JP2006144707A - Muffler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a muffler capable of driving each open close member by a simpler structure when each open close member is provided on each exhaust pipe in the muffler in the muffler applied on an engine provided with two banks and having exhaust gas from each bank merged in an outer cylinder. <P>SOLUTION: This muffler is provided with a first exhaust pipe 9 and a second exhaust pipe 10 to which exhaust gas from each bank of the engine is introduced respectively, exhaust gas discharged from the first exhaust pipe 9 and the second exhaust pipe 10 is merged in the outer cylinder 1. Tube parts in the outer cylinders 1 of the first exhaust pipe 9 and the second exhaust pipe 10 are provided with rectangular holes 14a, 14b opened and closed by a first valve 15a and a second valve 15b respectively. A rotatably supported shaft 16 is provided in the outer cylinder 1 and the shaft 16 and the first valve 15a are fixed by a first connecting plate 17a. The shaft 16 and the second valve 15b are fixed by a second connecting plate 17b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a muffler provided in an exhaust system of an engine.

  The muffler provided in the exhaust system of the engine is provided with a plurality of noise reduction chambers therein, and the exhaust noise is reduced each time exhaust gas passes through the plurality of noise reduction chambers. Here, as the number of times exhaust passes through the silencing chamber increases, the exhaust noise is further reduced and the silencing performance is improved. Since the pressure loss increases, the exhaust efficiency decreases and the engine output is affected.

Therefore, the muffler described in Patent Document 1 is provided with a hole in the exhaust pipe inside the muffler, and an open / close member (open / close valve) that opens and closes the hole so that the exhaust can bypass the sound deadening chamber through driving of the open / close member. I have to. In this muffler, the opening / closing valve is closed when the exhaust flow rate is small, such as when the engine is running at a low speed, and the exhaust from the engine is exhausted from the muffler after passing through a plurality of sound deadening chambers. On the other hand, when the exhaust flow rate increases, such as when the engine is running at high speed, the open / close valve is opened, so that the exhaust is discharged from the muffler with the number of passages through the muffler chamber being reduced. The increase in pressure loss is suppressed, and the exhaust efficiency at the time of high engine speed is improved.
JP-A-6-88514

By providing an openable / closable member in the exhaust pipe inside the muffler in this way, it is possible to improve the noise reduction performance at the time of low engine rotation and the exhaust efficiency at the time of high engine rotation.
By the way, in recent years, the number of exhaust system catalytic converters tends to increase in order to improve the exhaust purification performance, and the pressure loss of the exhaust system tends to increase accordingly. Therefore, it is desired to reduce the pressure loss of other components of the exhaust system.

  Here, an engine having two banks, such as a V-type engine, generally includes an independent exhaust manifold for each bank, and the exhaust discharged to each exhaust manifold is connected to each exhaust manifold. It is introduced into the muffler through the exhaust pipe. Thus, in an engine having two banks, the exhaust pipes are connected to each exhaust pipe upstream of the muffler and are introduced into the muffler in a state where the exhaust from each bank is merged. Inserting the downstream side into the muffler so that the exhausts from the banks merge in the muffler can suppress an increase in pressure loss of the exhaust system due to exhaust interference.

  By the way, when exhausts from the banks are combined in the muffler as described above, and the opening / closing members as described above are provided in the exhaust pipes in the muffler, the number of opening / closing member driving mechanisms is required. As a result, the structure of the muffler becomes complicated, for example, leading to an increase in cost and an increase in weight.

  The present invention has been made in view of such conventional circumstances, and an object of the present invention is to be applied to an engine including two banks, and in the muffler in which exhaust from each bank is merged in the outer cylinder, the muffler An object of the present invention is to provide a muffler capable of driving each open / close member with a simpler configuration when providing the open / close member in each exhaust pipe.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is applied to an engine including two banks, and includes an outer cylinder having a sound deadening chamber partitioned by a separator, and two exhaust pipes into which exhaust from each bank is respectively introduced. In the muffler in which the exhaust discharged from each exhaust pipe is merged in the outer cylinder, each of the exhaust pipes is provided with a hole that is opened and closed by an opening / closing member in each of the exhaust pipes. The opening and closing members for opening and closing these holes are connected to each other by a connecting mechanism.

  In this configuration, the exhaust gas discharged from the exhaust pipes is merged in the outer cylinder. Therefore, an increase in the pressure loss of the exhaust system due to the exhaust interference can be suppressed. In each exhaust pipe, a hole that is opened and closed by an opening / closing member is provided in a pipe portion in the outer cylinder. Therefore, for example, by opening and closing each of these opening and closing members according to the operating state of the engine, the muffler performance and exhaust efficiency of the muffler can be improved.

  Here, the open / close members provided in the exhaust pipes in the outer cylinder are connected to each other by a connecting mechanism, and the open / close members are simultaneously driven to open / close by driving the connecting mechanism. Therefore, according to the configuration, when the open / close members are provided in the exhaust pipes in the muffler, the open / close members can be driven with a simpler configuration. Therefore, for example, an increase in cost and an increase in weight due to the provision of a plurality of opening / closing members in the muffler can be suppressed.

  According to a second aspect of the present invention, in the muffler according to the first aspect, the coupling mechanism fixes a shaft rotatably supported in the outer cylinder, and the shaft and the opening / closing members. The gist is that the connecting member is used.

