JP2010059952A - Muffler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reducing effect also for transmitted noise, in a muffler 1 reducing intake noise by transmitting the intake noise from the inside of a duct 2 to the outside of the duct 2 by vibration of a thin film 15. <P>SOLUTION: A volumetric chamber 4 is formed on the outer peripheral side of an inner peripheral tube 3 composed of the thin film 15, and partitioned into first and second volumetric chambers 24, 25. Natural frequencies f<SB>11</SB>, f<SB>21</SB>of a primary mode of first and second thin film portions 26, 27 forming the first and second volumetric chambers 24, 25 are made different from each other by setting a rib 29 on the thin film portion 26, and the first and second volumetric chambers 24, 25 communicate with each other through a communication hole 30. Thereby, acoustic waves having a vibration frequency between the natural frequency f<SB>11</SB>and the natural frequency f<SB>21</SB>and transmitted through the first and second volumetric chambers 24, 25, have different phases from each other by 180°, overlap with each other through the communication hole 30, and offset. Therefore, it is possible to reduce the transmitted noise. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a silencer that reduces intake noise generated in an intake duct accompanying intake air into an engine.

  Conventionally, in order to reduce intake noise, various silencers have been considered and applied to intake ducts (hereinafter simply referred to as ducts). There is something to be part of. According to this silencer, due to the vibration of the thin film, the sound waves accompanying the intake pulsation and the air column resonance of the intake air are attenuated and partially transmitted outside the duct to reduce the intake sound (for example, see Patent Document 1). ).

  By the way, the sound wave transmitted through the thin film from the inside of the duct to the outside of the duct becomes a transmitted sound and constitutes noise separately from the intake sound. Therefore, in order to reduce the transmitted sound, a transmitted sound reducing means is required in addition to the intake sound reducing means, and various transmitted sound reducing means are considered. For example, according to the silencer of Patent Document 1, a sound absorbing material is arranged on the outer peripheral side of the thin film, and the transmitted sound is reduced by the sound absorbing material.

  However, the arrangement of the sound absorbing material increases the size of the silencer and increases the cost. Further, the sound absorbing material has a low silencing effect on low-frequency transmitted sound, and means other than the sound absorbing material is required for low-frequency transmitted sound.

  In addition, the silencer which has a highly rigid wall part on the outer peripheral side of a thin film, and has the volume chamber sealed between the thin film and the wall part is considered (for example, refer patent document 2). According to this silencer, since the sound wave transmitted to the volume chamber through the thin film is suppressed from being transmitted to the outside of the volume chamber by the wall portion, reduction of the transmitted sound can be achieved.

However, according to the silencer of Patent Document 2, since the volume chamber is hermetically sealed, the thin film cannot sufficiently vibrate. As a result, attenuation of sound waves accompanying intake air pulsation and air column resonance of intake air and There is a risk of insufficient transmission. For this reason, there exists a possibility that the silencer of patent document 2 cannot acquire the intake sound reduction effect.
JP 2004-346750 A Japanese Patent Laid-Open No. 2003-322062

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a reduction effect on transmitted sound in a silencer that reduces intake sound by vibration of a thin film.

[Means of Claim 1]
The silencer according to claim 1 includes an inner peripheral pipe that forms a part of an intake duct that communicates with the engine, and an outer peripheral pipe that forms a volume chamber on the outer peripheral side of the inner peripheral pipe. It is made of a thin film that is thinner than the other part, and the intake sound generated in the intake duct is transmitted outside the intake duct by the vibration of the thin film. The thin film includes a first thin film portion and a second thin film portion having different vibration characteristics. The mode order of the natural frequency of the first thin film portion and the mode order of the natural frequency of the second thin film portion are the same between the first thin film portion and the second thin film portion. There are specific orders with different natural frequency values.

  Here, the natural frequency of each thin film portion is determined by the dimensions and physical properties of each thin film portion, the volume of the volume chamber, and the like. And when the frequency of the sound wave input to each thin film portion is smaller than a specific natural frequency, the phase of the sound wave radiated from each thin film portion (that is, the sound wave transmitted through the thin film portion) does not change. When the frequency of the sound wave input to the thin film portion is larger than the specific natural frequency, the phase of the sound wave transmitted through the thin film portion changes by 180 °. Also, sound waves that are 180 degrees out of phase are effectively canceled when they overlap each other.

  Therefore, a specific order is included in the mode order of the natural frequency of the first and second thin film portions so that a difference is generated between at least one set of homogeneous natural frequencies of the first and second thin film portions. Set the membrane and volume chamber to be present. As a result, between the natural frequency of the specific order of the first thin film portion and the natural frequency of the specific order of the second thin film portion among the sound waves transmitted from the duct to the volume chamber through the first and second thin film portions. The sound waves having the frequencies of are different in phase from each other by 180 ° and cancel each other in the volume chamber. For this reason, in the silencer which reduces the intake sound by the vibration of the thin film, the effect of reducing the transmitted sound can be obtained.

[Means of claim 2]
According to the silencer of the second aspect, the outer peripheral pipe is provided with a hole for communicating the volume chamber and the outside air.
As a result, the volume chamber is not sealed, so that the thin film can sufficiently vibrate, and as a result, the sound waves are sufficiently attenuated and transmitted due to the intake pulsation and the air column resonance of the intake air. For this reason, it is possible to reliably achieve reduction of intake sound as well as reduction of transmitted sound.

[Means of claim 3]
According to the silencer according to claim 3, the volume chamber is divided into two chambers by the wall portion, and one thin film portion of the first thin film portion and the second thin film portion is only one of the two chambers. Form. The one chamber and the other chamber communicate with each other through a hole provided in the wall portion, and the hole in the outer peripheral tube communicates the other chamber with the outside air (the following [Means of Claim 3] to [Claim 3]. In the description of the means of item 5, for convenience, the thin film portion with the smaller specific frequency of the specific order is the first thin film portion, and the thin film portion with the larger specific frequency of the specific order is the second thin film portion. Part).

