According to the present invention, an internal combustion engine that can reliably suppress an increase in sound pressure level due to air column resonance of a tail pipe with a simple configuration while reducing an increase in weight and an increase in manufacturing cost. An exhaust device can be provided.

1 is a diagram illustrating a first embodiment of an exhaust device for an internal combustion engine according to the present invention, and is a configuration diagram of the exhaust device for the internal combustion engine. FIG. 1 is a view showing a first embodiment of an exhaust device for an internal combustion engine according to the present invention, and is a perspective view of a muffler to which a tail pipe is connected. FIG. It is a figure showing a 1st embodiment of an exhaust device of an internal-combustion engine concerning the present invention, and is a sectional view of a muffler with which a tail pipe was connected. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a perspective view by the side of the downstream opening end of a tail pipe. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a first embodiment of an exhaust device for an internal combustion engine according to the present invention, and is an exploded perspective view of a swing valve and a flutter suppression valve on a downstream opening end side of a tail pipe. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a front view of the axial direction of the rocking | fluctuation valve of a tail pipe. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a front view of the axial direction of the flapping suppression valve of a tail pipe. It is sectional drawing which shows the AA cross section of the tail pipe of FIG. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing which shows operation | movement of a rocking | fluctuation valve and a flutter suppression valve | bulb. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, The engine of the tail pipe which has a linear opening characteristic (dashed line) and the nonlinear opening characteristic (solid line) of 1st Embodiment It is a figure which shows the relationship between a rotation speed and the aperture ratio of a tail pipe. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, (1) thru | or (4) is a schematic diagram which shows the effect | action of a rocking | fluctuation valve and a flapping suppression valve. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a figure explaining the standing wave of the sound pressure distribution of air column resonance by the opening end reflection which generate | occur | produces in a tail pipe. Is a diagram showing a first embodiment of an exhaust system of an internal combustion engine according to the present invention, a diagram illustrating a state in which the incident wave G with the downstream open end is distributed to the transmission wave G ₁ and the reflected wave R _1, R ₂ is there. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a figure which shows the flow of the exhaust flow of the rocking | fluctuation valve which is not provided with the baffle plate. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a figure which shows the flow of the exhaust flow of the rocking | fluctuation valve provided with the baffle plate. It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a figure which shows the relationship between the engine speed which generate | occur | produces in a tail pipe, and a sound pressure level. It is a figure which shows 2nd Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the muffler with which the tail pipe was connected. It is a figure which shows 2nd Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing by the side of the upstream opening end of a tail pipe. It is a figure which shows 2nd Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing which shows operation | movement of a rocking | fluctuation valve and a flutter suppression valve | bulb. It is a figure which shows 3rd Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the muffler with which the tail pipe was connected. It is a figure which shows 4th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the muffler with which the tail pipe was connected. It is a figure which shows 4th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the rocking | swiveling valve and flapping suppression valve of the downstream opening end side of a tail pipe. It is a figure which shows 4th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing which shows operation | movement of a rocking | fluctuation valve and a flutter suppression valve | bulb. It is a figure which shows 5th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the muffler with which the tail pipe was connected. It is a figure which shows 5th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the rocking | swiveling valve and flapping suppression valve of the upstream opening end side of a tail pipe. It is a figure which shows 5th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing which shows operation | movement of a rocking | fluctuation valve and a flapping suppression valve. It is a figure which shows 6th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the muffler with which the tail pipe was connected. It is a figure which shows 7th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the muffler with which the tail pipe was connected. It is a figure which shows 7th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a perspective view of the downstream opening end side of a tail pipe. It is a figure which shows 7th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a disassembled perspective view of the rocking | swiveling valve and flapping suppression valve of the downstream opening end side of a tail pipe. It is a figure which shows 7th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a front view of the axial direction of the flapping suppression valve of a tail pipe. It is a figure which shows 7th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the rocking | swiveling valve and flapping suppression valve of the downstream opening end side of a tail pipe. It is a figure which shows 7th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing which shows operation | movement of a rocking | fluctuation valve and a fluttering suppression valve. It is a figure which shows 8th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing of the muffler with which the tail pipe was connected. It is a figure which shows 8th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is sectional drawing which shows a rocking | fluctuation valve and a flapping suppression valve. It is a block diagram of the exhaust apparatus of the conventional internal combustion engine.

  Hereinafter, first to eighth embodiments of an exhaust device for an internal combustion engine according to the present invention will be described with reference to the drawings.

(First embodiment)
1 to 16 are views showing a first embodiment of an exhaust device for an internal combustion engine according to the present invention.
First, the configuration will be described.

  As shown in FIG. 1, the exhaust device 20 in the first embodiment is applied as a device that exhausts exhaust gas discharged from an engine 21 as an in-line four-cylinder internal combustion engine into the atmosphere. An exhaust manifold 22 is connected to the engine 21, and the exhaust device 20 is connected to the exhaust manifold 22.

Here, the fluid exhausted from the engine 21 to the exhaust device 20 becomes exhaust gas when the throttle valve is opened, and becomes air when the throttle valve is closed and decelerates, and the flow of the exhaust gas and air corresponds to the exhaust flow.
The engine 21 is not limited to the in-line four cylinders, and may be in-line three cylinders or in-line five cylinders or more, or may be a V-type engine having three or more cylinders in each bank divided into left and right. Good.

  The exhaust manifold 22 includes four exhaust branch pipes 22a, 22b, 22c, and 22d, and exhaust branch pipes 22a, 22b, 22c, and 22d connected to exhaust ports that respectively communicate with the first cylinder to the fourth cylinder of the engine 21. The exhaust gas collecting pipe 22e that collects the downstream side of the exhaust gas is exhausted from each cylinder of the engine 21 and introduced into the exhaust collecting pipe 22e via the exhaust branch pipes 22a, 22b, 22c, and 22d. It is like that.

The exhaust device 20 includes a catalytic converter 23, a cylindrical front pipe 24, a cylindrical center pipe 25, a muffler 26, a tail pipe 27 as an exhaust pipe, a swing valve 40 as a first valve, and a second valve. A flutter suppression valve 50 as a valve is provided. Further, the exhaust device 20 is installed on the downstream side in the exhaust direction of the exhaust gas of the engine 21 so as to be elastically suspended below the floor of the vehicle body.
The upstream or simply upstream in the exhaust direction indicates upstream in the flow direction of the exhaust flow, and the downstream or simply downstream in the exhaust direction indicates downstream in the flow direction of the exhaust flow.

  The upstream end of the catalytic converter 23 is connected to the downstream end of the exhaust collecting pipe 22e, and the downstream end of the catalytic converter 23 is connected to the front pipe 24 via a universal joint 28. The catalytic converter 23 is composed of a honeycomb base or a granular activated alumina support with a catalyst such as platinum or palladium attached in a main body case for reducing NOx and oxidizing CO and HC. To do.

The universal joint 28 is composed of a spherical joint such as a ball joint, and allows relative displacement between the catalytic converter 23 and the front pipe 24. The upstream end of the center pipe 25 is connected to the downstream end of the front pipe 24 via a universal joint 29. The universal joint 29 is composed of a spherical joint such as a ball joint, and allows relative displacement between the front pipe 24 and the center pipe 25.
A downstream side of the center pipe 25 is connected to a muffler 26, and the muffler 26 is configured to mute the exhaust sound.

As shown in FIG. 2, the muffler 26 includes an outer shell 31 formed in a hollow cylindrical shape, end plates 32 and 33 that close both ends of the outer shell 31, and a partition plate 34.
By the partition plate 34, the outer shell 31 is divided into an expansion chamber 35 for expanding and suppressing the exhaust gas and a resonance chamber 36 for suppressing the exhaust sound of a specific frequency by Helmholtz resonance.

  3, the end plate 32 and the partition plate 34 have insertion holes 32a and 34a, respectively. The insertion holes 32a and 34a have a downstream side of the center pipe 25 (hereinafter, downstream of the center pipe 25). The side is referred to as an inlet pipe portion 25A).

  The inlet pipe portion 25 </ b> A is supported by the end plate 32 and the partition plate 34 so as to be accommodated in the expansion chamber 35 and the resonance chamber 36, and the downstream opening end 25 b opens in the resonance chamber 36. The inlet pipe portion 25A is formed with a plurality of small holes 25a in the axial direction (exhaust gas exhaust direction) and the circumferential direction of the inlet pipe portion 25A, and the interior of the inlet pipe portion 25A and the expansion chamber 35 are small. It communicates through the hole 25a.

Therefore, the exhaust gas introduced into the muffler 26 through the inlet pipe portion 25A of the center pipe 25 is introduced into the expansion chamber 35 through the small hole 25a and introduced into the resonance chamber 36 from the downstream opening end 25b of the inlet pipe portion 25A. Is done.
The muffler 26 is configured to be tunable in design so that when exhaust gas is introduced into the resonance chamber 36, exhaust sound of a specific frequency is silenced by Helmholtz resonance. Specifically, or to increase the volume of the resonance chamber 36, by increasing the length L ₁ of the projecting portion of the center pipe 25 which projects into the resonance chamber 36, it is possible to tune the resonant frequency to a low frequency side .
You can also reduce the volume of the resonance chamber 36, by shortening the length L ₁ of the projecting portion of the center pipe 25 which projects into the resonance chamber 36, it is possible to tune the resonant frequency to the high frequency side.

The tail pipe 27, as shown in FIGS. 2 to 5, and the upstream portion 27A is formed in a cylindrical shape, and a downstream portion 27B, and is formed at a predetermined length L _2. The upstream portion 27A is formed with an upstream opening end 27a connected to the muffler 26 on the upstream side of the exhaust gas discharged from the engine 21 in the exhaust direction. In the downstream portion 27B, a downstream opening end 27b for exhausting exhaust gas into the atmosphere is formed.

