JP5119230B2 - 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 an increase in sound pressure level due to air column resonance of a tail 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. 17 is known (for example, see Patent Document 1). As shown in FIG. 17, exhaust gas exhausted from the engine 1 as an internal combustion engine is introduced into the exhaust device 4 after passing through the exhaust manifold 2 and being purified by 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, and a tail pipe 8 connected to the main muffler 7. And a sub-muffler 9 interposed in the tail pipe 8.

  As shown in FIG. 18, the main muffler 7 includes an expansion chamber 7 a into which exhaust gas is expanded and introduced from a small hole 6 a of the center pipe 6, and a resonance chamber 7 b into which the downstream opening end 6 b of the center pipe 6 is inserted. The exhaust gas introduced into the resonance chamber 7b from the downstream opening end 6b of the center pipe 6 is silenced by the Helmholtz resonance.

Here, the length of the projecting portion of the center pipe 6 that projects into the resonance chamber 7b is L1 (m), the cross-sectional area of the center pipe 6 is S (m ² ), the volume of the resonance chamber 7b is V (m ³ ), air When the sound speed in the inside is c (m / s), the resonance frequency fn (Hz) in the air is obtained by the following equation (1) regarding Helmholtz resonance.

  As apparent from the above equation (1), the resonance frequency can be tuned to the low frequency side by increasing the volume V of the resonance chamber 7b or increasing the length L1 of the protruding portion of the center pipe 6. . Further, the resonance frequency can be tuned to the high frequency side by reducing the volume V of the resonance chamber 7b or shortening the length L1 of the protruding portion of the center pipe 6.

  The sub muffler 9 is configured to suppress an increase in sound pressure due to the occurrence of air column resonance corresponding to the length of the tail pipe 8 in the tail pipe 8 due to exhaust pulsation during operation of the engine 1.

  In general, the tail pipe 8 having the upstream opening end 8a and the downstream opening end 8b on the upstream side and the downstream side, respectively, in the exhaust direction of the exhaust gas has an incident wave caused by exhaust pulsation during operation of the engine 1 to the upstream opening end 8a of the tail pipe 8. By reflecting at the downstream opening end 8b, air column resonance having a wavelength at which a natural number multiple of the half wavelength becomes the tube length L is generated based on air column resonance with the tube length L of the tail pipe 8 being a half wavelength.

  For example, in the case where the tail pipe 8 not provided with the sub-muffler 9 extends rearward from the main muffler, as shown in FIG. 19A, as shown in FIG. The wavelength λ1 is approximately twice the tube length L of the tail pipe 8, and the wavelength λ2 of air column resonance of the secondary component is approximately 1 time the tube length L as shown in FIG. Further, as shown in FIG. 19 (c), the wavelength λ3 of air column resonance of the third order component is 2/3 times the tube length L. In this way, a standing wave is generated in the tail pipe 8 such that the upstream opening end 8a and the downstream opening end 8b are nodes of sound pressure.

ただし、ｃは音速（ｍ／ｓ）、Ｌはテールパイプの管長（ｍ）、ｎは次数とする。 Further, the air column resonance frequency fa of the tail pipe 8 is expressed by the following equation (2).

Where c is the speed of sound (m / s), L is the length of the tail pipe (m), and n is the order.

  As is clear from the above equation (2), the sound velocity c is a constant value corresponding to the temperature. Therefore, the longer the tube length L of the tail pipe 8, the more the air column resonance frequency fa shifts to the lower frequency side. It can be seen that the problem of noise due to air column resonance of the exhaust sound is likely to occur in the low frequency region.

ただし、Ｎｅはエンジン回転数（ｒｐｍ）、Ｎはエンジンの気筒数（自然数）とする。 Further, an exhaust pulsation frequency fe (Hz) of the engine 1 is expressed by the following equation (3).

Here, Ne is the engine speed (rpm), and N is the number of engine cylinders (natural number).

  Therefore, at a specific engine speed Ne, the exhaust pulsation frequency fe coincides with the air column resonance frequency fa. Therefore, as shown in FIG. 20, the sound pressure level (dB) of the exhaust sound becomes remarkably high at a specific engine speed Ne where the frequency fe of the exhaust pulsation becomes the primary component f1 of the exhaust sound due to air column resonance. Yes. In addition, the sound pressure level (dB) of the exhaust sound is remarkably high even at a specific engine speed Ne where the exhaust pulsation frequency fe is the secondary component f2 of the exhaust sound due to air column resonance.

  As described above, when the tail pipe 8 having a long pipe length is used, air column resonance may occur in a frequency region corresponding to the normal rotation region of the engine 1 (for example, 2000 rpm to 5000 rpm). Resonance exhaust sound is transmitted to the vehicle interior, causing a muffled sound in the vehicle interior, which causes discomfort to the driver.

  Therefore, when the length of the tail pipe 8 is long, the tail pipe 8 is optimally positioned with respect to the antinode a (see FIG. 19) where the sound pressures of the primary component f1 and the secondary component f2 of the exhaust sound due to air column resonance are high. A sub-muffler 9 having a smaller capacity than the main muffler 7 is provided to prevent air column resonance from occurring in the normal rotation region of the engine 1.

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

  That is, based on the equation (1), by increasing the volume V of the resonance chamber 7b or by increasing the length L1 of the protruding portion of the center pipe 6 to tune the resonance frequency of the resonance chamber 7b to the low frequency side, In the normal rotation range of the engine 1, it is conceivable to silence the air column resonance generated in the tail pipe 8 in advance in the resonance chamber 7b.

  However, since the accelerator pedal is released 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, and the air pressure introduced into the resonance chamber 7b decreases.

  For this reason, it is difficult to obtain an air amount sufficient to perform Helmholtz resonance in the resonance chamber 7b, and it becomes difficult to suppress air column resonance of the tail pipe 8. In particular, when the vehicle is decelerated, the rotational speed of the engine 1 sharply decreases, so the primary component f1 of the exhaust sound due to air column resonance enters the normal rotational range of the engine 1, and a loud noise is generated in the vehicle interior at a low rotational speed. This may cause the driver to feel uncomfortable.

  In order to reduce such noise during deceleration, there is known an exhaust device that includes a valve that opens and closes an exhaust pipe and includes a control device that controls the opening and closing of the valve (see, for example, Patent Document 2). .

  As shown in FIGS. 21 and 22, this exhaust system is provided with a silencer valve 10 at the downstream opening end 8 b of the tail pipe 8 that becomes a node of the sound pressure of the standing wave of air column resonance. 10 includes a valve case 11 and a butterfly valve type valve body 12 attached to the downstream opening end 8 b of the tail pipe 8, and an orifice 13 for restricting the passage cross-sectional area of the tail pipe 8 at the center of the valve body 12. Is formed.