  Thus, for example, when the first thin film portion forms one chamber, the sound wave transmitted from the duct through the first thin film portion to the one chamber further passes through the wall portion from the one chamber to the other chamber. When passing through the chamber, the amplitude is uniformly reduced regardless of the numerical value of the frequency. Therefore, the sound wave transmitted from the duct through the first thin film portion, the one chamber and the wall portion to the other chamber is more effectively offset with the sound wave transmitted through the second thin film portion and into the other chamber. Therefore, the transmitted sound reduction effect can be further enhanced.

  That is, the amplitude characteristic in which the amplitude of the sound wave transmitted through each thin film portion is drawn with respect to the frequency shows a peak at the natural frequency. And the amplitude characteristic of the sound wave transmitted through the first thin film part and the amplitude characteristic of the sound wave transmitted through the second thin film part differ in the numerical value of the natural frequency of the specific order between the first and second thin film parts. Therefore, the frequency showing the peak is different. For this reason, the sound waves transmitted from the inside of the duct to the volume chamber through the first and second thin film portions do not completely match in amplitude and cannot be completely canceled.

  Therefore, by transmitting the sound wave transmitted from the duct through the first thin film portion to the one chamber through the wall portion having the hole to the other chamber, the amplitude of the sound wave transmitted through the first thin film portion is uniform. To lower. Thereby, in the other chamber, the sound wave transmitted through the first thin film portion and the sound wave transmitted through the second thin film portion have an amplitude with a frequency in a range smaller than the frequency at which the two amplitude characteristics intersect. The value of approaches. For this reason, since the sound wave transmitted through the first thin film portion and the sound wave transmitted through the second thin film portion are more effectively offset, the transmitted sound reduction effect can be further enhanced.

  When the second thin film portion forms one chamber, the amplitude of the sound wave transmitted through the second thin film portion is uniformly reduced in the other chamber, so the frequency at which the two amplitude characteristics intersect. The numerical value of the amplitude approaches at a frequency in a larger range, and the transmitted sound reduction effect is enhanced.

[Means of claim 4]
According to the silencer of the fourth aspect, at least one of the first thin film portion and the second thin film portion is non-linear within a range in which the relationship between stress and strain is generated by the intake sound.
As a result, the amplitude characteristic in which the amplitude of the sound wave transmitted through the nonlinear thin film portion is drawn with respect to the vibration frequency is reduced uniformly as the peak in the natural frequency is reduced.

  For this reason, for example, when the first thin film portion is non-linear, the sound wave transmitted through the first thin film portion and the sound wave transmitted through the second thin film portion are smaller than the frequency at which the two amplitude characteristics intersect. Amplitude values approach at a range of frequencies (if the second thin film portion is non-linear, the amplitude values approach at a range of frequencies greater than the frequency at which the two amplitude characteristics intersect) . As a result, since the sound wave transmitted through the first thin film portion and the sound wave transmitted through the second thin film portion are more effectively offset, the transmitted sound reduction effect can be further enhanced.

[Means of claim 5]
According to the silencer according to claim 5, the amplitude at the natural frequency of the specific order of the sound wave transmitted through the first thin film portion and the amplitude at the natural frequency of the specific order of the sound wave transmitted through the second thin film portion. Are different from each other.
Thereby, for example, when the amplitude of the sound wave transmitted to the volume chamber through the second thin film portion is larger than the amplitude of the sound wave transmitted to the volume chamber through the first thin film portion, the sound wave transmitted through the first thin film portion. And the sound wave transmitted through the second thin film portion has a frequency in a range smaller than the frequency at which the two amplitude characteristics intersect, and the numerical value of the amplitude approaches (transmitted to the volume chamber through the first thin film portion). When the amplitude of the sound wave is larger than the amplitude of the sound wave that has passed through the second thin film portion and passed through the volume chamber, the numerical value of the amplitude is close to a frequency in a range larger than the frequency at which the two amplitude characteristics intersect. To do).

As a result, since the sound wave transmitted through the first thin film portion and the sound wave transmitted through the second thin film portion are more effectively offset, the transmitted sound reduction effect can be further enhanced.
The increase in the amplitude of each thin film portion can be achieved, for example, by using the following [Means of Claim 8] to [Means of Claim 13] or increasing the number of surfaces included in each thin film portion. Further, the amplitude reduction of each thin film portion can be achieved, for example, by using the following [Means of Claim 8] to [Means of Claim 13], or [Means of Claim 3] and [Means of Claim 4]. It can be achieved by using.

[Means of claim 6]
According to the silencer according to claim 6, the mode order of the natural frequency of the first thin film portion and the mode order of the natural frequency of the second thin film portion are the first thin film portion and the second thin film portion, respectively. There are a first specific order and a second specific order in which the numerical values of the natural frequencies coincide with each other even though the odd order is higher or lower.

  Thereby, for example, when the second specific order is lower than the first specific order by the first order, the first thin film portion lower than the first specific order among the sound waves input to the thin film by the first order. When a sound wave having a frequency in a numerical range between the natural frequency value and the natural frequency values of the first and second specific orders passes through the first thin film portion and passes through the volume chamber, the phase changes by 180 °. The phase does not change even if the light passes through the second thin film portion and passes through the volume chamber. For this reason, the sound waves having the frequency in this numerical range and transmitted through the first and second thin film portions to the volume chamber are 180 degrees out of phase with each other.

  In addition, among the sound waves input to the thin film, a sound wave having a frequency in a numerical range larger than the natural frequencies of the first and second specific orders changes in phase by 360 ° when transmitted through the first thin film portion and into the volume chamber. When the light passes through the second thin film portion and passes through the volume chamber, the phase changes by 180 °. For this reason, the sound waves having a frequency in this numerical range and transmitted through the volume chamber are 180 degrees out of phase with each other.

As a result, among the sound waves transmitted from the duct through the first and second thin film portions, the sound wave having a frequency in a numerical range that extends considerably including the natural frequencies of the first and second specific orders has a phase. They are 180 ° apart from each other and cancel each other in the volume chamber. For this reason, in the silencer which reduces the intake sound by the vibration of the thin film, the effect of reducing the transmitted sound can be obtained.
In addition, among the sound waves transmitted through the first and second thin film portions, the sound waves in the numerical range that is considerably spread have substantially the same amplitude, so that the sound waves transmitted through the first and second thin film portions are the same. They are effectively offset each other, and the transmitted sound reduction effect is extremely large.

