JP6823903B2 - Silencer - Google Patents

Description

The present invention relates to a muffling device that reduces noise propagating in a ventilation path. In particular, the present invention relates to a silencer including an expansion chamber provided in the ventilation path.

In the intake system of internal combustion engines for automobiles and the ventilation pipes (so-called ventilation ducts, ventilation ducts, ventilation hoses, etc.) of air conditioning systems and cooling air ventilation systems, the noise from the engine, fan, motor, etc. is the ventilation pipe. Since it propagates in the path and air column resonance occurs in the air duct, it has been desired to reduce the noise for some time.

A technique of providing an expansion chamber as a sound deadening element for noise propagating in the ventilation path of such an intake system or a blower pipe is well known. By providing the expansion chamber in which the cross section of the ventilation path changes suddenly, the propagation of noise is suppressed due to the impedance change in the portion where the cross section of the ventilation changes suddenly. However, with the expansion chamber technology, it has been difficult to efficiently eliminate noise in a specific frequency region.

Further, a resonance type silencer is known as a technique for silencing noise at a specific frequency in a ventilation path.
For example, Patent Document 1 discloses a resonance device of a Helmholtz type resonator having a resonance chamber and a communication portion, and discloses a resonance device in which a sound absorbing material is provided in the communication portion and the communication chamber. Further, Patent Document 2 discloses that an expansion portion (resonance chamber) and a slit-shaped communication hole are provided along a pipeline to form a resonator, and a sound absorbing material is provided in the resonance chamber.
According to these techniques, the resonator eliminates noise in a specific frequency band, while the sound absorbing material enhances the muffling effect.

Japanese Unexamined Patent Publication No. 06-081737 JP-A-2009-250183

Each of these expansion chambers and resonant silencers requires a predetermined volume. In order to save space in the muffler, a muffler having both the muffling characteristics of the expansion chamber and the muffling characteristics of the resonance type muffler has been desired, but it has been difficult to realize it.

An object of the present invention is to provide a muffling device including an expansion chamber capable of effectively enhancing muffling characteristics near a specific frequency.

As a result of diligent studies, the inventor has constructed an expansion chamber type silencer by connecting two pipes at specific positions to a rectangular parallelepiped expansion chamber, and further provides a specific form of partition wall in the chamber. And, it was found that the sound deadening characteristic near a specific frequency can be effectively enhanced, and the present invention was completed.

The present invention is a muffling device that silences noise propagating through a tube, wherein the muffling device includes a rectangular expansion chamber, a first tube connected to a substantially central portion of a first surface of the chamber, and the first tube. It has a second tube connected to approximately the center of the second surface of the chamber adjacent to the first surface, the side of the first tube is connected to the noise source, and the normal direction of the first surface is the first. One direction, the normal direction of the second surface is the second direction, the direction orthogonal to the first direction and the second direction is the third direction, and the second direction from the surface facing the second surface of the chamber. A partition wall is erected so as to extend to , and there is only one partition wall in the expansion chamber, and when viewed along the third direction, the internal space of the chamber is U-shaped due to the partition wall. In a sound deadening device provided with a partition wall so as to be partitioned into the above and so that the position of the partition wall in the first direction substantially coincides with the position of the center of the connection portion of the second pipe in the first direction. There is (first invention).

In the first invention, preferably, the height of the partition wall measured along the second direction is 1/4 to 2/3 of the length of the chamber in the second direction.
(Second invention).

According to the muffling device (first invention) of the present invention, although it is a muffling device including an expansion chamber, the resonance mode in the expansion chamber can be changed to effectively enhance the muffling characteristics near a specific frequency. .. In particular, when the height of the partition wall is set as in the second invention, the muffling characteristic near a specific frequency is more effectively enhanced.

It is a perspective view which shows the muffling device of 1st Embodiment. It is sectional drawing which shows the structure of the expansion chamber in 1st Embodiment. It is a figure which shows the muffling effect of the Example of the muffling device of 1st Embodiment. It is a figure which shows the resonance mode near the 1st resonance frequency in an Example. It is a figure which shows the resonance mode near the 1st resonance frequency in the comparative example. It is a figure which shows the resonance mode near the 2nd resonance frequency in an Example. It is a figure which shows the resonance mode near the 2nd resonance frequency in the comparative example. It is a schematic diagram which shows the method of measuring the acoustic attenuation amount.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, exemplifying a silencer used as a part of an intake system that supplies air to an automobile engine. The invention is not limited to the individual embodiments shown below, and the embodiments can be modified and implemented.
FIG. 1 is a perspective view showing the muffling device 10 of the first embodiment. Further, FIG. 2 is a cross-sectional view of the expansion chamber portion. The sound deadening device 10 is configured by connecting two blower pipes (hereinafter, also referred to as “tubes”) 1 and 2 to the expansion chamber 3. The internal space of the first pipe 1, the internal space of the expansion chamber 3, and the internal space of the second pipe 2 are sequentially connected to form a series of ventilation paths, through which air flows. The muffling device 10 has a change in the cross-sectional area of the internal space at the connection point between the pipe and the chamber, and thereby works as a so-called expansion chamber type muffling device to muffle the noise propagating in the pipe.

