JP2010090746A - Air cleaner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce low-frequency noise in an air cleaner 1 carrying a noise reduction function. <P>SOLUTION: In this air cleaner 1, a case 3 has thin film parts 15a-15h vibrated by an acoustic wave due to intake air, and the thin film parts 15a-15h are so set that each of natural frequencies f1-f8 of a primary mode is gradually increased. Therefore, it is possible to reduce the intake noise by transmitting the acoustic wave in the case 3 to the outside of the case 3 by the vibration of the thin film parts 15a-15h and to also reduce transmitted noise by an effect of offset due to different natural frequencies f1-f8. Regarding setting of the thin film parts 15a-15h, a frequency region where the effect of offset is obtained is tuned in to a low frequency, certainly reducing the low-frequency noise. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an air cleaner disposed in an intake system of an engine.

  Conventionally, sound waves generated in the intake system due to intake into the engine leak from the intake port to the outside, or transmit noise from the inside of the intake duct through the duct wall, etc. In order to reduce noise, various measures have been considered for the intake duct between the air cleaner and the throttle. In the following explanation, the noise that is constituted by sound waves accompanying intake air leaking from the intake port is referred to as `` intake sound '', and the noise that is constituted by being transmitted from the inside of the duct through the duct wall and the like to the outside. This is called “transmitted sound”.

  By the way, when adding a noise reduction function to the intake duct, it is necessary to lengthen the intake duct or connect a resonator to the intake duct in order to reduce low-frequency noise. Or pressure loss will increase. Therefore, in order to eliminate the drawbacks caused by adding a noise reduction function to the intake duct, studies have been made to add a noise reduction function to the air cleaner (see, for example, Patent Documents 1 to 3).

  According to Patent Document 1, a part of the case of the air cleaner is provided with a porous material, and sound waves are transmitted to the outside through the porous material, thereby reducing sound waves directed to the intake port and reducing intake sound. The transmitted sound is reduced according to the transmission loss of the porous material.

  According to Patent Document 2, the case of the air cleaner is divided into a main chamber and a sub chamber, the filter element is accommodated in the main chamber, and the inside and the sub chamber of the inlet or outlet side of the air cleaner are separated from each other. Communicate with the communication pipe. Moreover, the wall which divides a main chamber and a subchamber is provided with a semipermeable membrane. With such a configuration, the communication pipe and the sub chamber function as a resonator, and the energy of sound waves is reduced according to the viscous resistance of the semipermeable membrane.

  Further, according to Patent Document 3, the partition wall between the main chamber and the sub chamber is provided with an elastic portion that vibrates by sound waves and a communication hole that allows the main chamber and the sub chamber to communicate with each other. As a result, the pressure difference between the main chamber and the sub chamber accompanying the passage of the intake air in the main chamber is eliminated, and fluctuations in the vibration characteristics of the elastic portion are prevented.

  However, according to the air cleaner of patent document 1, the site | part provided using a porous material will be limited to the upstream of a filter element, and the freedom degree of the setting site | part of a porous material is low. Furthermore, low-frequency noise reduction is difficult with only porous materials.

Further, according to the air cleaners of Patent Documents 2 and 3, although the thin film part (semi-permeable film of Patent Document 2 and elastic part of Patent Document 3) that can vibrate even with low-frequency sound waves is provided, the thin film part is sufficiently In order to vibrate, it is necessary to increase the volume of the sub chamber to reduce the rigidity against vibration. Furthermore, even if the volume of the sub chamber is increased so that the thin film portion can sufficiently vibrate, it is effective in reducing the intake sound but may increase the transmitted sound.
As described above, the air cleaners of Patent Documents 1 to 3 are insufficient as a countermeasure against low-frequency noise, and a separate countermeasure is required.
JP 2002-21660 A JP 2002-266715 A JP 2003-227427 A

  The present invention has been made to solve the above problems, and an object of the present invention is to enable low-frequency noise to be reduced without increasing the physique in an air cleaner having a noise reduction function. .

[Means of Claim 1]
The air cleaner according to claim 1 removes foreign matter in the intake air sucked into the engine, and includes a filter element that captures the foreign matter and a case that houses the filter element. Further, the case has at least two thin film portions that can vibrate by sound waves accompanying inspiration, and the two thin film portions have different natural frequencies of the primary mode.