[Means of Claim 7]
According to the silencer of the seventh aspect, the outer peripheral pipe is provided with a hole for communicating the volume chamber and the outside air.
Thereby, the same effect as that of the means of claim 2 can be obtained.

[Means of Claim 8]
According to the silencer of the eighth aspect, the first thin film portion and the second thin film portion have different vibration areas.
This means represents a means for causing the specific order and the first and second specific orders to exist in the mode order of the natural frequency of the first and second thin film portions.

[Means of Claim 9]
According to the silencer of the ninth aspect, the first thin film portion and the second thin film portion have different vibration areas due to different rib settings.
This means shows one means for making a difference in vibration area between the first thin film portion and the second thin film portion.

[Means of Claim 10]
According to the silencer of the tenth aspect, the first thin film portion and the second thin film portion have different rigidity.
This means represents a means for causing the specific order and the first and second specific orders to exist in the mode order of the natural frequency of the first and second thin film portions.

[Means of Claim 11]
According to the silencer of the eleventh aspect, the first thin film portion and the second thin film portion have different vibration areas or rigidity due to different rib settings.
This means shows one means for making a difference in vibration area or rigidity between the first thin film portion and the second thin film portion.

[Means of Claim 12]
According to the silencer of the twelfth aspect, the first thin film portion and the second thin film portion have different masses.
This means represents a means for causing the specific order and the first and second specific orders to exist in the mode order of the natural frequency of the first and second thin film portions.

[Means of Claim 13]
According to the silencer of the thirteenth aspect, the first thin film portion and the second thin film portion have different film thicknesses.
This means represents a means for causing the specific order and the first and second specific orders to exist in the mode order of the natural frequency of the first and second thin film portions.

  The silencer of the best mode 1 includes an inner peripheral pipe that forms a part of an intake duct that communicates with the engine, and an outer peripheral pipe that forms a volume chamber on the outer peripheral side of the inner peripheral pipe. It consists of a thin film that is thinner than the other parts, and the intake sound generated inside the intake duct is transmitted outside the intake duct due to the vibration of the thin film. The thin film includes a first thin film portion and a second thin film portion having different vibration characteristics. The mode order of the natural frequency of the first thin film portion and the mode order of the natural frequency of the second thin film portion are the same between the first thin film portion and the second thin film portion. There are specific orders with different natural frequency values.

In addition, the outer peripheral pipe is provided with a hole for communicating the volume chamber and the outside air.
Further, the first thin film portion and the second thin film portion have different vibration areas and different rigidity. Furthermore, the first thin film portion and the second thin film portion have different vibration areas and rigidity due to different rib settings.

  According to the silencer of the best mode 2, the mode order of the natural frequency of the first thin film portion and the mode order of the natural frequency of the second thin film portion are respectively determined by the first thin film portion and the second thin film portion. Among them, there are a first specific order and a second specific order in which the numerical values of the natural frequencies coincide with each other even though the odd order is higher or lower.

  According to the silencer of the best mode 3, the volume chamber is divided into two chambers by the wall portion, and one thin film portion of the first thin film portion and the second thin film portion is limited to only one of the two chambers. Form. The one chamber communicates with the other chamber through a hole provided in the wall, and the hole in the outer peripheral tube communicates the other chamber with the outside air.

  According to the silencer of the best mode 4, at least one thin film portion of the first thin film portion and the second thin film portion is non-linear within a range where the relationship between stress and strain is generated by the intake sound.

  According to the silencer of the best mode 5, the amplitude of the sound wave transmitted through one of the first thin film portion and the second thin film portion is larger than the amplitude of the sound wave transmitted through the other thin film portion.

[Configuration of Example 1]
The structure of the silencer 1 of Example 1 is demonstrated using FIG. 1 and FIG.
The silencer 1 reduces intake noise generated in an intake duct (hereinafter referred to as a duct 2) in accordance with intake air to an engine (not shown), and an inner peripheral pipe 3 forming a part of the duct 2 And an outer peripheral tube 5 that forms a volume chamber 4 on the outer peripheral side of the inner peripheral tube 3.

  As shown in FIG. 1, the intake device 8 including the silencer 1 has a known configuration including an air cleaner 9, an air flow meter 10, a throttle device 11, and an intake manifold 12, and the silencer 1 is, for example, an air flow meter 10 and the throttle device 11.

  The inner peripheral pipe 3 is made of a thin film 15 thinner than the other part of the duct 2 and is provided, for example, by blow molding a polyester resin such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET). Then, the intake sound generated in the duct 2 is attenuated by the vibration of the thin film 15 and is partially transmitted through the volume chamber 4 to be transmitted sound.

  That is, the thin film 15 vibrates in response to the input of sound waves accompanying inspiration such as inspiration pulsation and air column resonance, thereby attenuating the sound waves accompanying inspiration and removing some of the sound waves accompanying inspiration outside the duct 2. Permeate to reduce intake noise.

  Then, in order to increase the vibration possible region of the thin film 15 as much as possible to enhance the intake noise reduction effect due to the vibration of the thin film 15, the inner peripheral tube 3 is perpendicular to the flow direction of the intake air, for example, as shown in FIG. The cut surface is provided as a flat hexagon.

  In addition, the inner peripheral pipe 3 is provided, for example, by joining two parts 16 and 17 that are divided into two parallel to the flow direction of intake air by welding or adhesion. Here, the joining portion 18 on one end side in the longitudinal direction of the parts 16 and 17 and the joining portion 19 on the other end side in the longitudinal direction of the parts 16 and 17 extend in the flow direction of the intake air at both longitudinal end portions of the hexagon in the cut surface. It is provided as follows.

  The outer peripheral tube 5 is provided as a highly rigid wall portion thicker than the thin film 15 and is disposed on the outer peripheral side of the inner peripheral tube 3. In addition, the outer peripheral pipe 5 is constituted by two parts 20 and 21 that are semi-elliptical in which a cut surface perpendicular to the flow direction of intake air is divided along the major axis, for example. That is, one end in the longitudinal direction of the two parts 20 and 21 is welded or bonded to the joint 18 so as to sandwich one end in the longitudinal direction of the joint 18, and the other end in the longitudinal direction of the two parts 20 and 21 is joined to the joint 19. Are welded or bonded to the joint 19 so as to sandwich the other end in the longitudinal direction.