  Further, the valve body 12 is provided with a drive shaft 14, and this drive shaft 14 is provided so as to extend in a direction perpendicular to the central axis in the extending direction of the tail pipe 8. The drive shaft 14 is connected to an electromagnetic actuator 17 via a drum 15 and a wire 16, and the electromagnetic actuator 17 is controlled to be turned on / off by a control unit 19.

  The control unit 19 outputs a command signal for on / off control of the electromagnetic actuator 17 to the electromagnetic actuator 17 based on a detection signal of a throttle sensor 18 that detects the opening of a throttle valve (not shown).

  Specifically, the control unit 19 normally outputs an off signal to the electromagnetic actuator 17 and keeps the valve body 12 in the open state by the electromagnetic actuator 17. The control unit 19 outputs an ON signal to the electromagnetic actuator 17 based on detection information from the throttle sensor 18 when the vehicle is decelerated, and causes the valve body 12 to be closed by the electromagnetic actuator 17.

  For this reason, it is possible to prevent the muffler valve 10 from hindering exhaust gas exhaust during steady running or acceleration of the vehicle. Further, when the vehicle decelerates, the exhaust gas passes only through the orifice 13, so that the particle motion is resisted at the node of the sound pressure of the standing wave of the air column resonance where the particle velocity of the exhaust gas is maximum, and the tail An increase in sound pressure due to air column resonance of the pipe 8 can be suppressed.

JP 2006-46121 A Japanese Patent Laid-Open No. 3-03912

  However, in such an exhaust system of the conventional engine 1, in the configuration in which the air column resonance of the tail pipe 8 is reduced by the resonance chamber 7b of the main muffler 7, it is necessary to increase the volume V of the resonance chamber 7b. Therefore, there is a problem that the main muffler 7 becomes large. In addition, the size of the main muffler 7 increases the weight of the exhaust device and increases the manufacturing cost of the exhaust device.

  Further, in the exhaust device that controls the opening and closing of the silencer valve 10 provided at the downstream opening end 8b of the tail pipe 8, it is possible to suppress an increase in sound pressure due to air column resonance of the tail pipe 8 when the vehicle is decelerated. Since it is necessary to control the opening and closing of the silencer valve 10 by the control unit 19 and the electromagnetic actuator 17, there is a problem that the structure and control of the exhaust device become complicated and the manufacturing cost of the exhaust device increases.

  The present invention has been made to solve the above-described conventional problems, and reduces the increase in weight and the manufacturing cost, and does not require complicated control and has a simple configuration, and the air column of the tail pipe. It is an object of the present invention to provide an exhaust device for an internal combustion engine that can suppress an increase in sound pressure level due to resonance.

  In order to solve the above problems, an exhaust system for an internal combustion engine according to the present invention includes (1) an upstream opening end for introducing exhaust gas discharged from the internal combustion engine, a downstream opening end for discharging the exhaust gas to the atmosphere, An exhaust system for an internal combustion engine having an exhaust pipe having a gas passage, wherein a part of a passage in the exhaust pipe is closed to suppress air column resonance generated in the exhaust pipe and exhaust of the introduced exhaust gas A valve body that changes an opening cross-sectional area of the passage by being swung by a flow, and an angle at which the valve body is swung is larger than a predetermined angle corresponding to air column resonance in the exhaust pipe And a load member for applying a load to the valve body.

With this configuration, since the valve body that closes a part of the passage in the exhaust pipe is provided, by reflecting the incident wave incident on the exhaust pipe by the valve body, the reflected reflection wave at the opening end that causes the occurrence of air column resonance and Closed-end reflected waves that are 180 degrees out of phase are generated, and the closed-end reflected waves interfere with the open-end reflected waves, thereby reducing the increase in weight and manufacturing cost and eliminating the need for complicated control. With a simple configuration, an increase in sound pressure level due to air column resonance can be suppressed.
In addition, since the opening cross-sectional area of the passage is changed by swinging the valve body provided in the exhaust pipe by the exhaust flow of exhaust gas, the cross-sectional area of the opening other than during air column resonance can be increased by swinging. In addition, an increase in exhaust gas back pressure and generation of airflow noise can be suppressed.

  Further, when the valve body is swung larger than a predetermined angle corresponding to air column resonance, the load member prevents the valve body from swinging, so that the rotation of the internal combustion engine is performed during deceleration and acceleration. Even if the number is the same, even if the angle of the valve body differs due to the difference in the flow rate of the exhaust gas, the valve body is accommodated within the angle that suppresses the air column resonance by the load member, and the air column is independent of the traveling state of the vehicle. Resonance can be suppressed.

  In order to solve the above problems, an exhaust system for an internal combustion engine according to the present invention is the exhaust system for an internal combustion engine according to (1), wherein (2) the angle at which the valve body is swung is the exhaust pipe. The opening area of the passage is smaller than a predetermined angle for suppressing the air column resonance, and the opening area of the passage is larger than the opening area of the passage for the predetermined angle for suppressing the air column resonance when the valve body swings. The valve body is arranged so as to be large.

  With this configuration, when the valve body swings less than a predetermined angle at which air column resonance is suppressed, the passage through which the exhaust gas flows is greatly opened, so that back pressure and airflow noise are suppressed. It can be carried out.

  Furthermore, an exhaust system for an internal combustion engine according to the present invention provides an exhaust system for an internal combustion engine according to the above (1) or (2), in order to solve the above-described problem, (3) It has a configuration characterized in that it is a weight that comes into contact with the valve body when it rotates by the predetermined angle and moves as the valve body rotates.

  With this configuration, by providing a weight that contacts and moves when the valve body rotates by a predetermined angle, a load can be applied to the swinging of the valve body. Thus, it is possible to easily apply a load, and it is possible to suppress air column resonance by suppressing the manufacturing cost.

  Furthermore, in order to solve the above problems, an exhaust system for an internal combustion engine according to the present invention is the exhaust system for an internal combustion engine according to (3), wherein (4) the rotary shaft that rotates together with the valve body, and the rotary shaft And a rotation transmitting portion that contacts the load member when the lens rotates more than the predetermined angle and moves the load member.

  With this configuration, by adjusting the angle at which the rotation transmitting portion contacts the load member, it is possible to adjust the angle that applies a load to the oscillation of the valve body, that is, the angle that suppresses the air column resonance. The opening amount of the passage can be easily adjusted by the angle of the valve body. Therefore, the suppression efficiency of the air column resonance that varies depending on the opening amount of the exhaust pipe passage can be easily adjusted.

Furthermore, an exhaust system for an internal combustion engine according to the present invention, in order to solve the above problems, in the exhaust system for an internal combustion engine according to any one of (1) to (4), (5) the load member is It has the structure characterized by being provided outside the exhaust pipe.
With this configuration, since the load member is outside the exhaust pipe, exhaust is not hindered by the load member, and the load member can be easily attached. Furthermore, since the load member is outside the exhaust pipe, the size of the load member is not restricted, and the moment of inertia can be easily increased. That is, by setting the center of gravity of the load member away from the rotation axis, the load on the valve body can be increased without increasing the weight.