In the intake system, the silencer 10 is connected, for example, to the end of the second pipe 2 with a duct member or the like on the intake port side, and to the end of the first pipe 1 with a duct member or the like on the engine side. Is used. The intake system may be equipped with other silencers, air cleaners, and the like. Further, the muffling device 10 can be used not only for the intake system of the internal combustion engine of an automobile, but also for the ventilation path of an air conditioner, the ventilation path of an air cooling system such as a battery, and the like.

The pipes 1 and 2 are hollow pipes. The specific shape of the blower pipes 1 and 2 is determined by various uses, and is made into a straight tubular shape, a curved shape, a bent shape, or the like, if necessary. The blower pipes 1 and 2 may be a rigid pipe or a flexible hose. The blower pipes 1 and 2 are preferably made of a non-breathable material, but a part or all of the blower pipes 1 and 2 may be made of a breathable material. Further, a through hole (for example, a drain hole or a tuning hole) for communicating the inside and outside of the pipe may be provided in a part of the blower pipes 1 and 2.

The expansion chamber 3 provided in the hollow shape has a rectangular parallelepiped shape. In particular, it is preferably square when viewed from the direction orthogonal to the first pipe 1 and the second pipe 2. The internal space of the expansion chamber 3 does not have to be a strict rectangular parallelepiped, and may be provided with a corner R, a punched taper, a gradient, and the like. Further, among the surfaces constituting the rectangular parallelepiped chamber, some surfaces may be formed on a curved surface such as a cylinder or a spherical surface. The internal space of the chamber as a whole may be rectangular parallelepiped. Further, the expansion chamber 3 may be formed with reinforcing ribs, beads, or the like. The material of the expansion chamber 3 is not particularly limited, but typically a non-breathable material, for example, a thermoplastic resin such as polypropylene resin is preferably used.

The first tube 1 is connected to a substantially central portion of the first surface P1 of the expansion chamber 3. The center line m1 of the first pipe 1 at the connection portion does not have to be exactly aligned with the center of the first surface P1, and even if they are separated from each other, the distance between them is one side of the first surface. It may be 20% or less of the length.

The second tube 2 is connected to a substantially central portion of the second surface P2 of the expansion chamber 3 adjacent to the first surface P1. The center line m2 of the second pipe 2 at the connection portion does not have to exactly coincide with the center of the second surface P2, and even if they are separated from each other, the distance between them is one side of the second surface. It may be 20% or less of the length. In the rectangular parallelepiped chamber, the second surface P2 adjacent to the first surface P1 is "2" "3" when the first surface is the "1" surface in terms of dice. It is one of the surfaces of "4" and "5".

In other words, the first pipe 1 and the second pipe 2 are attached to the chamber 3 so that the center lines m1 and m2 at the connection portion of the pipes are substantially orthogonal to each other, and the silencer 10 The ventilation path when viewed as is bent about 90 degrees at the portion of the expansion chamber 3.

The silencer 10 is used with the side of the first pipe 1 connected to the noise source. That is, in the case of the muffling device 10 used in the intake system of an automobile engine, as described above, the side of the first pipe 1 is on the side of the engine which is the noise source, and the side of the second pipe 2 is on the side of the intake port. Be connected. If the silencer 10 is used, for example, in the ventilation path of an air conditioner, the side of the first pipe 1 is connected to the side of the fan or motor which is a noise source.

The internal structure of the expansion chamber 3 will be described. Here, in FIGS. 1 and 2, the normal direction of the first surface P1 of the chamber is the first direction X, the normal direction of the second surface P2 of the chamber is the second direction Y, and the first direction. The direction orthogonal to X and the second direction Y is defined as the third direction Z. The center line m1 of the first pipe 1 near the connection portion and the first direction X may be parallel, and the center line m2 of the second pipe 2 near the connection portion and the second direction Y may be parallel. preferable.