Accordingly, the volume chamber 4 is divided into two chambers by the joint portions 18 and 19.
In the following description, the joint portions 18 and 19 are referred to as partition walls 18 and 19, and the upper chamber in the figure formed by the parts 16 and 20 of the volume chamber 4 is referred to as a first volume chamber 24. The lower chamber in the figure formed by 21 is called a second volume chamber 25 (see FIG. 2A). The portion of the thin film 15 of the part 16 that forms the first volume chamber 24 is called a first thin film portion 26, and the portion of the thin film 15 of the part 17 that forms the second volume chamber 25 is called a second thin film portion 27.

Here, a plurality of bowl-shaped ribs 29 are provided in the first thin film portion 26 so as to be perpendicular to the flow direction of the intake air, and the first thin film portion 26 is partitioned into a plurality of vibration surfaces by the ribs 29. For this reason, the first and second thin film portions 26 and 27 have different vibration areas and different rigidity. Then, due to the difference in vibration area and rigidity, the natural frequency f ₂₁ of the first mode of the second thin film portion 27 is larger than the natural frequency f ₁₁ of the first mode of the first thin film portion 26. It has become.

That is, the first and second thin film portions 26 and 27 are provided so that the natural frequencies f ₁₁ and f _{21 of the} primary mode are different from each other (see FIG. 3).
In addition, the numerical value of the natural frequency in each mode order of the first and second thin film portions 26 and 27 is the physical property and vibration area of the first and second thin film portions 26 and 27, and the first and second volume chambers 24, It is determined by the volume of 25 or the like. Then, the first thin section 26 is configured with ribs 29, first, by difference in vibration area and rigidity between the second thin film portions 26 and 27 occurs, the natural frequency _{f 21} is, the natural frequency _{f 11} Is bigger than.

Here, between the first and second thin film portions 26 and 27, the first and second thin film portions 26 and 27 are in the same order as in the first-order modes of the natural frequencies f ₁₁ and f _21. Mode orders with different natural frequency values are called specific orders. That is, in the first and second thin film portions 26 and 27 of the first embodiment, the primary mode is a specific order.

  The first and second volume chambers 24 and 25 communicate with each other through a communication hole 30 provided in the partition walls 18 and 19. Furthermore, the parts 20 and 21 are provided with holes 31 that allow the first and second volume chambers 24 and 25 to communicate with the outside air.

[Effects of Example 1]
The silencer 1 according to the first embodiment includes an inner peripheral pipe 3 made of a thin film 15 and forming a part of the duct 2, and an outer peripheral pipe 5 that forms a volume chamber 4 on the outer peripheral side of the inner peripheral pipe 3. The volume chamber 4 is partitioned into first and second volume chambers 24 and 25 by partition walls 18 and 19, and the first and second volume chambers 24 and 25 communicate with each other through a communication hole 30.

The first and second thin film portions 26 and 27 forming the first and second volume chambers 24 and 25 have their natural frequency f _{11 in} each primary mode depending on the setting of the rib 29 in the first thin film portion 26. , F ₂₁ are different from each other. That is, the numerical values of the primary mode natural frequencies f ₁₁ and f ₂₁ of the first and second thin film portions 26 and 27 are different from each other.

As a result, among the sound waves input to the thin film 15, the sound waves having a frequency between the natural frequencies f ₁₁ and f ₂₁ pass through the first thin film portion 26 and pass through the first volume chamber 24, and the phase changes by 180 °. When the light passes through the second thin film portion 27 and passes through the second volume chamber 25, the phase does not change (see FIG. 3A). For this reason, the sound waves having the frequency between the natural frequencies f ₁₁ and f ₂₁ and transmitted through the first and second volume chambers 24 and 25 are 180 degrees out of phase with each other.

As a result, the sound wave having a frequency between the natural frequencies f ₁₁ and f ₂₁ is transmitted through the first and second volume chambers 24 and 25 to be 180 ° out of phase, and then through the communication hole 30. They are overlapped with each other and canceled (see FIGS. 3B and 3C).
As described above, since the sound wave having the frequency between the natural frequencies f ₁₁ and f ₂₁ is canceled out of the sound waves constituting the transmitted sound, the transmitted sound can be reduced.

In addition, the amplitude of the sound wave transmitted through the first and second volume chambers 24 and 25 has a peak for each natural frequency. For this reason, even between the natural frequencies f ₁₁ and f ₂₁ , the sound waves transmitted through the first and second volume chambers 24 and 25 are not uniformly overlapped, and have an intermediate value between the natural frequencies f ₁₁ and f ₂₁ . The amplitudes coincide with each other in frequency and almost completely overlap, and the reduction effect shows the maximum peak.

Further, the outer pipe 5 is provided with a hole 31 for communicating the first and second volume chambers 24 and 25 with the outside air.
As a result, the first and second volume chambers 24 and 25 are not in a sealed state, so that both the first and second thin film portions 26 and 27 can sufficiently vibrate. Full penetration is achieved. For this reason, it is possible to reliably achieve reduction of intake sound as well as reduction of transmitted sound.

[Configuration of Example 2]
The silencer 1 of the second embodiment forms first and second volume chambers 24 and 25 similar to the silencer 1 of the first embodiment, and the first and second volume chambers 24 and 25 are connected via the communication holes 30. Communicate. The first thin film portion 26 is partitioned into a plurality of vibration surfaces by ribs 29. For this reason, the first and second thin film portions 26 and 27 have different vibration areas and different rigidity. Due to the difference in vibration area and rigidity, the natural frequency f ₁₂ of the second mode of the first thin film portion 26 and the natural frequency f ₂₁ of the first mode of the second thin film portion 27 are one. I'm doing it.

That is, in the first and second thin film portions 26 and 27, the natural frequency f ₁₂ of the second mode of the first thin film portion 26 and the natural frequency f ₂₁ of the first mode of the second thin film portion 27 match. Is provided. Further, by providing the first and second thin film portions 26 and 27 in this way, the natural frequencies f ₁₁ and f ₂₁ of the first mode of the first and second thin film portions 26 and 27 are necessarily different from each other. .