  Furthermore, an exhaust system for an internal combustion engine according to the present invention is the exhaust system for an internal combustion engine according to any one of (1) to (5) described above, in order to solve the above problems. Sometimes, when the rotational speed of the internal combustion engine becomes a rotational speed that generates air column resonance in the exhaust pipe, the angle of the valve body swung by the exhaust flow of the exhaust gas exhausted from the internal combustion engine is The valve body is provided so as to have a predetermined angle for suppressing air column resonance.

  With this configuration, since the angle of the valve body is a predetermined angle that effectively suppresses air column resonance during deceleration operation, the air column resonance is effectively suppressed during deceleration operation where air column resonance sound is particularly worrisome. In addition, the flow rate of the exhaust gas increases compared to when decelerating and the rocking angle of the valve body becomes larger.In acceleration and steady running, the load member can suppress the rocking angle of the valve body. Air column resonance can be suppressed.

  Furthermore, an exhaust system for an internal combustion engine according to the present invention provides an exhaust system for an internal combustion engine according to any one of (1) to (6) above, in order to solve the above-mentioned problems. However, it has the structure characterized by extending in the said rocking | swiveling direction in the circular arc shape which makes the distance from the rocking | fluctuation rotation center of the said valve body a radius.

  With this configuration, the end of the valve body extends in an arc shape, so that the valve body angle that minimizes the opening area of the exhaust pipe passage is wide, and the rotation angle due to the swinging of the valve body is slightly shifted. Even in the case, the opening area can be the same, and it is easy to adjust the angle at which the load is applied to the valve body by the load member. The air column resonance can be suppressed, and the air column resonance corresponding to the change in the running state can be suppressed.

  According to the present invention, while suppressing an increase in weight and an increase in manufacturing cost, a complicated configuration is not required and a simple configuration is used, and further, a sound pressure level is increased by air column resonance regardless of the running state of the vehicle. Therefore, it is possible to provide an exhaust device for an internal combustion engine that can prevent the occurrence of the exhaust gas.

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 an exhaust system of the internal combustion engine. 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 a perspective view of the muffler which shows the partial internal structure of the muffler with which the tail pipe was connected. FIG. 3 is a diagram showing a first embodiment of an exhaust device for an internal combustion engine according to the present invention, and is a longitudinal sectional view of a muffler cut along a plane passing through the central axis of the tail pipe and the center pipe of FIG. 2. 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 of the downstream opening end 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 downstream opening end 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 sectional drawing which shows the AA cross section 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 the AA cross section of FIG. 5 when a rocking | swiveling plate rock | fluctuates. Further, (a) is a cross-sectional view when the swing plate is in the lowest vertical position, (b) is a cross-sectional view when the swing plate is in the downstream inclined position, and (c) is It is sectional drawing in case a rocking plate exists in a downstream opening position. 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 gas in 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 rocking | fluctuation plate opening degree characteristic figure showing the relationship between an engine speed and the opening degree of a rocking | fluctuation plate. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, (a)-(c) is the determination of sound pressure distribution of the air column resonance by the open end reflection which generate | occur | produces in a tail pipe. It is a figure explaining a standing wave. 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 of a tail pipe, and a sound pressure level. 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 state by which the incident wave G is distributed to the transmitted wave G1 and reflected wave R1, R2 in a downstream opening end. . 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 the downstream opening end of a tail pipe when the edge part of a rocking | swiveling plate is made into circular arc shape. 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 of the muffler which shows the partial internal structure of the muffler with which the tail pipe from which a part of structure differs 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 a perspective view of the downstream 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 a perspective view of the downstream opening end and movable weight of a tail pipe. It is a block diagram of the exhaust system of the conventional internal combustion engine. It is a longitudinal cross-sectional view of a muffler to which a conventional tail pipe having both ends as open ends is connected. (A)-(c) 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 the conventional tail pipe. It is a figure which shows the relationship between the engine speed of a conventional tail pipe, and a sound pressure level. It is a block diagram of the exhaust system of the other structure of the conventional internal combustion engine. It is a perspective view of the conventional silencer valve.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
First, the configuration of the exhaust device for an internal combustion engine according to the first embodiment of the present invention will be described with reference to the schematic block diagram of the exhaust device for the internal combustion engine shown in FIG.

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

  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 24, a cylindrical front pipe 25, a cylindrical center pipe 26, a muffler 27 as a silencer, and a tail pipe 28 as a cylindrical exhaust pipe. 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 side indicates the upstream side in the exhaust direction of the exhaust gas, and the downstream side indicates the downstream side in the exhaust direction of the exhaust gas.

  The upstream end of the catalytic converter 24 is connected to the downstream end of the exhaust collecting pipe 22e, and the downstream end of the catalytic converter 24 is connected to the front pipe 25 via a universal joint 29. This catalytic converter 24 is composed of a honeycomb base or a granular activated alumina support to which a catalyst such as platinum or palladium is attached, which is housed in a main body case, and performs reduction of NOx and oxidation of CO and HC. To do.

  The universal joint 29 is composed of a spherical joint such as a ball joint, and allows relative displacement between the catalytic converter 24 and the front pipe 25. The upstream end of the center pipe 26 is connected to the downstream end of the front pipe 25 via a universal joint 30. The universal joint 30 is composed of a spherical joint such as a ball joint, and allows relative displacement between the front pipe 25 and the center pipe 26.

  A downstream side of the center pipe 26 is connected to a muffler 27, and the muffler 27 is configured to mute the exhaust sound.

  As shown in FIGS. 2 and 3, the muffler 27 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 an end plate 32 and an end plate 33. A silencer body is configured including the outer shell 31, end plates 32 and 33, and the partition plate 34.

  A partition plate 34 provided in the outer shell 31 divides the outer shell 31 into an expansion chamber 35 for expanding exhaust gas and a resonance chamber 36 for silencing exhaust sound of a specific frequency by Helmholtz resonance. . Further, the end plate 32 and the partition plate 34 are formed with insertion holes 32a and 34a, respectively. The insertion holes 32a and 34a have downstream ends of the center pipe 26, that is, the muffler 27 of the center pipe 26. 26A of inlet pipes which consist of the part accommodated in the inside are penetrated.

  The inlet pipe portion 26 </ 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 26 b is open to the resonance chamber 36.

  The inlet pipe portion 26A is formed with a plurality of small holes 26a in the extending direction (exhaust gas exhaust direction) and the circumferential direction of the inlet pipe portion 26A, and the inside of the inlet pipe portion 26A and the expansion chamber 35 Are communicated through a small hole 26a.