  According to this configuration, each opening / closing member is fixed to the shaft by the connecting member. Accordingly, by rotating one shaft, the respective opening / closing members can be driven simultaneously, and the drive mechanism of the opening / closing member itself, the number of actuators for driving it, and the like can be simplified.

  According to a third aspect of the present invention, in the muffler according to the first aspect, the connecting mechanism includes a first shaft and a second shaft that are rotatably supported in the outer cylinder and are connected to each other by a transmission mechanism. The first connecting member that fixes the first shaft and one of the opening / closing members, and the second connecting member that fixes the second shaft and the other opening / closing member. And

  According to this configuration, one opening / closing member is driven to open / close by rotating the first shaft. Here, since the first shaft and the second shaft are drivingly connected to each other, the second shaft is also rotated simultaneously by the rotation of the first shaft, and the other opening / closing member fixed to the second shaft is also opened / closed simultaneously. Driven. Thus, according to the same structure, it becomes possible to drive each opening and closing member simultaneously by giving a rotational driving force to one shaft (first shaft). Therefore, it is not necessary to provide a driving source for driving the opening / closing member for each opening / closing member, and the number of the driving sources can be simplified. Incidentally, examples of the transmission mechanism include a gear mechanism, a belt mechanism, and a chain mechanism.

  According to a fourth aspect of the present invention, in the muffler according to any one of the first to third aspects, a resonance chamber for attenuating a specific frequency is provided in the outer cylinder, and the outer cylinder The gist of the present invention is that the resonance chamber is connected to the pipe section on the exhaust downstream side of the outer cylinder and the resonance chamber in the exhaust pipe for discharging the exhaust inside.

  According to this configuration, the resonance chamber is compressed by the exhaust from the exhaust pipe that discharges the exhaust in the outer cylinder, so that a resonance effect in the resonance chamber is suitably obtained, and thus the exhaust sound due to the resonance effect is obtained. Reduction can be performed sufficiently. In addition, by changing the connection position between the exhaust pipe and the communication pipe, the resonance frequency of the air column resonance generated due to the length of the pipe portion on the downstream side of the exhaust from the outer cylinder can be easily changed. Therefore, it is possible to easily suppress resonance noise in a desired rotational speed range. Incidentally, the resonance frequency becomes higher as the distance from the exhaust pipe outlet to the connection position is shortened. Therefore, the engine rotation speed at which the sound pressure of the resonance sound generated by the air column resonance becomes maximum shifts to a higher rotation speed region as the distance from the exhaust pipe outlet to the connection position becomes shorter. As a result, the sound pressure of the resonance sound in the low rotational speed region can be suppressed.

(First embodiment)
A first embodiment that embodies a muffler according to the present invention configured as a muffler of an engine including two banks, such as a V-type engine, will be described below with reference to FIGS.

FIG. 1 shows a cross-sectional structure in the exhaust flow direction of the muffler of the present embodiment.
As shown in FIG. 1, the muffler according to the present embodiment includes a substantially cylindrical outer cylinder 1 and the like.

  The inside of the outer cylinder 1 is partitioned by a first separator 2, a second separator 3, and a third separator 4 in order from the exhaust upstream side, and the first silencing chamber 5 is formed between the first separator 2 and the outer cylinder 1. A compartment is formed. A second silencing chamber 6 is defined by the first separator 2, the second separator 3, and the outer cylinder 1. A third silencing chamber 7 is defined by the second separator 3, the third separator 4, and the inside of the outer cylinder 1. A resonance chamber 8 is defined by the third separator 4 and the inside of the outer cylinder 1.

  The first silencing chamber 5 and the second silencing chamber 6 communicate with each other through a communication hole 2 a provided in the first separator 2, and the second silencing chamber 6 and the third silencing chamber 7 are provided in the second separator 3. The communication holes 3a communicate with each other. In addition, the volume of the resonance chamber 8 is appropriately set so that a specific frequency can be attenuated among the constituent frequencies of the exhaust sound, and in this embodiment, particularly low frequency exhaust sound is efficiently used. The volume and the like are set so that they can be reduced well.

  A first exhaust pipe 9 into which exhaust from one bank of the engine is introduced and a second exhaust from which the exhaust from the other bank of the engine is introduced into a wall surface 1a on the exhaust upstream side of the outer cylinder 1. Exhaust pipes 10 are respectively provided. In addition, a third exhaust pipe 11 for discharging the exhaust gas in the outer cylinder 1 is provided on the wall surface 1b on the exhaust downstream side of the outer cylinder 1.

  One end of the third exhaust pipe 11 is inserted through the wall surface 1 b, the third separator 4, and the second separator 3 to the second silencing chamber 6. The other end of the third exhaust pipe 11 is open to the atmosphere. In addition, a communication pipe 13 that connects the inside of the third exhaust pipe 11 and the inside of the resonance chamber 8 is connected to a pipe portion in the third exhaust pipe 11 that is downstream of the wall surface 1b of the outer cylinder 1. ing.

