JP2010025020A - Muffler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact muffler suitable for reducing a low frequency sound generated by a reciprocating internal combustion engine of high output. <P>SOLUTION: A first side branch 2 of the length λ/4 having the first closing end 3 is coaxially communicated with a first main pipe 1 connected to and communicated with the internal combustion engine, and a branch pipe 4 having the length of (2n+1)λ/4 (here, n is an integer of 1 or more) or a value near to this value, is connected to a second main pipe 5 coaxial with the first main pipe from the communicating part, and a second side branch 6 of the length λ/4 having the second closing end 7 is connected to the upstream side of the second main pipe. An inlet of the branch pipe becomes a node to reduce the sound transmitted to the downstream side, and further reduces the sound by the interference effect of the second side branch in a position merging again with the main pipe. Both an inlet and an outlet of the branch pipe do not become the node by the length setting of the branch pipe. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a silencer that is provided in a reciprocating internal combustion engine having a large output of a rated output of 200 kW or more and reduces a low frequency of 100 Hz or less contained in exhaust gas, and more particularly, an interference type using a side branch. The present invention relates to improvement of a silencer.

  Silencers are used to reduce noise contained in engine exhaust. There are various types of silencers, such as expansion type, sound absorption type, resonance type, and interference type, depending on the purpose of noise reduction, the level of sound reduction to be achieved, and the frequency to be reduced. However, when it is desired to reduce the sound of a specific low-frequency component, a silencer using a side branch, which is a kind of interference type, is a relatively simple and often used device.

  FIG. 4 is a diagram showing a structure of a normal side branch that has been conventionally known. In the middle of the main pipe 100 connected to a sound source (left side in the figure), the length of a quarter wavelength of the frequency to be erased is shown. A side branch 101 called the side branch 101 is provided with a closed end. The sound wave coming from the main pipe 100 and splitting at the entrance (branch point) of the side branch 101 and entering the side branch 101 reciprocates in the pipe of the side branch 101 to return to the original branch point with a half-wave shift. The sound is erased by interfering with the sound wave from the sound source in the main pipe 100 in the opposite phase.

  When designing this side branch, the following issues must be taken into consideration, and it is actually difficult to adopt it in an actual engine due to design constraints.

  (1) The exhaust gas temperature of the engine changes according to the load factor, but if the temperature changes, the sound speed also changes. Therefore, if the frequency is fixed, the wavelength will change with the change of the sound speed. Since the frequency of noise generated from the engine is determined by the engine speed and the number of cylinders, considering the specific frequency that is the target of noise reduction in the noise generated by the engine, the sound wave of that frequency depends on the load factor of the engine. Therefore, the optimum length of the side branch for reducing the sound also changes according to the load factor.

  (2) The sound wave existing in the pipe of the silencer is a standing wave, and the side branch is effective when attached to the antinode of the standing wave where the sound pressure of the sound wave that is the target of sound reduction in the main pipe is maximum. However, the effect is not obtained even if it is installed at the position of the node where the sound pressure is minimum. In order to know the position of the antinodes and nodes of the sound wave that is the target of sound reduction in the main pipe, it is necessary to measure the sound pressure distribution in the pipe. In practice, it is difficult to measure the sound pressure while gradually shifting the position of.

  (3) As the frequency becomes lower, the wavelength of the sound wave becomes longer, so the optimum side branch length also becomes longer, making it difficult to secure the arrangement space and attach the support support.

  (4) In addition to the above-mentioned restriction that the length of the side branch is ¼ wavelength of the sound wave of the frequency to be reduced, there is also a restriction that it is preferable to make the length of the main pipe connecting the side branch more than twice. is there. When the length of the side branch is less than twice the diameter of the main pipe, the sound waves from the main pipe are reflected at various angles with respect to the inside of the side branch, so only the sound waves of the specific frequency that is the target of sound reduction. Cannot be erased by anti-phase interference, and rather than an interference-type silencer, it becomes closer to an expansion-type silencer, and there is a problem that it is difficult to obtain a sufficient silencing effect.

  In particular, in a reciprocating internal combustion engine with a large output, the diameter of the main pipe becomes considerably large, so that the length of a quarter wavelength becomes smaller than twice the diameter of the main pipe depending on the frequency to be reduced. There is. For example, when considering a case where a low frequency of 100 Hz or less is targeted for sound reduction, when the temperature is 300 ° C., the sound speed is 480 m / s, the frequency is 40 Hz, and the wavelength (λ) is 12 m, the length of the side branch is ( 1/4) λ = 3 m, but such a low frequency is a problem. For example, in a reciprocating internal combustion engine with an output of 200 kW or more, the length of this 1/4 wavelength is the internal combustion engine. It may be smaller than twice the diameter of the exhaust pipe.

