JP5126200B2 - 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 of exhaust sound due to air column resonance that occurs in an exhaust pipe.

Conventionally, as an exhaust device of this type of internal combustion engine, an upstream exhaust pipe connected to a catalytic converter that purifies the exhaust gas of the engine, a sub muffler connected to the upstream exhaust pipe, and an exhaust direction downstream side of the sub muffler A main muffler provided on the downstream side, a downstream exhaust pipe connected to the sub muffler and the main muffler, and a silencer valve provided on the downstream exhaust pipe are known (for example, Patent Documents). 1).
The silencer valve is opened and closed by an electromagnetic actuator, and the electromagnetic actuator is controlled by a control unit based on detection information from a throttle sensor.
In this exhaust system, exhaust sound during steady running or acceleration of the vehicle is silenced by the main muffler and the sub muffler. On the other hand, the exhaust sound during deceleration is muted as follows.
That is, when the control unit determines that the vehicle is decelerating based on the detection information of the throttle sensor, the silencer valve is closed by the electromagnetic actuator. When the silencing valve is closed, the flow rate of the exhaust gas in the downstream side exhaust pipe is reduced, and the particle speed of the exhaust sound is suppressed. As a result, an increase in the sound pressure of the exhaust sound is suppressed, and the exhaust sound is silenced.

As an exhaust device for a conventional internal combustion engine, one as shown in FIG. 30 is known.
As shown in FIG. 30, the exhaust device 4 includes a front pipe 5a, a center pipe 5b, a tail pipe 5c, a main muffler 6 connected to the tail pipe 5c, an outlet pipe 7 connected to the main muffler 6, and a center pipe. 5 and a sub-muffler 8 interposed between the tail pipe 5c. The front pipe 5 a is connected to the catalytic converter 3, and the exhaust gas flowing from the catalytic converter 3 flows into the main muffler 6 via the sub muffler 8. The catalytic converter 3 purifies exhaust gas exhausted from the engine 1 via the exhaust manifold 2.

  As shown in FIG. 31, the main muffler 6 includes an expansion chamber 6a into which exhaust gas is expanded and introduced from a small hole 5d of the tail pipe 5c, and a resonance chamber 6b into which the downstream opening end 5f of the tail pipe 5c is inserted. It has. When exhaust gas is introduced into the resonance chamber 6b from the downstream opening end 5f, exhaust sound of a specific frequency excites Helmholtz resonance in the resonance chamber 6b, and the exhaust sound is silenced by the Helmholtz resonance. It has become.

In the main muffler 6 having such a Helmholtz resonance structure, for example, if the length of the protruding portion of the tail pipe 5c protruding to the resonance chamber 6b is L ₀ (mm), the length L ₀ is increased. The resonance frequency is tuned to the low frequency side by increasing the volume of the resonance chamber 6b. On the other hand, so that tuning or shortening the length L _0, the resonance frequency or to reduce the volume of the resonance chamber 6b on the high frequency side.
Further, the sub muffler 8 increases the sound pressure of the air column resonance generated in the exhaust pipe corresponding to the length of the exhaust pipe constituted by the front pipe 5a, the center pipe 5b and the tail pipe 5c due to exhaust pulsation during operation of the engine 1. The exhaust pipe is provided at an optimum position so as to suppress the above.

ただし、Ｌは排気管の管長（ｍｍ）、ｄは排気管の直径（ｍｍ）、Ｃは排気ガスの温度Ｔ（°Ｋ）における音速（ｍ／ｓ）、ｍは次数をそれぞれ表す。
式（１）、（２）から明らかなように、音速Ｃは、温度Ｔ（°Ｋ）に応じた一定の値となるので、排気管の管長Ｌが長い程、周波数ｆａが問題となる低周波数側に移行してしまうことがわかる。 In general, in the tail pipe 5c having the upstream opening end 5e and the downstream opening end 5f on the upstream side and the downstream side in the exhaust direction of the exhaust gas, incident waves due to exhaust pulsation during operation of the engine 1 are caused by the upstream opening of the tail pipe 5c. The so-called open end reflection is performed at the end 5e and the downstream open end 5f. Due to the reflection at the opening end, a standing wave of air column resonance having a frequency in which the length of the exhaust pipe described above is a half wavelength is generated. Since the standing wave of air column resonance is generated even when the incident wave has a frequency that is a natural number multiple of the fundamental vibration consisting of the primary sound pressure mode, from the low-order sound pressure mode to the high-order sound pressure mode. Will occur at multiple frequencies. However, particularly in the low-order sound pressure mode in the low frequency region such as when decelerating, a muffled sound is generated in the passenger compartment due to air column resonance of the exhaust sound, and the problem of exhaust noise is likely to occur.
The frequency fa (Hz) of the standing wave due to such air column resonance is generally represented by the following opening end reflection formulas (1) and (2).

Where L is the length (mm) of the exhaust pipe, d is the diameter (mm) of the exhaust pipe, C is the speed of sound (m / s) at the exhaust gas temperature T (° K), and m is the order.
As apparent from the equations (1) and (2), the speed of sound C is a constant value corresponding to the temperature T (° K), so that the longer the exhaust pipe length L is, the lower the frequency fa becomes. It turns out that it shifts to the frequency side.

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）を表す。
図１１の破線で示すように、特定のエンジン回転数Ｎｅで、音圧レベル（ｄＢ）が高くなっていることがわかる。この音圧レベルの高い山の部分は、排気脈動に対応して発生した気柱共鳴によるもので、排気音の１次音圧モードｆ_１および２次音圧モードｆ_２で騒音の問題が生ずることになる。エンジン１の回転数Ｎｅが２０００ｒｐｍ〜５０００ｒｐｍの常用回転数領域で排気管内に気柱共鳴が発生すると、この気柱共鳴の排気音が車室内に伝達され、車室内にこもり音を生じさせてしまい、運転者に不快感を与えてしまうことになる。特に、エンジン１の排気脈動の周波数が１００Ｈｚ以下、すなわちエンジン回転数Ｎｅが３０００ｒｐｍ以下の低い回転数領域で気柱共鳴が発生するような場合に大きな騒音となる。 Since the air column resonance of the exhaust pipe is excited by the exhaust pulsation of the engine 1, the frequency fa (Hz) of the air column resonance and the frequency fe (Hz) of the exhaust pulsation have the same value.
The exhaust pulsation frequency fe (Hz) of the engine 1 is expressed by the following equation (3).

However, Ne represents the engine speed (rpm), and n represents the number of cylinders (natural number) of the engine.
As shown by the broken line in FIG. 11, it can be seen that the sound pressure level (dB) is high at a specific engine speed Ne. This mountain portion with a high sound pressure level is due to air column resonance generated corresponding to exhaust pulsation, and noise problems occur in the primary sound pressure mode f ₁ and the secondary sound pressure mode f ₂ of the exhaust sound. It will be. When air column resonance occurs in the exhaust pipe in the normal rotation speed region where the rotational speed Ne of the engine 1 is 2000 rpm to 5000 rpm, the exhaust sound of the air column resonance is transmitted to the vehicle interior, and a noise is generated in the vehicle interior. This will make the driver uncomfortable. In particular, the noise becomes loud when air column resonance occurs in a low rotational speed region where the frequency of exhaust pulsation of the engine 1 is 100 Hz or lower, that is, the engine rotational speed Ne is 3000 rpm or lower.

  For this reason, as shown in FIG. 32, a sub-muffler 8 having a capacity smaller than that of the main muffler 6 is provided at a position substantially in the center of the exhaust pipe that becomes the antinode a of the standing wave having a high sound pressure in the primary sound pressure mode of the exhaust sound. It is provided to reduce air column resonance when the vehicle is accelerating or decelerating. For the secondary sound pressure mode of exhaust sound, the resonance chamber 6b reduces the air column resonance sound during acceleration. As a result, in the conventional exhaust system, by providing the sub-muffler 8 in the exhaust pipe, it is possible to suppress the occurrence of a booming noise in the passenger compartment in the normal rotational speed region where the rotational speed Ne of the engine 1 is 2000 rpm to 5000 rpm. It is possible to prevent the driver from feeling uncomfortable.

  Further, as an exhaust device for a conventional internal combustion engine, a silencer main body, an exhaust pipe inserted through the silencer main body, a resonator pipe branched from the exhaust pipe and having a tip opened in the silencer main body, A communicating pipe that branches off from the middle of the resonator pipe and whose tip is connected to the exhaust pipe, an on-off valve that is provided in the middle of the communicating pipe and opens and closes the branch passage in the communicating pipe, and a control that controls the opening and closing of the on-off valve What is comprised with the apparatus is known (for example, refer patent document 2).

  In this exhaust system for an internal combustion engine, when the engine speed is relatively small and the frequency of the exhaust sound to be silenced is relatively small, the on-off valve is closed by the control device. By closing the on-off valve in this way, the exhaust gas flows through the exhaust pipe side, the entire length of the resonator pipe can be used, and the noise of low frequency components due to Helmholtz resonance is reduced. become. On the other hand, as the engine speed increases, the opening / closing valve is controlled by the control device so that the opening degree becomes larger. As a result, the flow rate of the exhaust gas flowing through the communication pipe increases, and the tip of the resonator pipe can be used from the branch part of the communication pipe in the resonator pipe, and noise of high frequency components due to Helmholtz resonance is reduced. become. As a result, noise of two frequencies consisting of a low frequency component and a high frequency component is reduced with a single structure.

Japanese Utility Model Publication No. 63-82022 Japanese Utility Model Publication 2-119915

  In the conventional exhaust apparatus described in Patent Document 1, exhaust sounds during steady running or acceleration of the vehicle are silenced by both the main muffler and the sub muffler, so the weight of the exhaust apparatus is reduced. There has been a problem that the manufacturing cost increases. Further, when the internal combustion engine is decelerated, the control unit closes the silencer valve based on the detection information of the throttle sensor, and muffles the exhaust sound by suppressing the particle velocity of the sound wave in the downstream exhaust pipe. Therefore, there is a problem that the structure becomes complicated and control takes time.

  Further, in the conventional exhaust system shown in FIG. 30, a sub muffler 8 is provided so that air column resonance noise during acceleration or deceleration of the vehicle is reduced by cooperation of the sub muffler 8 and the main muffler 6. Therefore, there is a problem that the weight of the exhaust device increases and the manufacturing cost increases. In this conventional exhaust device, even if the sub muffler 8 is eliminated as a solution and the air column resonance of the exhaust pipe is reduced by the resonance chamber 6b of the main muffler 6, it is necessary to increase the volume of the resonance chamber 6b. There is a problem that the main muffler 6 is enlarged. As a result, the weight of the exhaust device 4 increases as the main muffler 6 increases in size, and the manufacturing cost of the exhaust device 4 increases.