  One end of the first exhaust pipe 9 and the second exhaust pipe 10 is inserted through the wall surface 1 a, the first separator 2, and the second separator 3 to the third silencing chamber 7. That is, the exhaust downstream ends of the first exhaust pipe 9 and the second exhaust pipe 10 are opened to the third silencing chamber 7, and the exhaust discharged from each bank joins in the outer cylinder 1. ing. The other ends of the first exhaust pipe 9 and the second exhaust pipe 10 are each connected to a catalytic converter, and each catalytic converter is connected to an exhaust manifold provided in each bank.

  In the first exhaust pipe 9 and the second exhaust pipe 10, a plurality of small holes 12 are provided in the pipe portion in the first silencer chamber 5, and one of the exhaust gases in the first exhaust pipe 9 and the second exhaust pipe 10 is provided. The portion flows out from the small holes 12 into the first silencing chamber 5.

In the muffler of the present embodiment configured as described above, the exhaust discharged from the first exhaust pipe 9 and the second exhaust pipe 10 joins in the outer cylinder 1, and the following effects are exhibited.
In an exhaust system in which each exhaust pipe independent for each bank is connected upstream of the muffler, that is, in an exhaust system introduced into the muffler in a state where exhaust from each bank is joined by a collecting pipe or the like, Exhaust interference occurs at the exhaust confluence, and the pressure loss of the exhaust system increases. On the other hand, in the present embodiment, the exhaust discharged from each bank and introduced into the first exhaust pipe 9 and the second exhaust pipe 10 joins in the outer cylinder 1 having a larger volume than the joining portion of the collecting pipe. Therefore, an increase in the pressure loss of the exhaust system due to the exhaust interference can be suppressed as compared with the case where the exhaust from each bank is joined by the collecting pipe.

  Furthermore, in the first exhaust pipe 9 and the second exhaust pipe 10 of the muffler according to the present embodiment, an opening / closing member that opens and closes a hole formed in each of the exhaust pipes, and each opening / closing member provided in each hole is mutually connected. A valve mechanism including a coupling mechanism for coupling is provided.

  The structure of this valve mechanism will be described with reference to FIGS. Note that FIG. 2 is a diagram in which a part of the third exhaust pipe 11 is omitted from FIG. 1 in order to make it easier to show the structure of the valve mechanism. 3 shows the AA cross section of FIG. 1 when the valve mechanism is closed, and FIG. 4 shows the AA cross section of FIG. 1 when the valve mechanism is open. Show.

  As shown in FIG. 2, in the first exhaust pipe 9 and the second exhaust pipe 10, square holes 14 a and 14 b are respectively provided in the pipe portions in the second silencing chamber 6. These square holes 14a and 14b are opened and closed by a first valve 15a and a second valve 15b, respectively, constituting the opening and closing member.

The first and second valves 15a and 15b have a semicircular arc shape that matches the outer peripheral shape of the first exhaust pipe 9 and the second exhaust pipe 10 so as to cover the square holes 14a and 14b.
And these 1st and 2nd valves 15a and 15b are mutually connected by the connection mechanism. This connecting mechanism fixes the shaft 16 rotatably supported in the outer cylinder 1, the first connecting plate 17a for fixing the shaft 16 and the first valve 15a, and the shaft 16 and the second valve 15b. It consists of the second connecting plate 17b and the like.

  The shaft 16 is rotatably supported by support portions formed on the first separator 2 and the second separator 3. A flat plate-like first connecting plate 17a and a second connecting plate 17b are fixed to the outer peripheral surface of the shaft 16 in the diameter direction, respectively, and the first valve 15a is attached to the end of the first connecting plate 17a. However, the second valve 15b is fixed to the end of the second connecting plate 17b. Thus, the 1st connection plate 17a and the 2nd connection plate 17b comprise the said connection member which fixes a shaft and each opening-and-closing member, respectively.

  3 and 4, the square holes 14 a and the square holes 14 b are formed in the first exhaust pipe 9 and the second exhaust pipe 10 so as to be point-symmetric with respect to the central axis of the shaft 16. The square hole 14a is opened toward one side (upper surface side of the outer cylinder 1), and the square hole 14b is opened toward the other side (lower surface side of the outer cylinder 1). Therefore, the exhaust gas discharged from the square hole 14a and the square hole 14b flows out in different directions. The first valve 15 a and the second valve 15 b are also provided so as to be point-symmetric with respect to the central axis of the shaft 16 so that the square hole 14 a and the square hole 14 b can be opened and closed, respectively.

  Also, as shown in FIG. 2 and the like, one end of the shaft 16 protrudes from the wall surface 1a, and a spring 18 that urges the first valve 15a and the second valve 15b in the closing direction is provided at this end. ing. Further, an actuator 19 for opening and closing the first and second valves 15a and 15b is connected to one end. Through the drive control of the actuator 19, the first and second valves 15a and 15b are closed when the engine rotational speed is in a low rotational speed range below a certain level, and the engine rotational speed is in a high rotational speed range above a certain level. Sometimes the first and second valves 15a, 15b are opened. Thus, the valve mechanism is driven to open and close according to the engine operating state.