  Therefore, the exhaust gas introduced into the muffler 27 through the inlet pipe portion 26A of the center pipe 26 is introduced into the expansion chamber 35 through the small hole 26a, and is introduced into the resonance chamber 36 from the downstream opening end 26b of the inlet pipe portion 26A. Is done.

  The exhaust gas introduced into the resonance chamber 36 is silenced by a specific frequency due to Helmholtz resonance.

That is, the length from the most downstream side of the small hole 26a of the inlet pipe portion 26A to the protruding portion of the inlet pipe portion 26A protruding into the resonance chamber 36 is L1 (m), and the cross-sectional area of the inlet pipe portion 26A is S (m ² ), Where the volume of the resonance chamber 36 is V (m ³ ) and the sound velocity in the air is c (m / s), the resonance frequency fn (Hz) in the air is expressed by the following equation (4) regarding Helmholtz resonance. Desired.

  As apparent from the above equation (4), the volume V of the resonance chamber 36 is reduced, the length L1 of the protruding portion of the inlet pipe portion 26A is shortened, or the cross-sectional area S of the inlet pipe portion 26A is increased. Thus, the resonance frequency can be tuned to the high frequency side. Further, by increasing the volume V of the resonance chamber 36, increasing the length L1 of the protruding portion of the inlet pipe portion 26A, or reducing the cross-sectional area S of the inlet pipe portion 26A, the resonance frequency is lowered to the low frequency side. Can be tuned.

  On the other hand, the partition plate 34 and the end plate 33 are formed with insertion holes 34b and 33a, respectively. The insertion holes 34b and 33a are formed on the upstream end of the tail pipe 28, that is, among the tail pipes 28. An outlet pipe portion 28 </ b> A composed of a portion housed inside the muffler 27 is inserted.

The tail pipe 28 has an upstream opening end 28a formed at one end portion, and a downstream opening end 28b formed at the other end portion separated from the upstream opening end 28a by a distance L. The upstream opening end 28a of the tail pipe 28 opens into the expansion chamber 35, and the downstream opening end 28b of the tail pipe 28 communicates with the atmosphere. For this reason, the exhaust gas introduced from the expansion chamber 35 of the muffler 27 to the upstream opening end 28a of the tail pipe 28 is discharged to the atmosphere from the downstream opening end 28b through the tail pipe 28.
A movable weight 46 serving as a weight is provided outside the tail pipe 28 and in the vicinity of the downstream opening end 28b of the tail pipe 28.

  As shown in FIGS. 4 to 7, a swing plate 41 as a valve body is provided at the downstream opening end 28 b of the tail pipe 28. The swing plate 41 is provided in a direction orthogonal to the central axis of the tail pipe 28 in the extending direction, and receives an exhaust pressure receiving surface 41a that receives an exhaust flow at a predetermined angle by swinging the exhaust flow, and a direction substantially perpendicular to the exhaust pressure receiving surface 41a. And the plate side surface portion 41b covering the downstream side surface and the lower surface of the exhaust pressure receiving surface 41a. Further, an insertion hole 41c through which a shaft member 42 as a rotation shaft is inserted is formed in the upper portion of the plate side surface portion 41b of the swing plate 41.

  Further, the swing plate 41 is installed so that the exhaust pressure receiving surface 41a is inclined to the upstream side of the tail pipe 28 when the exhaust pressure receiving surface 41a does not receive the exhaust gas flow.

  The shaft member 42 is attached to the tail pipe 28 so as to be orthogonal to the central axis of the tail pipe 28 in the extending direction and to be separated from the outer peripheral side with respect to the central axis of the tail pipe 28 in the extending direction.

  Further, the shaft member 42 rotates together with the swing plate 41. Further, the shaft member 42 has a hook 42 a as a rotation transmitting portion that rotates integrally with the shaft member 42 and moves the movable weight 46 when it comes into contact with the movable weight 46 at one end portion on the side where the movable weight 46 is provided. Is provided.

Further, projecting pieces 43a and 43b are formed on the outer peripheral upper portion of the downstream opening end 28b of the tail pipe 28, and insertion holes 43c through which the shaft member 42 is inserted are formed in the projecting pieces 43a and 43b, respectively. Yes.
An insertion hole 28c is formed in the upper part of the downstream opening end 28b of the tail pipe 28, and the shaft member 42 is inserted into the insertion hole 28c.

An insertion hole 46a is formed in the upper portion of the movable weight 46, and the shaft member 42 is inserted into the insertion hole 46a.
Further, a protruding piece 43d is formed on the upper side of the movable weight 46 on the side opposite to the tail pipe 28, and an insertion hole 43e through which the shaft member 42 is inserted is formed in the protruding piece 43d.

  Further, when no torque is applied to the swing plate 41 and the swing plate 41 is balanced only by its own weight, the hook 42a provided on the shaft member 42 and the weight upper surface of the movable weight 46 are provided. 46b is installed at a predetermined angle A. In other words, the hook 42 a comes into contact with the weight upper surface 46 b of the movable weight 46 when the swing plate 41 is rotated by the angle A by the exhaust gas exhaust flow. Therefore, the movable weight 46 functions as a load member that applies a load when the angle at which the swing plate 41 is swung is larger than the angle A.

  Further, snap rings 44 are attached to both ends of the shaft member 42. The snap ring 44 locks the shaft member 42 to the protruding pieces 43a and 43d, and the shaft member 42 is inserted into the insertion hole 41c. , 28c, 43c, 46a, 43e are prevented from coming out.

  Accordingly, as shown in FIG. 6, the swing plate 41 is moved from a position where the passage sectional area of the downstream opening end 28b of the tail pipe 28 is a predetermined passage sectional area (hereinafter referred to as an upstream inclined position) to the position shown in FIG. As shown in FIG. 7C, after the position where the passage sectional area of the downstream opening end 28b of the tail pipe 28 is the smallest (hereinafter referred to as the vertical lowest position), as shown in FIG. The passage sectional area of the downstream opening end 28b of the tail pipe 28 can be varied by swinging with the shaft member 42 as a rotation axis between the position where the passage sectional area of the opening end 28b is increased (hereinafter referred to as the downstream opening position). It is supposed to be. 7B shows the passage cross-sectional area of the downstream opening end 28b of the tail pipe 28 between the vertical lowest position shown in FIG. 7A and the downstream opening position shown in FIG. 7C. It is a figure which shows the position (henceforth a downstream inclination position) of the rocking | fluctuation plate 41 used as a predetermined | prescribed channel cross-sectional area.

  In addition, an opening 45 having a certain opening area is defined between the swing plate 41 and the plate side surface 41b and the downstream opening end 28b. That is, the opening 45 corresponds to the passage cross-sectional area of the downstream opening end 28b of the tail pipe 28 that is narrowed according to the angle at which the swing plate 41 is swung.

