JP2006335125A - Duct of air-conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the noise by using a slit resonator and reduce the pressure loss. <P>SOLUTION: An influx cylinder 1 is connected with the influx side bottom part 30 of a case 30 while an outflow cylinder 2 is connected with the outflow side bottom part 31, and the section area of the outflow cylinder 2, at least at its open end face confronting the influx cylinder 1, is made larger than the section area of the influx cylinder 1 at its open end face confronting the outflow cylinder 2. As the air stream from the influx cylinder 1 flows into the outflow cylinder 1 smoothly, the pressure loss can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a duct used in an air conditioner for automobiles or houses, and more particularly to a duct capable of reducing noise during blowing.

  For example, a duct used in an air conditioner of an automobile is formed by blow molding or the like from a thermoplastic resin such as polyethylene. However, in such a resin duct, when noise generated during the operation of the blower enters the duct, it is reflected rather than absorbed, and there is a problem that indoor noise during blowing is large. In particular, in recent years, quietness in the passenger compartment has increased, and it is desired to further reduce noise from the air outlet.

  Japanese Patent Laid-Open No. 06-156051 proposes a duct structure in which an opening is provided in a part of a duct body and a sound absorbing material is attached to the opening. According to this duct structure, since sound wave reflection is reduced by the sound absorbing material, noise can be reduced. Japanese Patent Application Laid-Open No. 2005-104169 describes that a sound absorbing material is disposed in a housing portion formed in a duct body so as to face an air circulation space. Even if it does in this way, since reflection of a sound wave reduces with a sound-absorbing material, noise can be reduced.

  By arranging the sound absorbing material in the flow path in this way, the sound energy can be converted from the vibration energy of the sound absorbing material to the heat energy, so that the noise can be effectively reduced. However, when the sound absorbing material is disposed in the flow path, there is a problem that the pressure loss increases due to an increase in ventilation resistance or a disturbance in the airflow. In a duct of an air conditioner, if the pressure loss increases, the load of the blower must be increased, and this causes a problem that power consumption increases. Therefore, an increase in pressure loss must be avoided as much as possible.

  Therefore, for example, a duct having an expansion chamber as described in JP-A-2004-169645 may be considered. A duct having such an expansion chamber is also referred to as a slit resonator, and can muffle noise having a specific frequency based on Helmholtz resonance theory.

However, the slit resonator is used for an intake duct to an engine. Since the frequency band of the noise of the intake system is unevenly distributed higher than the frequency band of the noise of the air conditioner and the frequency band to be reduced is different, the slit resonator is not used for the duct for the air conditioner. Not. In the case of the intake duct, although noise reduction is emphasized, the pressure loss is hardly a problem. On the other hand, in the case of a duct for an air conditioner, it is necessary to design the pressure loss reduction first. For this reason, when the slit resonator of the intake system is directly applied to a duct for an air conditioner, there is a problem that pressure loss increases.
JP 06-156051 A JP 2005-104169 JP2004-169645

  The present invention has been made in view of the above circumstances, and an object to be solved is to reduce noise and reduce pressure loss using a slit resonator.

The feature of the duct of the present invention that solves the above problem is a duct that is arranged on the downstream side of the blower of the air conditioner and guides the airflow to the outlet,
A case comprising an inflow side bottom portion having an inflow side port, an outflow side bottom portion having an outflow side port, and a cylindrical portion forming an expansion chamber together with the inflow side bottom portion and the outflow side bottom portion;
An inflow tube connected to the inflow side port, and an outflow tube connected to the outflow side port,
The cross-sectional area of the opening end surface of the outflow tube facing the inflow tube is larger than the cross-sectional area of the opening end surface of the inflow tube facing the outflow tube.

  The outflow tube can be configured to have a funnel shape that increases in diameter as it approaches the inflow tube. In this case, it is desirable that a ring-shaped sound absorbing member is held at the funnel end facing the inflow cylinder of the outflow cylinder. Furthermore, the inner diameter of the ring-shaped sound absorbing member is desirably larger than the opening diameter of the inflow cylinder.

  According to the duct of the present invention, noise can be reduced due to the presence of the expansion chamber without using a sound absorbing member. And since the cross-sectional area of the opening end surface facing the inflow tube at least of the outflow tube is larger than the cross-sectional area of the opening end surface of the inflow tube facing the outflow tube, the pressure loss can be greatly reduced.

  Furthermore, if a ring-shaped sound absorbing member is held at the end of the funnel, the resonator function is reduced, and it becomes difficult to largely mute noise at a specific frequency, but noise can be reduced uniformly over a wide frequency range.

