JP2003065173A - Reduced noise duct - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reduced noise duct capable of preventing dust from entering, reducing noise requiring little installation space, and applicable to not only an intake duct but also an air conditioning duct. SOLUTION: The reduced noise duct is provided with a duct main body 1 for forming an air passage O for introducing outside air a communicating short pipe 2 communicating with and integrally formed with the duct main body 1, a film-shaped sheet 3 for closing the communicating hole 24 of the communicating short pipe 2, and a protecting cap 4 mounted on the communicating short pipe 2 covering the film-shaped sheet 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low noise duct useful for reducing noise in an intake duct for introducing outside air into a combustion chamber of a vehicle engine and a vehicle air conditioning duct.

[0002]

2. Description of the Related Art In recent years, there has been a demand for noise reduction outside the vehicle,
Various methods have been adopted for automobile air intake system parts. As a typical method, a sound absorbing method using glass wool, urethane foam, etc., which aims to attenuate the noise itself,
Air column resonance damping method using a porous material (fiber, sintered product, etc.) aiming at damping of resonance generated in the duct, silencer (resonator) that attenuates noise in a specific frequency band in the chamber by diffuse reflection , Etc., and these have been adopted until now in single or composite specifications.

[0003]

[Problems to be Solved by the Invention]
The above method had the following problems. As it is expected that the glass wool will be dispersed by the negative pressure of intake air (scattered into pieces), post-processing to maintain its shape is required. Urethane foam was basically unsuitable for use in the engine room. One of them is hydrolysis, which requires a waterproof cover. In addition, thermal deterioration is likely to occur and durability is poor. Furthermore, the sound attenuation region of glass wool and urethane foam is only in the high frequency band, and the attenuation effect could not be expected in other regions. The above is not a method of eliminating the noise itself, but a method of reducing the noise by increasing the noise caused by the air column resonance coming from the duct length by letting out the sound pressure from the middle of the duct pipe, and as a result, aiming for low noise. It had no structure to mute itself. Also, like a resonator, it was not possible to target only a specific frequency band. There may also be a problem such as the intake of hot air. further,
As is the case, since the communicating porous material is used, there is a possibility that dust may be mixed in, so it could only be used for so-called primary side intake parts on the intake side of the air cleaner. Although the above can be freely applied from low to high frequencies, basically a large capacity chamber is required, resulting in cost increase, and securing a setting space at the time of setting is essential.

The present invention solves the above-mentioned problems and realizes noise reduction without invading dust and requiring almost no installation space, and can be used not only for intake ducts but also for air conditioning ducts and the like. It is intended to provide a low noise duct.

[0005]

[Means for Solving the Problems] In order to achieve the above object,
The gist of the invention according to claim 1 is a duct body that forms a gas flow path, a communication short tube that is integrally formed in communication with the duct body, and a film-like sheet that closes a communication hole of the communication short tube. And a protective cap attached to the communication short pipe so as to cover the film-like sheet, and a low noise duct. The invention of a low noise duct described in claim 2 is the invention according to claim 1, characterized in that the film sheet is made of a thermoplastic elastomer.

When the film-like sheet for closing the communication hole of the communication short pipe is provided as in the first aspect of the invention, the sound absorbing effect due to the film vibration can be obtained. Then, when a protective cap attached to the communication short pipe is provided so as to cover the membrane sheet,
It is possible to prevent a rubble stone or the like while the vehicle is running from hitting and damaging the film sheet. You can expect long-term stable sound reduction. When the thermoplastic elastomer is used for the film-like sheet as in the second aspect of the invention, noise attenuation by the thermoplastic elastomer having excellent viscoelastic properties can be smoothly performed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The low noise duct according to the present invention will be described in detail below. 1 to 7 show an embodiment of the low noise duct of the present invention, FIG. 1 is an exploded perspective view thereof, and FIG. 2 is A of FIG.
FIG. 3 is a cross-sectional view of the protective cap with a film sheet in which the film sheet is integrated with the protective cap in a view taken along the line A, and FIG. 3 shows a low noise duct in which the protective cap with a film sheet of FIG. FIG. 4 is a longitudinal sectional view, FIG. 4 and FIG. 5 are explanatory views showing an example of how to make a film-like protective cap, FIG. 6 is a cross-sectional view of a film-like protective cap of another aspect, and FIG. Is. Applies to vehicle intake ducts.