Inside the expansion chamber 3, a partition wall 4 is erected so as to extend in the second direction Y from the surface P3 facing the second surface P2 of the chamber. That is, the partition wall 4 is provided inside the chamber 3 so as to extend from the surface P3 toward the second pipe P2. Here, the surface P3 facing the second surface P2 is, in terms of dice, the surface "6" when the second surface P2 is the surface "1".

Further, the partition wall 4 is provided so as to straddle between the left and right side walls 3a and 3b of the chamber in the right side view of FIG. 2, and the space under the chamber in the right side view of FIG. It is divided into a front side and a back side in the direction. As a result, as shown in the figure on the left side of FIG. 2, when viewed along the third direction Z, the partition wall 4 partitions the internal space of the chamber in a U shape with the lower side open.

The partition wall 4 is provided so that the position of the partition wall 4 in the first direction substantially coincides with the position of the center C2 of the connecting portion of the second pipe 2 in the first direction. In other words, the partition wall 4 is provided at a position substantially coincident with the central axis m2 in the vicinity of the connecting portion of the second pipe 2. It is not necessary that the position where the partition wall 4 is provided and the center C2 or the center axis m2 of the pipe 2 exactly coincide with each other, and even if the positions are separated, the distance is the length LX of the expansion chamber 3 in the first direction. It may be within 20% of.

The height H of the partition wall 4 measured along the second direction Y of the partition wall 4 is preferably 1/4 to 2/3 of the length LY of the chamber 3 in the second direction, preferably 1/3. It is particularly preferable that it is ~ 1/2.

The sound deadening device 10 of the first embodiment can be manufactured by using a known manufacturing technique, for example, injection molding or blow molding of a thermoplastic resin. The expansion chamber 3 may be manufactured by molding by blow molding or by welding a half-split body obtained by injection molding. Further, the blower pipes 1 and 2 may be formed by blow molding or the like. The connection between the expansion chamber 3 and the blower pipes 1 and 2 may also be based on a known connection structure and connection method. The connection portion between the expansion chamber 3 and the blower pipes 1 and 2 is preferably sealed as appropriate.

The operation and effect of the muffling device 10 of the first embodiment will be described. The muffling device 10 of the first embodiment has a muffling effect similar to that of a muffling device including a normal expansion chamber in a relatively low frequency band (for example, a frequency band of 1000 Hz or less). Further, in a relatively high frequency band (for example, a frequency band of 1000 Hz to 2000 Hz), the sound deadening device 10 is expanded at a specific frequency by providing a partition wall 4 of a specific form in the expansion chamber 3. A specific resonance mode appears in the space inside the chamber, and the muffling characteristics near such a specific frequency can be effectively enhanced.

The above effect will be described using the results of an acoustic analysis simulation in comparison with an example and a comparative example.

(Example)
As an example corresponding to the above embodiment, an acoustic model of a muffling device having the following specifications was created.
First pipe 1: Straight pipe with a diameter of 60 mm and a length of 230 mm Second pipe 2: Straight pipe with a diameter of 60 mm and a length of 250 mm Expansion chamber 3: Length in the first direction LX = 105 mm, Length in the second direction LY = 100 mm, third direction length LZ = 80 mm, with respect to the chamber, the first tube 1 is connected to the center of the first surface P1 and the second tube 2 is connected to the center of the second surface P2. ..
The partition wall 4 is installed at a position in the first direction that coincides with the center C2 of the second pipe 2 at a height H = 40 mm.

(Comparison example)
As a comparison target, an acoustic model of a sound deadening device different in that the expansion chamber 3 is not provided with the partition wall 4 was created, and this was used as a comparative example.

Acoustic analysis was performed on Examples and Comparative Examples to determine the amount of acoustic attenuation, and the sound deadening effect was investigated. The amount of sound attenuation is assumed to be that the end (end of the first tube) β of the sound deadening device to be examined is connected to the speaker device 99 that performs sound vibration, as shown in FIG. Create a simulation model that performs acoustic vibration, and the sound pressure Pα (sound pressure measured at position α) on the outlet side (end opening α of the second tube) and the sound pressure side (first It is an index for evaluating the sound deadening effect by measuring the sound pressure Pβ (sound pressure measured at the position β) at the end β) of the tube and taking the ratio (Pβ / Pα) of the two. A large value of the acoustic attenuation indicates that the muffling effect is large, and a small value of the acoustic attenuation indicates that the muffling effect is small. The acoustic simulation was performed by the finite element method (FEM method).