With regard to the muffler of the present embodiment configured as described above, an exhaust flow mode according to the engine operating state will be described with reference to FIG.
Exhaust gas discharged from each bank of the engine is introduced into the first exhaust pipe 9 and the second exhaust pipe 10, and a part of the exhaust gas introduced into the first exhaust pipe 9 and the second exhaust pipe 10 is the first exhaust pipe 9. The air is introduced into the first muffler chamber 5 through a small hole 12 provided in the exhaust pipe 9 or the second exhaust pipe 10. The exhaust gas introduced into the first silencing chamber 5 is opened to the second silencing chamber 6 after the exhaust noise is reduced in the first silencing chamber 5 and the second silencing chamber 6 communicated therewith. The third exhaust pipe 11 is introduced.

  On the other hand, most of the exhaust introduced into the first exhaust pipe 9 and the second exhaust pipe 10, and the exhaust that has advanced through each exhaust pipe without being introduced into the first silencing chamber 5 from the small hole 12, The flow mode differs depending on the state of the first and second valves 15a and 15b.

  First, as shown in FIG. 3, in a state where the engine speed is in the low speed range and the first and second valves 15 a and 15 b are closed, most of the exhaust is from the first exhaust pipe 9. Or from the end of the second exhaust pipe 10 to the third sound deadening chamber 7. Then, the exhaust gas introduced into the third silencing chamber 7 is reduced in the third silencing chamber 7 and the second silencing chamber 6 connected to the third silencing chamber 7, and then is discharged into the third exhaust pipe 11. be introduced.

  As described above, when the first and second valves 15a and 15b are closed, exhaust is introduced into the muffler through two systems such as the small hole 12 and the ends of the first exhaust pipe 9 and the second exhaust pipe 10, and these introductions are introduced. The exhausted air passes through a plurality of sound deadening chambers and is exhausted to the outside of the muffler in a sufficiently silenced state.

  On the other hand, as shown in FIG. 4, when the engine speed is in a high speed range and the first and second valves 15a and 15b are open, most of the exhaust gas flows into the square holes 14a and 14b. Are introduced into the second silencing chamber 6 and introduced into the third silencing chamber 7 from the ends of the first exhaust pipe 9 and the second exhaust pipe 10. The exhaust gas introduced into the second silencing chamber 6 from the square holes 14 a and 14 b is introduced into the third exhaust pipe 11 after the exhaust noise is reduced in the second silencing chamber 6. Further, the exhaust gas introduced from the end of the first exhaust pipe 9 and the second exhaust pipe 10 into the third silencer chamber 7 is exhausted in the third silencer chamber 7 and the second silencer chamber 6 communicated therewith. Is reduced and then introduced into the third exhaust pipe 11.

  As described above, when the first and second valves 15a and 15b are open, the exhaust is exhausted through the three systems including the small hole 12, the end of the first exhaust pipe 9 and the second exhaust pipe 10, and the square holes 14a and 14b. Introduced in. Among these, the exhaust gas introduced into the muffler from the square holes 14a and 14b in particular passes through only the second silencing chamber 6 and is discharged outside the muffler. That is, the exhaust passage from the square hole 14a and the square hole 14b to the third exhaust pipe 11 is more silencer than the exhaust passage from the end of the first exhaust pipe 9 or the second exhaust pipe 10 to the third exhaust pipe 11. Since the number of passages is small, the pressure loss is lower. Therefore, even at the time of high engine speed at which the exhaust gas flow rate increases, an increase in pressure loss in the muffler is suppressed, thereby improving the exhaust efficiency at the time of high engine speed.

  As the exhaust flow rate increases, the exhaust discharged from each bank becomes easier to flow into the flow path with lower pressure loss, that is, the exhaust flow path from the square hole 14a and the square hole 14b to the third exhaust pipe 11, The exhaust efficiency can be further increased.

  In the present embodiment, the exhaust discharged from the first exhaust pipe 9 and the second exhaust pipe 10 is joined in the outer cylinder 1 to suppress an increase in pressure loss due to exhaust interference. In order to realize this, the first exhaust pipe 9 and the second exhaust pipe 10 are inserted into the outer cylinder 1 in an independent state. A first valve 15a and a second valve 15b are provided on the first exhaust pipe 9 and the second exhaust pipe 10 inserted individually.

  Here, the first valve 15a and the second valve 15b are coupled to each other by a coupling mechanism such as the shaft 16, the first coupling plate 17a, and the second coupling plate 17b, and by rotating one shaft 16 The first valve 15a and the second valve 15b are opened and closed simultaneously. Therefore, in the case where the first exhaust pipe 9 and the second exhaust pipe 10 are provided with the first valve 15a and the second valve 15b, respectively, there is no need to individually provide a drive mechanism or a drive actuator for each valve. The drive mechanism itself of the first valve 15a and the second valve 15b, the number of actuators for driving the drive mechanism, and the like can be simplified. That is, the first valve 15a and the second valve 15b can be driven with a simple configuration. Therefore, for example, an increase in cost and an increase in weight due to the provision of a plurality of valve mechanisms in the muffler can be suppressed.

  On the other hand, in the present embodiment, the third exhaust pipe 11 and the pipe portion on the exhaust downstream side of the wall surface 1b of the outer cylinder 1 communicate with each other in the third exhaust pipe 11 and the resonance chamber 8. The tube 13 is connected. Therefore, the resonance chamber 8 can be sufficiently compressed by the exhaust from the third exhaust pipe 11 that exhausts the exhaust in the outer cylinder 1, and the resonance effect in the resonance chamber 8 can be suitably obtained. As a result, exhaust noise due to the resonance effect can be sufficiently reduced.