  The duct of the present invention includes a case, and an inflow cylinder and an outflow cylinder connected to the case. The case includes an inflow side bottom portion having an inflow side port, an outflow side bottom portion having an outflow side port, and a cylindrical portion, and forms an expansion chamber. The inflow tube and the outflow tube are connected to the inflow side port and the outflow side port, respectively, and the end surface openings of the inflow tube and the outflow tube face each other with an interval in the expansion chamber. That is, since the slit resonator is formed, the noise of a specific frequency based on the Helmholtz resonance theory can be silenced, and the noise can be reduced.

  Therefore, dimensions such as the shape (volume) of the expansion chamber and the interval (slit) between the end surfaces of the inflow cylinder and the outflow cylinder can be determined according to the frequency of the noise to be silenced. In the case of an air conditioner duct (equivalent to φ80) as in the present invention, the volume of the expansion chamber is preferably in the range of 0.5 to 1.0 L, and the distance (slit) between the end faces of the inflow cylinder and the outflow cylinder is 10 to 10 mm. A range of 30 mm is preferred.

  The greatest feature of the present invention is that the cross-sectional area of the open end surface of the outflow tube facing the inflow tube is larger than the cross-sectional area of the open end surface of the inflow tube facing the outflow tube. With this configuration, the airflow from the inflow cylinder smoothly flows into the outflow cylinder, so that an increase in ventilation resistance is suppressed and turbulence of the airflow is suppressed, and the pressure loss can be greatly reduced.

  In order to make the cross-sectional area of the opening end surface of the outflow cylinder larger than the cross-sectional area of the opening end surface facing the outflow cylinder of the inflow cylinder, the flow path cross-sectional area of the entire outflow cylinder may be larger than the flow path cross-sectional area of the inflow cylinder. And it can also be set as the funnel shape which expands in a trumpet shape as it approaches the inflow cylinder.

  It is also preferable to arrange a sound absorbing member in the duct of the present invention. The sound absorbing member can absorb noise in a relatively high frequency range, and the noise can be reduced in a wide frequency range together with the expansion chamber. In addition, the resonator function is reduced by the sound absorbing member, and it becomes difficult to mute the noise of a specific frequency greatly, but the noise can be reduced uniformly in a wide frequency range.

  The sound absorbing member is desirably provided in a ring shape on the opening end surface of the outflow tube facing the inflow tube. For example, if the opening end surface of the outflow tube is a funnel shape, the sound absorbing member is held at the tip. By doing so, the inner diameter of the sound absorbing member can be made larger than the opening diameter of the inflow cylinder, and it is possible to prevent the airflow flowing out from the opening of the inflow cylinder from becoming a ventilation resistance, thereby suppressing an increase in pressure loss. Can do.

  The sound absorbing member is a porous member having air permeability, and foamed urethane, non-woven fabric, woven fabric and the like can be used, but those formed from soft foamed urethane having excellent sound absorbing properties are preferable. By arranging this sound absorbing member, vibration energy in a high frequency region can be attenuated, and noise of about 2000 Hz or more can be reduced. Moreover, since the frequency range in which sound can be absorbed can be adjusted by the air permeability of the sound absorbing member, it is desirable to adjust the air permeability according to the purpose.

  In order to hold the sound absorbing member on at least the opening end surface of the outflow cylinder facing the inflow cylinder, the sound absorbing member may be mechanically held by claw engagement or a clip, or may be joined by adhesion or welding.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Example 1
The duct of a present Example is shown to FIGS. The duct includes an inflow tube 1 and an outflow tube 2 and a case 3 to which the inflow tube 1 and the outflow tube 2 are connected. The case 3 has a rectangular parallelepiped shape with an inner dimension of 100 mm × 120 mm × 140 mm, and has an inflow side bottom 30 at one end and an outflow side bottom 31 at the other end. The inflow side bottom 30 and the outflow side bottom 31 are cylindrical portions. It is linked with 32.

  The inflow cylinder 1 passes through the inflow side bottom 30 and extends at the end into the case 3, and the outflow cylinder 2 extends through the outflow side bottom 31 into the case 3. Both the inflow cylinder 1 and the outflow cylinder 2 are square cylinders having an inner dimension of 60 mm × 80 mm. The end surfaces of the inflow tube 1 and the outflow tube 2 are coaxially opposed to each other within the case 3 with an interval of 30 mm. That is, the inflow cylinder 1 and the outflow cylinder 2 and the case 3 constitute a slit resonator, and the case 3 functions as an expansion chamber. Therefore, noise at a specific frequency based on Helmholtz resonance theory can be silenced, and noise can be reduced.