The simulation results of the acoustic attenuation of the examples and the comparative examples are shown in FIG. In the region where the frequency is relatively low up to about 1000 Hz, the examples and the comparative examples show almost the same amount of acoustic attenuation (Attention in FIG. 3). It can be seen that in these frequency regions, the sound deadening effect is similar to that of the sound deadening device provided with the conventional expansion chamber.

In the sound deadening device of the embodiment, an increase in the amount of acoustic attenuation is observed with peaks of 1250 Hz (first resonance frequency f1) and 2200 Hz (second resonance frequency f2) as compared with the comparative example. That is, in the frequency band near the first resonance frequency f1 (1200 Hz to 1450 Hz) and the frequency band near the second resonance frequency f2 (2150 Hz to 2250 Hz), the sound attenuation of the silencer of the example is higher than that of the comparative example. It has become.

The sound pressure distribution (resonance mode) in the expansion chamber in the vicinity of the first resonance frequency f1 (1245 Hz) is shown in FIG. 4 for an example and FIG. 5 for a comparative example. These sound pressure distributions are a sound pressure distribution diagram in a cross section through the center of the pipe as seen from the third direction Z.

In the comparative example shown in FIG. 5, the sound pressure is high in the space at the lower right of the expansion chamber so that the air moves and vibrates in the diagonal direction rising to the left in the expansion chamber, and as it goes toward the upper left of the expansion chamber. A resonance mode of air is observed in which the sound pressure drops. Due to the relationship between this resonance mode and the arrangement of the connections between the first and second tubes, in the comparative example, the sound pressure at about the same level as that generated in the first tube is in the second tube. This also occurs, causing a decrease in the amount of acoustic attenuation.

On the other hand, in the embodiment shown in FIG. 4, the partition wall 4 is provided in the expansion chamber 3, and when viewed along the third direction Z, the partition wall 4 makes the internal space of the chamber U-shaped. The partition wall is provided so as to be partitioned so that the position of the partition wall 4 in the first direction X substantially coincides with the position of the center C2 of the connection portion of the second pipe 2 in the first direction X. Therefore, the resonance mode at the first resonance frequency f1 is changed (because the partition wall 4 is provided at a position substantially matching the central axis m2 near the connection portion of the second tube 2). That is, in the expansion chamber of the embodiment, the sound pressure is high in the lower left space of the expansion chamber, and the sound pressure is high in the lower right space separated by the partition wall 4 in the opposite phase. A resonance mode is observed in which the sound pressure decreases toward the upper side. That is, in this resonance mode, in the space inside the chamber shaped like a U by the partition wall 4, the resonance mode in which air moves along the direction of the U-shaped stroke and resonates is generated. The resonance mode is set so that the sound pressure near the connection portion of the tube 2 of 2 is lowered. Further, in this mode, in the vicinity of the connection portion with the second pipe 2, air vibrates so as to flow in a direction orthogonal to the central axis m2 of the second pipe 2, so that air can flow in and out of the second pipe 2. It is less likely to occur.

Due to the relationship between such a resonance mode and the arrangement of the connection portions of the first tube and the second tube, in the embodiment, the sound pressure generated in the first tube in the frequency band near the first resonance frequency f1. The sound pressure generated in the second tube is smaller than that of the second tube, and the amount of acoustic attenuation is increased.

As described above, according to the sound deadening device of the above embodiment, by providing the partition wall 4 of a specific form in the expansion chamber, it is possible to generate a resonance mode that effectively enhances the amount of acoustic attenuation. The sound deadening characteristic can be enhanced near a specific frequency.

From the viewpoint of more effectively generating the resonance mode as described above by adding the partition wall, the height H of the partition wall 4 measured along the second direction Y is the direction of the second direction of the chamber. The length LY is preferably 1/4 to 2/3, and particularly preferably 1/3 to 1/2. When the height H is low, the resonance mode as shown in FIG. 4 is less likely to appear. Further, if the height H is too large, the ventilation resistance of the sound deadening device 10 may increase.

The first resonance frequency f1 at which the resonance mode as shown in FIG. 4 occurs can be adjusted as follows. When the length LX in the first direction and the length LY in the second direction of the expansion chamber are increased, the first resonance frequency f1 changes in a lower direction. Further, when the height H of the partition wall 4 is increased, the first resonance frequency f1 changes in a slightly lower direction.

When the length LX in the first direction and the length LY in the second direction of the expansion chamber are set to about 70 to 150 mm and the height H of the partition wall 4 is set to about 25 to 70 mm, the first resonance frequency f1 is set to 1000 Hz to 1500 Hz. It can be brought in between and exhibits particularly favorable characteristics as a silencer for the intake system of an automobile engine equipped with a turbocharger.