Next, the operation will be described.
Exhaust gas exhausted from each cylinder of the engine 21 during operation of the engine 21 is introduced from the exhaust manifold 22 to the catalytic converter 24, where the catalytic converter 24 reduces NOx and oxidizes CO and HC.

  Exhaust gas exhausted from the catalytic converter 24 is introduced into the muffler 27 through the front pipe 25 and the center pipe 26. The exhaust gas introduced into the muffler 27 is introduced into the expansion chamber 35 through the small hole 26a of the inlet pipe portion 26A, and is introduced into the resonance chamber 36 from the downstream opening end 26b of the inlet pipe portion 26A. In the exhaust gas introduced into the exhaust gas, 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 28 through the upstream opening end 28a of the outlet pipe portion 28A, and then discharged to the atmosphere through the downstream opening end 28b of the tail pipe 28.

  The downstream opening end 28b of the tail pipe 28 is provided with a swinging plate 41 that changes the opening cross-sectional area of the downstream opening end 28b by being swung by the exhaust gas exhaust flow. An opening 45 having a certain opening area is defined between 41 and the inner peripheral portion of the downstream opening end 28b. For this reason, in the region where the engine speed is the idling engine speed where the exhaust amount of exhaust gas is small (hereinafter referred to as the idling engine speed range), as shown in FIG. Exhaust gas (indicated by an arrow) introduced into the pipe 28 is discharged to the atmosphere with the opening 45 being opened wider than when the swing plate 41 is in the lowest vertical position (see FIG. 6). . Thereby, in the idling rotation region, the passage through which the exhaust gas flows is greatly opened, so that it is possible to suppress back pressure and generation of airflow noise.

  FIG. 9 shows the opening characteristic of the swing plate 41 representing the relationship between the rotational speed of the engine 21 and the ratio of the opening 45 in the cross-sectional area of the tail pipe 28, that is, the opening of the swing plate 41.

  As in the idling engine speed range, in a region where the engine speed is low and the exhaust gas displacement is small (hereinafter referred to as the low engine speed region), the swing plate 41 is in the upstream tilt position, or the upstream tilt position and the vertical lowest position. The exhaust gas introduced into the tail pipe 28 is exhausted to the atmosphere with the opening 45 being opened wider than when the swing plate 41 is in the lowest vertical position (see FIG. 6). . As a result, the passage through which the exhaust gas circulates greatly opens even in the low rotation range, so that back pressure can be suppressed and generation of airflow noise can be suppressed.

  Further, in a region where the engine speed is high and the exhaust amount of exhaust gas is large (hereinafter referred to as a high rotation region), the swing plate 41 is swung greatly by the exhaust flow, and the swing plate 41 becomes the downstream opening position, and the tail pipe. The exhaust gas introduced into 28 is discharged to the atmosphere in a state where the opening 45 is opened further on the downstream side than the opening area at the upstream inclined position (see FIG. 7C). Therefore, in the high rotation range, the passage through which the exhaust gas flows is opened larger than in the idle rotation range, and it is possible to suppress back pressure and generation of airflow noise.

  On the other hand, when the throttle valve is closed and the vehicle is decelerated (hereinafter referred to as a deceleration rotation region) from such a high rotation region, the amount of exhaust gas discharged from the engine 21 decreases. As a result, the swinging plate 41 reaches the lowest position in the vertical direction through the downstream inclined position, and the exhaust gas introduced into the tail pipe 28 is discharged to the atmosphere with the opening 45 being most narrowed (FIG. 7A). )reference). As a result, in the decelerating rotation region, reflected waves are generated by the closed portion where the passage through which the exhaust gas flows is closed by the swing plate 41 and the opened opening 45, respectively. Noise generated in the tail pipe 28 can be suppressed. The generation and interference of the reflected wave will be described later.

  Further, when the throttle valve is opened and the vehicle is accelerated from the idle rotation range or the low rotation range (hereinafter referred to as acceleration rotation range), the amount of exhaust gas discharged from the engine 21 increases. As a result, the swinging plate 41 passes through the vertical lowest position and becomes the downstream inclined position, and the exhaust gas introduced into the tail pipe 28 is discharged to the atmosphere with the opening 45 being throttled to some extent (FIG. 7B). )reference).

  Here, when the swing plate 41 rotates to the lowest vertical position, the hook 42 a provided on the shaft member 42 that rotates together with the swing plate 41 contacts the weight upper surface 46 b of the movable weight 46. Thus, the swing plate 41 is rotated by the torque that rotates only the swing plate 41 from the upstream tilt position to the vertical lowest position, but from the vertical lowest position to the downstream tilt position and the downstream opening position direction. In order to rotate, torque that rotates the movable weight 46 in addition to the swing plate 41 is required.

  Accordingly, the torque for rotating the swing plate 41 from the vertical lowest position to the downstream tilt position and the downstream opening position is more than the torque for rotating the swing plate 41 from the upstream tilt position to the vertical lowest position. Even when the same torque is applied, the rotation angle that rotates from the vertical lowest position to the downstream inclination position and the downstream opening position is more than the rotation angle from the upstream inclination position to the vertical lowest position. Get smaller.

  For this reason, in the acceleration rotation region, the opening 45 is not greatly opened. Similarly to the deceleration rotation region, the passage where the exhaust gas flows is closed by the swing plate 41, and the opening 45 is opened. Thus, a reflected wave is generated, and noise generated in the tail pipe 28 due to interference of the reflected wave can be suppressed.

  Next, the reflected wave and interference generated by the downstream opening end 28b of the tail pipe 28 and the swing plate 41 will be described.

  The exhaust gas introduced into the tail pipe 28 by the operation of the engine 21 is input with an exhaust pulsation that changes according to the rotational speed of the engine 21. This exhaust pulsation becomes an incident wave of the tail pipe 28, and this incident wave has a frequency that increases as the rotational speed of the engine 21 increases.

  When an incident wave due to exhaust pulsation during operation of the engine 21 is introduced into the tail pipe 28, this incident wave is reflected at the opening 45 of the downstream opening end 28 b of the tail pipe 28, so-called opening end reflection. The reflected wave has the same phase as the incident wave and the traveling direction is opposite to the incident wave. Further, this reflected wave is again reflected at the upstream opening end 28a in the opposite direction with the same phase as this reflected wave. This reflected wave then becomes an incident wave and becomes a reflected wave at the opening 45 at the downstream opening end 28b.

  The reason for the reflection at the opening end is that the pressure of the exhaust gas flowing in the tail pipe 28 is high and the pressure outside the downstream opening end 28b of the tail pipe 28 is low. This is because the pressure of the exhaust gas in the end 28b is lowered, and the low pressure portion starts to advance through the tail pipe 28 toward the upstream opening end 28a.