  Here, the natural frequency of each thin film portion is determined by the dimensions and physical properties of each thin film portion. 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 °.

  Therefore, a part of the case is provided by at least two thin film portions, and these two thin film portions are set so that the natural frequencies of the primary mode are different from each other. As a result, among the sound waves transmitted from the case through the two thin film portions, the frequency between the natural frequency of the primary mode of one thin film portion and the natural frequency of the primary mode of the other thin film portion is calculated. The sound waves they have are out of phase with each other by 180 ° and cancel each other.

  For this reason, it is possible to reduce the intake sound by transmitting the sound wave inside the case to the outside by the vibration of the thin film portion, and also reduce the transmitted sound by the canceling effect due to the difference in the natural frequency of the primary mode. Can do. Therefore, regarding the setting of the thin film portion, by adjusting the frequency region where the canceling effect can be obtained to the low frequency, the low frequency noise can be reduced without increasing the physique in the air cleaner having the noise reduction function.

[Means of claim 2]
According to the air cleaner of the second aspect, the outer sides of the two thin film portions are covered with the sound absorbing material.
As a result, a sufficient reduction effect can be obtained even for transmitted sound in a high frequency range where a canceling effect cannot be obtained.

The air cleaner of the best mode is to remove foreign matter in the intake air sucked into the engine, and includes a filter element that captures the foreign matter and a case that houses the filter element. Further, the case has at least two thin film portions that can vibrate by sound waves accompanying inspiration, and the two thin film portions have different natural frequencies of the primary mode.
Further, the outer sides of the two thin film portions are covered with a sound absorbing material.

[Configuration of Example]
The structure of the air cleaner 1 of an Example is demonstrated using drawing.
The air cleaner 1 removes foreign matter in the intake air sucked into the engine, and includes a filter element 2 that captures the foreign matter and a case 3 that houses the filter element 2 as shown in FIG. The case 3 includes a primary side case 5 having a suction pipe 4 and a secondary side case 7 having a discharge pipe 6, and the filter element 2 is accommodated mainly in the secondary side case 7 together with the gasket 8. Has been.

  Here, the suction pipe 4 of the primary side case 5 has an intake port 10, and the discharge pipe 6 of the secondary side case 7 is equipped with an air flow meter 11 for detecting the flow rate of intake air, and a throttle device. A duct pipe 13 for guiding intake air to 12 is connected. Then, the outside air introduced from the intake port 10 passes through the filter element 2 as intake air to remove foreign matter, and is sucked into the engine via the throttle device 12. In addition, sound waves are generated in the case 3 and the duct pipe 13 along with the intake air into the engine.

Moreover, a part of secondary side case 7 consists of eight thin film parts 15a-15h which can be vibrated with the sound wave accompanying intake, for example. And each thin film part 15a-15h is set so that the natural frequency f1-f8 of each primary mode may satisfy | fill the relationship of the following numerical formula.
[Formula] f1 <f2 <f3 <f4 <f5 <f6 <f7 <f8
That is, the natural frequencies f1 to f8 are sequentially increased due to the different dimensions and physical properties of the thin film portions 15a to 15h.

  Here, for example, as shown in FIG. 2, the secondary case 7 includes four surface portions so that a cross section perpendicular to the flow direction of the intake air has a rectangular shape, and the thin film portions 15 a to 15 h are For example, two are provided on each surface portion.

  The thin film portions 15a to 15h are formed using, for example, a polyester resin such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET) as a raw material, and as shown in FIG. 3, high rigidity portions other than the thin film portions 15a to 15h. 17 and compression molding when integrally molded.

  Further, the outside of the thin film portions 15 a to 15 h is covered with a sound absorbing material 19 to form a volume chamber 20. Here, the sound absorbing material 19 is, for example, a porous material such as glass wool, rock wool, or a foamed resin material, or a perforated plate material made of resin or metal.

  With the above configuration, the sound wave generated in the case 3 and the duct pipe 13 is attenuated by the vibration of the thin film portions 15 a to 15 h and is transmitted to the volume chamber 20. The sound wave transmitted through the volume chamber 20 is reduced by the canceling effect or absorbed by the sound absorbing material 19 as described below.