The low noise duct of the present invention comprises a duct body 1, a communicating short pipe 2, a film sheet 3 and a protective cap 4. The duct body 1 is a conduit that forms a gas flow path O that takes in outside air. The duct main body 1 here is the air cleaner upstream side duct main body 1 from the intake port to the air cleaner, but it is also applicable to the secondary side duct main body from the air cleaner to the engine. Reference numeral 12 is a suction portion for introducing the atmosphere, and reference numeral 13 is a connection portion on the air cleaner side, and the fitting sealing material 5 is wound around the outer peripheral surface thereof.

The communicating short pipe 2 is a nozzle-like member which is erected at a predetermined position of the duct body 1. The communication short pipe 2 of this embodiment is a cylindrical short pipe that is integrally formed so as to communicate with the duct body 1. An opening 14 is formed at a predetermined position (generally in the center of FIG. 1) of the duct body 1, and a communication short pipe 2 having a communication hole 23 of substantially the same size as the opening 14 is attached to the opening 14. There is. The sizes of the openings 14 and the communication holes 23 that function to reduce noise are appropriately set. A stopper 22 for attaching the protective cap 4 is formed on the side wall of the communication short pipe 2. The stopper 22 here is formed of a wedge-shaped small protrusion (claw), and is provided at two locations on the side wall of the communicating short tube. It should be noted that in FIG. 3, the position of the stopper 22 is set to 90
° It draws with a shift.

The membranous sheet 3 is a sheet or a film which covers the communication hole 23 of the communication short pipe 2 and is attached to the communication short pipe 2 in a state capable of vibrating the film. The membranous sheet 3 has airtightness and can be attached to the communicating short tube 2 by directly closing the opening 24 of the communicating short tube 2, and of course, the membranous sheet 3 is integrally fixed to the protective cap 4 in advance. In addition, by attaching the protective cap 4 with the membrane sheet 3 to the communication short pipe 2, the membrane sheet 3 may be automatically attached to the communication short pipe 2 by closing the communication hole 23. I do not care.

The film-like sheet 3 may be a resin film or a metal foil. A resin film having more viscoelastic properties than metal is more preferable. Even in metal foil, it is possible to expect a certain sound absorption effect due to film vibration. However, in the case of the polymer resin, when kinetic energy is applied, it deforms and returns to its original state when the stress is removed, and during that, friction occurs between the molecules, which is replaced by heat energy. It is said that the mechanism of noise attenuation is the conversion of frictional energy into thermal energy by the movement of this molecular chain. The reason why a resin film, which is a polymer resin, is good is that it has both physical properties of viscoelasticity, which is an elasticity equivalent to hardness and a viscosity equivalent to stickiness, and energy loss occurs due to friction due to molecular motion. , Because it is efficiently converted into energy. In particular, a thermoplastic elastomer having excellent viscoelastic properties and vibration damping ability is preferable. It has been confirmed from experiments using various synthetic resin materials that the thermoplastic elastomer has a high noise damping performance. The thermoplastic elastomer (TPE) includes styrene-based TPE (SBC), olefin-based TPE (TPO), vinyl chloride-based TPE (TPV).
C), urethane type TPE (TPU), ester type TPE
(TPEE), amide type TPE (TPAE), ion-crosslinking type ethylene vinyl acetate copolymer (EVA), ethylene acrylic acid ester and the like.

The target frequency of the film sheet 3 is determined by its thickness, size, installation position, that is, the position of the communication hole 23, and the like. For example, in the present embodiment shown in FIG. 1, the duct length L is 800 mm and the duct diameter D is 90 mmφ.
The size of the communication hole 23 closed by the film sheet 3 is 50 mmφ.
Then, the thickness of the film sheet 3 is set to 0.2 mm.