Further, in the structure in which the air column resonance of the exhaust pipe is reduced by the resonance chamber 6b of the main muffler 6, the accelerator pedal is released when the internal combustion engine is decelerated, so that the flow rate of the gas exhausted from the engine 1 to the exhaust device 4 is reduced. The air pressure is suddenly decreased and the air pressure introduced into the resonance chamber 6b is reduced. For this reason, there is a problem that it is difficult to obtain air pressure sufficient to perform Helmholtz resonance in the resonance chamber 6b, and it is difficult to suppress the occurrence of air column resonance in the exhaust pipe. In particular, when the internal combustion engine is decelerated, the rotational speed of the engine 1 rapidly decreases, so that a loud noise is generated in the vehicle interior at a low rotational speed of about 2000 rpm (primary sound pressure mode of exhaust sound due to air column resonance). There was a problem that the driver was uncomfortable.
Therefore, in the conventional exhaust apparatus shown in FIG. 30, it is essential to provide the sub-muffler 8 at the optimum position of the exhaust pipe, and to suppress the increase in sound pressure due to the air column resonance of the exhaust pipe. As a result, the weight of the exhaust device 4 increases and the manufacturing cost of the exhaust device 4 increases.

  Further, in the exhaust device described in Patent Document 2, a communication pipe is formed which branches from the middle of the resonator pipe and whose tip is connected to the exhaust pipe, and the distribution route of the exhaust gas passes through the exhaust pipe. Since there are a plurality of routes including a route and a route through the resonator pipe and the communication pipe, there is a problem that the structure becomes complicated and the manufacturing cost of the exhaust device increases. In addition, since the opening / closing valve provided in the communication pipe is controlled by the control device to open and close the branch passage, the structure is further complicated, the opening / closing control is troublesome, and the manufacturing cost of the exhaust device 4 increases. There was a problem.

  The present invention has been made to solve the above-described conventional problems, and includes a muffler having a sub-muffler in the tail pipe and a large-capacity resonance chamber in the vicinity of the downstream opening end of the tail pipe. The exhaust of the internal combustion engine that can suppress the increase in sound pressure due to air column resonance of the tail pipe with a simple structure even when the internal combustion engine is decelerated, and can reduce the weight and manufacturing cost It is an object to provide an apparatus.

  In order to solve the above problems, an exhaust system for an internal combustion engine according to the present invention is (1) an exhaust system for an internal combustion engine provided with a silencer that silences the exhaust sound of exhaust gas flowing through the exhaust pipe of the internal combustion engine. A silencer is located on the silencer body in which an internal space is formed, a resonance chamber located on the upstream side in the exhaust direction of the exhaust gas, and a downstream side in the exhaust direction of the exhaust gas relative to the resonance chamber. A partition member that divides into an expansion chamber, a flow passage that is provided in the silencer body and has an upstream opening end connected to the downstream end of the exhaust pipe and a downstream opening end that opens in the expansion chamber is formed. An inlet pipe having a communication pipe in which a communication path is formed to communicate the flow path and the resonance chamber; and downstream of the resonance chamber in the exhaust direction, the downstream opening of the inlet pipe And an opening / closing member that is provided in any one of the flow passages located between the downstream opening end and the communication passage and opens and closes the flow passage according to the flow rate of the exhaust gas flowing in the flow passage. An upstream opening end provided in the silencer body and opening in the expansion chamber, and a downstream opening end located outside the silencer body and opening into the atmosphere, and exhaust gas from the expansion chamber to the atmosphere And an outlet pipe for discharging.

With this configuration, when the internal combustion engine is decelerated or in a low rotation region, the exhaust gas flows through the exhaust pipe, flows into the flow passage from the upstream open end of the inlet pipe connected to the downstream end of the exhaust pipe, and is closed Passes through a gap defined between the opening and closing member and the inlet pipe and flows into the expansion chamber. At this time, the volume of the exhaust gas is rapidly expanded, the pressure fluctuation formed by the exhaust pulsation of the internal combustion engine is weakened, and the sound pressure level of the exhaust noise is reduced over a wide frequency band.
The exhaust gas in the expansion chamber flows into the outlet pipe from the upstream opening end and is discharged to the atmosphere from the downstream opening end.
Further, the exhaust gas in the circulation passage of the inlet pipe flows into the resonance chamber through the communication passage of the communication pipe. At this time, that is, when the opening / closing member is in the closed state, resonance having the same frequency as the frequency of the air column resonance generated in the air column of the closed tube defined by the exhaust pipe and the inlet pipe is generated in the resonance chamber. The so-called Helmholtz resonance in the resonance chamber causes the exhaust gas to vibrate in the communication passage, and the vibration energy of the exhaust gas is converted into thermal energy by resistance such as friction between the inner wall of the communication pipe surrounding the communication passage and the exhaust gas. Sound is attenuated. In this case, since the opening / closing member at the downstream opening end of the inlet pipe is in a closed state, a state in which the sound pressure in the resonance chamber is high is ensured, and the exhaust sound attenuation action due to Helmholtz resonance is enhanced.

  On the other hand, when the internal combustion engine is in acceleration or in a high rotation region, the exhaust gas flows through the exhaust pipe, flows into the flow passage from the upstream open end of the inlet pipe connected to the downstream end of the exhaust pipe, The opening / closing member is opened by the back pressure and the fluid pressure. The exhaust gas passes through the opening / closing member and flows into the expansion chamber, and the sound pressure level of the exhaust noise is reduced over a wide frequency band due to the expansion effect described above. The exhaust gas in the expansion chamber flows into the outlet pipe from the upstream opening end and is discharged to the atmosphere from the downstream opening end.

  Further, the exhaust gas in the circulation passage of the inlet pipe flows into the resonance chamber through the communication passage of the communication pipe. At this time, that is, when the open / close member is in the open state, resonance having the same frequency as the frequency of the air column resonance generated in the air column of the open tube defined by the exhaust pipe and the inlet pipe is generated in the resonance chamber. The exhaust sound is attenuated by Helmholtz resonance in the resonance chamber. In this case, even when the opening / closing member at the downstream opening end of the inlet pipe is in an open state and the sound pressure in the vicinity thereof is reduced, if the internal combustion engine is in the high rotation region, the flow rate of the exhaust gas increases and the resonance chamber is increased. The sound pressure of is increased, and the exhaust sound due to Helmholtz resonance is effectively attenuated. Further, since the open / close member is in the open state, the back pressure does not increase in the exhaust pipe and the inlet pipe, and no load is applied to the internal combustion engine by the open / close member.

  As a result, even when the internal combustion engine is in the low rotation region, an increase in sound pressure due to air column resonance of the closed pipe defined by the exhaust pipe and the inlet pipe is suppressed. Further, when the internal combustion engine is in the high rotation region, an increase in sound pressure due to air column resonance of the open pipe defined by the exhaust pipe and the inlet pipe is suppressed. That is, an increase in the sound pressure of the exhaust sound is suppressed with a simple structure, and the weight and manufacturing cost are reduced.

  In the exhaust system for an internal combustion engine according to the above (1), preferably (2) the communication pipe projects from the inlet pipe so as to be substantially perpendicular to the axial line of the inlet pipe, It is comprised from what has the open end which opens.

With this configuration, since the communication pipe protrudes from the inlet pipe so as to be substantially orthogonal to the axial direction line of the inlet pipe, the communication path can be formed relatively long, and the resonance frequency of the Helmholtz resonance can be caused. It can be easily set to the low frequency side.
Further, the communication passage of the communication pipe and the resonance chamber can be positioned in the vicinity of the upstream side of the opening / closing member, and at the time of deceleration of the internal combustion engine, the closed pipe defined by the exhaust pipe and the inlet pipe has a high sound pressure portion. A communication path can be arranged. As a result, particularly when the internal combustion engine is decelerated or in a low rotation range, an increase in the sound pressure of the exhaust sound due to Helmholtz resonance is effectively suppressed.

  In the exhaust device for an internal combustion engine according to the above (1) or (2), preferably (3) the outer peripheral portion of the inlet pipe along the axial direction of the inlet pipe so that the communication pipe surrounds the inlet pipe The communication passage is defined by an inner peripheral surface of the communication pipe and an outer peripheral surface of the inlet pipe, and the communication passage is formed through the through hole provided in the outer peripheral portion of the inlet pipe. The pipe is configured to communicate with the flow passage.

With this configuration, the communication pipe is provided on the outer periphery of the inlet pipe along the axial direction of the inlet pipe so as to surround the communication pipe, so that the communication path can be formed relatively long, and the resonance frequency of Helmholtz resonance is a problem. It can be set to the low frequency side where it is likely to occur.
In addition, the communication passage of the communication pipe communicating with the resonance chamber can be positioned immediately upstream of the opening / closing member, and when the internal combustion engine is decelerated, the sound pressure of the closed pipe defined by the exhaust pipe and the inlet pipe is the highest. The communication passage can be arranged at a high portion. As a result, particularly when the internal combustion engine is decelerating, an increase in the sound pressure of the exhaust sound due to Helmholtz resonance is extremely effectively suppressed.

  In the exhaust device for an internal combustion engine according to any one of the above (1) to (3), preferably, (4) the silencer is provided at a most downstream position on the downstream side in the exhaust direction of the exhaust device. Composed of things.

  With this configuration, the silencer is provided at the most downstream position on the downstream side in the exhaust direction of the exhaust device, so that the sub-muffler on the upstream side of the exhaust device can be eliminated, and the weight and manufacturing cost are reduced.

  In the exhaust device for an internal combustion engine according to any one of the above (1) to (4), preferably, (5) the opening / closing member is in a closed state when the internal combustion engine is decelerated, and a passage cross-sectional area of the circulation passage is set. Consists of narrowing down.

With this configuration, the flow rate of the exhaust gas passing through the opening / closing member during deceleration of the internal combustion engine is reduced so as to be smaller than the flow rate of the exhaust gas passing through the opening / closing member during acceleration, so that the upstream side of the opening / closing member during deceleration of the internal combustion engine. The sound pressure of the exhaust sound near the side is increased.
That is, the peak of the sound pressure can be made near the upstream side of the opening / closing member when the internal combustion engine is decelerated, and the sound pressure in the resonance chamber is increased. As a result, the air column resonance generated in the closed pipe defined by the exhaust pipe and the inlet pipe during deceleration is suitably suppressed by the Helmholtz resonance.

  According to the present invention, it is not necessary to install a sub-muffler in the tail pipe and to install a silencer having a large-capacity resonance chamber in the vicinity of the downstream opening end of the tail pipe. An increase in sound pressure due to air column resonance of the pipe can be suppressed with a simple structure, and an exhaust device for an internal combustion engine that can reduce weight and manufacturing cost can be provided.

