JP3802312B2 - Air intake duct - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an intake duct as a passage for supplying air to an engine, and more particularly to an intake duct with reduced noise during intake.
[0002]
[Prior art]
In an intake system of an automobile engine, there is a problem that noise is generated in an intake duct such as an air cleaner hose or an intake duct during intake. This intake noise is particularly disturbing when the engine rotates at a low speed. Therefore, conventionally, as shown in FIG. 8, a side branch 101 and / or a resonator 102 is provided in the intake duct 100 to reduce noise of a specific frequency calculated based on Helmholtz resonance theory or the like. .
[0003]
However, the side branch 101 is about 30 cm in length, and the resonator 102 has a large volume of 14 liters. For this reason, the space occupied in the engine room of these sound absorbing devices is increased, resulting in a problem that the degree of freedom of mounting other components is reduced.
[0004]
Therefore, Japanese Utility Model Laid-Open No. 64-22866 discloses that an orifice is arranged in the intake duct and the intake noise is reduced by restricting the intake air at the position of the orifice. By restricting the intake passage in this way, the acoustic mass is increased, and the intake sound in the low frequency range can be reduced.
[0005]
Japanese Utility Model Publication No. 3-43576 discloses two intake ducts connected in parallel to an air cleaner case, branch pipes branched from the two intake ducts, and a common resonator in which the branch pipes are connected together. And an intake noise reduction device that includes an opening / closing valve that selectively opens according to the operating state on the upstream side of the connecting portion of the branch pipe in one of the intake ducts.
[0006]
According to the device disclosed in Japanese Utility Model Laid-Open No. 3-43576, the intake air amount is changed according to the engine speed by controlling the on-off valve according to the engine speed and switching the intake duct to one or two. And intake noise can be reduced.
[0007]
However, the above-described method for narrowing the intake passage has a problem that the amount of intake air is insufficient when the engine rotates at a high speed and the output is reduced.
[0008]
Further, the apparatus disclosed in Japanese Utility Model Publication No. 3-43576 uses an electronic control circuit, an electromagnetic on-off valve, or a diaphragm actuator to drive the on-off valve, which is not preferable from the viewpoint of cost. In addition, since an electronic control circuit, an electromagnetic on-off valve, and the like are required, the apparatus becomes complicated and expensive, and the maintenance man-hour is also great.
[0009]
Japanese Patent Laid-Open No. 11-343938 discloses an air intake duct formed from a nonwoven fabric containing thermoplastic resin fibers by heat compression molding. By forming the intake duct from the nonwoven fabric molded body in this way, it is possible to effectively reduce intake noise. In addition, the publication describes that the following three reasons are considered as reasons for reducing the intake noise, and that the intake noise is considered to be reduced by a synergistic effect thereof.
(1) Since the nonwoven fabric is an elastic body, it has a vibration damping action, and the generation of sound waves due to vibration of the tube wall is suppressed.
(2) The sound wave that has entered a large number of gaps between the fibers of the nonwoven fabric is weakened due to the viscosity of the gaps and the effect of heat conduction, and the sound energy is attenuated due to the resonance of the fibers themselves as the sound pressure fluctuates.
(3) Since at least a part of the tube wall has a certain degree of air permeability, the generation of a standing wave is suppressed by a part of the sound wave passing through the tube wall.
[0010]
[Problems to be solved by the invention]
However, since the nonwoven fabric molded body is more expensive than a general resin molded body, the intake duct formed from the nonwoven fabric molded body has a problem that it is extremely expensive compared to a conventional intake duct.
[0011]
The present invention has been made in view of such circumstances, and suppresses intake noise by optimally arranging a porous member such as a non-woven fabric, and reduces the amount of use to provide an inexpensive intake duct. Objective.
[0012]
[Means for Solving the Problems]
A feature of the intake duct of the present invention that solves the above problem is that, in an intake duct disposed between an outside air intake of an automobile and an intake manifold of an engine, a predetermined portion of the tube wall has a slit that is long in the longitudinal direction of the tube wall. Jo openings one has, opening whole is covered by a porous member, widthwise direction of the width of the opening is 1/20 or more and 1/4 or less of the circumference of the tube wall, the opening longitudinal The length is equal to or less than ¼ of the total length of the tube wall, and the center in the longitudinal direction of the opening lies in the position of ¼ of the total length of the tube wall from the end of the tube wall .