Further, as shown in FIG. 5, the downstream portion 27 </ b> B is provided with an accommodating portion 27 c for accommodating the swing valve 40 and the flutter suppression valve 50.
A pair of valve mounting holes 27d and 27e for mounting the swing valve 40 and a pair of valve mounting holes 27f and 27g for mounting the flapping suppression valve 50 are formed in the upper portion of the accommodating portion 27c. . Further, the downstream portion 27B is formed with an enlarged diameter portion 27h in which the passage sectional area of the downstream opening end 27b is enlarged so as to accommodate the swing valve 40 larger than the flutter suppression valve 50.

  The upstream portion 27A is connected to the muffler 26 by being inserted into insertion holes 34b and 33a formed in the partition plate 34 and the end plate 33 so that the upstream opening end 27a opens to the expansion chamber 35. Yes. Therefore, the exhaust gas introduced from the expansion chamber 35 of the muffler 26 to the upstream opening end 27a of the tail pipe 27 is exhausted through the tail pipe 27 from the downstream opening end 27b to the atmosphere.

As shown in FIGS. 4 to 6 and 8, the swing valve 40 includes a swing shaft 41 as a first swing shaft, a valve body 42 as a first valve body, a weight 43, and a snap ring 44. , 45.
As shown in FIG. 5, the oscillating shaft 41 is formed in a columnar shape and is rotatably inserted into the valve mounting holes 27d and 27e. Grooves 41a and 41b are formed in the swing shaft 41, and snap rings 44 and 45 are mounted, respectively, so that the swing shaft 41 does not come out of the accommodating portion 27c.

The valve body 42 includes a pressure receiving plate 46 that receives the flow pressure (MPa) of the exhaust flow, and a rectifying plate 47 that rectifies the exhaust flow.
The pressure receiving plate 46 has an upper part 46a formed in a square shape, a lower part 46b formed in a semicircular shape, and a pressure receiving surface part 46c formed on the upstream side with a flat surface.
The rectifying plate 47 has a uniform thickness and a flat surface, a pair of side portions 47a and 47b arranged opposite to each other, and a curved portion formed by bending the side portions 47a and 47b integrally. 47c.

A through hole 47d is formed in the side portion 47a, and the swing shaft 41 is inserted so as to be swingable. Further, a through hole 47e is formed in the side portion 47b, and the swing shaft 41 is inserted so as to be swingable.
The rectifying plate 47 may be integrally formed by separately producing the side portions 47a and 47b and the curved portion 47c and joining them by joining means such as welding. Further, the rectifying plate 47 may be joined to the pressure receiving plate 46 by a joining means such as welding and integrated with the pressure receiving plate 46, and the pressure receiving plate 46 and the rectifying plate 47 may be integrated by molding such as press working. You may make it form integrally from the beginning.

The weight 43 is made of a material having a relatively large specific gravity, such as metal, and has a mounting portion 43 a formed with a curved surface having the same shape as the curved portion 47 c of the rectifying plate 47. The weight 43 is fixed to the rectifying plate 47 by a joining means such as welding or a fastening means such as a rivet so that the mounting portion 43a and the curved portion 47c come into contact with each other.
When the swing valve 40 is not subjected to the flow pressure, the weight 43 has a function of keeping its posture vertically downward and smoothing the swing. Further, the weight 43 has a function of adjusting the position of the center of gravity of the swing valve 40, that is, the center of mass, by changing the mass (g).

また、揺動バルブ４０の弁体４２とテールパイプ２７の拡径部２７ｈの内壁面部２７ｎとの間の距離がＬ_４となるよう隙間が形成されており、この隙間を排気ガスが流通するようになっている。この揺動バルブ４０が下流側に揺動した際、所定の開口率、すなわちテールパイプ２７の排気通路の断面積に対する開口部分の断面積の割合で開口する開口部４８が画成されるようになっている。 As shown in FIG. 8, the center of mass P ₄₀ represents the center of the total weight of the valve body 42 and the weight 43, and is located below the axis J ₄₀ of the swing shaft 41 in the vertical direction. The length of the first length between the center of mass P ₄₀ and the axis J ₄₀ is L ₄₀ (m). The swing valve 40 receives only the flow pressure (MPa) of the exhaust flow and swings about the axis J ₄₀ of the swing shaft 41.
When the acceleration of gravity is g (9.8 m / sec ² ), the oscillating valve 40 oscillates at an oscillating cycle T ₄₀ represented by the following formula (2) (one reciprocating time in the left and right: sec). Configured to work.

The distance is formed a gap so as to be L ₄ between the inner wall surface 27n of the enlarged diameter portion 27h of the valve body 42 and the tail pipe 27 of the pivot valve 40, so that the gap exhaust gas flows It has become. When the swing valve 40 swings downstream, an opening 48 is defined that opens at a predetermined opening ratio, that is, a ratio of the cross-sectional area of the opening portion to the cross-sectional area of the exhaust passage of the tail pipe 27. It has become.

Further, as shown in FIG. 9, the swing valve 40 receives the flow pressure of the exhaust flow along the swing locus C ₄₀ and swings downstream, and when the flow pressure of the exhaust flow decreases, Due to the action, it swings upstream. State therefore, joined by the flow pressure of the exhaust stream, when the flow pressure is substantially constant state, the swing valve 40, which swings in the swinging period T ₄₀ described above, opened gradually attenuated at a constant aperture ratio It becomes.

When the air column resonance occurs in the tail pipe 27 according to the operating state of the engine 21, the valve body 42 of the swing valve 40 swings when the pressure receiving surface portion 46c receives the flow pressure of the exhaust flow of the exhaust flow rate. and the distance L ₄ between the valve body 42 and the inner wall surface portion 27w as is shortened, and is configured to narrow the passage sectional area between the valve body 42 and the inner wall surface 27w. That is, the valve body 42 defines an opening 48 having a small opening area by restricting the passage sectional area of the tail pipe 27 to a predetermined passage sectional area.

  As shown in FIG. 10, the swing valve 40 gradually opens in the engine speed range from the engine speed (rpm) during idling to the engine speed during resonance when air column resonance occurs in the tail pipe 27. Is configured to decrease. On the other hand, in the engine speed range exceeding the resonance speed, the opening ratio gradually increases, and the back pressure (MPa) is suppressed from being increased by the swing valve 40.

  As shown in FIGS. 4, 5, 7, and 8, the flutter suppression valve 50 includes a swing shaft 51 as a second swing shaft, a valve body 52 as a second valve body, a weight 53, Snap rings 54 and 55 are provided.

  As shown in FIG. 5, the oscillating shaft 51 is formed in a columnar shape and is rotatably inserted into the valve mounting holes 27f and 27g. Grooves 51a and 51b are formed in the swing shaft 51, and snap rings 54 and 55 are mounted, respectively, so that the swing shaft 51 does not come out of the accommodating portion 27c.

The valve body 52 includes a pressure receiving plate 56 that receives the flow pressure (MPa) of the exhaust flow and a rectifying plate 57 that rectifies the exhaust flow.
The pressure receiving plate 56 includes an upper portion 56a formed in a square shape, a lower portion 56b formed in a semicircular shape, and a pressure receiving surface portion 56c formed with a flat surface on the upstream side.
The rectifying plate 57 has a uniform thickness and a flat surface, and a pair of side portions 57a and 57b arranged to face each other, and a curved portion formed by bending the side portions 57a and 57b integrally. 57c.

A through hole 57d is formed in the side portion 57a, and the swing shaft 51 is inserted so as to be swingable. Further, a through hole 57e is formed in the side portion 57b, and the swing shaft 51 is inserted in a swingable manner.
As with the rectifying plate 47, the rectifying plate 57 may be formed by separately forming the side portions 57a and 57b and the curved portion 57c, and joining them by a joining means such as welding. In addition, the rectifying plate 57 may be joined to the pressure receiving plate 56 by a joining means such as welding and integrated with the pressure receiving plate 56. The pressure receiving plate 56 and the rectifying plate 57 may be integrated by molding such as pressing. You may make it form integrally from the beginning.

The weight 53 is made of a material having a relatively large specific gravity, such as metal, and has a mounting portion 53a formed of a curved surface having the same shape as the curved portion 57c of the rectifying plate 57. The weight 53 is fixed to the rectifying plate 57 by a joining means such as welding or a fastening means such as a rivet so that the mounting portion 53a and the curved portion 57c come into contact with each other.
The weight 53 has a function of making its posture stationary vertically downward and smoothing its swing when the flutter suppression valve 50 is not subjected to the flow pressure. Further, the weight 53 has a function of adjusting the center of gravity of the flutter suppression valve 50, that is, the position of the center of mass by design by changing the mass (g).

As shown in FIG. 8, the center of mass P ₅₀ represents the center of the total weight of the valve body 52 and the weight 53, and is located below the axis J ₅₀ of the swing shaft 51 in the vertical direction. The length as the second length between the center of mass P ₅₀ and the axis J ₅₀ is L ₅₀ (m). The flutter suppression valve 50 receives only the flow pressure of the exhaust flow and swings about the axis J ₅₀ of the swing shaft 51.
When the acceleration of gravity is g (9.8 m / sec ² ), the flutter suppression valve 50 swings at a swing period T ₅₀ (one reciprocating time: right and left) expressed by the following formula (3). Configured to work.

The distance between the inner wall surface 27w of the downstream portion 27B of the valve element 52 and the tail pipe 27 of the rattling suppression valve 50 is formed a gap so as to be L _5, this gap so that the exhaust gas flows It has become.
Further, as shown in FIG. 9, fluttering suppression valve 50, along the swing locus C _50, swings to the downstream side receives the flow pressure of the exhaust stream, when the flow pressure of the exhaust stream decreases, the self-weight Due to the action, it swings upstream. Therefore, when the flow pressure of the exhaust flow is substantially constant state, fluttering suppression valve 50 can be swung by swinging period T ₅₀ described above.