  An object of the present invention is to solve various conventional problems described above, and can cope with the wavelength variation of the sound wave to be reduced due to the variation of the load factor, in order to find the optimum mounting position with respect to the main pipe. It is not necessary to investigate the sound pressure distribution in the pipe, and is particularly suitable for a reciprocating internal combustion engine with a rated output of 200 kW or more that generates a low frequency of 100 Hz or less, and a compact silencer with high installation space efficiency. The object is to provide a device.

The silencer according to claim 1 is:
A silencer that is provided in a reciprocating internal combustion engine having a rated output of 200 kW or more that generates a low frequency of 100 Hz or less and reduces the low frequency of the wavelength λ contained in the exhaust gas from the internal combustion engine.
A first main pipe, one end of which is connected to the internal combustion engine and exhausted from the internal combustion engine;
One end is connected to and communicated with the other end of the first main pipe that is downstream in the exhaust direction, and the other end that extends in the same direction as the first main pipe and is downstream in the exhaust direction is a first closed end. A first side branch whose length is set to λ / 4,
The other end portion of the connected first main pipe and the one end portion of the first side branch branch off from the distal end in the exhaust direction and have a length of (2n + 1) λ / 4 (where n is 1). An integer greater than or equal to) or a branch pipe set to a value close thereto,
A second main pipe disposed coaxially with the first main pipe, connected to and communicated with the tip of the branch pipe at the other end, and discharges exhaust from one end downstream in the exhaust direction;
One end is connected to and communicated with the other end of the second main pipe and the tip of the branch pipe and extends in the same direction as the second main pipe with the other end serving as a second closed end. A second side branch with λ / 4 set to
It is characterized by having.

The silencer according to claim 2 is:
A silencer that is provided in a reciprocating internal combustion engine having a rated output of 200 kW or more that generates a low frequency of 100 Hz or less and reduces the low frequency of the wavelength λ contained in the exhaust gas from the internal combustion engine.
A first main pipe, one end of which is connected to the internal combustion engine and exhausted from the internal combustion engine;
One end is connected to and communicated with the other end of the first main pipe downstream in the exhaust direction, and is extended in a direction intersecting the first main pipe, with the other end being a first closed end, and its length. A first side branch where is set to λ / 4;
The other end of the first main pipe is branched in the opposite direction to the first side branch, and the tip is extended downstream in the exhaust direction. The length is (2n + 1) λ / 4 (where n is an integer of 1 or more) ) Or a branch pipe set to a value close to this,
A second main pipe disposed coaxially with the first main pipe, connected to and communicated with the tip of the branch pipe at the other end, and discharges exhaust from one end downstream in the exhaust direction;
One end is connected to and communicated with the other end of the second main pipe and the tip of the branch pipe, and is extended in the same direction as the branch pipe intersecting the second main pipe, with the other end being a second closed end. A second side branch whose length is set to λ / 4,
It is characterized by having.

The silencer according to claim 3 is the silencer according to claim 1 or 2,
The lengths of the first side branch and the second side branch are adjustable.

  According to the silencer of the present invention described in claims 1 and 2, the following effects can be obtained. Among the frequencies included in the original sound emitted from the exhaust outlet of the engine, particularly low frequencies are distributed as steady waves in the main pipe as constant and weak distortion based on the combustion timing of each cylinder of the engine. However, if the middle of the first main pipe is closed with the first closed end, and a branch pipe is attached at a quarter wavelength from there, this part becomes the first side branch, and the inlet of the branch pipe is a node (sound pressure). It is possible to lower the sound by working to break the distribution of strong and weak Liz 厶 in the main sound of the original sound. The sound wave remaining in this action is further reduced by the second side branch at a position where it joins the main pipe again after entering the branch pipe. Here, the length of the branch pipe is (2n + 1) λ / 4 (where n is an integer of 1 or more) or a value close thereto, for example, (2n + 0.5) λ / 4 or more, (2n + 1.5) λ / 4 or less ( However, by setting n to a numerical value in the range of 1 or more, there is no node at the inlet and outlet of the branch pipe, so both the first side branch and the second side branch are completely There is no loss of effectiveness.

  In particular, according to the silencer of the first aspect, since the side branch and the main pipe are continuous in the same direction and the side branch is not attached to the main pipe at a right angle, the protrusion in the side direction can be minimized.