  In addition, by changing the connection position between the third exhaust pipe 11 and the communication pipe 13, the resonance frequency of the air column resonance generated due to the length of the pipe portion on the exhaust downstream side of the outer cylinder 1 can be easily set. Therefore, it is possible to easily suppress the resonance noise in a desired rotational speed range.

  That is, the resonance frequency f of the air column can be obtained from the following equation (1).

そして、図５に示すように、第３排気管１１の管長が「Ｌ」であって、上記連通管１３を備えていないときの共鳴周波数を「ｆａ」とする。一方、同図５に二点鎖線にて示すように、上記連通管１３を備え、第３排気管１１の大気開放端側の出口から該連通管が接続された部位までの管長が「Ｌ１」に設定されているときの共鳴周波数を「ｆｂ」とする。この場合には、管長Ｌと管長Ｌ１との大小関係が「Ｌ＞Ｌ１」となるため、上記式（１）から共鳴周波数ｆａと共鳴周波数ｆｂとの大小関係は「ｆａ＜ｆｂ」となる。ここで、第３排気管１１にて発生する気柱共鳴は、該第３排気管１１に対する断続的な排気の導入が振動源となっているため、１分間に共鳴周波数ｆと同じ回数だけ、第３排気管１１に排気が導入されるとき、その共鳴音は最大となる。従って、共鳴音が最大となるエンジン回転速度（以下、共鳴回転速度ＦＮＥという）は次式（２）から求めることができる。

As shown in FIG. 5, the resonance frequency when the pipe length of the third exhaust pipe 11 is “L” and the communication pipe 13 is not provided is “fa”. On the other hand, as shown by a two-dot chain line in FIG. 5, the length from the outlet of the third exhaust pipe 11 on the atmosphere open end side to the portion where the communication pipe is connected is “L1”. The resonance frequency when set to is “fb”. In this case, since the magnitude relationship between the tube length L and the tube length L1 is “L> L1,” the magnitude relationship between the resonance frequency fa and the resonance frequency fb is “fa <fb” from the above equation (1). Here, since the air column resonance generated in the third exhaust pipe 11 is caused by the intermittent introduction of exhaust gas to the third exhaust pipe 11, the same number of times as the resonance frequency f per minute, When exhaust is introduced into the third exhaust pipe 11, the resonance noise is maximized. Therefore, the engine rotation speed at which the resonance noise becomes maximum (hereinafter referred to as resonance rotation speed FNE) can be obtained from the following equation (2).

Resonance rotational speed FNE = f / H × 60 (2)
f: resonance frequency H: number of exhaust strokes per crankshaft rotation

As shown in this equation (2), the higher the resonance frequency, the greater the resonance rotational speed FNE. Therefore, the magnitude relationship between the resonance rotation speed FNEa corresponding to the resonance frequency fa and the resonance rotation speed FNEb corresponding to the resonance frequency fb is “FNEa <FNEb”. Will grow. That is, the rotational speed range where the sound pressure of the resonance sound generated by the air column resonance in the third exhaust pipe 11 becomes maximum shifts to a higher rotational speed range.

  In this way, the resonance rotational speed FNE can be easily and arbitrarily changed by changing the pipe length L1, that is, by changing the connection position of the third exhaust pipe 11 and the communication pipe 13, so that a desired rotational speed can be obtained. It is also possible to easily suppress the resonance sound in the region. Further, as described above, the resonance rotation speed FNE at which the sound pressure of the resonance sound generated by the air column resonance becomes maximum shifts to a higher rotation speed region as the tube length L1 is shortened. The sound pressure of the resonance sound in the low rotational speed range can be suppressed.

  For example, when the muffler of this embodiment is applied to a V-type 8-cylinder engine, the tube length L of the third exhaust pipe 11 is set to “2100 mm”, and the diameter thereof is set to “70 mm”, the communication pipe 13 is The resonance rotational speed FNEa when the exhaust gas temperature is not “500 ° C.” and the exhaust temperature is “500 ° C.” is approximately “1935 r / min” from the above formulas (1) and (2). At this time, as indicated by a solid line in FIG. 6, when the engine rotation speed is in the vicinity of 1935 r / min, the sound pressure of the resonance sound generated by the air column resonance becomes maximum.

  On the other hand, when the muffler of this embodiment is applied to an engine of the same type, the pipe length L of the third exhaust pipe 11 is set to “2100 mm”, and the diameter thereof is set to “70 mm”, the communication pipe 13 is provided, The resonance rotational speed FNEb when the tube length L1 is set to “1250 mm” and the exhaust temperature is “500 ° C.” is approximately “3330 r / min” from the above formulas (1) and (2). At this time, as indicated by a two-dot chain line in FIG. 6, when the engine rotation speed becomes a speed in the vicinity of 3330 r / min, the sound pressure of the resonance sound generated by the air column resonance becomes maximum. As described above, when the communication pipe 13 is provided, the resonance rotational speed FNE can be shifted to a higher rotational speed side than in the case where the communication pipe 13 is not. The sound pressure, that is, the sound pressure in the low rotation speed region can be reduced.