The valve body 52 of the flutter suppression valve 50 swings when the pressure receiving surface portion 56c receives the flow pressure of the exhaust flow having an exhaust flow rate corresponding to the operating state of the engine 21, and the distance between the valve body 42 and the inner wall surface portion 27w. which L ₅ in the shorter, it is configured to narrow the passage sectional area between the valve body 42 and the inner wall surface 27 w. That is, the valve body 42 defines an opening 58 having a small opening area by restricting the passage sectional area of the tail pipe 27 to a predetermined passage sectional area.

The flutter suppression valve 50 and the swing valve 40 are configured such that the length L ₅₀ of the flutter suppression valve 50 is shorter than the length L _{40 of the} swing valve 40. Thus, the swing cycle _{T 50} of rattling suppression valve 50, the swing period _{T 40} of the swing valve 40 _is in the relation of T _{40> T 50,} are different from each other.
Thus, the swing cycle T ₅₀ of rattling suppression valve 50, so is different from the swinging period T ₄₀ of the swing valve 40, rattling suppression valve 50, by the action described later, the engine speed of the engine 21 It has a function of suppressing the fluttering of the oscillating valve 40 caused by a change in flow pressure such as an exhaust pulsation that changes accordingly.

The distance between the inner wall surface 27w of the downstream portion 27B of the valve element 52 and the tail pipe 27 of the rattling suppression valve 50 is formed a gap so as to be L _5, the exhaust gas is adapted to flow .

Flutter suppression valve 50, as shown in FIG. 8, so that the distance between the axial center J ₅₀ the axis J ₄₀ and flutter suppression valve 50 of the pivot valve 40 is L _3, extending the tail pipe 27 The swing valve 40 and the flutter suppression valve 50 are not in contact with each other even if they swing.

  As with the swing valve 40, the flutter suppression valve 50 gradually opens in the engine speed range from the engine speed (rpm) during idling to the engine speed during resonance when air column resonance occurs in the tail pipe 27. Is configured to decrease. On the other hand, in the engine speed range exceeding the resonance speed, the opening ratio gradually increases, and the backlash (MPa) is suppressed from being increased by the flapping suppression valve 50.

Here, the length L ₁ of the protruding portion of the center pipe 25, the predetermined length L ₂ of the tail pipe 27, the distance L ₃ between the shaft center J ₄₀ and the shaft center J ₅₀ , the valve body 42 and the inner wall surface portion 27n, The distance L ₄ between the valve body 52 and the inner wall surface portion 27w, the distance L ₅ , the swing period T ₄₀ , and the swing period T ₅₀ are the design of the vehicle to which the exhaust device 20 of the first embodiment is applied. It is selected as appropriate based on data such as specifications, simulations, experiments, and experience values.

  Next, the operation of the exhaust device 20 and the operation of the swing valve 40 and the flutter suppression valve 50 will be described.

  When the operation of the engine 21 shown in FIG. 1 is started, the exhaust gas exhausted from each cylinder of the engine 21 is introduced into the catalytic converter 23 from the exhaust manifold 22, and the catalytic converter 23 reduces NOx and CO and HC. Oxidation takes place.

  Exhaust gas exhausted from the catalytic converter 23 is introduced into the muffler 26 shown in FIG. 2 through the front pipe 24 and the center pipe 25 of the exhaust device 20. The exhaust gas introduced into the muffler 26 is introduced into the expansion chamber 35 through the small hole 25a of the inlet pipe portion 25A, and the exhaust noise is reduced. Then, the exhaust gas is introduced into the resonance chamber 36 from the downstream opening end 25b of the inlet pipe portion 25A, and the exhaust sound of a specific frequency is silenced by Helmholtz resonance.

  The exhaust gas introduced into the expansion chamber 35 is introduced into the tail pipe 27 through the upstream opening end 27a of the upstream portion 27A of the tail pipe 27, and then passes through the opening 58 of the flutter suppression valve 50, and further fluctuates. After passing through the opening 48 of the moving valve 40, the air is exhausted from the downstream opening end 27 b of the tail pipe 27 to the atmosphere.

  When the engine 21 is in a normal rotation range (2000 rpm to 5000 rpm) that is a low rotation range or a medium rotation range, when the pressure receiving surface portion 51a of the flutter suppression valve 50 receives an exhaust flow, the valve 21 The body 52 is inclined to the downstream side, the passage cross-sectional area of the tail pipe 27 is reduced to the minimum, and the opening 58 having a small opening area is defined. Similarly to the flapping suppression valve 50, the swing valve 40 swings downstream and the valve body 42 tilts downstream when the pressure receiving surface portion 46c receives the exhaust flow, and the passage cross-sectional area of the tail pipe 27 is increased. Is reduced to a minimum, and an opening 48 having a small opening area is defined.

  On the other hand, the amount of exhaust gas discharged from the engine 21 increases in the high rotation range (5000 rpm or more) of the engine 21. As a result, the valve body 52 of the flutter suppression valve 50 is greatly swung downstream (indicated by a phantom line in FIG. 9) in response to a large amount of exhaust flow, so that the passage sectional area of the tail pipe 27 increases. The exhaust gas introduced into the tail pipe 27 flows through the opening having a larger opening area than the opening 58.

  Similarly to the flapping suppression valve 50, the swing valve 40 also receives a large amount of exhaust flow, and the valve body 42 swings greatly downstream (indicated by a phantom line in FIG. 9). The exhaust gas introduced into the tail pipe 27 is exhausted into the atmosphere from the downstream opening end 27b through the opening having an opening area larger than that of the opening 48. Further, at the maximum rotation speed of the engine 21, the flutter suppression valve 50 and the swing valve 40 are substantially fully opened, and the back pressure applied to the engine 21 is minimized.

  On the other hand, when the throttle valve is closed and the vehicle is decelerated from the high speed range of the engine 21, the amount of exhaust gas discharged from the engine 21 is greatly reduced. As a result, the flutter suppression valve 50 and the swing valve 40 are quickly swung to the upstream side (in the state indicated by the solid line in FIG. 9), and the exhaust flow introduced into the tail pipe 27 is most restricted by the openings 58 and 48. Exhausted to the atmosphere.

  Even if the flow pressure of the oscillating valve 40 changes due to exhaust pulsation or the like that changes according to the engine speed of the engine 21, the fluttering suppression valve 50 suppresses the fluttering. Such flapping suppression of the flapping suppression valve 50 is performed in the entire range of the normal rotation range, the high rotation range, and the region where the vehicle is decelerated from the high rotation range regardless of the rotational speed of the engine 21.

  Specifically, the flapping suppression of the flapping suppression valve 50 is performed by changing the pressure (MPa) in the tail pipe 27 as follows depending on the difference between the rocking periods of the rocking valve 40 and the fluttering suppression valve 50. Is done. This change in pressure acts on the swing of the swing valve 40 and the swing of the flutter suppression valve 50. As a result, the flutter of the swing valve 40 is suppressed.

That is, as shown in FIG. 11 (1), when exhaust gas is introduced into the tail pipe 27, the pressure in the exhaust passage upstream of the flutter suppression valve 50 (hereinafter referred to as upstream portion) is relatively high. The pressure in the exhaust passage (hereinafter referred to as an intermediate portion) between the flapping suppression valve 50 and the swing valve 40 and the pressure in the exhaust passage on the downstream side of the swing valve 40 (hereinafter referred to as a downstream portion) is almost equal. At the same pressure as the atmospheric pressure, the pressure is relatively lower than the upstream pressure.
Then, as shown in FIG. 11 (2), when the flutter suppression valve 50 is rotated downstream by the exhaust gas flow pressure, the pressure at the intermediate portion is slightly increased and is also fluctuated by the exhaust gas flowing through the opening 58. The moving valve 40 is pressed downstream.
At this time, as shown in (3) of FIG. 11, the swing valve 40 is rotated downstream, the pressure in the intermediate portion is slightly lowered, and the pressure in the downstream portion is slightly increased. The swing valve 40 rotates downstream, and the flutter suppression valve 50 swings upstream due to its own weight against high pressure in the upstream portion.

Subsequently, as shown in FIG. 11 (4), the swing valve 40 swings vigorously by its own weight toward the intermediate portion that has become a pressure lower than the pressure in the downstream portion. At this time, since the flutter suppression valve 50 rotates downstream, the pressure in the intermediate portion is relatively increased. In this case, the swing of the swing valve 40 and the swing suppression valve 50 is suppressed by the relatively increased pressure at the intermediate portion, and the swing of both is suppressed.
In this case, the swing periods of the swing valve 40 and the flutter suppression valve 50 are different from each other as described above, such as the swing period T ₄₀ and the swing period T _50. The flutter suppression valve 50 does not oscillate at the same period, and suppresses swaying each other.

In FIGS. 11 (1) to (4), the case where the flow pressure of the exhaust gas does not change and is almost constant has been described for convenience. As described above, when the flow pressure is constant, it is known that the swing valve 40 and the flutter suppression valve 50 swing at the same cycle if they have the same swing cycle. When the valves are arranged in series in the exhaust passage and have the same swing cycle, the valves swing at the same cycle, resulting in periodic pressure fluctuations. Can not be suppressed. Since the swing valve 40 and the flutter suppression valve 50 of the first embodiment have different swing periods, the flutter of both valves is effectively suppressed.
This is because even if the flow pressure changes due to the exhaust pulsation or the like that changes according to the engine speed of the engine 21, the swing valve 40 and the flutter suppression valve 50 have different swing periods. The valve does not oscillate at the operation cycle, and fluttering of both valves is effectively suppressed as in the case where the flow pressure is constant.

  Further, the oscillating valve 40 is opened with a closed portion in which an exhaust gas exhaust passage is closed by the oscillating valve 40 at a predetermined opening ratio, which will be described later, during acceleration and deceleration in the normal rotation range of the engine 21. Opening 48 is defined. When exhaust sound enters the tail pipe 27 at the time of acceleration and deceleration, the incident wave is distributed to so-called closed end reflection that reflects at the closed portion and so-called open end reflection that reflects at the closed portion 48. A reflected wave is generated. These reflected waves interfere with each other, and an increase in sound pressure level due to air column resonance generated in the tail pipe 27 is suppressed.