  In particular, according to the silencer of the second aspect, since the side branch and the main pipe can be orthogonal to each other, the length of the main pipe communicating with the exhaust pipe in the same direction can be minimized.

  In particular, according to the silencer of the third aspect, the following effects can be obtained. In other words, the exhaust gas temperature of the engine changes according to the load factor, but the sound speed also changes as the temperature changes. And if the speed of sound changes, the length of the wavelength will change when looking at the specific frequency that is the target of noise reduction in the noise generated by the engine, so the optimal side branch length also depends on the load factor. Will change. For the change in the optimum length of the side branch due to such a change in the engine load factor, the lengths of the first side branch and the second side branch can be adjusted. It can be solved by setting the optimum length at the time of loading. In addition, even if it is necessary to adjust the optimum length according to the result of actual operation, the optimum length can be adjusted by means such as attaching a length adjustment pipe to the closed end of each side branch. can do.

A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view of the silencer according to the first embodiment, and FIG. 2 is a partial view of a modification of the silencer according to the first embodiment. With reference to these drawings, the configuration of the silencer of this example is illustrated. explain.
This silencer is provided in a reciprocating internal combustion engine having a rated output of 200 kW or more that generates a low frequency of 100 Hz or less, and reduces the low frequency (wavelength λ) contained in the exhaust from the internal combustion engine. It is something to be made.

  Although not shown, one end of the first main pipe 1 is connected to the exhaust pipe of the internal combustion engine so that exhaust gas is sent from the internal combustion engine.

  One end of a first side branch 2 having the same diameter as that of the first main pipe 1 is connected to the other end portion of the first main pipe 1 that is downstream in the exhaust direction, with the axis aligned with the first main pipe 1. . The other end of the first side branch 2 downstream of the exhaust direction (indicated by a white arrow in the figure) is closed, and this is called the first closed end 3. The length of the first side branch 2 is set to λ / 4 (¼ wavelength).

  A branch pipe 4 is branched from the other end of the connected first main pipe 1 and one end of the first side branch 2. The branch pipe 4 branches in a direction orthogonal to the first main pipe 1 and the first side branch 2, then curves toward the downstream in the exhaust direction, and extends in parallel to the first main pipe 1 and the first side branch 2. After that, it is further curved in a direction approaching the axis of the first main pipe 1, and its tip part is connected to the other end part of the second main pipe 5 that is coaxially arranged downstream of the first main pipe 1. Has been. The length of the branch pipe 4 is (2n + 1) λ / 4 (where n is an integer of 1 or more) or a value close thereto, for example, (2n + 0.5) λ / 4 or more, (2n + 1.5) λ / 4 or less ( However, n is set to a numerical value within a range (including numerical values at both ends of the range). More specifically, a value within a range of 2.5 / 4 wavelength to 3.5 / 4 wavelength including 3/4 wavelength (when n = 1 in the above formula), 5/4 wavelength (in the above formula) from 4.5 / 4 wavelength to 5.5 / 4 wavelength including n = 2), from 6.5 / 4 wavelength including 7/4 wavelength (when n = 3 in the above formula) It is set to a value within the range of 7.5 / 4 wavelength. In FIG. 1, the length of the branch pipe 4 is illustrated as being set to about 3/4 wavelength, about 5/4 wavelength, or about 7/4 wavelength. The second main pipe 5 discharges the exhaust gas flowing in from the distal end portion of the branch pipe 4 from one end portion on the downstream side.

  One end of a second side branch 6 having the same diameter as that of the second main pipe 5 is coaxially connected to and communicated with the second main pipe 5 at the other end of the second main pipe 5 to which the tip of the branch pipe 4 is connected. ing. The other end of the second side branch 6 is closed, which is referred to as a second closed end 7. The length of the second side branch 6 is set to λ / 4 (1/4 wavelength).

Next, the operation of the above configuration will be described.
Among the frequencies included in the original sound emitted from the exhaust outlet of the engine, particularly low frequencies are distributed as steady waves in the main pipe as constant and weak distortion based on the combustion timing of each cylinder of the engine.

  According to the structure of the silencer of the present example described above, when the end of the pipe continuous with the first main pipe 1 is closed as the first closed end 3 and the branch pipe 4 is attached at a position of λ / 4 therefrom, the branch pipe A portion ahead of the attachment portion 4 is the first side branch 2. At the first closed end 3, the standing wave becomes the antinode with the maximum sound pressure, and the standing wave becomes the node with the minimum sound pressure at the communicating portion of the branch pipe 4 located at λ / 4. Therefore, if the Liz 原 distribution of the intensity of the original sound that would have existed in the absence of the first closed end 3 is different from the distribution of the standing wave, the original sound circuit is destroyed to reduce the sound. The effect of can be produced.