  Here, although the second order mode of the natural frequency of the first thin film portion 26 and the first order mode of the natural frequency of the second thin film portion 27 are higher or lower than the odd order, The mode orders of the first and second thin film portions 26 and 27 having the same natural frequency between the first and second thin film portions 26 and 27 are called first and second specific orders, respectively. That is, in the first and second thin film portions 26 and 27 of the second embodiment, the secondary mode of the first thin film portion 26 is the first specific order, and the primary mode of the second thin film portion 27 is the second specific order. is there.

[Effects of Example 2]
According to the silencer 1 of the second embodiment, the first and second thin film portions 26 and 27 have the secondary mode natural frequency f _{12 of} the first thin film portion 26 according to the setting of the rib 29 in the first thin film portion 26. And the natural frequency f ₂₁ of the first mode of the second thin film portion 27 coincide with each other.

As a result, of the sound waves input to the thin film 15, sound waves having a frequency between the natural frequency f ₁₁ and the natural frequencies f ₁₂ and f ₂₁ pass through the first thin film portion 26 to the first volume chamber 24. When transmitted, the phase changes by 180 °, and the phase does not change even if transmitted through the second thin film portion 27 and into the second volume chamber 25 (see FIG. 4A). For this reason, the sound waves having a frequency between the natural frequency f ₁₁ and the natural frequencies f ₁₂ and f ₂₁ and transmitted through the first and second volume chambers 24 and 25 are 180 ° out of phase with each other.

In addition, among the sound waves input to the thin film 15, sound waves having frequencies higher than the natural frequencies f ₁₂ and f ₂₁ pass through the first thin film portion 26 and pass through the first volume chamber 24, and the phase changes by 360 °. When the light passes through the second thin film portion 27 and passes through the second volume chamber 25, the phase changes by 180 ° (see FIG. 4A). For this reason, the sound waves having a frequency higher than the natural frequencies f ₁₂ and f ₂₁ and transmitted through the first and second volume chambers 24 and 25 have phases different from each other by 180 °.

As a result, the sound wave having a frequency larger than the value of the natural frequency f ₁₁ is transmitted through the first and second volume chambers 24 and 25 to be 180 degrees out of phase, and then through the communication hole 30. They are superimposed on each other and canceled (see FIGS. 4B and 4C).
Thus, among the sound waves constituting the transmitted sound, the sound waves having a frequency greater than the value of the natural frequency f ₁₁ is canceled, it is possible to reduce the transmitted sound.

The amplitude of the sound wave transmitted through the first and second volume chambers 24 and 25 is larger than the frequency near the rise of the amplitude peaks at the natural frequencies f ₁₂ and f ₂₁ as shown in FIG. 4B. There is almost perfect agreement in frequency. For this reason, a great reduction effect can be obtained for sound waves having a wide range of frequencies including the natural frequencies f ₁₂ and f ₂₁ .

[Configuration of Example 3]
According to the silencer 1 of the third embodiment, as shown in FIG. 5, the inner peripheral tube 3 is composed of a single cylindrical part having the same cut surface as in the first and second embodiments, and the partition walls 18, 19. Does not have. The upstream and downstream ends of the outer peripheral pipe 5 are welded or joined to the flange portion 34 of the intake pipe 33 connected to the upstream and downstream ends of the inner peripheral pipe 3. Further, the downstream portion of the inner peripheral pipe 3 is provided so that the value of the natural frequency of the primary mode is larger than that of the upstream portion.

In other words, if the upper and downstream portions on the inner peripheral tube 3 are the first and second thin film portions 26 and 27, respectively, the first and second thin film portions 26 and 27 have the natural frequency f of the primary mode. _{11, f 21} is provided so as to be different from each other. That is, in the first and second thin film portions 26 and 27 of the third embodiment, the primary mode is the specific order as in the first embodiment.

  The volume chamber 4 is divided into two chambers by a wall portion 35. The wall portion 35 includes a vertical portion 36 extending perpendicularly to the outer peripheral side from the boundary line between the first and second thin film portions 26, 27, and a parallel portion 37 parallel to the first thin film portion 26. It extends from the outer peripheral end of the vertical portion 36 to the upstream side and is welded or joined to the flange portion 34 of the intake pipe 33. Thus, the volume chamber 4 is divided into two chambers, and the first thin film portion 26 is prevented from directly facing the outer peripheral tube 5 by the wall portion 35, and only the second thin film portion 27 is directly opposed to the outer peripheral tube 5. .

  Of the two chambers partitioned by the wall portion 35, a chamber formed by the first thin film portion 26, the wall portion 35 and the flange portion 34 is defined as a first volume chamber 24, and the second thin film portion 27, the wall portion 35, Assuming that the chamber formed by the outer peripheral tube 5 and the flange portion 34 is the second volume chamber 25, the first and second volume chambers 24, 25 communicate with each other through a hole 38 provided in the wall portion 35. And the hole 31 of the outer periphery pipe | tube 5 is making the 2nd volume chamber 25 and external air communicate.

[Effects of Example 3]
According to the silencer 1 of the third embodiment, the volume chamber 4 is partitioned into the first and second volume chambers 24 and 25 by the wall portion 35, and the first and second thin film portions 26 and 27 are respectively the first and second volume chambers 26 and 27. Only the second volume chambers 24 and 25 are formed. The first and second volume chambers 24 and 25 communicate with each other through a hole 38 in the wall portion 35, and the hole 31 in the outer peripheral tube 5 communicates the second volume chamber 25 with outside air.
As a result, the sound wave transmitted from the duct 2 to the first volume chamber 24 through the first thin film portion 26 is further vibrated when transmitted from the first volume chamber 24 to the second volume chamber 25 through the wall portion 35. The amplitude decreases uniformly regardless of the numerical value (see FIG. 5C).