Next, the reflected wave and interference generated by the aforementioned closed portion and opening portion 48 in the tail pipe 27 will be described.
The exhaust gas introduced into the tail pipe 27 by the operation of the engine 21 is input with an exhaust pulsation that changes according to the engine speed. This exhaust pulsation becomes an incident wave of the tail pipe 27, and this incident wave has a frequency that increases as the engine speed increases.

  When an incident wave due to exhaust pulsation during operation of the engine 21 is introduced into the tail pipe 27, the incident wave has the same phase as the incident wave in the opening 48 of the tail pipe 27 and the traveling direction is opposite to the incident wave. Reflection at the open end occurs toward the upstream side. This reflected wave is again reflected at the upstream opening end 27a in the same phase as the reflected wave in the opposite direction, ie, toward the downstream side. This reflected wave becomes an incident wave this time, becomes a re-reflected wave at the opening 48, and such reflection is repeated.

  Originally, at the boundary between media having the same medium, such as the open end of a pipe, the medium is the same, reflection does not occur, and it seems that sound waves are transmitted. However, the exhaust sound that travels in a pipe having a sufficiently small cross-sectional dimension with respect to the wavelength of the exhaust sound, such as the tail pipe 27, becomes a parallel wave composed of a dense wave, and the downstream opening and the upstream opening end 27a. Will be reflected.

  The reason why the open end reflection occurs in the downstream opening is as follows. That is, the pressure of the exhaust gas flowing in the tail pipe 27 is high, and the atmospheric pressure outside the opening on the downstream side of the tail pipe 27 is lower than the pressure of the exhaust gas flowing in the tail pipe 27. For this reason, the incident wave rushes out from the downstream opening to the atmosphere to generate a low pressure part in which the pressure of the exhaust gas in the downstream opening decreases, and this low pressure part passes through the tail pipe 27 to the upstream opening end. It is because it starts to advance toward 27a.

  Therefore, the reflected wave becomes a parallel wave in the opposite direction to the incident wave, and travels in the opposite direction to the incident wave. The reason why the reflected wave is generated on the upstream opening end 27a side is the same as the reason why the reflected wave is generated on the downstream opening.

  If the structure is not provided with the oscillating valve 40, the incident wave toward the downstream opening 48 and the reflected wave opposite to the incident wave interfere with each other, so that the tail pipe 27 Thus, a standing wave is created in which the upstream opening end 27a and the downstream opening end 27b become nodes of the sound pressure distribution.

Further, the standing wave has a significantly large amplitude and air column resonance occurs when the tube length L ₂ (see FIG. 2) of the tail pipe 27 and the wavelength λ of the standing wave have a specific relationship. The air column resonance, the basic standing wave tube length L ₂ was a half wavelength of the tail pipe 27, a natural number multiple of a half wavelength occurs and standing waves of a wavelength which is a pipe length L ₂ sound pressure is increased And it becomes noise.

More specifically, as shown the sound pressure distribution of a standing wave of air column resonance in FIG. 12, the wavelength λ1 of the columnar resonance of the fundamental vibration (primary component), twice the pipe length L ₂ of the tail pipe 27 , the wavelength λ2 of the air column resonance of the secondary component, is 1 times the pipe length L _2. The wavelength λ3 of columnar resonance tertiary component becomes 2/3 times the pipe length L _2, the respective standing waves, and nodes of the upstream open end 27a and a downstream opening end 27b Gaoto pressure distribution of the tail pipe 27 Become.
Further, the oscillating valve 40 of the first embodiment is provided at a position closest to the opening of the downstream opening end 27b of the tail pipe 27 so as to be located at a node of the sound pressure distribution of the standing wave of air column resonance. . Therefore, when air column resonance occurs in the tail pipe 27, an increase in the sound pressure level of the air column resonance can be suppressed most effectively.

Further, as shown in FIG. 16, the sound pressure level (dB) of the exhaust sound is such that the resonance frequency (Hz) of the primary component f ₁ and the secondary component f _{2 as} the engine speed Ne (rpm) increases. Each of the engine speeds Ne corresponding to

Here, the frequency fk (Hz) of air column resonance of the tail pipe 27 when the speed of sound is c (m / s), the length of the tail pipe 27 is L ₂ (m), and the order is m, is It is represented by (4).
fk = (c / 2L ₂ ) · m (4)
Further, the exhaust pulsation frequency fe (Hz) of the engine 21 when the engine speed is Ne (rpm) and the number of cylinders is N is expressed by the following equation (5).
fe = (Ne / 60) · (N / 2) · · · (5)
Equation (4), as is clear from (5), the longer the tube length L ₂ of the tail pipe 27, air column resonance frequency fk is thus shifted to the low frequency region is low rotational speed Ne of the engine 21 .

  Therefore, when the tail pipe 27 having a long pipe length is used, air column resonance may occur in the normal rotation region where the engine speed Ne is low, exhaust noise becomes worse, and the driver feels uncomfortable. Will give.

  At the air column resonance frequency of the third-order component, the engine speed Ne is equal to or higher than the steady rotation region of the engine 21. Therefore, noise caused by air column resonance is caused by various noises generated at high speed such as wind noise. The exhaust pulsation of the engine 21 becomes relatively small. Therefore, the third order component and higher order components are not a problem.

Therefore, as described above, the exhaust device 20 of the first embodiment has the swing shaft 41 at the downstream opening end 27b of the downstream portion 27B so as to receive only the exhaust flow and change the passage cross-sectional area in the tail pipe 27. It is provided with a swing valve 40 which swings axis _{J 40.} When air column resonance occurs in the tail pipe 27 in the swing valve 40, the passage of the tail pipe 27 is interrupted when the valve body 42 swings due to the exhaust flow rate corresponding to the operating state of the engine 21. By reducing the area to the minimum, two reflected waves of the open end reflection and the closed end reflection are generated in the swing valve 40 of the downstream portion 27B, and the sound pressure level (dB) increases due to air column resonance. I try to suppress it.

  Hereinafter, the reason why an increase in sound pressure level can be suppressed by air column resonance will be described.

Here, assuming that the reflectance of the exhaust sound is Rp, the specific acoustic impedance of the medium inside the tail pipe 27 is Z ₁ , and the specific acoustic impedance of the medium near the downstream opening end 27b outside the tail pipe 27 is Z ₂ , the exhaust sound. The reflectance Rp is expressed by the following formula (6). Originally, the reflectance Rp of the exhaust sound is represented by the relationship between the specific acoustic impedances Z ₁ and Z ₂ , but the sectional area of the opening area S ₁ of the opening 48 and the sectional area S ₂ of the exhaust passage of the tail pipe 27. Since the change is not so great and the sound wave propagates continuously in a substantially plane, it can be expressed by a value obtained by multiplying the specific acoustic impedances Z ₁ and Z ₂ of each medium by each area. That represents _{Z 1} in _Z 1 _{S 1,} since the _{Z 2} can be represented by _Z 2 _{S 2,} the reflectivity Rp of the exhaust sound is a following equation (6).

Here, the specific acoustic impedance is represented by the product of the density ρ (Kg / m ³ ) of the medium and the sound velocity c (m / s), so that Z ₁ = ρ ₁ c ₁ , Z ₂ = ρ ₂ c ₂ Become. The medium ρ ₁ and the sound velocity c ₁ inside the tail pipe 27 and the medium ρ ₂ and the sound velocity c ₂ near the downstream opening end 27 b outside the tail pipe 27 are both exhaust gases. In addition, when the engine 21 is rotating in a fuel non-injection state, air may be generated. In the case of both exhaust gas and air, ρ ₁ c ₁ = ρ ₂ c ₂ , so that Z ₁ = Z ₂ , and the reflectance Rp is expressed by the following equation (7).

したがって、テールパイプ２７の排気通路の断面積Ｓ_２、すなわち下流開口端２７ｂの開口面積Ｓ_２に対する開口面積Ｓ_１の開口部４８の開口率は１／３となり、約３３％になる。なお、この開口率は、約３３％が最も好ましい値となり、音圧レベルが最も抑制される。 When the optimum value 0.5 of the reflectance Rp is substituted into the above equation (7), the following equation (8) is obtained.

Therefore, the cross-sectional area S ₂ of the exhaust passage of the tail pipe 27, that is, the opening ratio of the opening 48 of the opening area S ₁ with respect to the opening area S ₂ of the downstream opening end 27b is 1/3, which is about 33%. The aperture ratio is most preferably about 33%, and the sound pressure level is most suppressed.

Hereinafter, the incident wave G of exhaust pulsation during operation of the engine 21 is incident on the tail pipe 27, the wavelength of the incident wave G is the case of the pipe length L ₂ of the tail pipe 27 is an incident wave G to a half wavelength description To do.

As shown in FIG. 13, the incident wave G is in the opening 48 of the tail pipe 27, the transmitted wave G together ₁ is transmitted to the atmosphere, the reflected wave R ₁ from the opening 48 toward the upstream open end 27a ( (Open end reflection wave) is reflected. Further, the reflected wave (closed end reflected wave) R _{2 of} the incident wave G is reflected from the opening 48 toward the upstream opening end 27 a by the swing valve 40.

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. 13, since the reflected wave R ₁ is in phase with the incident wave G, the incident wave G and the reflected wave R ₁ overlap, but 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 tail pipe 27, 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. 16, 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 tail pipe 27, 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 a maximum). 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 tail pipe 27, the sound due to the interference of the reflected wave R ₁ which is the opening 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 downstream opening end 27b is closed by the swing of the swing valve 40, and the opening 48 becomes 1/3 of the opening area of the downstream opening end 27b, the sound pressure level due to the air column resonance. However, even if the opening area of the opening 48 is not 1/3 of the opening area of the downstream opening end 27b, the effect of suppressing the sound pressure level of the air column resonance due to the interference of the closed end reflected wave is ,appear.
However, when the predetermined ratio, for example, the opening ratio of the opening 48 becomes 70% or more, the effect of suppressing the sound pressure level is significantly reduced.
Therefore, the opening ratio of the opening 48 is preferably set to less than 70%. In the first embodiment, the aperture ratio of the opening 48 is set to a small aperture ratio of 20%.