  The sound wave remaining in this operation also enters the branch pipe 4 and then splits into two directions, the second main pipe 5 and the second side branch 6 at a position where it merges with the second main pipe 5 again. The sound is further reduced and discharged. Here, the length of the branch pipe 4 is (2n + 1) λ / 4 (where n is an integer of 1 or more) or a value close thereto, for example, (2n + 0.5) λ / 4 or more, (2n + 1.5) λ / 4. It is set to a numerical value (including numerical values at both ends of the range) within the following range (where n is an integer of 1 or more). More specifically, a value within a range of 2.5 / 4 wavelength to 3.5 / 4 wavelength including 3/4 wavelength (when n = 1 in the above formula), 5/4 wavelength (in the above formula) from 4.5 / 4 wavelength to 5.5 / 4 wavelength including n = 2), from 6.5 / 4 wavelength including 7/4 wavelength (when n = 3 in the above formula) It is set to a value within the range of 7.5 / 4 wavelength. Accordingly, the standing wave is generally the antinode of the maximum sound pressure at the outlet part of the branch pipe 4 (the position connected to the second main pipe 5), and both the inlet part and the outlet part of the branch pipe 4 do not become nodes. It is impossible for both the first side branch 2 and the second side branch 6 to be completely ineffective.

  Further, according to the silencer of this example, the first main pipe 1, the first side branch 2, the second side branch 6 and the second main pipe 5 are all continuously arranged in the same direction, Since it is not a structure that attaches at right angles to the main pipe, the bulge in the side direction can be minimized. For this reason, it is possible to easily cope with restrictions on installation space.

  FIG. 2 is a diagram illustrating a modification of the first side branch 2 in the first embodiment. In FIG. 2, the other end side (the first closed end 3 side) of the first side branch 2 is composed of a tube 9 that is interchangeably connected by a flange 8, and the length of the tube 9 to be replaced (for example, The length of the first side branch 2 can be adjusted by variously setting L1, L2).

  That is, as described above, the exhaust gas temperature changes according to the load factor of the engine, and the sound speed also changes as the exhaust gas temperature changes. If the speed of sound changes, the specific frequency that is the target of noise reduction in the noise generated by the engine will change the wavelength length, and the optimal side branch length will also change according to the load factor. It will be.

  Such a change in the optimum length of the side branch due to a change in the engine load factor can be dealt with by adjusting the lengths of the first side branch 2 and the second side branch 6 with the above-described configuration. For example, by selecting and connecting the pipes 9 having appropriate lengths, it is possible to obtain an optimum length when the load is low and an optimum length when the load is high. The same applies when the optimum length needs to be adjusted according to the actual driving result.

A second embodiment of the present invention will be described with reference to FIG.
FIG. 3 is a cross-sectional view of the silencer according to the second embodiment.
This silencer is provided in a reciprocating internal combustion engine having a rated output of 200 kW or more that generates a low frequency of 100 Hz or less, and reduces the low frequency (wavelength λ) contained in the exhaust from the internal combustion engine. It is something to be made.

  Although not shown, one end of the first main pipe 11 is connected to the exhaust pipe of the internal combustion engine so that exhaust gas is sent from the internal combustion engine.

  One end of the first side branch 12 having the same diameter as the first main pipe 11 is orthogonal to the first main pipe 11 at the other end of the first main pipe 11 downstream of the exhaust direction (indicated by the white arrow in the figure). Connected in direction. The other end of the first side branch 12 is closed, and this is referred to as a first closed end 13. The length of the first side branch 12 is set to λ / 4 (1/4 wavelength).

  A branch pipe 14 is branched from the other end of the first main pipe 11 in a direction opposite to the first side branch 12. The branch pipe 14 branches in a direction opposite to the first side branch 12 along a direction orthogonal to the first main pipe 11, then curves downstream in the exhaust direction, and extends in parallel with the first main pipe 11. After that, it is further curved in a direction approaching the axis of the first main pipe 11, and its distal end is connected to the other end of the second main pipe 15 disposed coaxially with the first main pipe 11. It is communicated. The length of the branch pipe 14 is (2n + 1) λ / 4 (where n is an integer of 1 or more) or a value close to this, for example, (2n + 0.5) λ / 4 or more, (2n + 1.5) λ / 4 or less ( However, n is set to a numerical value within a range (including numerical values at both ends of the range) (specifically, each value in the case of n = 1, 2,... Is the same as in the first embodiment). .) In FIG. 3, the length of the branch pipe 14 is illustrated as being set to about 3/4 wavelength, about 5/4 wavelength, or about 7/4 wavelength. The second main pipe 15 discharges the exhaust gas flowing in from the distal end portion of the branch pipe 14 from one end portion on the downstream side.