The protective cap 4 is a lid which is attached to the communication short pipe 2 so as to cover the membrane sheet 3 that closes the communication hole 23 so as to cover it. The protective cap 4 literally protects the membranous sheet 3 from being torn or damaged. In the vehicle intake duct and the vehicle air-conditioning duct, pebbles and the like that are running may jump and break the membrane sheet 3, and once broken, the noise reduction function of the membrane sheet 3 is lost. The protective cap 4 protects the membranous sheet 3 and exhibits stable sound absorbing performance.

As described above, the membranous sheet 3 has the communication hole 23.
The opening 24 may be closed and the protective cap 4 may be covered from above to be attached to the communication short pipe 2. However, in the present embodiment, as shown in FIG.
Is attached in a vibrating state, and the protective cap 4 is attached to the communication short pipe 2 so that the membrane sheet 3 closes the communication hole 23. The protective cap 4 is provided with a fitting hole 41 at a position corresponding to the stopper 22, and the protective cap 4 can be securely attached by pushing it into the communicating short pipe 2 as shown in FIG. When the protective cap 4 with the membrane sheet 3 is attached to the communication short pipe 2, the membrane sheet 3 is arranged at a position slightly apart from the communication short pipe 2 as shown in FIG. 3, and the airtight membrane sheet 3 is connected. The hole 23 is closed. This is the low noise duct of the present invention.

As shown in FIGS. 2 and 3, in order to form the protective cap 4 with the membranous sheet 3 in which the membranous sheet 3 is stretched inside the protective cap 4, for example, as shown in FIG. 4, an inner cap 4a and an outer cap 4b are provided. The film-like sheet 3 is sandwiched between and and welded and bonded by using the ultrasonic horn 6 or the like. A plurality of welding projections 42 are provided on the lower end of the inner cap 4a (4 in FIG. 5).
The projection 42 is welded to the outer cap 4b, and the film sheet 3 is spot-bonded. By such a method, the protective cap 4 with the film-shaped sheet 3 can be manufactured relatively easily. It is not necessary that the entire circumference of the film sheet 3 be bonded to the protective cap 4.

The protective cap 4 may be a closed cap as shown in FIGS. 2 to 5, but if it is possible to prevent pebbles bounced off during traveling from being hit and broken, it is not in a closed state but an open type protective cap. 4 is acceptable. The film-like sheet 3 closes the communication hole 23 in a state where the film can vibrate, and the protective cap 4 makes the inside and outside of the cap conductive. For example, as shown in FIG. 6A, the protective cap 4 is attached to the communicating short pipe 2 by covering the membrane sheet 3 with the mesh wire net 43. Alternatively, as shown in FIG. 6B, the portion that covers the membranous sheet 3 is the protective cap 4 formed of the porous plate 44. In the closed cap, the membrane sheet 3 and the void S formed by the bottom of the cap may resonate (Fig. 2), and the air layer height L is 5 m.
Although it is necessary to secure m or more, such a problem does not occur in the open type cap. In addition, in FIGS. 6A and 6B, the membranous sheet 3 is directly placed so as to cover the opening 24 (communication hole 23) of the communication short tube 2, and thereafter, the protective cap 4 is placed on the membranous sheet 3. It is attached to the communicating short pipe 2 so as to cover.

Next, a performance comparison test was conducted and is shown in FIG. The solid line is the result of noise reduction measurement using the product of this embodiment in FIG. An ethylene-vinyl acetate copolymer sheet having a thickness of 0.2 mm is used as the film sheet 3. The alternate long and short dash line represents the sound reduction measurement result of the porous sheet (glass wool is used here) instead of the film-like sheet 3 that blocks the communication hole 23 of the communication short tube 2. The dotted line shows the sound reduction measurement result of only the duct main body 1 without the communication short pipe 2. The duct body 1 has the same shape. In the case of only the duct body 1, the volume reduction is deteriorated due to air column resonance at the point Y. As can be seen in the Z zone, the product of the present invention is found to be useful for reducing noise in the frequency band around 200 Hz, which is of concern to people, even when compared with the porous body. Although illustration is omitted, the noise attenuation frequency band could be adjusted depending on the thickness and size of the film sheet 3, its installation location, and the like. For example, regarding the thickness of the film sheet 3, it has been confirmed that the smaller the thickness is in the range of 0.1 mm to 0.5 mm, the greater the sound reduction effect is.