  For this reason, in the second volume chamber 25, the sound wave transmitted through the first thin film portion 26 and the wall portion 35 and the sound wave transmitted through only the second thin film portion 27 have a frequency at which two amplitude characteristics intersect. Also, the amplitude value approaches at a small frequency range. As a result, the sound wave transmitted from the duct 2 to the second volume chamber 25 through the first thin film portion 26 and the wall portion 35 is more effective than the sound wave transmitted to the second volume chamber 25 only through the second thin film portion 27. Therefore, the transmitted sound reduction effect can be further enhanced.

Example 4
According to the silencer 1 of Example 4, as shown in FIG. 6, the inner peripheral tube 3 is composed of a single cylindrical part having the same cut surface as in Examples 1 to 3, and the volume chamber 4 is It is not partitioned by the partition walls 18 and 19 or the wall portion 35, and forms a single annular space. The upstream and downstream ends of the outer peripheral pipe 5 are welded or joined to the flange portion 34. Moreover, the 1st, 2nd thin film parts 26 and 27 occupy the upper part and the downstream part of the inner peripheral pipe 3, respectively, similarly to Example 3. The first and second thin film portions 26 and 27 are provided such that the natural frequencies f ₁₁ and f _{21 in} the first mode are different from each other.

  Further, the first thin film portion 26 is non-linear within a range in which the relationship between stress and strain is generated by the intake sound, as indicated by the correlation line L1 or the correlation line L2 in FIG. For this reason, the amplitude characteristic of the amplitude with respect to the frequency of the sound wave transmitted through the first thin film portion 26 is larger than that in the case of the correlation line L3 in which the relationship between stress and strain is linear, as shown in FIG. The peak of the natural frequency decreases and the amplitude decreases uniformly.

  Therefore, the sound wave transmitted to the volume chamber 4 through the first thin film portion 26 and the sound wave transmitted to the volume chamber 4 through the second thin film portion 27 are 2 in the same manner as in FIG. Amplitude values approach at a frequency in a range smaller than the frequency at which two amplitude characteristics intersect. As a result, the sound wave transmitted to the volume chamber 4 through the first thin film portion 26 is more effectively offset with the sound wave transmitted to the volume chamber 4 through the second thin film portion 27, so that the transmitted sound reduction effect is further improved. Can be increased.

Example 5
According to the silencer 1 of Example 5, as shown in FIG. 8, the inner peripheral tube 3 is composed of a single cylindrical part having the same cut surface as in Examples 1 to 4, and the volume chamber 4 is It is not partitioned by the partition walls 18 and 19 or the wall portion 35, and forms a single annular space. The upstream and downstream ends of the outer peripheral pipe 5 are welded or joined to the flange portion 34. The first thin film portion 26 occupies the upper and lower two surfaces shown in FIG. 8B, and the second thin film portion 27 occupies the four left and right surfaces shown in FIG. 8B.

Here, in the first and second thin film portions 26 and 27, the natural frequency f ₂₁ of the primary mode of each surface of the second thin film portion 27 is the natural frequency of the primary mode of each surface of the first thin film portion 26. provided to be larger than f _11. Then, since the number of surfaces of the second thin film portion 27 is larger than the number of surfaces of the first thin film portion 26, the amplitude of the sound wave transmitted through the second thin film portion 27 to the volume chamber 4 passes through the first thin film portion 26. It becomes larger than the amplitude of the sound wave transmitted through the volume chamber 4.

  For this reason, as shown in FIG. 8C, the sound wave transmitted through the first thin film portion 26 and the sound wave transmitted through the second thin film portion 27 are smaller than the frequency at which the two amplitude characteristics intersect. Amplitude values approach at a range of frequencies. As a result, the sound wave transmitted through the first thin film portion 26 and the sound wave transmitted through the second thin film portion 27 are more effectively offset, so that the transmitted sound reduction effect can be further enhanced.

[Modification]
According to the silencer 1 of the first and second embodiments, the partition walls 18 and 19 partition the volume chamber 4 into two chambers parallel to the flow direction of the intake air to form first and second volume chambers 24 and 25. The first and second thin film portions 26 and 27 are included in the parts 16 and 17 to form the first and second volume chambers 24 and 25, respectively. The first and second volume chambers 24 and 25 are formed by dividing the volume chamber 4 into two chambers on the downstream side, and the first and second thin film portions 26 and 27 are disposed on the upstream and downstream of the parts 16 and 17, respectively. You may make it form the 1st, 2nd volume chambers 24 and 25 included in the part of the side.

  Further, the first and second volume chambers 24 and 25 may be partitioned so as to have different volumes. Furthermore, the inner peripheral tube 3 may be provided in a cylindrical shape without the partition walls 18 and 19, and the volume chamber 4 may be provided as a single annular space.

  According to the silencer 1 of the third embodiment, the wall portion 35 includes a vertical portion 36 extending perpendicularly from the boundary line of the first and second thin film portions 26 and 27 to the outer peripheral side, and a parallel portion parallel to the first thin film portion 26. The parallel portion 37 extends upstream from the outer peripheral end of the vertical portion 36 and is welded or joined to the flange portion 34 of the intake pipe 33, but is not limited to such a form. For example, in the silencer 1 having the partition walls 18 and 19 as in the first and second embodiments, the hole 31 may be provided only in the part 21 of the outer peripheral tube 5 that forms the second volume chamber 25. The same effect as the container 1 can be obtained.

  The silencer 1 of the fourth and fifth embodiments does not have the partition walls 18 and 19 and the volume chamber 4 is provided as an annular space. However, the volume chamber 4 is provided as the first and second volumes by providing a partition wall. The inner peripheral pipe 3 may be provided so that the first and second volume chambers 24 and 25 are formed by dividing the chambers 24 and 25 into the first and second thin film portions 26 and 27.

  According to the silencer 1 of Examples 1 and 2, the partition walls 18 and 19 were joined portions of the parts 16 and 17 of the inner peripheral pipe 3, but the partition walls 18 and 19 using the inner peripheral pipe 3 as an insert part. The inner peripheral tube 3 may be blow-molded using the partition walls 18 and 19 as insert parts, or the inner peripheral tube 3 and the partition walls 18 and 19 may be integrally formed.

According to the silencer 1 of the first embodiment, the ribs 29 are set in the first thin film portion 26, and the first and second thin film portions 26 and 27 are different in vibration area and rigidity. Although the values of the natural frequencies f ₁₁ and f ₂₁ of the primary modes of the two thin film portions 26 and 27 are different from each other, the present invention is not limited to such a mode.