  Therefore, the reflected wave has the same phase as the incident wave and reverse direction. The reason why the reflected wave is generated on the upstream opening end 28a side is the same as the reason why the reflected wave is generated on the downstream opening end 28b.

  The incident wave toward the opening 45 of the downstream opening end 28b and the reflected wave opposite to the opening 45 of the downstream opening end 28b interfere with each other, so that the upstream opening end 28a and the downstream opening end 28b of the tail pipe 28 A standing wave is created in which the opening 45 becomes a node of the sound pressure distribution.

  Further, when the standing wave 28 has a specific relationship between the length L of the tail pipe 28 and the wavelength λ of the standing wave, the standing wave has an extremely large amplitude and air column resonance occurs. This air column resonance is based on a standing wave with the pipe length L of the tail pipe 28 as a half wavelength, and a standing wave having a wavelength at which the natural number multiple of the half wavelength is the tube length L is generated, increasing the sound pressure. It becomes noise.

  Specifically, as shown in FIG. 10A, the sound pressure distribution of the standing wave of the air column resonance, the wavelength λ1 of the air column resonance of the fundamental vibration (primary component) is 2 of the tube length L of the tail pipe 28. As shown in FIG. 10B, the air column resonance wavelength λ2 of the secondary component is one time the tube length L. Further, as shown in FIG. 10C, the wavelength λ3 of the air column resonance of the third order component is 2/3 times the tube length L, and each standing wave has the upstream opening end 28a and the downstream opening of the tail pipe 28. The end 28b is a node of the sound pressure distribution. Further, since the rocking plate 41 of the present embodiment is provided at the downstream opening end 28b of the tail pipe 28, it is located at the node of the sound pressure distribution of the standing wave of air column resonance.

  Further, as shown in FIG. 11, the sound pressure level (dB) of the exhaust sound corresponds to the resonance frequency (Hz) of the primary component f1 and the secondary component f2 as the engine speed (rpm) increases. Each becomes maximum at the engine speed Ne.

Here, the air column resonance frequency fc (Hz) of the tail pipe 28 when the sound velocity is c (m / s), the length of the tail pipe 28 is L (m), and the order is n is the following equation (5). ).

Further, the frequency fe of the exhaust pulsation of the engine when the engine speed is Ne and the number of cylinders is N is expressed by the following equation (6).

  When the sound speed c is 400 m / s and the pipe length L of the tail pipe 28 is 3.0 m, the primary component f1 of the exhaust sound due to the air column resonance of the tail pipe 28 is based on the above equation (5). 66.7 Hz and the secondary component f2 are 133.3 Hz.

  In the present embodiment, since the engine 21 has four cylinders, N = 4, and the exhaust pulsation frequency fe is 66.7 Hz when the engine speed is 2000 rpm based on the above equation (6). And coincides with the primary component f1 of the air column resonance, and the exhaust noise increases. Further, when the engine speed is 4000 rpm, the frequency fe of the exhaust pulsation becomes 133.3 Hz, which coincides with the secondary component f2 of the air column resonance, and the exhaust noise increases.

  In particular, in a low speed rotation range (a rotation range where the engine speed is 3000 rpm or less) that generates a low frequency of 100 Hz or less, a muffled sound is generated in the passenger compartment, which causes discomfort to the driver.

  At the third-order air column resonance frequency, the engine speed is about 6000 rpm, and the vehicle is in a high speed running state. Therefore, noise caused by air column resonance is driven by various noises generated at high speed such as wind noise. The person who does not care about the person. Therefore, the third order component and higher order components are not a problem.

  Therefore, the exhaust device 20 of the present embodiment swings around the shaft member 42 as the central axis so that the downstream opening end 28b of the outlet pipe portion 28A receives only the exhaust flow and changes the passage cross-sectional area in the tail pipe 28. By providing an oscillating plate 41 that moves, and setting the position of the oscillating plate 41 that oscillates according to the flow rate of the exhaust flow to be the position of the node of the sound pressure distribution of the standing wave of air column resonance, Two reflected waves of an open end reflection and a closed end reflection are generated at the downstream opening end 28b of the outlet pipe portion 28A to suppress an increase in sound pressure level (dB) due to air column resonance. .

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

When the opening area of the opening 45 is S1, the opening area of the downstream opening end 28b is S2, and the acoustic impedance of the medium is Z1 and Z2, respectively, the sound reflectance Rp is expressed by the following equation (7).

Here, the acoustic impedance is the product of the density of the medium and the speed of sound. In this case, since the medium is exhaust gas, Z1 = Z2, and the sound reflectance Rp is expressed by the following equation (8). expressed.

  When the closed end reflected wave by the swing plate 41 and the open end reflected wave by the opening 45 have the same intensity, both reflected waves are most suppressed by interference. In order to make the closed end reflected wave by the swing plate 41 and the open end reflected wave by the opening 45 have the same strength, the reflectance Rp may be set to 0.5. S1 = (1/3) · S2. Therefore, when the swing plate 41 is swung, the opening area of the opening 45 in the state where the downstream opening end 28b is closed becomes 1/3 of the opening area of the downstream opening end 28b. The level will be most suppressed.

  Hereinafter, a case where an incident wave G due to exhaust pulsation during operation of the engine 21 is incident on the tail pipe 28 and the wavelength of the incident wave G is an incident wave G having the tube length L of the tail pipe 28 as a half wavelength will be described. .

  As shown in FIG. 12, the incident wave G is transmitted to the atmosphere through the opening 45 at the downstream opening end 28b of the tail pipe 28, and reflected from the downstream opening end 28b toward the upstream opening end 28a. The wave R1 (open end reflection wave) is reflected. Further, the reflected wave (closed end reflected wave) R2 of the incident wave G is reflected by the swing plate 41 from the downstream opening end 28b toward the upstream opening end 28a.

The reflected wave R1 is an open end reflected wave having the same phase as the incident wave G, and the reflected wave R2 is a closed end reflected wave having a phase difference of 180 degrees with respect to the incident wave G.
In FIG. 12, since the reflected wave R1 has the same phase as the incident wave G, the incident wave G and the reflected wave R1 overlap each other. However, for convenience of explanation, the reflected wave R1 is compared with the incident wave G. It is shifted downward.

  Thus, since the reflected wave R1 has the same phase as the incident wave G, when the frequency of the incident wave G becomes the air column resonance frequency of the tail pipe 28, the reflected wave R1 reinforces each other due to interference between the incident wave G and the reflected wave R1. The sound pressure level of the exhaust sound is increased.