1 is a diagram showing a first embodiment of an exhaust device for an internal combustion engine according to the present invention, and is a perspective view showing a configuration of an exhaust system of the internal combustion engine. FIG. 1 is a diagram showing a first embodiment of an exhaust device for an internal combustion engine according to the present invention, and is a perspective view of the muffler showing a part of the muffler in cross section. 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 side view of the muffler seen from the upstream. 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 of the muffler 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 shows the relationship between the cross-sectional area S of the communicating member for reducing the sound of a specific frequency, the length L of a communicating member, and the volume V of a cavity. It is a schematic diagram shown. 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 an inlet 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 inlet pipe seen from the downstream opening end side. 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 of the inlet pipe which shows the BB 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, (a) is a figure which shows the flow of the exhaust gas in a closed inlet pipe, a muffler, and an outlet pipe, (b) is a figure. It is a figure which shows the flow of the exhaust gas in an open state inlet pipe, a muffler, and an outlet pipe. 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) shows the standing wave of the air column resonance which generate | occur | produces in a closed tail pipe, and shows a sound pressure on a vertical axis | shaft. It is a figure explaining with the sound pressure distribution which represented the position of the tail pipe on the axis | shaft typically, (b) is the standing wave of the air column resonance which generate | occur | produces in the tail pipe of an open state, and the sound pressure on the ordinate. It is a figure explaining with the sound pressure distribution which represented the position of the tail pipe typically on the horizontal axis. 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 sound pressure level of a tail pipe, and engine speed Ne. 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 muffler which shows a part of muffler in cross section. FIG. 13 is a view showing a second embodiment of the 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 inlet pipe and the outlet pipe of FIG. 12. 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 inlet pipe which shows a part in cross section. 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 front view of the inlet pipe seen from the downstream opening end side. 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 longitudinal cross-sectional view which shows CC cross section of FIG. It is a figure which shows 2nd Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, (a) is a figure which shows the flow of the exhaust gas in a closed inlet pipe, a muffler, and an outlet pipe, (b) is a figure. It is a figure which shows the flow of the exhaust gas in an open state inlet pipe, a muffler, and an outlet pipe. It is a figure which shows 3rd 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 a part of muffler in cross section. FIG. 21 is a view showing a third embodiment of the 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 inlet pipe and the outlet pipe of FIG. 20. It is a figure which shows 3rd Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a front view of the inlet pipe seen from the downstream opening end side. 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 inlet pipe and communication pipe which show the DD cross section of FIG. It is a figure which shows 3rd Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, (a) is a figure which shows the flow of the exhaust gas in a closed inlet pipe, a muffler, and an outlet pipe, (b) is a figure. It is a figure which shows the flow of the exhaust gas in an open state inlet pipe, a muffler, and an outlet 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 a perspective view of the muffler which shows a part of muffler in cross section. FIG. 24 is a view showing a fourth embodiment of the 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 inlet pipe and the outlet pipe of FIG. 23. It is a figure which shows 4th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a front view of the inlet pipe seen from the arrow E direction of FIG. 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 inlet pipe which shows the FF cross section of FIG. It is a figure which shows 4th Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention, (a) is a figure which shows the flow of the exhaust gas in a closed inlet pipe, a muffler, and an outlet pipe, (b) is a figure. It is a figure which shows the flow of the exhaust gas in an open state inlet pipe, a muffler, and an outlet pipe. It is a figure which shows the modification of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a perspective view of the muffler which shows a part of muffler in cross section. It is a figure which shows the modification of the exhaust apparatus of the internal combustion engine which concerns on this invention, and is a longitudinal cross-sectional view of the muffler cut | disconnected by the surface which passes along the central axis of the inlet pipe and outlet pipe of FIG. It is a perspective view which shows the structure of the exhaust system provided with the conventional exhaust apparatus. It is a figure which shows the exhaust system provided with the conventional exhaust apparatus, and is a longitudinal cross-sectional view of the muffler with which the tail pipe and the outlet pipe were connected. It is a figure which shows the exhaust system provided with the conventional exhaust apparatus, The standing wave of the air column resonance which generate | occur | produces in a tail pipe is represented, the vertical axis represents sound pressure, and the horizontal axis represents the position of the tail pipe schematically It is a figure explaining with sound pressure distribution.

  Hereinafter, first to fourth 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)
FIGS. 1-11 is a figure which shows 1st Embodiment of the exhaust apparatus of the internal combustion engine which concerns on this invention.
First, the configuration will be described.
As shown in FIG. 1, the exhaust device 20 according to the first embodiment is connected to an engine 10 as an in-line four-cylinder internal combustion engine, purifies exhaust gas exhausted from the engine 10, and generates exhaust noise. It is configured to suppress generation and exhaust gas to the atmosphere.

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

  The exhaust manifold 12 includes four exhaust branch pipes 12a, 12b, 12c, and 12d connected to exhaust ports communicating with the first to fourth cylinders of the engine body 11, and exhaust branch pipes 12a, 12b, 12c, The exhaust collecting pipe 12e collects the downstream side of 12d. The exhaust gas exhausted from each cylinder of the engine 10 is introduced into the exhaust collecting pipe 12e through the exhaust branch pipes 12a, 12b, 12c, and 12d.

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

The catalytic converter 21 is formed by attaching a catalyst such as platinum or palladium to a honeycomb substrate or a granular activated alumina support, and is accommodated in a main body case. The upstream end of the catalytic converter 21 is connected to the downstream end of the exhaust collecting pipe 12e so that NOx in exhaust gas flowing from the exhaust collecting pipe 12e is reduced and CO and HC are oxidized.
The universal joint 22 is composed of a spherical joint such as a ball joint, and allows relative displacement between the catalytic converter 21 and the front pipe 23. The universal joint 24 is also composed of a spherical joint such as a ball joint, like the universal joint 22, and allows relative displacement between the front pipe 23 and the center pipe 25.

  The front pipe 23 is formed in a cylindrical shape, communicates with the exhaust gas outlet of the catalytic converter 21 at the upstream end 23a, and has an exhaust passage 23c through which the exhaust gas flowing out from the catalytic converter 21 flows from the upstream end 23a to the downstream end 23b. Have. Similarly to the front pipe 23, the center pipe 25 has an exhaust passage 25c, and exhaust gas flowing out from the front pipe 23 is circulated from the upstream end 25a to the downstream end 25b. A downstream end 25 b of the center pipe 25 is connected to the muffler 30, and exhaust gas flows into the muffler 30 from the downstream end 25 b.

  2 to 4, the muffler 30 includes a muffler main body 31 as a silencer main body, separators 32 and 33 as partition members, an inlet pipe 34, an outlet pipe 35, and a valve 36 as an opening / closing member. It is comprised including. The exhaust gas flowing into the muffler body 31 from the inlet pipe 34 is discharged from the outlet pipe 35, and the exhaust sound is silenced in the muffler body 31.

The muffler main body 31 includes an outer shell 41 formed in a cylindrical shape, and end plates 42 and 43 that close both ends of the outer shell 41 and define an internal space. The end plates 42 and 43 are fixed to the outer shell 41 by fixing means such as a caulking structure, respectively, so that exhaust gas does not leak from the internal space to the outside.
A separator 32 is interposed between the end plate 42 and the end plate 43, and a separator 33 is interposed between the separator 32 and the end plate 43.

The separator 32 divides the internal space in the muffler body 31 into a resonance chamber 30A located upstream in the exhaust direction and an expansion chamber 30B located downstream in the exhaust direction of the resonance chamber 30A.
The separator 33 partitions the internal space in the muffler main body 31 into an expansion chamber 30B and an expansion chamber 30C located on the downstream side of the expansion chamber 30B in the exhaust direction.
The end plate 42 has an insertion hole 42a, the separator 32 has an insertion hole 32a, and the separator 33 has an insertion hole 33a. The insertion holes 42a, 32a, 33a An inlet pipe 34 is inserted.

  Further, an insertion hole 43a is formed in the end plate 43, an insertion hole 33b is formed in the separator 33, and an outlet pipe 35 is inserted into the insertion holes 43a and 33b. Further, the separator 33 is formed with a communication hole 33c that allows the expansion chamber 30C and the expansion chamber 30B to communicate with each other, and when the exhaust gas in the expansion chamber 30C flows into the expansion chamber 30B through the communication hole 33c. It has been expanded further.

As shown in FIG. 4, the inlet pipe 34 has an upstream opening end 34a connected to the downstream end 25b of the center pipe 25, a downstream opening end 34b that opens in the expansion chamber 30C, and the upstream opening end 34a and the downstream opening end. And a circulation passage 34c formed between the passage 34b.
Further, the inlet pipe 34 has a communication pipe 34d in which a communication path 34e that connects the flow path 34c and the resonance chamber 30A is formed. The communication pipe 34d protrudes from the inlet pipe 34 so as to be substantially orthogonal to the axial direction of the inlet pipe 34, and the leading end of the inlet pipe 34 has an opening end 34f that opens in the resonance chamber 30A. .
The inlet pipe 34, the front pipe 23 and the center pipe 25 constitute a tail pipe 40 as an exhaust pipe of the present invention.

Here, the expansion chamber generally has a relatively large cross-sectional area (mm ²⁾ with respect to the cross-sectional area of the flow passage in the inlet pipe (mm ^2), the cavity having a predetermined volume (mm ³⁾ Become.
In this expansion chamber, when the exhaust gas flows into the expansion chamber from the circulation passage, the volume thereof is rapidly expanded, the pressure fluctuation due to the exhaust pulsation of the internal combustion engine is weakened, and the sound pressure level (dB) of the exhaust sound is reduced. ) Is reduced over a wide frequency band.

The resonance chamber is generally composed of a cavity having a predetermined volume (mm ³ ) so as to resonate exhaust sound of a specific frequency (Hz) using the Helmholtz resonance principle. The resonance chamber is composed of a cavity k formed inside the resonance member K as schematically shown in FIG. The resonance member K is connected to the tubular member T via the communication member R. The tubular member T has an air flow passage t, and the communication member R has a communication passage r including a so-called neck portion that connects the air flow passage t and the cavity k. With this configuration, exhaust sound having a specific frequency (Hz) resonates in the cavity h.

The specific frequency is fk (Hz), the cross-sectional area of the communication passage r is S (mm ² ), the length of the communication passage r is L (mm), the volume of the cavity h is V (mm ³ ), and C is When the speed of sound in air (m / s) is known, the specific frequency fk is known to be expressed by the following equation (4).

In this case, when the frequency (Hz) of the exhaust sound propagating from the communication path r to the cavity h substantially matches the set specific frequency fk (Hz), the exhaust sound resonates within the cavity h.
When resonance occurs in the cavity h, the air vibrates vigorously in the communication path r, and the vibration energy of the air is converted into heat energy by the resistance such as friction between the inner wall of the communication member R and the air, so that the exhaust sound is generated. It will be attenuated. As a result, the sound pressure level (dB) of the exhaust sound resonated in the cavity h is reduced.

  In this way, if the cross-sectional area S and length L of the communication passage r and the volume V of the cavity h are designed to resonate at a specific frequency f with a high sound pressure level (dB) of the exhaust sound, the primary sound pressure mode can be obtained. Resonance is excited not only at the frequency of, but also at frequencies of sound pressure modes that are integer multiples such as the secondary sound pressure mode and the tertiary sound pressure mode, so that exhaust sounds at a plurality of frequencies can also be reduced. For example, if the specific frequency f generated by the rotational speed (rpm) of the engine 10 is 100 Hz and the above-described cross-sectional area S, length L, and volume V are designed so that f becomes 100 Hz, exhaust of 100 Hz It is possible to reduce not only the sound but also the sound pressure level of the exhaust sound in an integer multiple sound pressure mode such as 200 Hz in the secondary sound pressure mode and 300 Hz in the third sound pressure mode.