As described above, according to the present embodiment, the following effects can be obtained.
(1) Exhaust gas discharged from each bank of the engine is merged in the muffler (inside the outer cylinder 1). Therefore, an increase in the pressure loss of the exhaust system due to the exhaust interference can be suppressed.

  (2) The first exhaust pipe 9 and the second exhaust pipe 10 are provided with the first valve 15a and the second valve 15b, which are opened and closed according to the engine operating state, respectively. Therefore, the noise reduction performance at the time of low engine rotation and the exhaust efficiency at the time of high engine rotation can be improved. Here, in the present embodiment, the first valve 15a and the second valve 15b are connected to each other by a connecting mechanism. Accordingly, the first valve 15a and the second valve 15b can be simultaneously opened and closed by driving the coupling mechanism, and the first valve 15a and the second valve 10 are respectively connected to the first exhaust pipe 9 and the second exhaust pipe 10 in the muffler. When the two valves 15b are provided, the first valve 15a and the second valve 15b can be driven with a simple configuration. For this reason, for example, an increase in cost and an increase in weight due to the provision of a plurality of valve mechanisms in the muffler can be suppressed.

  (3) The connection mechanism includes the shaft 16 rotatably supported in the outer cylinder 1, the first connection plate 17a for fixing the shaft 16 and the first valve 15a, and the shaft 16 and the second valve 15b. The second connecting plate 17b to be fixed is configured. Thus, since the first valve 15a and the second valve 15b are fixed to the same shaft 16 via the first connection plate 17a and the second connection plate 17b, by rotating one shaft 16 The first valve 15a and the second valve 15b can be driven simultaneously. Accordingly, it is possible to simplify the drive mechanism itself of the first valve 15a and the second valve 15b, the number of actuators for driving the drive mechanism, and the like.

  (4) A resonance chamber 8 for attenuating a specific frequency is provided in the outer cylinder 1, and is located in the third exhaust pipe 11 for discharging the exhaust gas in the outer cylinder 1, and is located downstream of the outer cylinder 1. And the resonance chamber 8 are connected by a communication pipe 13. Therefore, the resonance chamber 8 is compressed by the exhaust from the third exhaust pipe 11 that discharges the exhaust in the outer cylinder 1, and the resonance effect in the resonance chamber 8 is suitably obtained, and thus the exhaust sound is reduced by the resonance effect. Will be able to do enough.

(5) Further, by changing the connection position of the third exhaust pipe 11 and the communication pipe 13, the resonance of the air column resonance that occurs due to the length of the pipe portion on the exhaust downstream side of the outer cylinder 1. It is possible to easily change the frequency, and it is possible to easily suppress the resonance sound in a desired rotational speed range. By the way, the shorter the distance from the outlet of the third exhaust pipe 11 to the connection position, the higher the resonance frequency. Therefore, the engine rotation speed at which the sound pressure of the resonance sound generated by the air column resonance becomes maximum shifts to a higher rotation speed region as the distance from the outlet of the third exhaust pipe 11 to the connection position is shortened. As a result, the sound pressure of the resonance sound in the low rotational speed range can be suppressed.
(Second Embodiment)
Next, a second embodiment in which the muffler according to the present invention is embodied will be described with reference to FIGS.

  In the present embodiment, the first valve 15a and the second valve 15b are connected by a connection mechanism different from that of the first embodiment. Except for this point, the first embodiment is basically the same as the first embodiment. is there. Therefore, in the following, the muffler according to the present embodiment will be described focusing on this difference. 7 to 9, the same members as those described in the first embodiment are denoted by the same reference numerals.

  FIG. 7 shows a cross-sectional structure in the exhaust flow direction of the muffler of the present embodiment. Like FIG. 2, a part of the third exhaust pipe 11 is shown to facilitate the structure of the valve mechanism. FIG. 8 shows a BB cross section of FIG. 7 when the valve mechanism is closed, and FIG. 9 shows a BB cross section of FIG. 7 when the valve mechanism is open. Show.

  As shown in FIG. 7, in the first exhaust pipe 9 and the second exhaust pipe 10, square holes 14 a and 14 b are respectively provided in the pipe portions in the second silencing chamber 6, and these square holes 14 a and 14 b are provided. Are opened and closed by a first valve 15a and a second valve 15b, respectively.

The first and second valves 15a and 15b have a semicircular arc shape that matches the outer peripheral shape of the first exhaust pipe 9 and the second exhaust pipe 10 so as to cover the square holes 14a and 14b.
And these 1st and 2nd valves 15a and 15b are mutually connected by the connection mechanism.

  In the present embodiment, the coupling mechanism includes a first shaft 20a that is rotatably supported in the outer cylinder 1, a second shaft 20b that is also rotatably supported in the outer cylinder 1, a first shaft 20a, and a first shaft 20a. The first connecting plate 22a for fixing the valve 15a, the second connecting plate 22b for fixing the second shaft 20b and the second valve 15b, and the like are included.

  The first shaft 20a is rotatably supported by a support portion formed on the first separator 2 and the second separator 3, and a first gear 23a is provided on a part thereof. A flat plate-like first connecting plate 22a is fixed in the diameter direction on the outer peripheral surface of the first shaft 20a, and a first valve 15a is fixed to an end of the first connecting plate 22a. The first connecting plate 22a constitutes the first connecting member.