  In this embodiment, a funnel portion 20 corresponding to R = 10, which increases in diameter as it approaches the inflow tube 1, is formed on the opening end surface of the outflow tube 2 facing the inflow tube 1. With this configuration, the airflow flowing out from the inflow cylinder 1 smoothly flows into the outflow cylinder 2, so that increase in ventilation resistance is suppressed and turbulence of the airflow is suppressed, thereby reducing pressure loss. it can.

(Comparative Example 1)
It was formed in the same manner as in Example 1 except that the funnel portion 20 was not formed in the outflow cylinder 2.

(Comparative Example 2)
The opposite end surfaces of the inflow cylinder 1 and the outflow cylinder 2 were connected to each other and formed in the same manner as in Comparative Example 1 except that the case 3 was not formed.

<Simulation evaluation>
The case where white noise is introduced from the inflow cylinder 1 side and the sound pressure is evaluated on the outflow cylinder 2 side is simulated, and the result is shown in FIG. In the ducts of Example 1 and Comparative Example 1, it can be seen that the sound pressure level is lower than that of Comparative Example 2 in the range of 800 to 1700 Hz, which is clearly the effect of configuring a slit resonator. In the duct of the first embodiment, the sound pressure level near 1200 Hz is greatly reduced as compared with the first comparative example, which is an effect obtained by providing the funnel portion 20. Moreover, in the duct of Example 1, pressure loss can be reduced compared with the comparative example 1 which does not have a funnel part.

(Example 2)
FIG. 4 shows a cross-sectional view of the duct of this embodiment. The duct of this example has the same structure as that of Example 1 except that a ring-shaped sound absorbing member 4 is attached to the tip of the funnel portion 20. The sound absorbing member 4 is made of soft foamed urethane and has a thickness of 5 mm.

  According to the duct of the present embodiment, pressure loss can be suppressed as in the first embodiment, and noise in a frequency region of 2000 Hz or more can be further reduced by the sound absorbing member 4. Since the resonator function is smoothed by the sound absorbing member 4, it is difficult to mute the noise of a specific frequency greatly, but the noise can be reduced almost uniformly in a wide frequency range.

  Furthermore, since the inner diameter of the sound absorbing member 4 is larger than the inner diameter of the inflow cylinder 1, an increase in pressure loss due to the sound absorbing member 4 can be suppressed.

(Example 3)
FIG. 5 shows a sectional view of the duct of this embodiment. The duct of the present embodiment has the same structure as that of the first embodiment except that the inner dimension of the outflow cylinder 2 is 70 mm × 90 mm larger than the inner dimension of the inflow cylinder 1 and the funnel portion 20 is not formed. .

  The duct of the present embodiment can suppress pressure loss as in the first embodiment. Further, as shown in FIG. 6, if the sound absorbing member 4 ′ is disposed on the end face of the outflow cylinder 2, the same noise suppression effect as that of the second embodiment is exhibited.

It is a principal part perspective view of the duct of one Example of this invention. It is principal part sectional drawing of the duct of one Example of this invention. It is a graph which shows the relationship between a frequency and a noise level. It is principal part sectional drawing of the duct which concerns on the 2nd Example of this invention. It is principal part sectional drawing of the duct which concerns on the 3rd Example of this invention. It is principal part sectional drawing which shows the other aspect of the duct which concerns on the 3rd Example of this invention.

Explanation of symbols

1: Inflow cylinder 2: Outflow cylinder 3: Case 4: Sound absorbing member 20: Funnel section

Claims (4)

It is a duct that is arranged on the downstream side of the blower of the air conditioner and guides the airflow to the outlet,
A case comprising: an inflow side bottom portion having an inflow side port; an outflow side bottom portion having an outflow side port; a cylindrical portion forming an expansion chamber together with the inflow side bottom portion and the outflow side bottom portion;
An inflow tube connected to the inflow side port;
An outflow tube connected to the outflow side port,
A duct characterized in that a cross-sectional area of at least an open end surface of the outflow tube facing the inflow tube is larger than a cross-sectional area of an open end surface of the inflow tube facing the outflow tube.   The duct according to claim 1, wherein the outflow tube has a funnel shape that expands in diameter as it approaches the inflow tube.   The duct according to claim 2, wherein a ring-shaped sound absorbing member is held at a funnel end portion of the outflow tube facing the inflow tube.   The duct according to claim 3, wherein an inner diameter of the ring-shaped sound absorbing member is larger than an opening diameter of the inflow cylinder.

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