In this muffler 30, as shown in FIG. 4, the length of the communication passage 34e communicating pipe 34d, i.e. the length from the communicating portion and distribution passage 34c and the communication passage 34e to the opening end 34f is formed by L ₁ ing. Further, the cross-sectional area of the communication passage 34e is S ₁ , and the volume of the resonance chamber 30A is V ₁ , and a specific resonance frequency (Hz) based on each set item is set.
Therefore, in this muffler 30, exhaust gas is introduced into the resonance chamber 30A from the flow passage 34c of the inlet pipe 34 through the communication passage 34e, so that the exhaust sound of a specific frequency (Hz) is generated by Helmholtz resonance. The sound pressure level is reduced. That is, the exhaust sound is silenced in the resonance chamber 30A.

  The outlet pipe 35 includes an upstream opening end 35a that opens in the expansion chamber 30B, a downstream opening end 35b that is located outside the muffler body 31 and opens into the atmosphere, and the upstream opening end 35a and the downstream opening end 35b. And a flow passage 35c formed therebetween. The exhaust gas in the expansion chamber 30B flows from the upstream opening end 35a, passes through the flow passage 35c, and is discharged from the downstream opening end 35b to the atmosphere.

  As shown in FIGS. 6 to 8, the valve 36 includes bearing portions 51 and 52, a rotation shaft 53, restriction rings 54 and 55 that restrict movement of the rotation shaft 53 in the axial direction, and a valve body 56. It is comprised including. The bearing 51 protrudes from the outer peripheral portion 34g of the downstream opening end 34b of the inlet pipe 34 and has a through hole 51a. The through hole 34h is provided through the through hole 51a and the inlet pipe 34. One end of the rotation shaft 53 is rotatably inserted into the shaft. Similarly to the bearing portion 51, the bearing portion 52 has a through hole 52a that protrudes from the outer peripheral portion 34g of the downstream opening end 34b of the inlet pipe 34 and has the same axis as the through hole 51a. The other end of the rotation shaft 53 is rotatably inserted into a through hole 34h provided through the through hole 52a and the inlet pipe 34.

  The valve body 56 is made of a disk having a diameter slightly smaller than the inner diameter of the inlet pipe 34, and includes a main body portion 56 a and a connecting portion 56 b connected to the rotating shaft 53. A cutout 56c is formed in the main body 56a below the gravitational direction indicated by the arrow g. When the valve body 56 closes the flow passage 34c of the inlet pipe 34, the exhaust gas flows through the gap 36a formed between the notch 56c and the inner wall portion of the inlet pipe 34. ing. A through hole 56d is formed in the connecting portion 56b, and the rotation shaft 53 is inserted therethrough.

In the valve 36, as shown in FIG. 8, when the flow pressure (Pa) of the exhaust gas flowing through the flow passage 34c of the inlet pipe 34 becomes equal to or higher than a predetermined pressure (Pa), the valve body 56 is rotated. It smoothly rotates around 53 and the flow passage 34c is opened.
When the flow pressure (Pa) of the exhaust gas is less than a predetermined pressure (Pa), the valve body 56 rotates about the rotation shaft 53 in the gravity direction of the arrow g due to its own weight and enters a closed state.

The inner diameter (mm), thickness (mm) and length (mm) of the front pipe 23 and the center pipe 25 of the exhaust device 20 according to the present embodiment, the length (mm) of the muffler main body 31, the size of the outer shape (mm), Inner diameter (mm), thickness (mm) and length (mm) of the inlet pipe 34 and outlet pipe 35, a predetermined value (Pa) of the flow pressure of exhaust gas that opens the valve 36, and the length of the communication pipe 34d L ₁ (mm), the cross-sectional area _S 1 of the communication passage 34e ^(mm 2), the volume _V 1 of the resonance chamber 30A ^(mm 3), expansion chamber 30B, the volume of the 30C ^(mm 3), and material of each component These design specifications are appropriately selected based on data such as design specifications, simulations, experiments, and experience values of the vehicle to which the exhaust device 20 according to the present embodiment is applied.

  Next, the action of the exhaust device 20 and air column resonance generated in the tail pipe 40 will be described.

  First, when the engine 10 on the upstream side of the exhaust device 20 shown in FIG. 1 is started, the exhaust gas exhausted from each cylinder of the engine 10 is introduced from the exhaust manifold 12 to the catalytic converter 21, and the catalytic converter 21 performs NOx. Exhaust gas purification such as reduction of CO and oxidation of CO and HC is performed. The purified exhaust gas is introduced into the inlet pipe 34 through the front pipe 23 and the center pipe 25.

A part of the exhaust gas introduced into the inlet pipe 34 circulates in the circulation passage 34c as shown by an arrow in FIG. 9A, and is introduced into the resonance chamber 30A from the open end 34f through the communication passage 34e. Is done.
When the engine speed is in a relatively low speed range immediately after the engine 10 is started or when the engine 10 is decelerating, the flow rate of the exhaust gas passing through the flow passage 34c is relatively small. Even if the flow pressure of the exhaust gas is applied, it does not rotate. As a result, the circulation passage 34c is maintained in a closed state.
In this case, the exhaust gas that has not flowed into the communication passage 34e flows into the expansion chamber 30C through the gap 36a shown in FIG. The exhaust gas flowing into the expansion chamber 30C further flows into the expansion chamber 30B through the communication hole 33c of the separator 33, flows into the flow passage 35c from the upstream opening end 35a of the outlet pipe 35, and enters the atmosphere from the downstream opening end 35b. Discharged.

ただし、Ｌ_ｂはテールパイプ４０の管長（ｍｍ）、ｄ_ｂはテールパイプ４０の内径（ｍｍ）、Ｃは前述の式（２）で表される排気ガスの温度Ｔ（°Ｋ）における音速（ｍ／ｓ）、ｍは次数をそれぞれ表す。
この気柱共鳴は、図１０（ａ）に示すように、長さＬ_ｂが（１／４）λの波長とほぼ一致する１次音圧モードとなり、バルブ３６の上流側で音圧（Ｐａ）が最も高くなる腹を有している。また、２次音圧モードでは、長さＬ_ｂが（３／４）λの波長とほぼ一致する気柱共鳴となり、バルブ３６の上流側で音圧（Ｐａ）が最も高くなる腹を有している。 When the circulation passage 34c is in a closed state, the tail pipe 40 has an upstream end 23a as an open end and a downstream open end 34b as a closed end, as shown in FIG. 10 (a). In this case, the tail pipe 40 becomes closed tube, columnar resonance frequency f _b represented by the following formula (5) will occur.

However, _{L b} is the sound velocity in the pipe length of the tail pipe 40 (mm), _{d b} is the tail pipe 40 inside diameter (mm), the temperature T of the exhaust gas C is represented by the aforementioned formula (2) (° K) ( m / s) and m each represent an order.
The air column resonance, as shown in FIG. 10 (a), becomes one Tsugion圧mode length L _b substantially coincides with the wavelength of the (1/4) lambda, the sound pressure at the upstream side of the valve 36 (Pa ) Has the highest belly. Further, 2 in Tsugion圧mode, the length L _b is (3/4) becomes approximately matching columnar resonance wavelength of lambda, has a belly sound pressure upstream of the valve 36 (Pa) is the highest ing.

ただし、図４に示すように、長さＬ_１は、連通通路３４ｅの長さ（ｍｍ）、断面積Ｓ_１は、連通通路３４ｅの断面積（ｍｍ^２）、体積Ｖ_１は、共鳴室３０Ａの体積（ｍｍ^３）をそれぞれ表している。
この共鳴室３０Ａにおいては、長さＬ_ｂとほぼ一致する（１／４）λの波長の周波数の自然数倍となる複数の周波数の共鳴を減衰させることができる。 Columnar resonance frequency f _b generated in the tail pipe 40 within, by exciting the Helmholtz resonance in the resonance chamber 30A of the muffler 30, can be attenuated.
That is, the frequency of the Helmholtz resonance of the resonant chamber 30A by substantially matches the frequency f _b of the air column resonance, it is possible to attenuate the air column resonance frequency f _b.
Therefore, by setting the frequency of the Helmholtz resonance is expressed by the following equation (6) and f _b, columnar resonance frequency f _b generated in the tail pipe 40 within decays.

However, as shown in FIG. 4, the length _{L 1} is the length of the communication passage 34e (mm) cross-sectional area _{S 1} is the cross-sectional area of the communication passage 34e ^(mm 2), the volume _{V 1} was, resonant chamber 30A Represents the volume (mm ³ ).
In this resonance chamber 30A, it is possible to attenuate the resonance of a plurality of frequencies of natural number times the frequency of the wavelength of the length L _b substantially matches (1/4) λ.

  Even when the flow rate of the exhaust gas is small, such as during deceleration of the internal combustion engine, and the pressure in the flow passage 34c is small, the resonance chamber 30A is in the vicinity of the belly where the sound pressure (Pa) is highest on the upstream side of the valve 36. Since it is provided, Helmholtz resonance can function effectively.

On the other hand, when the engine 10 is in a relatively high rotational speed region, such as during acceleration, the flow rate of the exhaust gas passing through the flow passage 34c is relatively large. Therefore, as shown in FIG. It is rotated by the flow pressure of the exhaust gas. As a result, the circulation passage 34c is opened.
Then, the exhaust gas passes through the downstream opening end 34b of the inlet pipe 34 and flows into the expansion chamber 30C. The exhaust gas further flows into the expansion chamber 30B through the communication hole 33c of the separator 33, flows into the flow passage 35c from the upstream opening end 35a of the outlet pipe 35, and is discharged to the atmosphere from the downstream opening end 35b.
Further, a part of the exhaust gas introduced into the inlet pipe 34 circulates in the circulation passage 34c, and is introduced into the resonance chamber 30A from the open end 34f through the communication passage 34e.

ただし、Ｌ_ｂはテールパイプ４０の管長（ｍｍ）、ｄ_ｂはテールパイプ４０の内径（ｍｍ）、Ｃは前述の式（２）で表される排気ガスの温度Ｔ（°Ｋ）における音速（ｍ／ｓ）、ｍは次数をそれぞれ表す。
この気柱共鳴は、図１０（ｂ）に示すように、長さＬ_ｂが（１／２）λの波長とほぼ一致する１次音圧モードとなり、テールパイプ４０の排気方向の中間部で音圧（Ｐａ）が最も高くなる腹を有している。また、２次音圧モードでは、長さＬ_ｂが１λの波長とほぼ一致する気柱共鳴となり、テールパイプ４０の排気方向の二箇所で音圧（Ｐａ）が最も高くなる腹を有している。 When the circulation passage 34c is in an open state, the tail pipe 40 has an upstream end 23a as an open end and a downstream open end 34b as an open end, as shown in FIG. 10 (b). In this case, the tail pipe 40 becomes open tube, columnar resonance frequency f _c represented by the following formula (7) will occur.