Since the exhaust device 20 of the first embodiment is configured as described above, the following effects can be obtained.
That is, the exhaust device 20 is provided with a swing valve 40 having a swing shaft 41, a valve body 42, and a weight 43 so as to be separated from the swing valve 40 in the extending direction of the tail pipe 27. A flutter suppression valve 50 having a moving shaft 51, a valve body 52 and a weight 53 is provided. Then, in the exhaust device 20 includes an oscillating period _{T 40} of the swing valve 40, and the swing period _{T 50} of rattling suppression valve 50 is in a relationship of _{T 40> T 50} when subjected to fluid pressure in the exhaust stream Thus, it is comprised so that a rocking | fluctuation period may differ.

  As a result, when the exhaust gas discharged according to the engine speed of the engine 21 is introduced into the tail pipe 27, the swing valve 40 and the flutter suppression valve 50 do not swing at the same cycle. Swinging each other is suppressed. If the swing periods are different from each other, a phase difference is generated between the opening degrees of the swing valve 40 and the flutter suppression valve 50, and pressures act on each other, so that the pressure fluctuations do not become periodic, and the occurrence of flapping occurs. It is suppressed. Therefore, the fluttering of the oscillating valve 40 is suppressed by the fluttering suppression valve 50, and the effect of suppressing the generation of abnormal noise due to the fluttering is obtained.

  Even if the flow pressure changes due to exhaust pulsation or the like that changes according to the engine speed of the engine 21, the swing valve 40 and the flutter suppression valve 50 have different swing cycles. Therefore, the occurrence of flapping of both valves can be effectively suppressed, and the effect of suppressing the generation of noise due to flapping can be obtained.

  Further, since the tail pipe 27 has the enlarged diameter portion 27h, the flow velocity of the exhaust gas flowing through the enlarged diameter portion 27h should be relatively slower than the flow velocity of the exhaust gas flowing through the portion of the exhaust pipe where the diameter is not expanded. The flow pressure that reaches the swing valve 40 can be made lower than that of the flutter suppression valve 50. If the flow pressures are different from each other, the rotational sensitivity of the rotation of each valve to the flow of exhaust gas changes, and the fluttering excited by the swing valve 40 is suppressed, and the generation of noise due to the fluttering is suppressed.

Also, due to the difference in rotational sensitivity, there is a difference in response to each valve, and even when there is a fluctuation in the flow pressure of exhaust gas, the fluttering sound due to the opening and closing operation of each valve due to pressure fluctuation does not change abruptly, Generation of abnormal noise is suppressed.
Thus, fluttering of the oscillating valve 40 is suppressed, so that when the air column resonance occurs in the tail pipe 27, the silencing effect due to the interference between the open end reflection and the closed end reflection is surely obtained. The effect of reliably preventing the generation of noise due to an increase in the sound pressure bell due to air column resonance can be obtained.

In addition, the swing valve 40 and the flutter suppression valve 50 have the swing shafts 41 and 51 in the tail pipe 27 with simple configurations of swing shafts 41 and 51, valve bodies 42 and 52, and weights 43 and 53, respectively. Since the shaft centers J ₄₀ and J ₅₀ are respectively rotated, an effect of reducing an increase in weight and an increase in manufacturing cost can be obtained.

Further, in the swing valve 40 and the flutter suppression valve 50, there is an effect that it is not necessary to prevent the flutter by urging a pair of rotating plates with the spring 7 as in the conventional exhaust device.
In the exhaust device 20, even when the engine 21 rotates at a high speed, the exhaust device 20 smoothly swings around the axis J ₄₀ of the swing shaft 41, so that the back pressure increases and an extra load is applied to the engine 21. The conventional back pressure problem is eliminated, and the exhaust performance of the engine 21 is improved.

By receiving only exhaust stream flowing through the tail pipe 27, the swing valve 40 about the axis J ₄₀ of the pivot shaft 41 so as to vary the size of the passage cross-sectional area of the tail pipe 27 to swing When the air column resonance occurs, the swing valve 40 can be swung based on the flow pressure of the exhaust flow having the exhaust flow rate corresponding to the operating state of the engine 21.

For this reason, when the air column resonance of the primary component f ₁ and the secondary component f ₂ occurs in the steady rotation region of the engine 21, the swing valve 40 can suppress an increase in the sound pressure level due to the air column resonance. The effect is obtained. That is, since the opening ratio of the opening 48 of the tail pipe 27 is reduced to about 20% by the oscillating valve 40, the open end reflected wave causing the air column resonance and the closed end reflected wave have a phase of 180 degrees. Both different closed end reflected waves can be generated, and the open end reflected wave and the closed end reflected wave can be made to interfere with each other. This interference can suppress an increase in sound pressure level due to air column resonance.

Further, since the swing valve 40 swings smoothly around the axis J ₄₀ of the swing shaft 41, when the engine 21 is in a high speed range and the throttle valve is closed and decelerated, the exhaust flow rate is reduced. Even if the flow pressure received by the pressure receiving surface portion 46c of the oscillating valve 40 decreases significantly, the oscillating valve 40 oscillates quickly upstream, so that the opening ratio of the opening 48 of the tail pipe 27 is quickly increased. Can be reduced to about 20%. Therefore, even when the engine 21 is decelerated, a closed-end reflected wave that is 180 degrees out of phase with the open-end reflected wave that causes the occurrence of air column resonance is quickly generated. And an increase in sound pressure level due to air column resonance can be suppressed.

Further, since the oscillating valve 40 is provided with the rectifying plate 47 on the valve body 42, an effect of suppressing the generation of airflow noise when the exhaust flow passes through the valve body 42 is obtained.
That is, in the case of the valve body 42 provided with the rectifying plate 47, compared with the case of the valve body not provided with the rectifying plate shown in FIG. 14, the flow noise of the exhaust gas passing through the valve body is generated. It is supposed to be suppressed.
In the case of the valve body not provided with the rectifying plate shown in FIG. 14, the gap between the semicircular lower end portion and the linear width direction both end portions of the valve body and the inner peripheral surface of the tail pipe (not shown) is exhausted. At the moment when the flows a and b pass, a turbulent flow such as a vortex is generated and an air flow noise is generated.

  On the other hand, as shown in FIG. 15, in the case of the valve body 42 provided with the rectifying plate 47, between the lower end portion of the valve body 42 and both side portions in the width direction and the inner peripheral surface of the tail pipe 27 (not shown). When the exhaust flows a1 and b2 pass through the gap, the exhaust flows a1 and b2 are rectified, so that the generation of turbulent flow such as vortex flow is suppressed.

In the exhaust device 20 of the first embodiment, the valve element 42 of the swing valve 40 is constituted by a pressure receiving plate 46 and a rectifying plate 47. The rectifying plate 47 is formed with a uniform thickness, and a weight 43 is provided. The case where it fixed to the curved part 47c of the baffle plate 47 was demonstrated.
However, you may make it comprise the valve body 42 of the rocking | fluctuation valve 40 by another structure. For example, the bending portion 47c of the rectifying plate 47 may be formed to have a large thickness, and the bending portion 47c may be configured to have a weight function.

Also in the flutter suppression valve 50, the valve body 52 is constituted by a pressure receiving plate 56 and a rectifying plate 57, the rectifying plate 57 is formed with a uniform thickness, and the weight 53 is formed on the curved portion 57c of the rectifying plate 57. The case of fixing was explained.
However, also in the flapping suppression valve 50, the valve body 52 may be configured with another structure. Similarly to the oscillating valve 40, the bending portion 57c of the rectifying plate 57 may be formed to be thick, and the bending portion 57c may be configured to have a function of a weight.

  Further, in the exhaust device 20 of the first embodiment, the swing valve 40 is provided at a position closest to the opening of the downstream opening end 27b of the tail pipe 27, and the swing valve 40 is provided at the node of the sound pressure distribution in the tail pipe 27. The case where it was positioned was explained. However, the oscillating valve 40 may be positioned at a node of the sound pressure distribution of the standing wave of air column resonance, and may be disposed at a position other than the downstream opening end 27b. For example, as shown in FIG. 12, the swing valve 40 may be provided so as to be positioned at the middle node of the sound pressure distribution of the secondary component, that is, at the center of the tail pipe 27. Further, the swing valve 40 may be provided at the upstream opening end 27 a of the tail pipe 27.

(Second Embodiment)
FIGS. 17 to 19 are views showing a second embodiment of the exhaust system for an internal combustion engine according to the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIGS. 17 and 18, the tail pipe 67 constituting the exhaust device 60 of the second embodiment includes an upstream portion 67A in which an upstream opening end 67a is formed and a downstream portion 67B in which a downstream opening end 67b is formed. And have.

The upstream portion 67A is provided with an enlarged diameter portion 67h in which the passage cross-sectional area of the accommodating portion 67c and the upstream opening end 67a is enlarged. The accommodating portion 67c, the swing valve 40 is accommodated in the vicinity of the opening of the upstream open end 67a, fluttering suppression valve 50, the axis _{J 50} the axis _{J 40} and flutter suppression valve 50 of the pivot valve 40 the distance between the so as to be L _3, is housed on the downstream side of the pivot valve 40 so as to apart from the extending direction of the tail pipe 67.
Further, the swing valve 40, the opening 68 made from a gap of a distance L ₄ between the inner surface 67n of the lower end and the tail pipe 67 is defined, the fluttering suppression valve 50, its lower end opening 69 consisting of a gap of a distance L ₅ between the inner wall surface 67w of the tail pipe 67 is defined.

