JP2010285871A - Ventilation duct - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a ventilation resistance of air flowing through a ventilation duct in a duct having a through hole provided in a duct wall.
SOLUTION: A ventilation duct 1 for sucking air, wherein the ventilation duct is provided with a recessed portion 4 in which the inner peripheral surface of the duct wall is recessed toward the outside of the duct from the basic shape of the duct wall. A through hole 3 penetrating the duct wall is provided in the upstream portion 41 of the recessed portion, and the length of the recessed portion 4 in the direction along the flow in the duct is made longer than the size of the through hole 3. A direction in which the recessed portion downstream portion 42 is substantially parallel to the through-hole 3, the recessed portion downstream portion 42 is convex toward the inside of the duct, or an angle with the duct central axis is 0 to 60 degrees. It is preferable to provide a through hole.
[Selection] Figure 2

Description

The present invention relates to a ventilation duct that allows air to flow inside a duct. In particular, the present invention relates to a ventilation duct in which a through-hole communicating with the inside and outside of the duct wall is provided in the duct wall.

Ventilation ducts are used as members that form a series of ventilation duct systems, particularly in the intake systems of internal combustion engines for automobiles, intake systems of fuel cells, cooling air blowing systems and air conditioning systems for cooling secondary batteries, etc. Has been. In such a duct system, a duct made of a non-breathable material such as a synthetic resin, a metal plate, or a pipe is generally used for the duct wall. For some time, it has been desired to reduce noise by propagating air or by air column resonance occurring in the duct system.

Therefore, in these ventilation ducts, a duct wall called a tuning hole is used to prevent / suppress the air column resonance generated in the duct system, or to dissipate and attenuate the noise propagating in the duct to the outside of the duct. There may be a case where a through-hole penetrating is provided.

In many cases, the tuning hole is simply provided with a through hole in the duct wall of the ventilation duct. However, as another mode in which the tuning hole is provided, for example, as disclosed in Patent Document 1, the tuning hole is provided. 2. Description of the Related Art There is known an intake duct configuration in which a protector member to be covered is attached to face a tuning hole so that a gap is provided between the protector member and the duct.

JP 2001-41122 A

On the other hand, not only the above-mentioned acoustic performance but also the performance of the strength side of the ventilation duct such as its strength and durability, and the performance of reducing the ventilation resistance of the airflow flowing through the inside are emphasized for these ventilation ducts. In particular, the reduction of ventilation resistance is particularly important in the intake duct for supplying a large amount of intake air to the internal combustion engine and the fuel cell through the intake system, and is also important in the air conditioning duct and the cooling air blowing duct. .

However, it has been found that when a through hole such as a tuning hole is provided in the ventilation duct, air is sucked from the through hole, so that the airflow inside the intake duct is disturbed and the ventilation resistance increases.

Accordingly, an object of the present invention is to reduce the ventilation resistance of air flowing through the ventilation duct in a duct having a through hole provided in the duct wall.

As a result of intensive studies, the inventor has provided a recessed portion in which the inner peripheral surface of the ventilation duct is recessed toward the outside of the duct rather than the basic shape of the duct wall, and a through hole is provided in the upstream side portion of the recessed portion. As a result, it was found that the deterioration of the ventilation resistance due to the provision of the through hole could be suppressed, and the present invention was completed.

The present invention is a ventilation duct for configuring a ventilation path for sucking air, and the ventilation duct is provided with a recessed portion in which the inner peripheral surface of the duct wall is recessed toward the outside of the duct rather than the basic shape of the duct wall. In addition, a through hole is provided in the upstream portion of the recess so that air can flow from the outside of the duct to the inside of the duct through the duct wall. The vent duct is characterized in that the length of the recessed portion in the direction along the flow in the duct is longer than the size of the through hole.

In the present invention, the through hole is provided so as to be inclined upstream with respect to the radial direction of the duct, and the downstream side portion of the recessed portion is substantially parallel to the direction of the through hole in the cross section including the central axis of the ventilation duct. It is preferable that the recessed portion is formed so that the recessed amount becomes smaller toward the downstream side (Claim 2), and further, the downstream side of the recessed portion in the section including the central axis of the ventilation duct. It is preferable that the portion is formed to be convex toward the inside of the duct, and is smoothly connected to the basic shape of the ventilation duct. And it is especially preferable that a through hole is provided in the direction in which the angle formed with the duct central axis is 0 degrees to 60 degrees.