However, _{L b} is the sound velocity in the pipe length of the tail pipe 40 (mm), _{d b} is the tail pipe 40 inside diameter (mm), the temperature T of the exhaust gas C is represented by the aforementioned formula (2) (° K) ( m / s) and m each represent an order.
The air column resonance, as shown in FIG. 10 (b), becomes one Tsugion圧mode length L _b substantially coincides with the wavelength of the (1/2) lambda, at an intermediate portion of the exhaust direction of the tail pipe 40 The belly has the highest sound pressure (Pa). Further, in the 2 Tsugion圧mode, a belly length L _b is a columnar resonance which substantially coincides with the wavelength of 1 [lambda, the sound pressure (Pa) is the highest in two locations in the exhaust direction of the tail pipe 40 Yes.

Columnar resonance frequency f _c generated in the tail pipe 40 within, by exciting the Helmholtz resonance in the resonance chamber 30A of the muffler 30, can be attenuated.
That is, the frequency of the Helmholtz resonance of the resonant chamber 30A is set to substantially coincide with the frequency f _b as described above, when the frequency f _b and the fundamental frequency, the resonance of the natural number times the frequency of the fundamental frequency Can be attenuated. Specifically, since the basic frequency f _b has a wavelength of (1/4) λ, the frequency of the wavelength of (1/2) λ that is twice this wavelength, 3 of this wavelength. It is possible to attenuate the resonance of a plurality of frequencies such as a frequency having a wavelength of (3/4) λ that is doubled and a frequency having a wavelength of 1λ that is four times this wavelength.

Accordingly, even when the engine speed is in a relatively high speed region, such as when the engine 10 is accelerated, and the flow passage 34c is opened, the Helmholtz resonance of the resonance chamber 30A causes the resonance to occur as shown in FIG. , the attenuating the air column resonance of 2 Tsugion圧mode 1 Tsugion圧mode and the length L _b of length L _b substantially coincides with the wavelength of the (1/2) lambda substantially coincides with the wavelength of the 1λ Can do. In this case, the resonance chamber 30A is located at a portion where the sound pressure on the upstream side of the valve 36 appears to be relatively low. However, in the relatively high rotation speed region, the flow rate of exhaust gas is high and the flow pressure is high. Attenuation due to resonance works effectively.

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

  That is, in the exhaust device 20, when the engine 10 is decelerated or in the low rotation region, the valve 36 keeps the flow passage 34c closed, so that the tail pipe 40 is closed. In the case of such a closed tube, when air column resonance occurs in the tail pipe 40, the sound pressure distribution as shown in FIG. 10A is obtained, and the exhaust of the valve 36 is performed in the primary sound pressure mode and the secondary sound pressure mode. The sound pressure is high on the upstream side. This high sound pressure acts on the resonance chamber 30A disposed on the upstream side in the exhaust direction with respect to the valve 36, and an effect of enhancing the attenuation effect of the Helmholtz resonance exhaust sound in the resonance chamber 30A is obtained.

  Therefore, even when the engine 10 is in the low rotation region, an increase in sound pressure due to air column resonance occurring in the tail pipe 40 can be suitably suppressed. As a result, it is not necessary to install a sub-muffler for suppressing the air column resonance that is required in the conventional exhaust device and is provided in the tail pipe, the structure is simplified, and an effect of reducing weight and manufacturing cost can be obtained.

  Specifically, as shown in FIG. 11, in the conventional exhaust system, broken lines of the primary sound pressure mode and the secondary sound pressure mode due to air column resonance that cause the engine speed Ne to occur in a relatively low speed region. The peak portion of the high sound pressure level (dB) indicated by is reduced to the sound pressure level indicated by the solid line. As a result, the exhaust sound of the air column resonance is transmitted to the vehicle interior, and a humming noise is generated in the vehicle interior, so that the problem that the driver feels uncomfortable is solved.

  On the other hand, when the engine 10 is in acceleration or in a high rotation region, the valve 36 opens the flow passage 34c, so that the tail pipe 40 is opened. In the case of such an open tube, when air column resonance occurs in the tail pipe 40, the sound pressure distribution as shown in FIG. 10 (b) is obtained, and the valve 36 is in the primary sound pressure mode and the secondary sound pressure mode. The sound pressure is low on the upstream side in the exhaust direction.

As described above, even when the sound pressure on the upstream side of the exhaust direction of the valve 36 is low, when the engine 10 is in the high rotation region, the flow rate of the exhaust gas flowing in the flow passage 34c of the inlet pipe 34 is increased. Since the flow pressure is also increasing, the damping effect of the exhaust sound of Helmholtz resonance in the resonance chamber 30A is enhanced. Therefore, even when the engine 10 is in the high rotation region, it is possible to suitably suppress an increase in the sound pressure of the exhaust sound due to the air column resonance generated in the tail pipe 40.
Further, since the valve 36 opens the flow passage 34c, the exhaust gas flowing in the flow passage 34c can be smoothly flown into the expansion chamber 30C from the valve 36, and the back pressure is increased in the tail pipe 40. That is, no load is applied to the engine 10.

  As a result, even when the engine 10 is in a deceleration or low rotation region, or in an acceleration or high rotation region, it is necessary in the conventional exhaust system and suppresses the air column resonance provided in the tail pipe. This eliminates the need for installing a sub-muffler, simplifies the structure, and reduces the weight and manufacturing cost. Further, since the expansion chambers 30B and 30C are provided on the downstream side in the exhaust direction from the resonance chamber 30A, the Helmholtz resonance in the resonance chamber 30A is not affected. When the exhaust gas flows into the expansion chamber 30C from the circulation passage 34c, the volume is rapidly expanded, so that the exhaust noise can be reduced over the entire frequency range. Furthermore, when the exhaust gas flows into the expansion chamber 30B from the expansion chamber 30C, the volume is rapidly expanded again, so that exhaust noise can be further reduced over the entire frequency range, and the exhaust gas is discharged from the outlet pipe 35 to the atmosphere. When exhausted, exhaust noise can be significantly reduced.

  Further, since the communication pipe 34d protrudes from the inlet pipe 34 so as to be substantially orthogonal to the axial line of the inlet pipe 34, the communication path 34e can be formed relatively long with a simple structure, and the resonance frequency of Helmholtz resonance can be increased. Thus, it is possible to obtain an effect that it can be set on the low frequency side where problems are likely to occur. In addition, since the muffler 30 is provided on the most downstream side in the exhaust direction of the tail pipe 40, the following effects can be obtained.

That is, the communication passage 34e and the resonance chamber 30A can be positioned in the vicinity of the upstream side of the valve 36, and the communication passage 34e can be disposed in a portion where the sound pressure of air column resonance is high.
As a result, particularly when the engine 10 is decelerated, an increase in the sound pressure of the exhaust sound due to Helmholtz resonance can be effectively suppressed. Further, when the valve 36 is in the closed state, as shown in FIGS. 7 and 8, the gap 36a is formed to be extremely smaller than the cross-sectional area of the flow passage 34c. The sound pressure on the upstream side can be increased more effectively.

(Second Embodiment)
In addition, although the exhaust apparatus 60 which concerns on 2nd Embodiment is replaced with the muffler 30 of 1st Embodiment, it is comprised by the muffler 70, Others are comprised similarly. Therefore, the same configuration will be described using the same reference numerals as those in the first embodiment shown in FIGS. 1 to 11, and only differences will be described in detail.

The exhaust device 60 shown in FIG. 1 has the same configuration as that of the first embodiment except for the muffler 70. As shown in FIGS. 12 and 13, the muffler 70 has an inlet pipe 61 and a valve 50 as an opening / closing member. The rest is configured in the same manner as in the first embodiment.
The inlet pipe 61 has an upstream opening end 61a, a downstream opening end 61b, a flow passage 61c, and a communication pipe 61d in which a communication passage 61e is formed. The communication pipe 61d has an open end 61f whose tip end in the protruding direction opens in the resonance chamber 30A.
The inlet pipe 61, the front pipe 23, and the center pipe 25 constitute a tail pipe 40a as an exhaust pipe of the present invention.

In this muffler 70, as shown in FIG. 13, the length of the communication path 61e of the communication pipe 61d is L ₂ , the cross-sectional area of the communication path 61e is S ₂ , and the volume of the resonance chamber 30A, as in the first embodiment. Is formed of V ₂ , and a specific resonance frequency (Hz) based on each set item is set.

  As shown in FIGS. 14 to 16, the valve 50 includes bearing portions 63 and 64, a rotation shaft 65, restriction rings 66 and 67 that restrict movement of the rotation shaft 65 in the axial direction, and a valve body 68. And a weight 69. The bearing portion 63 is provided so as to protrude from the outer peripheral portion 61g between the upstream opening end 61a and the downstream opening end 61b of the inlet pipe 61, and has a through hole 63a. The through hole 63a and the inlet pipe 61 are penetrated. One end of the rotation shaft 65 is rotatably inserted into the through hole 61h provided. The bearing portion 64 is provided so as to protrude from the outer peripheral portion 61 g facing the bearing portion 63, and has a through hole 64 a having the same axis as the through hole 63 a, and penetrates the through hole 64 a and the inlet pipe 61. The other end of the rotation shaft 65 is rotatably inserted into the through hole 61h provided.

  The valve body 68 is made of a disk having a diameter slightly smaller than the inner diameter of the inlet pipe 61, and has a main body portion 68 a and a connecting portion 68 b connected to the rotating shaft 65. A cutout 68c is formed in the main body 68a above the gravitational direction indicated by the arrow g in FIG. When the valve body 68 closes the flow passage 61c of the inlet pipe 61, the exhaust gas flows through the gap 50a formed between the notch 68c and the inner wall portion of the inlet pipe 61. ing.

A through hole 68d is formed in the connecting portion 68b, and the rotating shaft 65 is inserted therethrough.
In this valve 50, as shown in FIG. 16, when the flow pressure (Pa) of the exhaust gas flowing through the flow passage 61c of the inlet pipe 61 becomes equal to or higher than a predetermined pressure (Pa), the valve body 68 is rotated. Rotating smoothly around 65, the flow passage 61c is opened.
The weight 69 is provided below the connecting portion 68b of the valve body 68 in the gravity direction indicated by the arrow g. When the exhaust gas flow pressure is less than a predetermined pressure, the valve body 68 is orthogonal to the flow passage 61c. It is configured to maintain the posture, that is, the closed state.

  Next, the action of the exhaust device 60 and air column resonance generated in the tail pipe 40a will be described.

First, when the engine 10 shown in FIG. 1 is started, as in the first embodiment, exhaust gas is introduced into the inlet pipe 61 and passes through the communication passage 61e as shown by the arrow in FIG. Then, it is introduced into the resonance chamber 30A from the opening end 61f. When the engine 10 is in the low engine speed region, the flow rate of the exhaust gas passing through the circulation passage 61c is relatively small. Therefore, the valve 50 does not rotate even when the exhaust gas flow pressure is applied, and the circulation passage 61c. Is kept closed.
In this case, the exhaust gas flows into the expansion chamber 30C through the gap 50a shown in FIG. 15, and further flows into the expansion chamber 30B. The exhaust sound is reduced over the entire frequency band, and the atmospheric air flows from the downstream opening end 35b. To be discharged.