For example, without setting the rib 29, the first and second thin film portions 26 and 27 have different film thicknesses, or the first and second thin film portions 26 and 27 are attached with weights, and the weight mass. The first and second thin film portions 26 and 27, the tension acting in the surface direction between the first and second thin film portions 26 and 27, the first and second volumes, The values of the natural frequencies f ₁₁ and f ₂₁ may be varied by making the volumes of the chambers 24 and 25 different. Various modes for making the values of the natural frequencies f ₁₁ and f ₂₁ different may be combined.

According to the silencer 1 of the second embodiment, the ribs 29 are set on the first thin film portion 26, and the first thin film portion 26 and 27 have a difference in vibration area and rigidity. the value of the natural frequency f ₁₂ of the second-order mode parts 26 and the value of the natural frequency f ₂₁ of the first-order mode of the second thin section 27 is coincident, but is not limited to such a mode.

For example, without setting the rib 29, the first and second thin film portions 26 and 27 have different film thicknesses, or the first and second thin film portions 26 and 27 are attached with weights, and the weight mass. The first and second thin film portions 26 and 27, the tension acting in the surface direction between the first and second thin film portions 26 and 27, the first and second volumes, The values of the natural frequencies f ₁₂ and f ₂₁ may be made to coincide by making the volumes of the chambers 24 and 25 different. Various modes for matching the values of the natural frequencies f ₁₂ and f ₂₁ may be combined.

  According to the silencer 1 of the first and second embodiments, the first and second volume chambers 24 and 25 are communicated with each other by the communication holes 30 provided in the partition walls 18 and 19. The first and second volume chambers 24 and 25 may be communicated with each other by connecting to 20 and 21 and opening the first and second volume chambers 24 and 25.

  According to the silencer 1 of Examples 1 to 5, the vibration of the thin film 15 was ensured by the volume chamber 4 and the outside air communicating with each other through the hole 31 provided in the outer peripheral tube 5. The hole 31 may not be provided if it can be secured by setting conditions other than the setting of the hole 31.

According to the silencer 1 of Examples 1 and 3 to 5, the values of the natural frequencies f ₁₁ and f ₂₁ of the primary modes of the first and second thin film portions 26 and 27 are different from each other (ie, the first In the natural frequency of the second thin film portions 26 and 27, the first-order mode is a specific order), and thus the transmitted sound reduction effect has been obtained. However, the present invention is not limited to such a mode.

In other words, if the natural frequencies of the first and second thin film portions 26 and 27 are different, the transmitted sound reduction effect similar to that of the first and third to fifth embodiments can be obtained. The values of the natural frequencies f ₁₂ and f ₂₂ of the secondary modes of the thin film portions 26 and 27 may be different from each other (that is, the secondary mode at the natural frequencies of the first and second thin film portions 26 and 27). The natural frequencies f _1n and f _2n of the third and higher order n-order modes may be different from each other (that is, the natural frequencies of the first and second thin film portions 26 and 27). The n-order mode may be a specific order in FIG.

Further, the first and second thin film portions 26 and 27 may be set so that the natural frequencies of the first and second thin film portions 26 and 27 are different in a plurality of mode orders. For example, the values of the natural frequencies f ₁₁ and f _{21 in} the primary mode may be different from each other, and the values of the natural frequencies f ₁₂ and f _{22 in} the secondary mode may be different from each other (that is, the first and first frequencies). The first and second modes may be set as the specific order at the natural frequency of the two thin film portions 26 and 27).

According to silencer 1 of Example 2, the natural frequency f ₁₂ of the second mode of the first thin section 26 and the natural frequency f ₂₁ of the first mode the second thin section 27 are matched (i.e., the Although the secondary mode of the first thin film portion 26 is the first specific order and the primary mode of the second thin film portion 27 is the second specific order), an effect of reducing transmitted sound has been obtained. It is not limited to such an embodiment.

That is, the natural frequency of the predetermined mode order of the first thin film portion 26 and the natural frequency higher or lower than the predetermined mode order among the natural frequencies of the second thin film portion 27. If they match, the transmitted sound reduction effect similar to that of the second embodiment can be obtained. For example, the third-order natural frequency f _{13 of} the first thin film portion 26 and the second-order mode natural frequency f of the second thin film portion 27 are obtained. ₂₂ (that is, the third mode of the first thin film portion 26 may be the first specific order and the second mode of the second thin film portion 27 may be the second specific order), or the first thin film portion natural frequency f ₁₁ of the first-order mode 26 and may be allowed to coincide with the fourth-order natural frequency f ₂₄ of the second thin section 27 (i.e., the first mode of the first thin section 26 a first specific order And the fourth order mode of the second thin film portion 27 may be the second specific order).

Further, in the first and second thin film portions 26 and 27, the natural frequency of the predetermined mode order of the first thin film portion 26 and the odd order of the natural frequency of the second thin film portion 27 than the predetermined mode order. It is also possible to set a plurality of combinations whose high-order or low-order natural frequencies coincide with each other. For example, the natural frequency f ₁₂ of the second mode of the first thin film portion 26 is matched with the natural frequency f ₂₁ of the first mode of the second thin film portion 27, and the third order natural vibration of the first thin film portion 26 is matched. The number f ₁₃ and the natural frequency f ₂₂ of the second-order mode of the second thin film portion 27 may be matched (that is, the second and third-order modes of the first thin-film portion 26 are set as the first specific order, the second The primary and secondary modes of the thin film portion 27 may be the second specific order).

  According to the silencer 1 of Examples 1 to 5, the cut surface of the inner peripheral tube 3 perpendicular to the flow direction of the intake air is a flat hexagon, but this cut surface is other than a hexagon such as a triangle or a quadrangle. The inner peripheral tube 3 may be provided so as to have a polygonal shape.

  According to the silencer 1 of the fifth embodiment, the first and second thin film portions 26 and 27 are different in the number of surfaces by occupying two surfaces and four surfaces, respectively, among the six surfaces of the inner peripheral tube 3. However, for example, the number of surfaces occupied by the first and second thin film portions 26 and 27 may be increased by providing ribs or the like on one surface and dividing the surface into two surfaces.