  In the other end of the second main pipe 15 to which the tip of the branch pipe 14 is connected and communicated, one end of the second side branch 16 having the same diameter as the second main pipe 15 is connected to the branch pipe 14, that is, the first The two main pipes 15 are connected and communicated in a direction orthogonal to the main pipe 15. The other end of the second side branch 16 is closed, and this is referred to as a second closed end 17. The length of the second side branch 16 is set to λ / 4 (1/4 wavelength).

  Also in this example, effective silencing can be performed by the same operation as in the first example.

  In particular, according to the silencer of this example, since the first and second side branches 12 and 16 and the first and second main pipes 11 and 15 are orthogonal to each other, they communicate with the exhaust pipe in the same direction. The length of the main pipes 11 and 15 in the longitudinal direction can be minimized. For this reason, it is possible to easily cope with restrictions on installation space.

  Note that the side branch length adjusting means (the tube 9 having the flange 8) described in the first embodiment with reference to FIG. 2 can be similarly employed in this example.

FIG. 1 is a cross-sectional view of the silencer according to the first embodiment. FIG. 2 is a partial view of a modification of the silencer according to the first embodiment. FIG. 3 is a cross-sectional view of the silencer according to the second embodiment. FIG. 4 is a cross-sectional view of a conventional interference silencer using a side branch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 ... 1st main pipe 2,12 ... 1st side branch 3,13 ... 1st closed end 4,14 ... Branch pipe 5,15 ... 2nd main pipe 6,16 ... 2nd side branch 7,17 ... 2nd Closed end 8 ... Flange 9 ... Pipe

Claims (3)

A silencer that is provided in a reciprocating internal combustion engine having a rated output of 200 kW or more that generates a low frequency of 100 Hz or less and reduces the low frequency of the wavelength λ contained in the exhaust gas from the internal combustion engine.
A first main pipe, one end of which is connected to the internal combustion engine and exhausted from the internal combustion engine;
One end is connected to and communicated with the other end of the first main pipe that is downstream in the exhaust direction, and the other end that extends in the same direction as the first main pipe and is downstream in the exhaust direction is a first closed end. A first side branch whose length is set to λ / 4,
The other end portion of the connected first main pipe and the one end portion of the first side branch branch off from the distal end in the exhaust direction and have a length of (2n + 1) λ / 4 (where n is 1). An integer greater than or equal to) or a branch pipe set to a value close thereto,
A second main pipe disposed coaxially with the first main pipe, connected to and communicated with the tip of the branch pipe at the other end, and discharges exhaust from one end downstream in the exhaust direction;
One end is connected to and communicated with the other end of the second main pipe and the tip of the branch pipe and extends in the same direction as the second main pipe with the other end serving as a second closed end. A second side branch with λ / 4 set to
A muffler characterized by comprising: A silencer that is provided in a reciprocating internal combustion engine having a rated output of 200 kW or more that generates a low frequency of 100 Hz or less and reduces the low frequency of the wavelength λ contained in the exhaust gas from the internal combustion engine.
A first main pipe, one end of which is connected to the internal combustion engine and exhausted from the internal combustion engine;
One end is connected to and communicated with the other end of the first main pipe downstream in the exhaust direction, and is extended in a direction intersecting the first main pipe, with the other end being a first closed end, and its length. A first side branch where is set to λ / 4;
The other end of the first main pipe is branched in the opposite direction to the first side branch, and the tip is extended downstream in the exhaust direction. The length is (2n + 1) λ / 4 (where n is an integer of 1 or more) ) Or a branch pipe set to a value close to this,
A second main pipe disposed coaxially with the first main pipe, connected to and communicated with the tip of the branch pipe at the other end, and discharges exhaust from one end downstream in the exhaust direction;
One end is connected to and communicated with the other end of the second main pipe and the tip of the branch pipe, and is extended in the same direction as the branch pipe intersecting the second main pipe, with the other end being a second closed end. A second side branch whose length is set to λ / 4,
A muffler characterized by comprising: The silencer according to claim 1 or 2, wherein lengths of the first side branch and the second side branch are adjustable.

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