When flow passage 61c is in the closed state, the tail pipe 40a, as in the first embodiment, the upstream side of the valve 50 becomes closed end, since the tail pipe 40a becomes a closed tube having a length L _b, the above-mentioned formula ( As in 5), air column resonance of a specific frequency occurs. The air column resonance, as in the first embodiment, it is 1 Tsugion圧mode length L _b substantially coincides with the wavelength of the (1/4) lambda, the sound pressure at the upstream side of the valve 50 (Pa) is the most A rising belly will be formed. Further, in the secondary sound pressure mode, the length L _b becomes air column resonance that substantially matches the wavelength of (3/4) λ, and an antinode is formed on the upstream side of the valve 50 where the sound pressure (Pa) is highest. Will be.

  The air column resonance of the specific frequency generated in the tail pipe 40a can be attenuated by exciting the Helmholtz resonance in the resonance chamber 30A of the muffler 70, as in the first embodiment. Even when the flow rate of the exhaust gas is small when the internal combustion engine is decelerated and the pressure in the flow passage 61c is small, the resonance chamber 30A has the highest sound pressure (Pa) on the upstream side of the valve 50 as in the first embodiment. Therefore, the Helmholtz resonance can be functioned effectively.

  When the engine 10 is in the high engine speed region, the flow rate of the exhaust gas passing through the flow passage 61c is relatively large. Therefore, as shown in FIG. 17B, the valve 50 is rotated by the flow pressure of the exhaust gas. As a result, the flow passage 61c is opened. Then, the exhaust gas flows into the expansion chamber 30C through the downstream opening end 61b, further flows into the expansion chamber 30B, and is discharged from the downstream opening end 35b of the outlet pipe 35 to the atmosphere. Further, part of the exhaust gas is vigorously introduced into the resonance chamber 30A from the opening end 61f through the communication passage 61e.

When flow passage 61c is in open state, the tail pipe 40a, as in the first embodiment, the downstream open end 61b is an open end, since the open tube having a length L _b, the above-mentioned formula (7 The air column resonance of the specific frequency represented by) occurs. The air column resonance, like the first embodiment, L _b is (1/2) becomes approximately matching 1 Tsugion圧mode and wavelength of lambda, the sound pressure (Pa at an intermediate portion of the exhaust direction of the tail pipe 40a ) Has the highest belly. Further, 2 in Tsugion圧mode, L _b is almost coincident columnar resonance with the wavelength of 1 [lambda, the sound pressure at two locations in the exhaust direction of the tail pipe 40a (Pa) has a highest becomes belly.

Engine speed, such as during acceleration of the engine 10 is located relatively high rotational speed region, when the flow passage 61c is opened also by Helmholtz resonance resonance chamber 30A, the length L _b (1/2) It is possible to attenuate the columnar resonance in the primary sound pressure mode that substantially matches the wavelength of λ and the secondary sound pressure mode in which the length L _b substantially matches the wavelength of 1λ.
In this case, as in the first embodiment, the resonance chamber 30A is located in a portion where the sound pressure on the upstream side of the valve 50 appears to be relatively low, but in a relatively high rotational speed region, the flow rate of the exhaust gas. Since there are many and flow pressure is high, the attenuation by Helmholtz resonance functions effectively.

  Since the exhaust device 60 according to the second embodiment is configured as described above, the following effects can be obtained.

  That is, in the exhaust device 60, when the engine 10 is in the low rotation region, the valve 50 is provided closer to the resonance chamber 30A than in the first embodiment. The side has a higher sound pressure than in the first embodiment. This high sound pressure enhances the exhaust sound attenuation effect of Helmholtz resonance in the resonance chamber 30 </ b> A, and an effect that the increase in the sound pressure of the exhaust sound due to the air column resonance can be more suitably suppressed is obtained. As a result, the effect of eliminating the noise of the vehicle interior is obtained, and a sub-muffler for suppressing air column resonance is installed even when the engine 10 is in the low rotation region, as in the first embodiment. It becomes unnecessary, the structure becomes simple, and the effect of reducing the weight and manufacturing cost can be obtained.

On the other hand, when the engine 10 is in the high rotation region, the valve 50 opens the flow passage 61c, so that the tail pipe 40a is opened. In the case of such an open tube, as in the first embodiment, even in the primary sound pressure mode and the secondary sound pressure mode, even if the sound pressure on the upstream side in the exhaust direction of the valve 50 is low, the flow is circulated in the circulation passage 61c. Since the flow rate of the exhaust gas to be increased and the flow pressure of the exhaust gas have also increased, the attenuation effect of the exhaust sound of Helmholtz resonance in the resonance chamber 30A is enhanced. Therefore, even in the high rotation region, an effect that the increase of the sound pressure of the exhaust sound due to the air column resonance in the tail pipe 40a can be suitably suppressed is obtained.
Further, as in the first embodiment, since the valve 50 opens the flow passage 61c, the exhaust gas can smoothly flow into the expansion chamber 30C, and the back pressure is increased in the tail pipe 40a. No load is applied to the engine 10.

  As a result, since the increase in the sound pressure of the exhaust sound due to the air column resonance is suppressed in the entire region from the low rotation to the high rotation of the engine 10, the sub muffler provided in the tail pipe is required in the conventional exhaust system. Installation becomes unnecessary, the structure is simplified, and the effect of reducing the weight and manufacturing cost can be obtained.

(Third embodiment)
In addition, although the exhaust apparatus 80 which concerns on 3rd Embodiment is replaced with the muffler 30 of 1st Embodiment, it is comprised by the muffler 90, Others are comprised similarly. Therefore, the same configuration will be described using the same reference numerals as those in the first embodiment shown in FIGS. 1 to 11, and only differences will be described in detail.

  The exhaust device 80 shown in FIG. 1 is configured in the same manner as the first embodiment except for the muffler 90. As shown in FIGS. 18 to 20, in the muffler 90, in addition to the inlet pipe 81 and the separators 74 and 75, Is configured in the same manner as in the first embodiment.

  The inlet pipe 81 has an upstream opening end 81a, a downstream opening end 81b, a flow passage 81c, and a communication pipe 82. The communication pipe 82 includes a cylindrical portion 82a that surrounds the outer peripheral portion 81d of the inlet pipe 81 along the axial direction of the inlet pipe 81, and a connecting portion 82b that connects the cylindrical portion 82a and the outer peripheral portion 81d of the inlet pipe 81. And an open end 82c that opens in the resonance chamber 30A. A communication passage 83 that connects the flow passage 81c of the inlet pipe 81 and the resonance chamber 30A is defined between the inner peripheral surface of the communication pipe 82, the outer peripheral surface of the outer peripheral portion 81d of the inlet pipe 81, and the inner wall surface of the connecting portion 82b. It is made. The communication passage 83 communicates with the flow passage 81 c through a through hole 81 e having a diameter d provided in the outer peripheral portion 81 d of the inlet pipe 81. The size of the diameter d is not limited as long as the exhaust gas flows smoothly, and a plurality of diameters d may be formed in the circumferential direction of the outer peripheral portion 81d. The position of the through hole 81e is preferably in the vicinity of the valve 36 having a high sound pressure.

The inlet pipe 81, the front pipe 23, and the center pipe 25 constitute a tail pipe 40b as an exhaust pipe of the present invention.
In this muffler 90, as in the first embodiment, the length of the communication passage 83 of the communication pipe 82, the cross-sectional area of the communication passage 83, and the volume of the resonance chamber 30A are formed with predetermined dimensions, and are set respectively. A specific resonance frequency (Hz) based on each specification is set.

  As shown in FIG. 20, the rotation shaft 53 of the valve 50 is inserted into a through hole 81 f provided in the outer peripheral portion 81 d of the inlet pipe 81, and the valve body 56 rotates about the rotation shaft 53. It is like that. A gap 36 a is defined between the notch 56 c of the valve body 56 and the inner wall portion of the inlet pipe 81.

As shown in FIG. 19, the separator 74 divides the internal space in the muffler body 31 into a resonance chamber 30A located on the upstream side in the exhaust direction and an expansion chamber 30B located on the downstream side in the exhaust direction of the resonance chamber 30A. ing. The separator 75 partitions the internal space in the muffler main body 31 into an expansion chamber 30B and an expansion chamber 30C located on the downstream side of the expansion chamber 30B in the exhaust direction.
An insertion hole 74a is formed in the separator 74, and further, an insertion hole 75a is formed in the separator 75, and an inlet pipe 81 is inserted through these insertion holes 74a and 75a. An insertion hole 75b is formed in the separator 75, and the outlet pipe 35 is inserted into the insertion hole 75b.

  Next, the action of the exhaust device 80 and air column resonance generated in the tail pipe 40b will be described.

  First, when the engine 10 shown in FIG. 1 is started, the exhaust gas is introduced into the inlet pipe 81 as in the first embodiment, and as shown by the arrows in FIG. The gas is introduced into the resonance chamber 30 </ b> A from the open end 82 c through the communication passage 83. When the engine 10 is in the low engine speed region, the flow rate of the exhaust gas passing through the circulation passage 81c is relatively small. Therefore, the valve 36 does not rotate even when the exhaust gas flow pressure is applied, and the circulation passage 81c. Is kept closed. In this case, the exhaust gas flows into the expansion chamber 30C through the gap 36a shown in FIG. 20, and further flows into the expansion chamber 30B. The exhaust noise is reduced over the entire frequency band, and the downstream opening of the outlet pipe 35 is opened. The gas is discharged from the end 35b to the atmosphere.

When flow passage 81c is in the closed state, the tail pipe 40b, as in the first embodiment, it is upstream closed end of the valve 36, since the closed tube having a length L _b, and the above-mentioned formula (5) Similarly, air column resonance of a specific frequency occurs. The air column resonance, as in the first embodiment, it is 1 Tsugion圧mode length L _b substantially coincides with the wavelength of the (1/4) lambda, the sound pressure at the upstream side of the valve 36 (Pa) is the most A rising belly will be formed. Further, in the secondary sound pressure mode, the length L _b becomes air column resonance that substantially matches the wavelength of (3/4) λ, and an antinode that has the highest sound pressure (Pa) is formed on the upstream side of the valve 36. Will be.

  The air column resonance having a specific frequency generated in the tail pipe 40b can be attenuated by exciting the Helmholtz resonance in the resonance chamber 30A of the muffler 90, as in the first embodiment. Even when the flow rate of the exhaust gas at the time of deceleration of the internal combustion engine is small and the pressure in the flow passage 81c is small, the resonance chamber 30A has a sound pressure (Pa) on the upstream side of the valve 36 as in the first embodiment. Since it is provided in the vicinity of the highest belly, Helmholtz resonance can function effectively.