  According to the silencer 1 of Example 3, the first thin film portion 26 was prevented from directly facing the outer peripheral tube 5 by the wall portion 35, and only the second thin film portion 27 was directly opposed to the outer peripheral tube 5. The second thin film portion 27 may be prevented from directly facing the outer peripheral tube 5, and only the first thin film portion 26 may be directly opposed to the outer peripheral tube 5.

According to the silencer 1 of the fourth embodiment, the first thin film portion 26 is provided nonlinearly, but the second thin film portion 27 may be provided nonlinearly, and both the first and second thin film portions 26 and 27 are provided. Both may be provided non-linearly.
According to the silencer 1 of the fifth embodiment, the second thin film portion 27 is provided so as to have a larger amplitude than the first thin film portion 26, but the first thin film portion 26 is provided in the second thin film portion. Alternatively, the amplitude may be larger than 27.

(Example 1) which is explanatory drawing which shows the structure of an intake device. (A) is sectional drawing of a silencer perpendicular | vertical to the flow direction of intake air, (b) is a top view of an inner peripheral pipe, (c) is a bottom view of an inner peripheral pipe (Example 1). (A) is a correlation diagram between the frequency and the phase of the transmitted sound, (b) is a correlation diagram between the frequency and the amplitude of the transmitted sound, and (c) is the relationship between the frequency of the transmitted sound and the reduction effect. It is a correlation diagram (Example 1). (A) is a correlation diagram between the frequency and the phase of the transmitted sound, (b) is a correlation diagram between the frequency and the amplitude of the transmitted sound, and (c) is the relationship between the frequency of the transmitted sound and the reduction effect. It is a correlation diagram (Example 2). (A) is a cross-sectional view of the silencer parallel to the flow direction of the intake air, (b) is a cross-sectional view taken along the line AA of (a), and (c) is a correlation diagram between the frequency and amplitude of transmitted sound. (Example 3). (A) is sectional drawing of the silencer parallel to the flow direction of intake air, (b) is BB sectional drawing of (a) (Example 4). (A) is a correlation diagram between stress and strain in a thin film, (b) is a correlation diagram between the frequency and amplitude of transmitted sound that has passed through the thin film having the correlation of (a), and (c) is a transmission diagram. (Example 4) which is a correlation diagram of the frequency and amplitude of sound. (A) is a cross-sectional view of the silencer parallel to the flow direction of the intake air, (b) is a CC cross-sectional view of (a), and (c) is a correlation diagram of the frequency and amplitude of transmitted sound. (Example 5).

Explanation of symbols

1 Silencer 2 Duct (intake duct)
3 inner peripheral tube 4 volume chamber 5 outer tube 15 thin film 24 first volume chamber (chamber)
25 Second volume chamber (chamber)
26 first thin section 27 a second thin section 29 the rib 31 holes 35 walls 38 holes _{f 11, f 12, f 21} natural frequency

Claims (13)

An inner peripheral pipe that forms a part of an intake duct that communicates with the engine, and an outer peripheral pipe that forms a volume chamber on the outer peripheral side of the inner peripheral pipe;
The inner peripheral pipe is made of a thin film that is thinner than the other part of the intake duct,
In the silencer in which the intake sound generated in the intake duct is transmitted outside the intake duct by the vibration of the thin film,
The thin film includes a first thin film portion and a second thin film portion having different vibration characteristics,
The mode order of the natural frequency of the first thin film part and the mode order of the natural frequency of the second thin film part are the same order between the first thin film part and the second thin film part. A silencer characterized by the presence of specific orders with different natural frequency values. The silencer according to claim 1,
The silencer, wherein the outer peripheral pipe is provided with a hole for communicating the volume chamber and the outside air. The silencer according to claim 2,
The volume chamber is divided into two chambers by a wall portion,
One thin film portion of the first thin film portion and the second thin film portion forms only one of the two chambers,
The one chamber and the other chamber communicate with each other through a hole provided in the wall portion,
The hole in the outer peripheral pipe communicates the other chamber with the outside air. The silencer according to any one of claims 1 to 3,
The silencer characterized in that at least one of the first thin film portion and the second thin film portion is non-linear within a range in which a relationship between stress and strain is generated by an intake sound. The silencer according to any one of claims 1 to 4,
The amplitude at the natural frequency of the specific order of the sound wave transmitted through the first thin film portion is different from the amplitude at the natural frequency of the specific order of the sound wave transmitted through the second thin film portion. A silencer. An inner peripheral pipe that forms a part of an intake duct that communicates with the engine, and an outer peripheral pipe that forms a volume chamber on the outer peripheral side of the inner peripheral pipe;
The inner peripheral pipe is made of a thin film that is thinner than the other part of the intake duct,
In the silencer in which the intake sound generated in the intake duct is transmitted outside the intake duct by the vibration of the thin film,
The thin film includes a first thin film portion and a second thin film portion having different vibration characteristics,
The mode order of the natural frequency of the first thin film portion and the mode order of the natural frequency of the second thin film portion are higher by odd orders between the first thin film portion and the second thin film portion, respectively. A muffler characterized by the presence of a first specific order and a second specific order in which the numerical values of the natural frequencies coincide with each other even though the order is low or high. The silencer according to claim 7,
The silencer, wherein the outer peripheral pipe is provided with a hole for communicating the volume chamber and the outside air. The silencer according to any one of claims 1 to 7,
The muffler characterized in that the first thin film portion and the second thin film portion have different vibration areas. The muffler according to claim 8,
The muffler characterized in that the first thin film portion and the second thin film portion have different vibration areas due to different rib settings. The silencer according to any one of claims 1 to 9,
The muffler characterized in that the first thin film portion and the second thin film portion have different rigidity. The silencer according to claim 10,
The silencer characterized in that the first thin film portion and the second thin film portion have different vibration areas or rigidity due to different rib settings. The muffler according to any one of claims 1 to 11,
The muffler characterized in that the first thin film portion and the second thin film portion have different masses. The silencer according to any one of claims 1 to 12,
The silencer, wherein the first thin film portion and the second thin film portion have different film thicknesses.

Images