According to the low noise duct constructed as described above, the film-like sheet 3 for closing the communication hole 23 is attached, so that unlike the high frequency band such as glass wool, the low / medium wave number band is regarded as a problem due to noise. Powerful for noise reduction. Moreover, it is possible to reduce the sound of a desired frequency by changing the thickness and size of the film sheet 3. Since the membrane sheet 3 closes the communication hole 23, the problem of dust entering the duct body 1 is solved. If the closed protective cap 4 as shown in FIGS. 1 to 3 is provided, hot air in the engine compartment is not sucked in. The pebbles that the film-like sheet 3 jumps up when the vehicle is running,
Since the protection cap 4 protects against the risk of being broken by gravel and the like, it is possible to take stable noise reduction measures for a long period of time. There is no problem of clogging that is likely to occur when a porous material is used. Further, the low-noise duct of the present invention requires only the space of the protective cap 4 to cover the communicating short pipe 2 protruding like a nozzle in the duct body 1, and does not require a large-capacity chamber like a resonator. No need to worry about securing the installation space. It is possible to immediately switch to the current mass-produced parts. In addition, if the protective cap 4 with the membranous sheet 3 is used so that it can be removably attached to the communication short pipe 2, the attachment is easy and the membranous sheet 3 can be easily replaced for maintenance or the like. The weight of the membranous sheet 3 is extremely small (3% or less) when viewed from the whole duct, and even if the membranous sheet 3 is a dissimilar material, the physical properties of the material are not deteriorated, and the integral regeneration is possible. If EVA (ethylene vinyl acetate copolymer) or the like is used for the film sheet 3, there is an advantage that it can be manufactured at low cost.

The present invention is not limited to those shown in the above-mentioned embodiment, but can be variously modified within the scope of the present invention depending on the purpose and application. The shapes and sizes of the duct body 1, the communicating short tube 2, the membrane sheet 3, the protective cap 4, and the like, and their materials can be appropriately selected according to the application. Although the embodiment is applied to the intake duct, it can also be applied to a vehicle air-conditioning duct.
In the embodiment, the communication short pipe 2 is attached to the duct main body 1 downward as shown in FIG. 1, but it may be oriented upward or sideways.

[0020]

As described above, the low-noise duct according to the present invention not only requires almost no installation space but enables selective noise reduction in the low and medium frequency bands, and is not only dust-free. , The protective cap protects against damages caused by pebbles caused by being mounted on the vehicle, so that a long-term stable damping effect can be expected, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an embodiment of a low noise duct of the present invention.

FIG. 2 is a cross-sectional view of the protective cap with a film-like sheet in which the film-like sheet is integrated with the protective cap 4, taken along the line AA of FIG.

FIG. 3 is a vertical cross-sectional view of a low noise duct in which the protective cap with the membrane sheet of FIG. 2 is attached to the duct body.

FIG. 4 is an explanatory view showing an example of how to make a film-like protective cap.

FIG. 5 is an explanatory view showing an example of how to make a film-like protective cap.

FIG. 6 is a cross-sectional view of another aspect of the film-formed protective cap.

FIG. 7 is a performance comparison test result graph.

[Explanation of symbols]

1 duct body 2 communication short pipe 3 Membrane sheet 4 Protective cap O 2 gas flow path

Claims (2)

[Claims] 1. A duct main body that forms a gas flow path, a communication short tube that is integrally formed so as to communicate with the duct main body, a film-like sheet that closes a communication hole of the communication short tube, and the film-like sheet. A low noise duct, comprising: a protective cap attached to the communication short pipe so as to cover it. 2. The low noise duct according to claim 1, wherein the film sheet is made of a thermoplastic elastomer.