As shown in FIG. 19, the oscillating valve 40 oscillates downstream in response to the flow pressure of the exhaust flow along the oscillating trajectory C _40. And swings upstream. State therefore, joined by the flow pressure of the exhaust stream, when the flow pressure is substantially constant state, the swing valve 40, which swings in the swinging period T ₄₀ described above, opened gradually attenuated at a constant aperture ratio It becomes.

Further, rattling suppression valve 50 is swung along a swing path C _50, swings to the downstream side receives the flow pressure of the exhaust stream, when the flow pressure of the exhaust stream decreases, the upstream side by the action of its own weight It is supposed to be. Therefore, when the flow pressure of the exhaust flow is substantially constant state, fluttering suppression valve 50 can be swung by swinging period T ₅₀ described above.

Since the exhaust device 60 of the second embodiment is configured as described above, the same effect as the exhaust device 20 of the first embodiment can be obtained.
That is, the oscillating valve 40 and the flutter suppression valve 50 do not oscillate at the same cycle, but sway each other. Therefore, the fluttering of the oscillating valve 40 is suppressed by the fluttering suppression valve 50, and the effect of suppressing the generation of abnormal noise due to the fluttering is obtained.
Thus, fluttering of the oscillating valve 40 is suppressed, so that when the air column resonance occurs in the tail pipe 67, the silencing effect due to the interference between the open end reflection and the closed end reflection is surely obtained. The effect of reliably preventing the generation of noise due to an increase in the sound pressure bell due to air column resonance can be obtained.

  Further, since the exhaust device 60 of the second embodiment is constituted by the swing valve 40 and the flutter suppression valve 50, respectively, as in the first embodiment, an increase in weight and an increase in manufacturing cost are reduced. The effect is obtained. Further, the back pressure does not increase and an extra load is not applied to the engine 21, so that the problem of the conventional back pressure is solved and the exhaust performance of the engine 21 is improved.

Since the opening ratio of the opening 68 of the tail pipe 67 is reduced to about 20% by the oscillating valve 40, the open end reflected wave causing the air column resonance and the closed end reflected wave are 180 degrees out of phase. Both end reflection waves can be generated, and the opening end reflection wave and the closed end reflection wave can be made to interfere with each other. This interference can suppress an increase in sound pressure level due to air column resonance.
Compared with the exhaust device 20 of the first embodiment, the exhaust device 60 of the second embodiment has a cylindrical simple shape because the downstream opening end 67b of the tail pipe 67 is not formed with the accommodating portion 27c. Even if the part is exposed from the rear part, the effect that the appearance is not impaired is obtained.

(Third embodiment)
FIG. 20 is a diagram showing a third embodiment of the exhaust system for an internal combustion engine according to the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

As shown in FIG. 20, the tail pipe 77 constituting the exhaust device 70 of the third embodiment has an upstream portion 77A where the upstream opening end 77a is formed and a downstream portion 77B where the downstream opening end 77b is formed. is doing.
As in the second embodiment, a swing valve 40 and a flutter suppression valve 50 are provided at the upstream opening end 77a of the upstream portion 77A. In addition, a swing valve 40 and a flutter suppression valve 50 are provided at the downstream opening end 77b of the downstream portion 77B, as in the first embodiment.

Since the exhaust device 70 of the third embodiment is configured as described above, the same effect as the exhaust device 20 of the first embodiment can be obtained.
That is, the swing valve 40 and the flutter suppression valve 50 provided at both the upstream opening end 77a and the downstream opening end 77b do not swing at the same cycle, but suppress the swinging from each other. Therefore, the fluttering of the oscillating valve 40 is suppressed by the fluttering suppression valve 50, and the effect of suppressing the generation of abnormal noise due to the fluttering is obtained.

In this way, fluttering of the swing valve 40 provided at both the upstream opening end 77a and the downstream opening end 77b is suppressed, and when air column resonance occurs in the tail pipe 77, the upstream opening end 77a and By the oscillating valves 40 provided at both the downstream opening ends 77b, the silencing effect due to the interference between the opening end reflection and the closing end reflection can be obtained.
Therefore, the exhaust device 70 of the third embodiment is more reliable in generating noise due to an increase in the sound pressure bell due to air column resonance than the exhaust device 20 of the first embodiment and the exhaust device 60 of the second embodiment. The effect of being prevented is obtained.

(Fourth embodiment)
FIGS. 21 to 23 are views showing a fourth embodiment of the exhaust system for an internal combustion engine according to the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIGS. 21 and 22, the tail pipe 87 constituting the exhaust device 80 of the fourth embodiment includes an upstream portion 87A in which an upstream opening end 87a is formed and a downstream portion 87B in which a downstream opening end 87b is formed. And have.

The downstream portion 87B is provided with an enlarged diameter portion 87h in which the passage sectional area of the accommodating portion 87c and the downstream opening end 87b is enlarged. The accommodating portion 87c, the swing valve 81 is accommodated in the vicinity of the opening of the downstream open end 87b, fluttering suppression valve 82 is in the axis _{J 50} the axis _{J 40} and flutter suppression valve 82 of the swing valve 81 as the distance between becomes L _3, it is housed on the upstream side of the swing valve 81 so as to apart from the extending direction of the tail pipe 87.
Further, the swing valve 81 has its opening 88 consisting of a gap of a distance L ₅ between the inner surface 87n of the lower end and the tail pipe 87 is defined, the fluttering suppression valve 82, its lower end opening 89 consisting of a gap of distance L ₄ between the inner wall surface 87w of the tail pipe 87 is defined.

The swing valve 81, as shown in FIG. 22 has the same configuration as the rattling suppression valve 50 of the first embodiment, as shown in FIG. 23 along the swing locus C _81, the exhaust stream When the flow pressure of the exhaust flow is lowered by receiving the flow pressure, the flow is swung to the upstream side by the action of its own weight. State therefore, joined by the flow pressure of the exhaust stream, when the substantially constant state flow pressure, the swing valve 81, which swings in the swinging period T ₄₀ described above, opened gradually attenuated at a constant aperture ratio It becomes.

Further, rattling suppression valve 82, as shown in FIG. 22 has the same configuration as the swing valve 40 of the first embodiment, as shown in FIG. 23 along the swing locus C _82, the exhaust stream When the flow pressure of the exhaust flow is reduced by receiving the flow pressure of the exhaust gas, the flow is swung upstream by the action of its own weight. Therefore, when the flow pressure of the exhaust flow is substantially constant state, fluttering suppression valve 82 can be swung by swinging period T ₅₀ described above.

Since the exhaust device 80 of the fourth embodiment is configured as described above, the same effect as the exhaust device 20 of the first embodiment can be obtained.
That is, the oscillating valve 81 and the flutter suppression valve 82 do not oscillate at the same cycle, and suppress swaying each other. Therefore, the fluttering of the swing valve 81 is suppressed by the flutter suppression valve 82, and the effect of suppressing the generation of abnormal noise due to the fluttering is obtained.

  In this way, fluttering of the swing valve 81 is suppressed, so that when the air column resonance occurs in the tail pipe 87, the silencing effect due to the interference between the opening end reflection and the closing end reflection can be reliably obtained. The effect of reliably preventing the generation of noise due to an increase in the sound pressure bell due to air column resonance can be obtained.

  Further, the swing valve 81 and the flutter suppression valve 82 are respectively configured in the same manner as the flutter suppression valve 50 and the swing valve 40 of the first embodiment, so that an increase in weight and an increase in manufacturing cost are reduced. The effect is obtained. Further, the back pressure does not increase and an extra load is not applied to the engine 21, so that the problem of the conventional back pressure is solved and the exhaust performance of the engine 21 is improved.

  Since the opening ratio of the opening 88 of the tail pipe 87 is reduced to about 20% by the swing valve 81, the open end reflected wave causing the air column resonance and the closed end different in phase from the closed end reflected wave by 180 degrees. Both end reflection waves can be generated, and the opening end reflection wave and the closed end reflection wave can be made to interfere with each other. This interference can suppress an increase in sound pressure level due to air column resonance.

(Fifth embodiment)
FIGS. 24 to 26 are views showing a fifth embodiment of the exhaust device for an internal combustion engine according to the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIGS. 24 and 25, the tail pipe 97 constituting the exhaust device 90 of the fifth embodiment includes an upstream portion 97A in which an upstream opening end 97a is formed and a downstream portion 97B in which a downstream opening end 97b is formed. And have.

The upstream portion 97B is provided with an enlarged diameter portion 97h in which the passage sectional area of the accommodating portion 97c and the upstream opening end 97a is enlarged. The accommodating portion 97c, the swing valve 91 is accommodated in the vicinity of the opening of the upstream open end 97a, fluttering suppression valve 92, the axis _{J 50} the axis _{J 40} and flutter suppression valve 92 of the pivot valve 91 the distance between the so as to be L _3, is housed on the downstream side of the swing valve 91 so as to apart from the extending direction of the tail pipe 97.
Further, the swing valve 91 has its lower end an opening 98 comprising a gap distance L ₅ between the inner surface 97n of the tail pipe 97 is defined, the fluttering suppression valve 92, its lower end opening 99 consisting of a gap of distance L ₄ between the inner wall surface 97w of the tail pipe 97 is defined.

The swing valve 91, as shown in FIG. 25 has the same configuration as the rattling suppression valve 50 of the first embodiment, as shown in FIG. 26 along the swing locus C _91, the exhaust stream When the flow pressure of the exhaust flow is lowered by receiving the flow pressure, the flow is swung to the upstream side by the action of its own weight. State therefore, joined by the flow pressure of the exhaust stream, when the substantially constant state flow pressure, swing valve 91, which swings in the swinging period T ₄₀ described above, opened gradually attenuated at a constant aperture ratio It becomes.

Further, rattling suppression valve 92, as shown in FIG. 25 has the same configuration as the swing valve 40 of the first embodiment, as shown in FIG. 26 along the swing locus C _92, the exhaust stream When the flow pressure of the exhaust flow is reduced by receiving the flow pressure of the exhaust gas, the flow is swung upstream by the action of its own weight. Therefore, when the flow pressure of the exhaust flow is substantially constant state, fluttering suppression valve 92 can be swung by swinging period T ₅₀ described above.