Further, in the above embodiment, the acoustic attenuation is improved even in the vicinity of the second resonance frequency f2. The sound pressure distribution (resonance mode) in the expansion chamber in the vicinity of the second resonance frequency f2 (2155 Hz) is shown in FIG. 6 for an example and FIG. 7 for a comparative example.
In the comparative example of FIG. 7, the resonance mode in which the sound pressure is high on the left side and the right side of the expansion chamber is set, but the higher sound pressure on the left side of the chamber is transmitted to the side of the second tube, and the amount of acoustic attenuation is reduced. ing.
On the other hand, in the embodiment of FIG. 6, high sound pressure is generated in the lower left and upper right portions, high sound pressure is generated in opposite phases in the lower right and upper left portions, and a region with low sound pressure appears in the portion between them. ing. Further, even in this mode, in the vicinity of the connection portion with the second pipe 2, air vibrates so as to flow in a direction orthogonal to the central axis m2 of the second pipe 2, so that air enters and exits the second pipe 2. Is less likely to occur.

Due to the relationship between such a resonance mode and the arrangement of the connection portions of the first tube and the second tube, the sound pressure of the second tube 2 becomes low even in the vicinity of the second resonance frequency f2, and the sound becomes acoustic. The amount of attenuation increases. It should be noted that the improvement in the amount of acoustic attenuation in the vicinity of the second resonance frequency f2 may not be as remarkable as in the above embodiment because the appearing frequency is a relatively high frequency.

The invention is not limited to the above embodiment, and can be implemented with various modifications. Other embodiments of the invention will be described below, but in the following description, parts different from the above-described embodiments will be mainly described, and detailed description of similar parts will be omitted. In addition, these embodiments can be implemented by combining some of them with each other or replacing some of them.

If the resonance mode as described above occurs, the form of the partition wall 4 may be changed.
For example, the partition wall 4 may be a plate-shaped one erected from the wall surface toward the inside of the expansion chamber, or may be a fold-shaped one formed by recessing the wall surface of the expansion chamber. Good.

Further, in the above embodiment, the partition wall 4 is provided in a flat plate shape along the third direction Z, but the partition wall 4 may be in a curved form. Further, in the above embodiment, the height H of the partition wall 4 is constant over the third direction Z, but the height H of the partition wall may change over the third direction Z. Further, it is not necessary for the partition wall 4 to completely partition the lower portion of the internal space of the chamber, and the partition wall 4 may be provided with a through hole or a slit.

Further, in the description of the first embodiment, the muffling device 10 is configured by a pipe or an expansion chamber independent of other members, but these pipes and the expansion chamber do not necessarily have to be independent. However, it may be integrated with other members. For example, a part of the air cleaner module provided in the intake system of the automobile engine and a part of the cooling air blower may have the configuration of the muffling device 10 described above. That is, the silencer 10 may be integrally incorporated in such an air cleaner module or a blower.

The muffling device of the above embodiment can be used, for example, in the intake system of an automobile engine, and has high industrial utility value.

10 Silent device 1 1st tube 2 2nd tube 3 Expansion chamber P1 1st surface P2 2nd surface X 1st direction Y 2nd direction Z 3rd direction LX Expansion chamber 1st direction Length LY Expansion chamber 2nd direction length LZ 3rd direction length of expansion chamber 4 Partition wall H Height of partition wall

Claims (2)

It is a silencer that silences the noise propagating through the pipe.
The silencer is a rectangular parallelepiped expansion chamber,
A first tube connected to approximately the center of the first surface of the chamber,
It has a second tube connected to approximately the center of the second surface of the chamber adjacent to the first surface.
The side of the first tube is connected to the noise source,
The normal direction of the first surface is the first direction,
The normal direction of the second surface is the second direction,
The direction orthogonal to the first direction and the second direction is defined as the third direction.
A partition wall is erected so as to extend in the second direction from the surface facing the second surface of the chamber.
There is only one partition wall in the expansion chamber,
When viewed along the third direction, the partition wall partitions the interior space of the chamber in a U-shape.
A sound deadening device in which the partition wall is provided so that the position of the partition wall in the first direction substantially coincides with the position of the center of the connection portion of the second pipe in the first direction. The silencer according to claim 1, wherein the height of the partition wall measured along the second direction is 1/4 to 2/3 of the length in the second direction of the chamber.