[Effects of Examples]
According to the air cleaner 1 of the embodiment, the secondary case 7 has the thin film portions 15a to 15h that can be vibrated by the sound waves accompanying the intake air, and the thin film portions 15a to 15h are the natural vibrations of the respective primary modes. The numbers f1 to f8 are different so as to increase sequentially.

  As a result, among the sound waves accompanying the intake air, the sound wave having a frequency lower than the natural frequency f1 does not change in phase even when transmitted through the thin film portion 15a to the volume chamber 20, and the frequency is higher than the natural frequency f1. When a large sound wave is transmitted through the thin film portion 15a and into the volume chamber 20, the phase changes by 180 °. In addition, a sound wave having a frequency lower than the natural frequency f2 does not change in phase even if it passes through the thin film portion 15b and passes through the volume chamber 20, and a sound wave having a higher frequency than the natural frequency f2 After passing through the volume chamber 20, the phase changes by 180 °.

For this reason, the sound waves having the frequency in the range of the natural frequencies f1 to f2 are transmitted through the thin film portions 15a and 15b to the volume chamber 20, so that the phases are offset from each other by 180 degrees.
Similarly, the sound waves whose frequencies are in the range of natural frequencies f2 to f3, f3 to f4, f4 to f5, f5 to f6, f6 to f7, and f7 to f8 are the thin film portions 15b and 15c and the thin film portion 15c, respectively. , 15d, the thin film portions 15d and 15e, the thin film portions 15e and 15f, the thin film portions 15f and 15g, and the thin film portions 15g and 15h are transmitted through the volume chamber 20 to be mutually offset by 180 °.

  For this reason, inhalation sound can be reduced by transmitting the sound wave in the case 3 to the outside of the case 3 by the vibration of the thin film portions 15a to 15h, and the transmitted sound can be reduced by the canceling effect due to the different natural frequencies f1 to f8. Can also be reduced. Therefore, regarding the setting of the thin film portions 15a to 15h, the low frequency noise can be surely reduced by matching the frequency region where the canceling effect is obtained to the low frequency.

Further, the outer sides of the thin film portions 15 a to 15 h are covered with a sound absorbing material 19.
As a result, a sufficient reduction effect can be obtained even for a high-frequency frequency region where the canceling effect cannot be obtained, that is, a transmitted sound having a frequency greater than the natural frequency f8.
Furthermore, even if the volume chamber 20 is set to be small, the rigidity against vibration of the thin film portions 15a to 15h can be kept low.

[Modification]
According to the air cleaner 1 of the embodiment, the case 3 is provided with the eight thin film portions 15a to 15h, and the natural frequencies f1 to f8 of each primary mode are set to sequentially increase. The number of the thin film portions is arbitrary as long as it is 2 or more. That is, the number of thin film portions can be set arbitrarily as long as the canceling effect due to the different natural frequencies of the primary mode can be obtained.

  According to the air cleaner 1 of an Example, although the thin film parts 15a-15h were provided by compression molding, the setting method of the thin film parts 15a-15h is not limited to such an aspect. For example, the thin film portions 15a to 15h previously molded may be inserted into a mold when the high-rigidity portion 17 is molded, and insert molding may be performed (see FIG. 4).

  According to the air cleaner 1 of the embodiment, the outer sides of the thin film portions 15a to 15h are covered with the sound absorbing material 19, but the equipment of the sound absorbing material 19 is not indispensable, and the sound absorbing material depends on the frequency of the sound wave to be silenced. It may be determined whether 19 is equipped.

It is a block diagram of an air cleaner (Example). It is sectional drawing of a case perpendicular | vertical to the flow direction of intake air (Example). It is explanatory drawing which shows the shaping | molding state of a thin film part (Example). It is explanatory drawing which shows the shaping | molding state of a thin film part (modification).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air cleaner 2 Filter element 3 Case 15a-15h Thin film part 19 Sound-absorbing material f1-f8 Natural frequency of primary mode

Claims (2)

In an air cleaner that removes foreign matter in the intake air sucked into the engine,
A filter element that captures foreign matter, and a case that accommodates the filter element,
This case has at least two thin film portions that can be vibrated by sound waves accompanying inspiration,
The air cleaner characterized in that the two thin film portions have different natural frequencies of the primary mode. The air cleaner according to claim 1,
An air cleaner characterized in that the outer sides of the two thin film portions are covered with a sound absorbing material.

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