Since the exhaust device 90 of the fifth embodiment is configured as described above, the same effect as the exhaust device 20 of the first embodiment can be obtained.
That is, the oscillating valve 91 and the flutter suppression valve 92 do not oscillate at the same period, and suppress the oscillation of each other. Therefore, the fluttering of the swing valve 91 is suppressed by the fluttering suppression valve 92, and the effect of suppressing the generation of abnormal noise due to the fluttering is obtained.
In this way, fluttering of the swing valve 91 is suppressed, so that when the air column resonance occurs in the tail pipe 97, the silencing effect due to the interference between the open end reflection and the closed end reflection can be reliably obtained. The effect of reliably preventing the generation of noise due to an increase in the sound pressure bell due to air column resonance can be obtained.

  Further, the swing valve 91 and the flutter suppression valve 92 are respectively configured in the same manner as the flutter suppression valve 50 and the swing valve 40 of the first embodiment, so that an increase in weight and an increase in manufacturing cost are reduced. The effect is obtained. Further, the back pressure does not increase and an extra load is not applied to the engine 21, so that the problem of the conventional back pressure is solved and the exhaust performance of the engine 21 is improved.

  Since the opening ratio of the opening 98 of the tail pipe 97 is reduced to about 20% by the oscillating valve 91, the open end reflected wave causing the air column resonance and the closed end reflected wave are 180 degrees out of phase. Both end reflection waves can be generated, and the opening end reflection wave and the closed end reflection wave can be made to interfere with each other. This interference can suppress an increase in sound pressure level due to air column resonance.

(Sixth embodiment)
FIG. 27 is a view showing a sixth embodiment of the exhaust device for an internal combustion engine according to the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

As shown in FIG. 27, the tail pipe 107 constituting the exhaust device 100 of the sixth embodiment has an upstream portion 107A in which the upstream opening end 107a is formed and a downstream portion 107B in which the downstream opening end 107b is formed. is doing.
As in the fifth embodiment, a swing valve 91 and a flutter suppression valve 92 are provided at the upstream opening end 107a of the upstream portion 107A. Further, a swing valve 81 and a flutter suppression valve 82 are provided at the downstream opening end 107b of the downstream portion 107B, as in the fourth embodiment.

Since the exhaust device 100 of the sixth embodiment is configured as described above, the same effect as the exhaust device 20 of the first embodiment can be obtained.
That is, the oscillating valves 91 and 81 and the flutter suppression valves 92 and 82 provided at both the upstream opening end 107a and the downstream opening end 107b do not oscillate at the same period, and suppress swaying from each other. It will be. Therefore, the fluttering of the swing valves 91 and 81 is suppressed by the flutter suppression valves 92 and 82, and the effect of suppressing the generation of abnormal noise due to the fluttering is obtained.

In this way, fluttering of the swing valves 91 and 81 provided at both the upstream opening end 107a and the downstream opening end 107b is suppressed, and when air column resonance occurs in the tail pipe 107, the upstream opening end Oscillating valves 91 and 81 provided at both the 107a and the downstream opening end 107b respectively provide a silencing effect due to the interference between the opening end reflection and the closing end reflection.
Therefore, in the exhaust device 100 of the sixth embodiment, noise is more reliably generated due to an increase in the sound pressure bell due to air column resonance, compared to the exhaust device 80 of the fourth embodiment and the exhaust device 90 of the fifth embodiment. The effect of being prevented is obtained.

(Seventh embodiment)
FIGS. 28 to 33 are views showing a seventh embodiment of the exhaust device for an internal combustion engine according to the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

  As shown in FIGS. 28 to 30, the exhaust device 110 according to the seventh embodiment includes a tail pipe 117 as an exhaust pipe, a swing valve 111 as a first valve, and a flapping suppression valve 112 as a second valve. The other components are configured similarly to the exhaust device 20 of the first embodiment.

Tail pipe 117 includes an upstream portion 117A which is formed in a cylindrical shape, and a downstream portion 117B, is formed in a predetermined length _{L 2.} An upstream opening end 117a is formed in the upstream portion 117A, and a downstream opening end 117b is formed in the downstream portion 117B.
Further, as shown in FIGS. 29 and 30, the downstream portion 117B is provided with a storage portion 117c. A pair of valve mounting holes 117d and 117e for mounting the swing valve 111 and a pair of valve mounting holes 117f and 117g for mounting the flutter suppression valve 112 are formed in the upper portion of the accommodating portion 27c, respectively. .

The accommodating portion 117c, the swing valve 111 is accommodated in the vicinity of the opening of the downstream open end 117b, fluttering suppression valve 112, the axis _{J 112} the axis _{J 111} and flutter suppression valve 112 of the pivot valve 111 as the distance between becomes L _3, it is housed on the upstream side of the pivot valve 111 so as to apart from the extending direction of the tail pipe 117.
Further, the swing valve 111, the opening 118 made from a gap of a distance L ₄ between the inner wall surface 117n of the lower end and the tail pipe 117 is defined, the fluttering suppression valve 112 includes a lower end portion opening 119 comprising a gap distance _{L 4} between the inner surface 117w of the tail pipe 117 is defined.

As shown in FIGS. 30 and 32, the swing valve 111 is configured in the same manner as the swing valve 40 of the first embodiment, and as shown in FIG. 33, along the swing locus C ₁₁₁ , In response to the flow pressure of the exhaust flow, it swings downstream, and when the flow pressure of the exhaust flow decreases, it swings upstream due to its own weight. State therefore, joined by the flow pressure of the exhaust stream, when the substantially constant state flow pressure, swing valve 111, which swings in the swinging period T ₄₀ described above, opened gradually attenuated at a constant aperture ratio It becomes.
As shown in FIGS. 30 to 32, the flutter suppression valve 112 includes a swing shaft 41 as a second swing shaft, a valve body 113 as a second valve body, a weight 43, a snap ring 44, 45.

The valve body 113 includes a pressure receiving plate 46 and a rectifying plate 114. The rectifying plate 114 has a uniform thickness and a flat surface, a pair of side portions 114a and 114b arranged opposite to each other, and a curved portion formed by bending the side portions 114a and 114b integrally. 114c.
A through hole 114d is formed in the side portion 114a so as to be spaced apart from the upper end portion in the direction of the curved portion 114c, and the swing shaft 41 is inserted in a swingable manner. Further, a through hole 114e is also formed in the side portion 114b so as to be separated from the upper end portion in the direction of the curved portion 114c, and the swing shaft 41 is inserted so as to be swingable.

As shown in FIG. 32, the length as the second length between the center of mass P ₁₁₂ of the flutter suppression valve 112 and the axis J ₁₁₂ is L ₁₁₂ (m). When the acceleration of gravity is g (9.8 m / sec ² ), the flutter suppression valve 112 swings at a swing period T ₁₁₂ (one reciprocating time in the left and right: sec) represented by the following equation (9). Configured to work.

The distance between the inner wall surface 117w of the downstream portion 117B of the valve body 113 and the tail pipe 117 of the rattling suppression valve 112 is formed a gap so as to be L _4, this gap so that the exhaust gas flows It has become.
Further, as shown in FIG. 33, the flutter suppression valve 112 receives the flow pressure of the exhaust flow along the swing locus C ₁₁₂ and swings downstream, and when the flow pressure of the exhaust flow decreases, Due to the action, it swings upstream. Therefore, when the flow pressure of the exhaust flow is substantially constant state, fluttering suppression valve 112 can be swung by swinging period T ₁₁₂ described above.

The flutter suppression valve 112 and the swing valve 111 are configured such that the length L ₁₁₂ of the flutter suppression valve 112 shown in FIG. 32 is shorter than the length L _{40 of the} swing valve 111. Thus, the swing cycle _{T 112} of rattling suppression valve 112, and the swing period _{T 40} of the swing valve _111, located on the relation of T _{40> T 112,} are different from each other.

  Since the exhaust device 110 of the seventh embodiment is configured as described above, the same effect as the exhaust device 20 of the first embodiment can be obtained.

  That is, the oscillating valve 111 and the flutter suppression valve 112 do not oscillate at the same cycle, and suppress the oscillation of each other. Therefore, the fluttering of the swing valve 111 is suppressed by the fluttering suppression valve 112, and the effect of suppressing the generation of abnormal noise due to the fluttering is obtained.

  In this way, fluttering of the swing valve 111 is suppressed, so that when the air column resonance occurs in the tail pipe 117, the silencing effect due to the interference between the opening end reflection and the closing end reflection is surely obtained. The effect of reliably preventing the generation of noise due to an increase in the sound pressure bell due to air column resonance can be obtained.

  Further, since the swing valve 111 and the flutter suppression valve 112 are respectively configured in the same manner as the swing valve 40 of the first embodiment, an effect of reducing an increase in weight and an increase in manufacturing cost can be obtained. Further, the back pressure does not increase and an extra load is not applied to the engine 21, so that the problem of the conventional back pressure is solved and the exhaust performance of the engine 21 is improved.

  Since the opening ratio of the opening 118 of the tail pipe 117 is reduced to about 20% by the oscillating valve 111, the open end reflected wave causing the air column resonance and the closed end reflected wave are 180 degrees out of phase. Both end reflection waves can be generated, and the opening end reflection wave and the closed end reflection wave can be made to interfere with each other. This interference can suppress an increase in sound pressure level due to air column resonance.

(Eighth embodiment)
FIGS. 34 and 35 are views showing an eighth embodiment of the exhaust system for an internal combustion engine according to the present invention. The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIGS. 34 and 35, the exhaust device 120 of the eighth embodiment includes a tail pipe 127 as an exhaust pipe, a swing valve 121 as a first valve, and a flutter suppression valve 122 as a second valve. The other components are configured similarly to the exhaust device 110 of the seventh embodiment.