On the other hand, since the reflected wave R2 is 180 degrees out of phase with the reflected wave R1 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. 11, when the frequency of the incident wave G due to the exhaust pulsation becomes the primary component f1 of the air column resonance frequency of the tail pipe 28, only the interference due to the reflected wave R1 that is the open end reflected wave is a broken line. As shown, the sound pressure level increases (becomes a maximum), but due to interference by the reflected wave R2 that is the closed-end reflected wave, the sound pressure level increases due to air column resonance, as shown by the solid line. And the sound pressure level of the exhaust sound can be greatly reduced.

  Similarly, when the frequency of the incident wave G due to the exhaust pulsation becomes the secondary component f2 of the air column resonance frequency of the tail pipe 28, the sound pressure level due to the interference of the reflected wave R1 that is the open end reflected wave Is suppressed by the interference of the reflected wave R2, which is a closed-end reflected wave, and the sound pressure level of the exhaust sound can be greatly reduced.

  Here, in the above description, when the downstream opening end 28b is closed by the swinging of the swinging plate 41, and the opening 45 becomes 1/3 of the opening area of the downstream opening end 28b, the sound pressure level due to air column resonance. However, even if the opening area of the opening 45 is not 1/3 of the opening area of the downstream opening end 28b, the effect of suppressing the sound pressure level of the air column resonance due to interference of the closed end reflected wave is ,appear. However, if the predetermined ratio, for example, the opening area is 70% or more, the effect of suppressing the sound pressure level is significantly reduced.

  Therefore, in the present embodiment, when the engine speed becomes the air column resonance speed during deceleration, the position where the swing plate 41 minimizes the opening area of the downstream opening end 28b, that is, the vertical lowest position, Set as follows. When the rocking plate 41 reaches the lowest vertical position, for example, the sound pressure level generated by air column resonance can be most effectively suppressed. 28b is closed so that the opening area of the opening 45 is ３ of the opening area of the downstream opening end 28b.

  Here, the rocking plate 41 opens largely downstream because the exhaust gas flows more in comparison with the exhaust gas during deceleration during acceleration or steady running, but is moved downstream from the vertical lowest position by the movable weight 46. Since the load is applied to the rotation to the side, the rotation to the downstream side is suppressed, and the position of the swing plate 41 becomes the downstream inclined position without opening to the downstream opening position.

  Therefore, as described above, the angle of the oscillating plate 41 is set to an angle that most effectively suppresses the air column resonance at the time of deceleration. The sound pressure level can be effectively suppressed, and the flow rate of the exhaust gas is increased compared with that during deceleration, and the rocking plate 41 is swung by the movable weight 46 at the time of acceleration or steady running when the rocking angle is increased. Since the swing angle of the plate 41 can be suppressed, the sound pressure level generated by air column resonance can be suppressed even during deceleration.

  Further, by setting the opening area of the opening 45 when the swinging plate 41 is at the lowest position in the vertical direction to be smaller than 1/3 of the downstream opening end 28b, the opening area of the opening 45 during acceleration is also increased. It can be suppressed to a small value, and the effect of suppressing the sound pressure level during acceleration can be enhanced.

  Thus, in this embodiment, by providing a swing plate 41 that closes a part of the downstream opening end 28b of the tail pipe 28 and changes the opening cross-sectional area of the passage by being swung by the exhaust flow, A closed end reflected wave that is 180 degrees out of phase with the open end reflected wave that causes the air column resonance can be generated, and the closed end reflected wave and the open end reflected wave can interfere with each other. An increase in pressure level can be suppressed.

  As a result, it is not necessary to control the swing plate 41 by the control unit and the electromagnetic actuator, to enlarge the muffler 27 (corresponding to the conventional main muffler), or to install the sub muffler in the tail pipe 28 as in the past. Therefore, it is possible to prevent an increase in the weight of the exhaust device 20, prevent an increase in the manufacturing cost of the exhaust device 20, and a sound pressure level due to air column resonance with a simple configuration that prevents the addition of complicated control. Can be suppressed.

  Further, the rocking plate 41 is swung by the exhaust flow of the exhaust gas, thereby changing the opening cross-sectional area of the passage and greatly opening the opening 45 in the idle rotation speed range and the high rotation speed range. Increase in gas back pressure and generation of airflow noise can be suppressed.

  Further, by providing a movable weight 46 that applies a load to the swing of the swing plate 41 when the swing plate 41 is swung to the downstream side of the vertical lowest position, the swing plate 41 is moved to the vertical lowest position. When the rocker is swung further downstream, the rocking is hindered by the movable weight 46. Therefore, even if the engine 21 has the same rotational speed as during deceleration and acceleration, the rocking plate varies depending on the flow rate of the exhaust gas. Even when the angle of 41 differs, the movable weight 46 allows the swing plate 41 to be contained within an angle that suppresses air column resonance, and the air column resonance can be suppressed regardless of the traveling state of the vehicle.

  Further, the swing plate 41 of the present embodiment is configured so that a load is applied to the rotation when the hook 42 a that rotates integrally with the shaft member 42 contacts the weight upper surface 46 b of the movable weight 46. Therefore, by adjusting the set angle between the hook 42a and the weight upper surface 46b, the angle that applies a load to the swing of the swing plate 41, that is, the angle that suppresses the air column resonance can be adjusted. 28, the angle of the swinging plate 41 that changes the opening area of the opening 45 can be easily adjusted, and the suppression efficiency of air column resonance can be easily adjusted.

  Further, since the movable weight 46 of the present embodiment is provided outside the tail pipe 28, the movable weight 46 does not hinder the exhaust in the tail pipe 28, and the movable weight 46 can be easily attached.

  Further, as shown in FIG. 13, a swing plate 53 is provided in place of the swing plate 41, and the plate bottom 53 b of the swing plate 53 is a circle whose radius is the distance from the swing rotation center of the swing plate 53. It can be made into the shape extended in the rocking | fluctuation direction in an arc shape.

  With this configuration, the plate bottom 53b of the swing plate 53 extends in an arc shape, so that the angle of the swing plate 53 that minimizes the opening area of the passage cross-sectional area of the tail pipe 28 extends over a wide range. Even when the rotation angle due to the swing of 53 is slightly deviated, the opening area can be the same, and the angle at which the load is applied to the swing plate 53 by the movable weight 46 can be easily adjusted. Even if the angle of the swing plate 53 is deviated depending on the running state of the vehicle, the same air column resonance can be suppressed, and the air column resonance corresponding to the change in the running state can be suppressed.

  In the present embodiment, the swing plate 41 is in the lowest vertical position when the engine speed reaches the air column resonance speed during deceleration. However, the present invention is not limited to this, and the engine speed is not limited to this. However, the rocking plate 41 may be set at the vertical lowest position at a rotational speed smaller than the air column resonance rotational speed. In this case, since the difference in opening of the swing plate 41 between the time of deceleration and the time of acceleration is reduced, the efficiency of suppressing the sound pressure level due to air column resonance can be improved both during the deceleration and during the acceleration.