  Further, one end of the first shaft 20a protrudes from the wall surface 1a on the exhaust upstream side of the outer cylinder 1, and a spring 18 that urges the first valve 15a and the second valve 15b in the closing direction is provided at this end. ing. The one end is connected to the actuator 19 for opening and closing the first and second valves 15a and 15b.

  The second shaft 20b is arranged in parallel to the side opposite to the side where the first connecting plate 22a is provided in the first shaft 20a, and is formed in the first separator 2 and the second separator 3. It is rotatably supported by the support portion. In addition, a second gear 23b that meshes with the first gear 23a is provided at a part thereof. A flat plate-like second connecting plate 22b is fixed in the diameter direction on the outer peripheral surface of the second shaft 20b, and a second valve 15b is fixed to an end of the second connecting plate 22b. The second connecting plate 22b constitutes the second connecting member.

  As shown in FIGS. 8 and 9, both the square hole 14a and the square hole 14b of this embodiment are opened toward one side (the upper surface side of the outer cylinder 1), and the square hole 14a or The exhaust discharged from the square hole 14b flows out in the same direction. The first valve 15a and the second valve 15b are also provided on one side of the first exhaust pipe 9 and the second exhaust pipe 10 so that the square hole 14a and the square hole 14b can be opened and closed, respectively.

  In the muffler of the present embodiment configured as described above, particularly the coupling mechanism thereof, the first valve 15a is driven to open and close by rotating the first shaft 20a by the actuator 19. Here, since the first shaft 20a and the second shaft 20b are connected to each other by a transmission mechanism such as the first gear 23a and the second gear 23b, the second shaft 20b is also rotated simultaneously by the rotation of the first shaft 20a. The second valve 15b fixed to the second shaft 20b is also opened and closed simultaneously with the first valve 15a.

  Thus, according to the present embodiment, the first valve 15a and the second valve 15b can be driven simultaneously by applying a rotational driving force to one shaft (the first shaft 20a). Therefore, it is not necessary to provide a drive source (actuator 19 in this embodiment) for driving the first valve 15a and the second valve 15b for each valve, and the number of the drive sources can be simplified. Will be able to. That is, also in this embodiment, when the first valve 15a and the second valve 15b are provided in the first exhaust pipe 9 and the second exhaust pipe 10 in the muffler, respectively, the first valve 15a and the second valve 15b are simplified. It becomes possible to drive with the configuration. For this reason, for example, an increase in cost and an increase in weight due to the provision of a plurality of valve mechanisms in the muffler can be suppressed.

In addition, each said embodiment can also be changed and implemented as follows.
In the first embodiment, the drive source for driving the first valve 15a and the second valve 15b is the actuator 19, but this may be changed to a spring. For example, as illustrated in FIG. 10, a shaft 16 ′ is rotatably supported on a support portion formed on the first separator 2 and the second separator 3, and the first connecting plate 17 a and the second connecting shaft 17 ′ are supported on the shaft 16 ′. The connecting plate 17b is fixed. A spring 30 that urges the first valve 15a and the second valve 15b in the closing direction is provided at one end of the shaft 16 ′ and protruding from the first separator 2 toward the wall surface 1a. Further, the spring constant of the spring 30 is set so that the first valve 15a and the second valve 15b are opened by an increase in exhaust pressure accompanying an increase in the rotational speed of the engine. Also by such a modification, the same effect as 1st Embodiment can be acquired. In particular, in this modified example, the actuator 19 and its control device are not required, so that the first valve 15a and the second valve 15b can be opened and closed with a simpler configuration. In addition, you may make it provide the said spring 30 in the part which protruded toward the wall surface 1b side from the 2nd separator 3 at one end of shaft 16 '.

  In addition, the aspect concerning such a modification can be similarly applied to the second embodiment. For example, as illustrated in FIG. 11, a first shaft 20 a ′ is rotatably supported on a support portion formed on the first separator 2 and the second separator 3, and the first connecting plate is supported on the first shaft 20 a ′. 22a is fixed. Further, the first gear 23a meshing with the second gear 23b is provided on the first shaft 20a '. A spring 40 that biases the first valve 15a and the second valve 15b in the closing direction is provided at one end of the first shaft 20a ′ and protruding from the first separator 2 toward the wall surface 1a. . The spring constant of the spring 40 is also set such that the first valve 15a and the second valve 15b are opened by an increase in exhaust pressure accompanying an increase in engine speed. Also according to the modified example configured as described above, the same effects as those of the second embodiment can be obtained. That is, it is not necessary to provide a driving source (in this modification, the spring 40) for driving the first valve 15a and the second valve 15b for each valve, and the number of the driving sources can be simplified. Will be able to. In particular, in this modification, the actuator 19, its control device, and the like are not required, so that the first valve 15a and the second valve 15b can be opened and closed with a simpler configuration. In addition, you may make it provide the said spring 40 in the part which protruded toward the wall surface 1b side from the 2nd separator 3 at the end of 1st shaft 20a '.

Incidentally, a leaf spring or the like can be used as the spring 30 or the spring 40 in addition to the coil spring shown in FIGS.
The spring 18 described in the first and second embodiments may be omitted.