Tail pipe 127, an upstream portion 127A which is formed in a cylindrical shape, and a downstream portion 127B, is formed in a predetermined length _{L 2.} An upstream opening end 127a is formed in the upstream portion 127A, and a downstream opening end 127b is formed in the downstream portion 127B.

Moreover, as shown in FIG. 35, the accommodation part 127c is provided in the downstream part 127B.
The accommodating portion 127c, the swing valve 121 is accommodated in the vicinity of the opening of the downstream open end 127b, fluttering suppression valve 122, the axis _{J 122} the axis _{J 121} and flutter suppression valve 122 of the pivot valve 121 as the distance between becomes L _3, it is housed on the upstream side of the pivot valve 121 so as to apart from the extending direction of the tail pipe 127.
Further, the swing valve 121 has an opening 128 formed by a gap of a distance L ₄ between the lower end portion thereof and the inner wall surface portion 127 n of the tail pipe 127. opening 129 comprising a gap distance _{L 4} between the inner surface 127w of the tail pipe 127 is defined.

また、ばたつき抑制バルブ１２２は、第２錘としての錘１２４を含み第１実施形態の揺動バルブ４０と同様に構成されている。 The swing valve 121 includes a weight 123 as a first weight and is configured in the same manner as the swing valve 40 of the first embodiment. The center of mass _{P 121} of the swing valve 121, the length of the first length between the axial center _{J 121 has} a _{L 121} (m). When the acceleration of gravity is g (9.8 m / sec ² ), the oscillating valve 121 oscillates at an oscillating cycle T ₁₂₁ represented by the following equation (10) (one reciprocating time in the left and right: sec). Configured to work.

The flutter suppression valve 122 includes a weight 124 as a second weight and is configured in the same manner as the swing valve 40 of the first embodiment.

The center of mass _{P 122} of the rattling suppression valve 122, the length of the second length between the axial center _{J 122 has} a _{L 122} (m). When the acceleration of gravity is g (9.8 m / sec ² ), the flutter suppression valve 122 swings at a swing period T ₁₂₂ (time for one reciprocal movement in the left and right: sec) expressed by the following equation (11). Configured to work.

Since the length L ₁₂₂ of the flutter suppression valve 122 is shorter than the length L ₁₂₁ of the swing valve 121, the flutter suppression valve 122 and the swing are controlled so that the weight of the weight 123 is larger than the weight of the weight 124. Each of the valves 121 is configured. Thus, the swing cycle _{T 122} of rattling suppression valve 122, and the swing period _{T 121} of the swing valve _121, have a relationship of T _{121> T 122,} are different from each other.

Since the exhaust device 120 of the eighth embodiment is configured as described above, the same effect as the exhaust device 20 of the first embodiment can be obtained.
That is, the oscillating valve 121 and the flutter suppression valve 122 do not oscillate at the same period, and suppress the oscillation of each other. Therefore, the fluttering of the swing valve 121 is suppressed by the fluttering suppression valve 122, and an effect that the generation of abnormal noise due to the flapping is suppressed is obtained.

Since the weight of the weight 123 is configured to be larger than the weight of the weight 124, the rotational sensitivity to the flow pressure applied to the swing valve 40 is changed, and the fluttering excited by the swing valve 40 is suppressed. Sound generation is suppressed.
Also, due to the difference in rotational sensitivity, there is a difference in response to each valve, and even when there is fluctuation in the flow pressure of exhaust gas, the exhaust sound due to opening and closing operation of each valve due to pressure fluctuation does not change suddenly, Generation of abnormal noise is reliably suppressed.

  Thus, fluttering of the oscillating valve 121 is suppressed, so that when the air column resonance occurs in the tail pipe 127, the silencing effect due to the interference between the opening end reflection and the closing end reflection is surely obtained. The effect of reliably preventing the generation of noise due to an increase in the sound pressure bell due to air column resonance can be obtained.

  Further, since the swing valve 121 and the flutter suppression valve 122 are configured in the same manner as the swing valve 40 of the first embodiment except for the weights 123 and 124, an increase in weight and an increase in manufacturing cost are reduced. The effect is obtained. Further, the back pressure does not increase and an extra load is not applied to the engine 21, so that the problem of the conventional back pressure is solved and the exhaust performance of the engine 21 is improved.

  Since the opening ratio of the opening 128 of the tail pipe 127 is reduced to about 20% by the oscillating valve 121, the open end reflected wave causing the air column resonance and the closed end reflected wave are 180 degrees out of phase. Both end reflection waves can be generated, and the opening end reflection wave and the closed end reflection wave can be made to interfere with each other. This interference can suppress an increase in sound pressure level due to air column resonance.

  In the exhaust device 110 according to the seventh embodiment and the exhaust device 120 according to the eighth embodiment, the case where the swing valves 111 and 121 are accommodated near the openings of the downstream opening ends 117b and 127b has been described. However, you may make it comprise by structures other than the structure accommodated in the vicinity of the opening of the downstream opening ends 117b and 127b. For example, the oscillating valves 111 and 121 may be accommodated in the vicinity of the openings of the upstream opening ends 117a and 127a. The swing valves 111 and 121 may be accommodated in the vicinity of both the upstream opening ends 117a and 127a and the downstream opening ends 117b and 127b, respectively.

  In the case of these structures, as with the exhaust device 110 of the seventh embodiment and the exhaust device 120 of the eighth embodiment, a flutter suppression valve is provided separately from each of the swing valves 111 and 121 to Flapping excitation of the valves 111 and 121 is suppressed.

  As described above, the exhaust system for an internal combustion engine according to the present invention reduces the increase in weight and the increase in manufacturing cost, and increases the sound pressure level due to air column resonance of the tail pipe with a simple configuration. An exhaust system for an internal combustion engine that has the effect of being able to reliably suppress this, and that suppresses an increase in sound pressure level due to air column resonance of a tail pipe provided at the most downstream in the exhaust gas exhaust direction. Useful as.

20, 60, 70, 80, 90, 100, 110, 120 Exhaust device 21 Engine (internal combustion engine)
27, 67, 77, 87, 97, 107, 117, 127 Tail pipe 27A, 67A, 77A, 87A, 97A, 107A, 117A, 127A Upstream part 27B, 67B, 77B, 87B, 97B, 107B, 117B, 127B Downstream 27a, 67a, 77a, 87a, 97a, 107a, 117a, 127a Upstream opening end 27b, 67b, 77b, 87b, 97b, 107b, 117b, 127b Downstream opening end 27c, 67c, 87c, 97c, 117c, 127c 27h, 67h, 87h, 97h Expanded portion 40, 81, 91, 111, 121 Oscillating valve (first valve)
41 oscillating shaft (first oscillating shaft, second oscillating shaft)
42 Valve body (first valve body)
43,123 weights (first weight)
46, 56 Pressure receiving plate 47, 57, 114 Rectifying plate 48, 58, 68, 69, 88, 89, 98, 99, 118, 119, 128, 129 Opening 50, 82, 92, 112, 122 Flutter suppression valve ( Second valve)
51 Oscillation axis (second oscillation axis)
52, 113 Valve body (second valve body)
53,124 weight (second weight)
L _40, L ₁₂₁ length (first length)
L _50, L ₁₂₂ length (second length)
T40 _{, T121} swing cycle (swing cycle of the first valve)
T _50, T ₁₂₂ swing period (second valve swing period)

Claims (6)

Provided on the downstream side in the exhaust direction of the internal combustion engine, and having a downstream opening end on the downstream side in the exhaust direction for exhausting the exhaust gas of the internal combustion engine into the atmosphere, and an upstream opening end for introducing the exhaust gas in the upstream in the exhaust direction In the exhaust device provided with the exhaust pipe on the side,
The first rocking shaft is attached to the upper part of the exhaust pipe and receives only the exhaust flow flowing through the exhaust pipe, so that the size of the first cross-sectional area of the exhaust pipe is variable. A first valve having a first valve body that swings about a dynamic axis;
The second swing shaft is attached to the upper portion of the exhaust pipe so as to be spaced apart from the first swing shaft in the extending direction of the exhaust pipe, and receives only the exhaust flow flowing through the exhaust pipe. And a second valve having a second valve body that swings about the second swing shaft so as to vary the size of the passage cross-sectional area of the exhaust pipe.
An exhaust system for an internal combustion engine, wherein a swing cycle of the first valve when receiving the exhaust flow is different from a swing cycle of the second valve. The first valve and the second valve are provided on the downstream opening end side so that the second valve is located upstream of the first valve in the exhaust direction of the exhaust flow,
The first length from the center of the first swing shaft of the first valve to the center of mass of the first valve body is set to the second valve body from the center of the second swing shaft of the second valve. 2. The exhaust system for an internal combustion engine according to claim 1, wherein the exhaust system is longer than a second length up to the center of mass. The first valve and the second valve are provided on the downstream opening end side so that the second valve is located upstream of the first valve in the exhaust direction of the exhaust flow,
The first length from the center of the first swing shaft of the first valve to the center of mass of the first valve body is set to the second valve body from the center of the second swing shaft of the second valve. The exhaust system for an internal combustion engine according to claim 1, wherein the exhaust system is shorter than a second length to the center of mass of the internal combustion engine.   The diameter of the part of the exhaust pipe in which the longer one of the first length and the second length is accommodated is larger than the part of the exhaust pipe in which the shorter one of the valves is accommodated. An exhaust system for an internal combustion engine according to claim 2 or claim 3, wherein   The length from the axial center of the first oscillating shaft of the first valve to the lower end of the first valve body, and the lower end of the second valve body from the axial center of the second oscillating shaft of the second valve. The exhaust system for an internal combustion engine according to claim 1, wherein the length to the portion is made different.   A first weight is disposed at the lower end portion of the first valve body, and a second weight is disposed at the lower end portion of the second valve body so that the weight of the first weight is different from the weight of the second weight. The exhaust system for an internal combustion engine according to claim 1, wherein

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