  When the engine 10 is in the high engine speed region, the flow rate of the exhaust gas passing through the flow passage 81c is relatively large. Therefore, as shown in FIG. 22B, the valve 36 is rotated by the exhaust gas flow pressure. The distribution passage 81c is opened. Then, the exhaust gas flows into the expansion chamber 30C through the downstream opening end 81b, and further flows into the expansion chamber 30B. The exhaust sound is reduced over the entire frequency band, and is discharged from the downstream opening end 35b to the atmosphere. . A part of the exhaust gas is vigorously introduced into the resonance chamber 30A from the open end 82c through the through hole 81e and the communication passage 83.

When flow passage 81c is in open state, the tail pipe 40b, as in the first embodiment, the downstream open end 81b is an open end, since the open tube having a length L _b, the above-mentioned formula (7 The air column resonance of the specific frequency represented by) occurs. The air column resonance, like the first embodiment, L _b is (1/2) becomes approximately matching 1 Tsugion圧mode and wavelength of lambda, the sound pressure (Pa at an intermediate portion of the exhaust direction of the tail pipe 40b ) Has the highest belly. Further, 2 in Tsugion圧mode, L _b is almost coincident columnar resonance with the wavelength of 1 [lambda, the sound pressure at two locations in the exhaust direction of the tail pipe 40b (Pa) has a highest becomes belly.

Engine speed, such as during acceleration of the engine 10 is located relatively high rotational speed region, when the flow passage 81c is opened also by Helmholtz resonance resonance chamber 30A, the length L _b (1/2) It is possible to attenuate the columnar resonance in the primary sound pressure mode that substantially matches the wavelength of λ and the secondary sound pressure mode in which the length L _b substantially matches the wavelength of 1λ.
In this case, as in the first embodiment, the resonance chamber 30A is located at a portion where the sound pressure on the upstream side of the valve 36 appears to be relatively low, but in a relatively high rotational speed region, the flow rate of the exhaust gas. Since there are many and flow pressure is high, the attenuation by Helmholtz resonance functions effectively.

  Since the exhaust device 80 according to the third embodiment is configured as described above, the following effects can be obtained.

  That is, in the exhaust device 80, when the engine 10 is in the low rotation region, the upstream side in the exhaust direction of the valve 36 has a high sound pressure, as in the first embodiment. This high sound pressure enhances the exhaust sound attenuation effect of Helmholtz resonance in the resonance chamber 30 </ b> A, and an effect is obtained that the increase in the sound pressure of the exhaust sound due to air column resonance can be suitably suppressed. As a result, an effect that the problem of the booming noise due to the exhaust noise of the air column resonance is solved is obtained, and the air column resonance is suppressed even when the engine 10 is in the low speed region as in the first embodiment. The sub-muffler is not required to be installed, the structure is simplified, and the effect of reducing the weight and manufacturing cost can be obtained.

  On the other hand, when the engine 10 is in the high rotation region, the valve 36 opens the flow passage 81c, so that the tail pipe 40b is opened. In the case of such an open tube, as in the first embodiment, even in the primary sound pressure mode and the secondary sound pressure mode, even if the sound pressure on the upstream side in the exhaust direction of the valve 36 is low, the flow pressure of the exhaust gas is Since it is increasing, the attenuation effect of the exhaust sound of Helmholtz resonance in the resonance chamber 30A is enhanced. Therefore, even when the engine 10 is in the high rotation region, it is possible to suitably suppress an increase in the sound pressure of the exhaust sound due to the air column resonance in the tail pipe 40b. Further, as in the first embodiment, since the valve 36 opens the flow passage 81c, the exhaust gas can smoothly flow into the expansion chamber 30C from the valve 36, and the back pressure is increased in the tail pipe 40b. There is no increase, and no load is applied to the engine 10.

As a result, since the increase in the sound pressure of the exhaust sound due to the air column resonance is suppressed in the entire region from the low rotation to the high rotation of the engine 10, it is necessary in the conventional exhaust device and the air that is provided in the tail pipe is used. A sub-muffler for suppressing column resonance is not required to be installed, the structure is simplified, and an effect of reducing weight and manufacturing cost can be obtained.
Compared with the first and second embodiments, the resonance chamber 30A can be positioned very close to the upstream side of the valve 36. In particular, when the engine 10 is decelerated, the tail pipe 40b is closed. Then, the resonance chamber 30A can be arranged in a portion where the sound pressure of air column resonance is high. As a result, particularly when the engine 10 is decelerated, an increase in the sound pressure of the exhaust sound due to Helmholtz resonance can be effectively suppressed.

(Fourth embodiment)
In addition, although the exhaust apparatus 100 which concerns on 4th Embodiment is replaced with the muffler 30 of 1st Embodiment, it is comprised by the muffler 110, Others are comprised similarly. Therefore, the same configuration will be described using the same reference numerals as those in the first embodiment shown in FIGS. 1 to 11, and only differences will be described in detail.

  The exhaust device 100 shown in FIG. 1 is configured in the same manner as the first embodiment except for the muffler 110. As shown in FIGS. 23 to 26, the muffler 110 includes an inlet pipe 85, separators 86 and 87, and an open / close state. Other than the valve 88 as a member, it is configured similarly to the first embodiment. The inlet pipe 85 has an upstream opening end 85a, a downstream opening end 85b, a flow passage 85c, and a communication pipe 85d.

The separator 86 divides the internal space in the muffler body 31 into a resonance chamber 110A located on the upstream side in the exhaust direction and an expansion chamber 110B located on the downstream side in the exhaust direction of the resonance chamber 110A. The separator 87 partitions the internal space in the muffler main body 31 into an expansion chamber 110C and an expansion chamber 110B located on the downstream side of the expansion chamber 110C in the exhaust direction.
An insertion hole 86a is formed in the separator 86, and further, an insertion hole 87a is formed in the separator 87, and an inlet pipe 85 is inserted through these insertion holes 86a and 87a. An insertion hole 86b is formed in the separator 86, and the outlet pipe 35 is inserted into the insertion hole 86b.

  Further, the downstream opening end 85b of the inlet pipe 85 is formed by being bent by a bent portion 85h so as to open in the expansion chamber 110C so as to be substantially orthogonal to the axial direction of the inlet pipe 85 in the expansion chamber 110C. The communication pipe 85d is formed extending from the bent portion 85h in the axial direction of the inlet pipe 85, and has an open end 85f that opens in the resonance chamber 110A. The communication pipe 85d has a communication path 85e that communicates the flow path 85c with the resonance chamber 110A.

The inlet pipe 85, the front pipe 23, and the center pipe 25 constitute a tail pipe 40c as an exhaust pipe of the present invention.
In the muffler 110, as in the first embodiment, the length L ₃ from the bent portion 85h of the communication passage 85e to the opening end 85f of the communication pipe 85d, the cross-sectional area S ₃ of the communication passage 85e, and the volume of the resonance chamber 110A. V ₃ is formed in a predetermined dimension, a specific resonance frequency based on each parameter that has been set, respectively (Hz) is set.

As shown in FIGS. 25 and 26, the valve 88 includes a valve body 88a and a retainer 88b. The valve body 88a is made of a disk having a diameter slightly smaller than the inner diameter of the inlet pipe 85, and a notch 88c is formed. When the valve body 88a closes the flow passage 85c of the inlet pipe 85, the exhaust gas flows through the gap 89 formed between the notch 88c and the inner wall portion of the inlet pipe 85. ing.
The retainer 88b is formed integrally with the valve body 88a so as to bend toward the flow passage 85c of the inlet pipe 85 on the side facing the notch 88c of the valve body 88a.
The retainer 88b is formed to be curved so as to be in close contact with the inner wall portion of the inlet pipe 85, and is attached to the inner wall portion of the inlet pipe 85 by a joining means such as spot welding or a fixing means such as a rivet.

The valve 88 is made of an elastic material such as a spring material, and as shown in FIG. 26, when the flow pressure (Pa) of the exhaust gas flowing through the flow passage 85c of the inlet pipe 85 becomes equal to or higher than a predetermined pressure (Pa). The valve body 88a is configured to be elastically deformed in the exhaust gas outflow direction around the connecting portion between the valve body 88a and the retainer 88b, so that the flow passage 85c is opened.
When the flow pressure (Pa) of the exhaust gas is less than a predetermined pressure (Pa), the closed state is maintained against the dead weight applied in the direction of gravity indicated by the arrow g in FIG.

  Next, the action of the exhaust device 110 and air column resonance occurring in the tail pipe 40c will be described.

First, when the engine 10 shown in FIG. 1 is started, as in the first embodiment, exhaust gas is introduced into the inlet pipe 85, and as shown by an arrow in FIG. It is introduced into the resonance chamber 110A through the open end 85f. When the engine 10 is in the low engine speed region, the flow rate of the exhaust gas passing through the circulation passage 85c is relatively small. Therefore, the valve 88 does not elastically deform even when the exhaust gas flow pressure is applied, and the circulation passage 85c. Is kept closed. In this case, the exhaust gas flows into the expansion chamber 110C through the gap 89 shown in FIG. 25, and further flows into the expansion chamber 110B. The exhaust noise is reduced over the entire frequency band, and the exhaust gas enters the atmosphere from the downstream opening end 35b. Discharged.
When flow passage 85c is in the closed state, the tail pipe 40c, as in the first embodiment, the upstream side of the valve 88 becomes closed end, since the tail pipe 40c is a closed tube having a length L _b, the aforementioned As in the equation (5), air column resonance of a specific frequency occurs.

The air column resonance, as in the first embodiment, it is 1 Tsugion圧mode length L _b substantially coincides with the wavelength of the (1/4) lambda, the sound pressure at the upstream side of the valve 88 (Pa) is the most A rising belly will be formed. Further, in the 2 Tsugion圧mode, the length L _b is (3/4) becomes approximately matching columnar resonance wavelength of lambda, the sound pressure at the upstream side of the valve 88 (Pa) is the highest becomes antinode formed Will be. The air column resonance of a specific frequency generated in the tail pipe 40c can be attenuated by exciting the Helmholtz resonance in the resonance chamber 30A of the muffler 90, as in the first embodiment. Even when the flow rate of the exhaust gas is low during deceleration and the pressure in the flow passage 85c is small, as in the first embodiment, the resonance chamber 30A has a sound pressure (on the upstream side of the valve 88 via the communication passage 85e). Since it is provided in the vicinity of the antinode where Pa) is highest, the Helmholtz resonance can be effectively functioned.

When the engine 10 is in a relatively high rotation speed region such as during acceleration, the flow rate of the exhaust gas passing through the flow passage 85c is relatively large, so that the valve 88 is exhausted as shown in FIG. The flow passage 85c is opened due to elastic deformation in the exhaust direction due to the gas flow pressure.
Then, the exhaust gas flows into the expansion chamber 110C through the downstream opening end 85b, and further flows into the expansion chamber 110B. The exhaust sound is reduced over the entire frequency band and is discharged from the downstream opening end 35b to the atmosphere. . Further, part of the exhaust gas is vigorously introduced into the resonance chamber 110A from the opening end 85f through the communication passage 85e.