  Further, in the present embodiment, the swing plate 41 is provided only at the downstream opening end 28b of the tail pipe 28. However, as shown in FIG. It may be provided only at the end 28a. Further, in addition to the swing plate 41 at the downstream opening end 28 b of the tail pipe 28, a swing plate 52 may be provided at the upstream opening end 28 a of the tail pipe 28.

  In this way, the swing plate 52 is provided only at the upstream opening end 28a of the tail pipe 28 and the swing plates 41 and 52 are provided at both the upstream opening end 28a and the downstream opening end 28b of the tail pipe 28. Even so, the reflected wave reflected from the upstream opening end 28a of the tail pipe 28 is divided into two reflected waves, a reflected wave R1 by the opening 45 of the swing plate 52 and a reflected wave R2 by the swing plate 52. And increase in sound pressure due to air column resonance can be suppressed.

  In this embodiment, the swing plate 41 is provided at the downstream opening end 28b of the tail pipe 28. However, when the swing plate 41 is at the lowest vertical position, the sound of standing wave of air column resonance is obtained. The swing plate 41 may be provided so as to be located at the node of the pressure distribution, for example, so as to be positioned at the middle node of the sound pressure distribution of FIG.

  Furthermore, in the present embodiment, a load is applied by the movable weight 46 so that the swing plate 41 is less likely to swing in the downstream direction from the lowest vertical position. For example, a load may be applied to the swing plate 41 by a spring or the like. In this case, the same effect as the exhaust device for the internal combustion engine described above can be obtained.

(Second Embodiment)
Next, the configuration of the exhaust device for an internal combustion engine according to the second embodiment of the present invention will be described with reference to FIGS. 15 and 16. In the present embodiment, the same components as those in the exhaust device for the internal combustion engine of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 15, in the exhaust device for an internal combustion engine of the present embodiment, a hook member 42 b is provided on a shaft member 42 that rotates integrally with the swing plate 41. The tail pipe 28 is provided with a movable weight 47 in the vicinity of the hook 42b.

  The movable weight 47 has a rotating shaft 47a fixed to the tail pipe 28, and is rotatable about the rotating shaft 47a as a central axis. Further, the rotation shaft 47 a of the movable weight 47 is provided in parallel with the shaft member 42 with the axis line different from that of the shaft member 42.

  Further, the hook 42 b rotates integrally with the shaft member 42 so as to come into contact with the movable weight 47 when rotated by a predetermined angle A. Therefore, the movable weight 47 does not participate in the rotation of the shaft member 42 up to the predetermined angle A. However, when the shaft member 42 tries to rotate more than the predetermined angle A, the movable weight 47 is pivoted by its own weight via the hook 42b. The rotation of the member 42 is prevented. That is, the swinging plate 41 rotates up to the vertical lowest position regardless of the movable weight 47, but if it tries to rotate further downstream than the vertical lowest position, the movable weight 47 prevents the rotation.

  As described above, according to the present embodiment, the shaft member 42 that supports the swing plate 41 and the rotary shaft 47a that supports the movable weight 47 are provided separately. Since the load 47 is not applied, the load applied to the bearings supporting the swing plate 41 and the shaft member 42 can be reduced.

  As described above, the exhaust device for an internal combustion engine according to the present invention has a simple configuration that does not require complicated control while reducing an increase in weight and an increase in manufacturing cost, and further, regardless of the traveling state of the vehicle. The increase in the sound pressure level due to the air column resonance of the tail pipe provided at the most downstream in the exhaust gas exhaust direction has the effect of suppressing the increase in the sound pressure level due to the air column resonance. This is useful as an exhaust device for an internal combustion engine that suppresses the above.

20 exhaust system 21 engine (internal combustion engine)
22 Exhaust Manifold 22a, 22b, 22c, 22d Exhaust Branch Pipe 22e Exhaust Collecting Pipe 24 Catalytic Converter 25 Front Pipe 26 Center Pipe 26A Inlet Pipe Portion 26a Small Hole 26b, 28b Downstream Open End 27 Muffler 28 Tail Pipe (Exhaust Pipe)
28A Outlet pipe portion 28a Upstream opening end 28c, 32a, 33a, 34a, 34b, 41c, 43c, 43e, 46a Insertion hole 29, 30 Universal joint 31 Outer shell 32, 33 End plate 34 Partition plate 35 Expansion chamber 36 Resonance chamber 41, 52, 53 Oscillating plate (valve element)
41a Exhaust pressure receiving surface 41b Plate side surface 42 Shaft member 42a, 42b Hook (rotation transmitting portion)
43a, 43b, 43d Projection piece 44 Snap ring 45 Opening 46, 47 Movable weight (load member, weight)
46b Weight upper surface 47a Rotating shaft 53b Plate bottom (end of valve body)

Claims (5)

An exhaust system for an internal combustion engine comprising an exhaust pipe having an upstream opening end for introducing exhaust gas discharged from the internal combustion engine and a downstream opening end for discharging the exhaust gas to the atmosphere,
A portion of the passage in the exhaust pipe is closed to suppress air column resonance generated in the exhaust pipe, and the opening cross-sectional area of the passage is changed by being swung by the exhaust flow of the introduced exhaust gas. A valve body to
And a load member which gives a load to the valve body when the valve body to swing in the downstream side of the exhaust pipe than the predetermined angle to suppress the columnar resonance,
The valve body is swung by an exhaust flow of exhaust gas exhausted from the internal combustion engine when the rotational speed of the internal combustion engine becomes a rotational speed that generates the air column resonance during deceleration operation of the internal combustion engine. Are arranged at the predetermined angle,
When the valve body is positioned on the upstream side of the exhaust pipe with respect to the state where the valve body is swung at the predetermined angle, the valve body is swung at a predetermined angle with respect to the opening cross-sectional area of the passage. An exhaust system for an internal combustion engine, wherein the exhaust system is disposed so as to be larger than an opening cross-sectional area of the passage . 2. The internal combustion engine according to claim 1, wherein the load member is a weight that comes into contact with the valve body when the valve body rotates by the predetermined angle and moves as the valve body rotates. Exhaust system. A rotating shaft that rotates together with the valve body;
A rotation transmission unit that contacts the load member when the rotation shaft rotates more than the predetermined angle, and moves the load member;
An exhaust system of an internal combustion engine according to claim 2, further comprising a. The exhaust device for an internal combustion engine according to any one of claims 1 to 3, wherein the load member is provided outside the exhaust pipe . The valve body has a bottom portion that forms the gap with the inner surface of the exhaust pipe,
The bottom portion is curved from the upstream side to the downstream side of the exhaust flow in an arc shape having a radius from the swing rotation center of the valve body in a state where the valve body swings at the predetermined angle. The exhaust device for an internal combustion engine according to any one of claims 1 to 4 , wherein the exhaust device is an internal combustion engine.

Images