[0013]
The position in the longitudinal direction of the opening is desirably set so as to overlap the antinode position of the generated resonance wave. The center in the longitudinal direction of the opening is preferably at a position that is 1/4 of the entire length of the tube wall from the end of the tube wall facing the outside air intake port.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Noise generated during intake is mainly due to standing waves of sound waves generated inside the intake duct, and the frequency of the standing wave is determined by the intake duct length, intake duct diameter, intake duct material, and the like. Therefore, in the present invention, an elongated opening is formed in a part of the tube wall, and the entire opening is covered with a porous member such as a nonwoven fabric. As a result, the above-described three actions are performed, and intake noise is reduced.
[0015]
In the present invention, the width in the short direction of the opening is set to 1/20 or more of the circumferential length of the tube wall. By arranging the porous member in such a slit-like opening, the intake noise can be greatly reduced although the reason is unknown. If the width in the short direction of the opening is smaller than 1/20 of the circumferential length of the tube wall, it is difficult to obtain the effect of disposing the porous member, and intake noise increases. The upper limit of the width in the short direction of the opening is not particularly limited, but even if the width is increased, the effect of reducing the intake noise hardly changes, and there is a problem that the cost increases due to the increase in the amount of the porous member. . Therefore, the actual opening width considering the molding process or the joining process of the nonwoven fabric in addition to the cost problem is set to 1/20 or less and 1/4 or less of the circumferential length of the tube wall .
[0016]
In addition, the longer the length of the opening in the longitudinal direction, the more the intake noise can be reduced. However, since the amount of the porous member increases, the problem of increasing the cost also increases. Considering the balance, the length of the opening is set to 1/4 or less of the entire length of the tube wall.
[0017]
The center in the longitudinal direction of the opening is at a position that is 1/4 of the total length of the tube wall from the end of the tube wall . By doing so, intake noise can be further reduced. In the intake duct, a primary resonant sound having the same wavelength as twice the length of the intake duct, a secondary resonant sound having the same wavelength as the length of the intake duct, a tertiary resonant sound having a wavelength that is 2/3 of the length of the intake duct, etc. Are generated and these become intake noise. In order to reduce the resonance noise, it is preferable to provide an opening by removing the position corresponding to the node of each sound wave. That is, it is desirable to set the position in the longitudinal direction of the opening so as to overlap the antinode position of the generated resonance wave. If the center in the longitudinal direction of the opening is set to ¼ of the total length of the tube wall from the end of the tube wall, it is possible to effectively reduce the primary resonance sound and the secondary resonance sound that are particularly loud. .
[0018]
Further, the center in the longitudinal direction of the opening is more preferably set at a position that is 1/4 of the total length of the tube wall from the end of the tube wall facing the outside air intake. By doing so, the opening can be further away from the engine, and noise from the engine can be suppressed from being heard through the opening and the porous member, so that the noise can be further suppressed.
[0019]
As the porous member, those formed from fibers of various materials, paper, foam, or the like can be used. Nonwoven fabrics, woven fabrics, knitted fabrics, and the like formed from thermoplastic fibers are particularly desirable. If a nonwoven fabric made of thermoplastic resin fibers or the like is used, even an intake duct having a complicated shape can be easily shaped by hot press molding or the like, so that it can be easily adapted to the shape of the opening. Moreover, since it can join to a pipe wall by welding, the man-hour of the process of covering opening can be reduced. The thermoplastic resin fiber may constitute a part of a nonwoven fabric or the like, or the whole may be composed of thermoplastic resin fibers. In addition, even a cloth in which a non-thermoplastic fiber is impregnated with a thermoplastic resin binder can be shaped by hot press molding or the like in the same manner as a cloth formed from a thermoplastic resin fiber.
[0020]
If the air permeability of the porous member is too high, the sound wave in the air intake duct passes through the opening and the porous member and leaks to the outside, which increases the noise. Therefore, it is desirable that the degree of air permeability is 6000 m ³ / h or less per 1 m ² of air flow when the pressure difference is 98 Pa. The air flow rate means the amount of air per unit time passing through the unit area of the test specimen when the pressure difference between the two chambers partitioned by the test specimen is set to 98 Pa. Of course, the limitation of 6000 m ³ / h or less per unit area is a limitation in the case of air with a pressure difference of 98 Pa, and it goes without saying that the limit value of the air flow rate is different if the pressure of intake air is different.