The small holes 12 provided in the first exhaust pipe 9 and the second exhaust pipe 20 may be omitted.
In each of the above embodiments, the square holes 14a and 14b are provided in the first exhaust pipe 9 and the second exhaust pipe 10 one by one. In addition, a plurality of square holes 14 a and 14 b are provided in the first exhaust pipe 9 and the second exhaust pipe 10. The opening / closing member for opening / closing the plurality of square holes 14a provided in the first exhaust pipe 9 and the opening / closing member for opening / closing the plurality of square holes 14b provided in the second exhaust pipe 10 are connected as described above. You may make it mutually connect with a mechanism.

The shape of the holes (square holes 14a and 14b) provided in the first exhaust pipe 9 and the second exhaust pipe 10 and opened and closed by the first valve 15a and the second valve 15b can be arbitrarily changed.
-The number of sound deadening rooms provided in the muffler can be changed arbitrarily.

The resonance chamber 8 and the communication pipe 13 may be omitted. Even in this case, the effects other than (4) and (5) described in the first embodiment can be obtained.
-The connection mechanism demonstrated by each said embodiment is an example, and in short, if it is a mechanism which connects each opening-and-closing member provided in each exhaust pipe mutually, the structure can be changed suitably and can be implemented.

  In the second embodiment, the gear mechanism is employed as a transmission mechanism that drives and connects the first shaft 20a and the second shaft 20b. However, the transmission mechanism transmits a driving force between different movable members. Any mechanism can be used. Therefore, a belt mechanism or a chain mechanism can be employed as the transmission mechanism.

  The muffler according to the present invention can be applied to an engine having two banks and any exhaust system in which exhaust is discharged independently for each bank. For example, not only a V-type engine but also a muffler provided in an exhaust system such as a W-type engine having two pairs of banks or a horizontally opposed engine can be applied.

The schematic diagram which shows the cross-sectional structure about 1st Embodiment of the muffler concerning this invention. The schematic diagram which abbreviate | omitted a part of exhaust pipe in FIG. 1, and showed the structure of the valve mechanism. The schematic diagram which shows the AA cross section of FIG. 1 when the valve mechanism is made into the closed state in the embodiment. The schematic diagram which shows the AA cross section of FIG. 1 when the valve mechanism is made into the open state in the embodiment. Schematic for demonstrating the generation | occurrence | production aspect of air column resonance in the same embodiment. The graph which shows the change aspect by the presence or absence of a communicating pipe about the sound pressure of the resonance sound which generate | occur | produces by air column resonance. The schematic diagram which shows the cross-sectional structure about 2nd Embodiment of the muffler concerning this invention. The schematic diagram which shows the BB cross section of FIG. 7 when the valve mechanism is made into the closed state in the embodiment. The schematic diagram which shows the BB cross section of FIG. 7 when the valve mechanism is made into the open state in the embodiment. The schematic diagram which showed the structure of the valve mechanism about the modification of the muffler concerning 1st Embodiment. The schematic diagram which showed the structure of the valve mechanism about the modification of the muffler concerning 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Outer cylinder, 1a ... Wall surface, 1b ... Wall surface, 2 ... 1st separator, 2a ... Communication hole, 3 ... 2nd separator, 3a ... Communication hole, 4 ... 3rd separator, 5 ... 1st silencer chamber, 6 ... 2nd silencer chamber, 7 ... 3rd silencer chamber, 8 ... Resonance chamber, 9 ... 1st exhaust pipe, 10 ... 2nd exhaust pipe, 11 ... 3rd exhaust pipe, 12 ... Small hole, 13 ... Communication pipe, 14a, 14b ... Square hole, 15a ... first valve, 15b ... second valve, 16, 16 '... shaft, 17a ... first connecting plate, 17b ... second connecting plate, 18 ... spring, 19 ... actuator, 20 ... second exhaust Pipe, 20a, 20a '... first shaft, 20b ... second shaft, 22a ... first connecting plate, 22b ... second connecting plate, 23a ... first gear, 23b ... second gear, 30, 40 ... spring.

Claims (4)

Applied to an engine having two banks, and includes an outer cylinder having a sound deadening chamber partitioned by a separator, and two exhaust pipes into which exhaust from each bank is introduced, and exhausted from each exhaust pipe In the muffler where the exhaust gas is joined in the outer cylinder,
Each exhaust pipe is provided with a hole that is opened and closed by an opening / closing member in a tube portion in the outer cylinder, and the opening / closing members that open and close the holes are connected to each other by a connecting mechanism. A muffler characterized by that. The muffler according to claim 1, wherein the coupling mechanism includes a shaft that is rotatably supported in the outer cylinder, and a coupling member that fixes the shaft and the opening / closing members. The coupling mechanism is fixed to the first and second shafts rotatably supported in the outer cylinder and connected to each other by a transmission mechanism, and the first shaft and one of the opening / closing members. The muffler according to claim 1, comprising a connecting member, and a second connecting member that fixes the second shaft and the other of the open / close members. In the muffler of any one of Claims 1-3,
A resonance chamber for attenuating a specific frequency is provided in the outer cylinder. The resonance chamber is disposed in an exhaust pipe for exhausting the exhaust gas in the outer cylinder and the pipe section on the exhaust gas downstream side of the outer cylinder. A muffler characterized in that it is connected to the chamber by a communication pipe.

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