When flow passage 85c is in open state, the tail pipe 40c, as in the first embodiment, the downstream open end 81b is an open end, since the open tube having a length L _b, the above-mentioned formula (7 The air column resonance of the specific frequency represented by) occurs. The air column resonance, like the first embodiment, L _b is (1/2) becomes approximately matching 1 Tsugion圧mode and wavelength of lambda, the sound pressure (Pa at an intermediate portion of the exhaust direction of the tail pipe 40c ) Has the highest belly. Further, 2 in Tsugion圧mode, L _b is almost coincident columnar resonance with the wavelength of 1 [lambda, the sound pressure at two locations in the exhaust direction of the tail pipe 40c (Pa) has a highest becomes belly.

Engine 10 is in the high rotational speed region, such as during acceleration, when the flow passage 85c is opened also by Helmholtz resonator resonance chambers 110A, substantially equal length L _b is the wavelength of the (1/2) lambda 1 Tsugion圧mode and the length L _b of it can be attenuated substantially coincident 2 Tsugion圧mode columnar resonance with the wavelength of 1 [lambda.
In this case, similarly to the first embodiment, the resonance chamber 110A is located in a portion where the sound pressure on the upstream side of the valve 88 appears to be relatively low. However, in the relatively high rotational speed region, the flow rate of the exhaust gas. Since there are many and flow pressure is high, the attenuation by Helmholtz resonance functions effectively.

  Since the exhaust device 100 according to the fourth embodiment is configured as described above, the following effects can be obtained.

  That is, in the exhaust device 100, when the engine 10 is decelerated or in the low rotation region, the upstream side in the exhaust direction of the valve 88 has a high sound pressure, as in the first embodiment. This high sound pressure enhances the exhaust sound attenuating action of Helmholtz resonance in the resonance chamber 110 </ b> A, and it is possible to suitably suppress an increase in the sound pressure of the exhaust sound due to air column resonance. As a result, the exhaust noise of the air column resonance is transmitted to the vehicle interior, and a humming noise is generated in the vehicle interior, which eliminates the problem that the driver feels uncomfortable. Similarly to the embodiment, even when the engine 10 is in the low rotation region, it is not necessary to install a sub-muffler for suppressing air column resonance, the structure is simplified, and the effect of reducing weight and manufacturing cost can be obtained.

  On the other hand, when the engine 10 is in the high rotation region, the valve 88 opens the flow passage 85c, so that the tail pipe 40c is opened. In the case of such an open tube, as in the first embodiment, in the primary sound pressure mode and the secondary sound pressure mode, even if the sound pressure on the upstream side in the exhaust direction of the valve 88 becomes low, the flow pressure increases. Therefore, the attenuation effect of the exhaust sound of Helmholtz resonance in the resonance chamber 110A is enhanced. Therefore, even in the high rotation region, it is possible to suitably suppress an increase in the sound pressure of the exhaust sound due to the air column resonance generated in the tail pipe 40c. Further, as in the first embodiment, since the valve 88 opens the flow passage 85c, the exhaust gas can smoothly flow into the expansion chamber 110C from the valve 88, and the back pressure is increased in the tail pipe 40c. There is no increase, and no load is applied to the engine 10.

  As a result, since the increase in the sound pressure of the exhaust sound due to the air column resonance is suppressed in the entire region from the low rotation to the high rotation of the engine 10, it is necessary in the conventional exhaust device and the air that is provided in the tail pipe is used. A sub-muffler for suppressing column resonance is not required to be installed, the structure is simplified, and an effect of reducing weight and manufacturing cost can be obtained.

  In addition, compared with the first and second embodiments, the resonance chamber 110A can be positioned very close to the upstream side of the valve 36. In particular, when the engine 10 is decelerated, the tail pipe 40c is closed. 110A, the resonance chamber 110A can be arranged in a portion where the sound pressure of air column resonance is high. As a result, particularly when the engine 10 is decelerated, an increase in the sound pressure of the exhaust sound due to Helmholtz resonance can be effectively suppressed. Moreover, since the communication pipe 85d can be set longer than the first embodiment and the second embodiment, the resonance frequency in the resonance chamber 110A can be set to a lower frequency side. As a result, it is possible to solve the problem of noise caused by the booming noise generated on the lower frequency side.

(Modification)
The mufflers 30, 70, 90, 110 of the first to fourth embodiments are all configured in a three-chamber structure in which one resonance chamber and two expansion chambers are formed in the internal space. The muffler may be configured by other structures. For example, as shown in FIGS. 28 and 29, the muffler may be configured with a two-chamber structure.

  As shown in FIGS. 28 and 29, the two-chamber muffler 120 includes a muffler main body 91 as a silencer main body, a separator 32 as a partition member, an inlet pipe 92, an outlet pipe 95, and an opening / closing member. The valve 36 is configured. The muffler main body 91 includes an outer shell 93 formed in a cylindrical shape, and end plates 42 and 43 that close both ends of the outer shell 93 and define an internal space. A separator 32 is interposed between the end plate 42 and the end plate 43.

  The separator 32 partitions the internal space in the muffler main body 91 into a resonance chamber 120A located on the upstream side in the exhaust direction and an expansion chamber 120B located on the downstream side in the exhaust direction of the resonance chamber 120A. Further, an insertion hole 42a is formed in the end plate 42, an insertion hole 32a is formed in the separator 32, and an inlet pipe 92 is inserted through these insertion holes 42a and 32a. Further, an insertion hole 43a is formed in the end plate 43, and the outlet pipe 95 is inserted.

The inlet pipe 92 is formed between an upstream opening end 92a connected to the downstream end 25b of the center pipe 25, a downstream opening end 92b opening in the expansion chamber 120B, and the upstream opening end 92a and the downstream opening end 92b. Distribution passage 92c. In addition, the inlet pipe 92 has a communication pipe 92d in which a communication passage 92e that connects the flow passage 92c and the resonance chamber 120A is formed, and has an open end 92f that opens in the resonance chamber 120A.
The outlet pipe 95 includes an upstream opening end 95a that opens in the expansion chamber 120B, a downstream opening end 95b that opens to the atmosphere outside the muffler body 91, and a flow passage that communicates from the upstream opening end 95a to the downstream opening end 95b. 95c. Thus, since the muffler 120 is configured, as in the first embodiment, the increase in the sound pressure of the exhaust sound due to the air column resonance is suppressed in the entire region from the low rotation to the high rotation of the engine 10. A sub-muffler for suppressing air column resonance, which is required in the exhaust device and provided in the tail pipe, is not required to be installed, the structure is simplified, and the effect of reducing weight and manufacturing cost can be obtained.

  The valve 36 as the opening / closing member of the first embodiment includes bearing portions 51 and 52, a rotation shaft 53, restriction rings 54 and 55 for restricting movement of the rotation shaft 53 in the axial direction, and a valve body. 56 is described. However, the opening / closing member of the present invention may be configured with a structure other than the bearing structure having such a bearing portion. For example, a valve body having an outer shape formed slightly smaller than the inner diameter of the inlet pipe and an attachment member made of an elastic material that can be elastically deformed so as to attach the valve body to the inner wall surface of the inlet pipe. May be. Further, an integral structure in which the valve body and the mounting member are integrally formed may be used. With this structure, the valve can be formed with a simpler structure, and the manufacturing cost can be further reduced.

  As described above, the exhaust device for an internal combustion engine according to the present invention does not require the installation of a sub-muffler in the tail pipe or the installation of a silencer having a large-capacity resonance chamber in the vicinity of the downstream opening end of the tail pipe. Therefore, even when the internal combustion engine is decelerating, an increase in sound pressure due to air column resonance of the tail pipe can be suppressed with a simple structure, and the weight and manufacturing cost can be reduced. Useful for.

10 Engine (Internal combustion engine)
20, 60, 80, 100 Exhaust device 23 Front pipe (exhaust pipe)
25 Center pipe (exhaust pipe)
30, 70, 90, 110, 120 Muffler (silencer)
30A, 110A, 120A Resonance chamber 30B, 30C, 110B, 110C, 120B Expansion chamber 31, 91 Muffler body (muffler body)
32, 33, 74, 75, 86, 87 Separator (partition member)
34, 61, 81, 85, 92 Inlet pipe (exhaust pipe)
34a, 35a, 61a, 81a, 85a, 92a, 95a Upstream opening end 34b, 35b, 61b, 81b, 85b, 92b, 95b Downstream opening end 34c, 61c, 81c, 85c, 92c, 95c Distribution passage 34d, 61d, 82 , 85d, 92d Communication pipe 34e, 61e, 83, 85e, 92e Communication passage 34f, 61f, 82c, 85f, 92f Open end 35, 95 Outlet pipe 36, 50, 88 Valve 40, 40a, 40b, 40c Tail pipe (exhaust tube)

Claims (4)

In an exhaust system for an internal combustion engine equipped with a silencer that silences exhaust sound of exhaust gas flowing through the exhaust pipe of the internal combustion engine,
The silencer
A silencer body with an internal space formed,
A partition member that divides the internal space into a resonance chamber positioned upstream of the exhaust gas in the exhaust direction and an expansion chamber positioned downstream of the resonance chamber in the exhaust direction of the exhaust gas;
A flow passage provided in the silencer body and having an upstream open end connected to the downstream end of the exhaust pipe and a downstream open end opened in the expansion chamber is formed, and the flow passage and the resonance chamber are An inlet pipe having a communication pipe in which a communication passage is formed;
Provided in any one of the downstream opening end of the inlet pipe and the flow passage located between the downstream opening end and the communication passage on the downstream side in the exhaust direction with respect to the resonance chamber, An opening and closing member that opens and closes the flow passage according to the flow rate of the exhaust gas flowing through the flow passage;
The silencer body is provided with an upstream opening end that opens in the expansion chamber and a downstream opening end that is located outside the silencer body and opens to the atmosphere, and exhausts exhaust gas from the expansion chamber to the atmosphere. Bei example and outlet pipe, the which, during deceleration of the internal combustion engine, by the opening and closing member are closed while defining a clearance between the inner peripheral portion of the inlet pipe, the passage cross-sectional of the flow passage An exhaust system for an internal combustion engine characterized by narrowing down an area .   2. The internal combustion engine according to claim 1, wherein the communication pipe has an open end that protrudes from the inlet pipe so as to be substantially orthogonal to an axial line of the inlet pipe and opens at a front end portion in the protruding direction. Exhaust system. The communication pipe is provided in an outer peripheral portion of the inlet pipe along an axial direction of the inlet pipe so as to surround the inlet pipe, and the communication passage is defined by an inner peripheral surface of the communication pipe and an outer peripheral surface of the inlet pipe. 2. The exhaust system for an internal combustion engine according to claim 1, wherein the exhaust passage is defined and communicates with the flow passage of the inlet pipe through a through hole provided in the outer peripheral portion of the inlet pipe. . It said muffler, exhaust equipment of internal combustion engine according to any one of claims 1 to claim 3, characterized in that provided on the most downstream position in the exhaust downstream side.

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