[0021]
When the air flow rate per 1 m ² of air at a pressure difference of 98 Pa exceeds 6000 m ³ / h, the number of sound waves that pass through the openings and the nonwoven fabric increases and the transmitted sound increases. If the airflow is zero, the noise suppression effect in the low frequency range of 200 Hz or less is reduced, but the noise can be suppressed as compared with the conventional intake duct. In order to obtain a porous member having zero ventilation, a film-like skin layer may be formed on the outer surface of the porous member. Even if a skin layer is formed on the inner surface, the air flow rate can be reduced to zero, but it is not preferable because it is difficult to reduce noise due to the reason (2) described above. Note aeration amount of air when the pressure difference 98Pa in the porous member is preferably larger 4200m less than ³ / h than zero, 0 <particularly preferred range of the air permeability of <3000 m ³ / h.
[0022]
In addition, the thickness and characteristics of the nonwoven fabric change due to aging, moisture intrusion, etc., and the balance between the sound transmitted through the opening and porous member and the sound emitted from the air intake at the tip of the air intake duct is disrupted, resulting in intake noise. Suppression performance may change.
[0023]
Therefore, it is desirable that the porous member has a functional layer provided with a predetermined function. Examples of the functional layer include a water-repellent layer, a clogging prevention layer, and the like, and the functional layer can be easily formed by using a porous member in which fibers having respective functions are mixed. Moreover, you may use the film which has each function laminated | stacked on a porous member.
[0024]
The position of this functional layer can be appropriately set in the thickness direction of the porous member. For example, when a water repellent layer is used, it is desirable to provide it on the surface layer or intermediate layer of the porous member. This prevents moisture from entering and prevents changes in the characteristics of the porous member, so that the intake noise reduction effect can be maintained for a long time. In addition, since water permeation into the air cleaner is also suppressed, engine malfunction due to a loss of air permeability of the air cleaner element can be suppressed.
[0025]
As a method of covering the opening with the porous member, various known methods such as an integral molding method, a heat welding method, an adhesion method, and a mechanical engagement method can be employed. The porous member may be formed so as to cover an area larger than the opening, but it is desirable to cover the entire opening with an area as small as possible, which is almost equal to the opening area, from the cost viewpoint.
[0026]
【Example】
Hereinafter, the present invention will be specifically described with reference to test examples and examples.
[0027]
(Test Example 1)
A portion of the wall of the straight pipe 1 made of high-density polyethylene having an inner diameter of 65 mm and a length of 650 mm is cut into a slit shape in the longitudinal direction, and a PET (polyethylene terephthalate) fiber nonwoven fabric 2 (weight per unit area) is cut in the cut portion. A test piece shown in FIG. 1 was formed by bonding 1000 g / m ² and a gas flow rate in the thickness direction of 160 to 190 m ³ / h). Various test pieces were formed in the range of the circumferential length (width) of the cut portion from 0% (no cut portion) to 100% (the entire pipe was non-woven fabric).
[0028]
Next, using the test apparatus shown in FIG. 2, the sound absorption characteristics of the various test pieces described above were investigated. In this test apparatus, one end of the test piece penetrates the sound insulation wall 3, and the entire test piece is disposed in the soundproof room. A speaker 4 is disposed in the vicinity of one end of the test piece penetrating the sound insulating wall 3, and a microphone 5 is disposed at a position 10 mm away from the other end opening of the test piece. In addition, in FIG. 2, the test piece produced in the below-mentioned test example 2 is shown as a test piece.
[0029]
Then, white noise is emitted from the speaker 4 and the sound pressure level of the exit sound from the other end opening of the test piece from the microphone 5 is measured for each of the primary resonance sound and the secondary resonance sound, and the results are shown in FIG.
[0030]
From FIG. 3, the sound pressure level sharply decreases from zero in the circumferential direction (width) of the cut portion to 1/20 of the entire circumference of the pipe 1, and the sound pressure is greater than 1/20 of the entire circumference. Level is low and stable. Therefore, it can be seen that the circumferential length (width) of the cut portion is desirably 1/20 or more of the entire circumference of the pipe 1.
[0031]
(Test Example 2)
Next, the pipe wall of pipe 1 made of high-density polyethylene with an inner diameter of 65 mm and a length of 650 mm is cut by a length of 100 mm, and a PET (polyethylene terephthalate) fiber nonwoven fabric (weight per unit area: 1000 g / m ² , thickness) is 3.5 mm, the ventilation amount 16800m ³ / h · m ²⁾ from becomes an inner diameter 65 mm, by bonding nonwoven fabric tube 2 'of length 167 mm, to form a test piece shown in FIG. Various test pieces were formed by variously changing the distance (X in FIG. 2) from the end face of the pipe 1 at the central position (P) in the axial direction of the cut portion, and each test piece was the same as in Test Example 1. The sound pressure level of the exit sound was measured. In addition, the transmitted sound which permeate | transmits nonwoven fabric cylinder 2 'was also measured by making the position of the microphone 5 into the side surface of a test piece. The results are shown in FIG. 5 as overall values.
[0032]
FIG. 5 shows that a minimum value is recognized when the longitudinal center (P) of the excised portion is at a position 1/4 of the total length of the tube wall from the end of the tube wall, and it is 1/4 of the total length of the tube wall. It can be seen that it is particularly desirable to provide the position.
[0033]
Therefore, based on the results of both test examples, the intake duct of the example was formed as follows.
[0034]
(Example)
6 and 7 show an intake duct according to an embodiment of the present invention. The intake duct 10 has a cylindrical shape having an inlet end portion 11 arranged at an outside air intake of an automobile and an outlet end portion 12 fixed to an intake manifold of the engine, and is long on one side of the inlet end portion 11 side. A long opening 13 is formed in the direction, and the opening 13 is covered with a nonwoven fabric 14. The intake duct 10 is formed from high-density polyethylene by blow molding, and an opening 13 is formed by cutting a part thereof.
[0035]
The opening 13 has a circumferential length, which is the width in the short direction, of ¼ of the general circumferential length of the intake duct 10 and is ¼ of the entire length of the intake duct 10 and is formed in a slit shape. Has been. The center of the opening 13 in the longitudinal direction is at a position that is 1/4 of the entire length from the inlet end 11.
[0036]
Non-woven fabric 14 is made of PET (polyethylene terephthalate) fiber non-woven fabric (weight per unit of 1000g / m ² , thickness 3.5mm, air flow 1680m ³ / h · m ² ), cut into a shape that is slightly larger than the opening 13 and heat-welded It covers the opening 13 and is integrated with the intake duct 10.
[0037]
For the intake duct 10 of this example and the intake duct of the comparative example that is not formed of the opening 13 and is entirely made of high-density polyethylene, the sound pressure level was measured in the same manner using the same test apparatus as the test example. did. As a result, in the intake duct 10 of the present embodiment, the sound pressure level of the intake sound was reduced by about 70% compared to the intake duct of the comparative example, and the intake noise was greatly reduced.
[0038]
【The invention's effect】
That is, according to the intake duct of the present invention, the intake noise can be well suppressed and the amount of the nonwoven fabric used is reduced, so that it is extremely inexpensive.
[Brief description of the drawings]
FIG. 1 is a perspective view of a test piece used in Test Example 1. FIG.
FIG. 2 is an explanatory diagram showing a configuration of a test apparatus used in Test Example 1 and Test Example 2;
FIG. 3 is a graph showing the results of Test Example 1 and showing the relationship between the width of the excised part and the sound pressure level.
4 is a perspective view of a test piece used in Test Example 2. FIG.
FIG. 5 is a graph showing the result of Test Example 2 and showing the relationship between the central position of the excised part and the sound pressure level.
FIG. 6 is a perspective view of an intake duct according to an embodiment of the present invention.
FIG. 7 is a cross-sectional view of an essential part of an intake duct according to an embodiment of the present invention.
FIG. 8 is a perspective view of a conventional intake duct.
[Explanation of symbols]
10: Intake duct 11: Inlet end 12: Outlet end
13: Opening 14: Nonwoven fabric

Claims (2)

In the intake duct arranged between the outside air intake of the automobile and the intake manifold of the engine,
A predetermined portion of the tube wall has one slit-like opening that is long in the longitudinal direction of the tube wall, and the opening is entirely covered with a porous member,
The width in the short direction of the opening is 1/20 or more and 1/4 or less of the circumference of the tube wall, and the length in the longitudinal direction of the opening is 1/4 or less of the total length of the tube wall, An air intake duct characterized in that the center in the longitudinal direction of the opening is located at ¼ of the total length of the tube wall from the end of the tube wall .   2. The intake duct according to claim 1, wherein the center of the opening in the longitudinal direction is at a position that is ¼ of the total length of the tube wall from an end portion of the tube wall facing the outside air intake port.

Images