According to the present invention, in a ventilation duct in which a through hole is provided in a duct wall, the air flow sucked from the through hole can be guided toward the downstream side of the duct, and the flow from the through hole can It is possible to reduce the ventilation resistance of the air flowing through the ventilation duct by suppressing the deterioration of the ventilation resistance due to the disturbance of the flow.

In addition, the downstream portion of the recessed portion is made substantially parallel to the through hole, the downstream portion of the recessed portion is convex toward the inside of the duct, or the angle formed with the duct central axis is in the direction of 0 to 60 degrees. By providing the through hole, the ventilation resistance can be more effectively reduced.

It is a perspective view of an air intake duct which is an embodiment of the present invention. It is an expanded sectional view near a penetration hole and a recessed part of an air intake duct of an embodiment of the present invention. It is a figure which shows the detailed shape of the through-hole and recessed part of an intake duct of embodiment of this invention. It is a schematic diagram which shows the flow of the through-hole vicinity when there is no recessed part. It is a schematic diagram which shows the flow of the through-hole vicinity in this invention. It is a figure which shows the flow line of the flow from the through-hole in the intake duct of a comparative example. It is a figure which shows the flow line of the flow from the through-hole in the intake duct of this invention embodiment. It is a graph which shows the result of the ventilation simulation of the Example and comparative example of this invention. It is a figure which shows the shape of the through-hole and recessed part of the intake duct of other embodiment of this invention. It is sectional drawing which shows the shape of the through-hole and recessed part of the intake duct of other embodiment of this invention. It is a perspective view which shows the shape of the through-hole and recessed part of the intake duct of other embodiment of this invention. It is a figure which shows the flow line of the flow from the through-hole in the intake duct of other embodiment of this invention. It is a figure which shows the streamline of the flow from the through-hole in the intake duct of other embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an appearance of an intake duct 1 according to an embodiment of the present invention. In FIG. 2, the cross section along the duct axial direction of the through-hole 3 vicinity of the intake duct 1 of this invention is expanded and shown. The ventilation duct of the present invention includes a part of an intake system for supplying air to an automobile engine (internal combustion engine), a part of an intake system for supplying air to a fuel cell, a battery, and the like. Used as part of the air duct for cooling. In the present embodiment, the intake duct 1 is an intake duct that forms part of an intake system for supplying air to the internal combustion engine, and the intake duct 1 is connected to the upstream side of another duct member or an air cleaner. It is a duct member.

The intake duct 1 is integrally formed with a duct body 2 having a hollow cylindrical duct wall formed of a synthetic resin (in this embodiment, polypropylene resin), and a recessed portion 4 in which the inner peripheral surface of the duct is recessed toward the outside of the duct. The duct member is formed with a through hole 3 penetrating the duct wall in the upstream portion of the recessed portion 4 in the flow direction of the air flowing through the intake duct. The duct body 2 is a hollow member through which air flows, and in this embodiment, a funnel portion 21 for sucking air from the open atmosphere into the duct is formed at the upstream end portion thereof. At the downstream end thereof, a cylindrical duct portion (mouth portion) 22 is provided for connecting with other subsequent duct components, connector members, etc. and forming a series of air flow paths together with the other members. ing. The intake duct 1 may be provided with a mounting member (not shown) as necessary.

The intake duct 1 according to the present invention is characterized in that a recessed portion 4 is provided in the intake duct 1 and a through hole 3 is provided in an upstream portion of the recessed portion 4. The recessed portion 4 is recessed so that the inner peripheral surface of the duct is recessed toward the outside of the duct as compared with the inner peripheral surface (basic shape surface which is a non-recessed portion) of the basic shape portion 23 of the duct wall that defines the duct internal space. In the present embodiment, in the recessed portion 4, the duct wall is formed so as to protrude in a protruding shape toward the outside of the duct rather than the basic shape of the duct wall.

In the present embodiment, the recessed portion 4 is formed integrally with the duct main body 2 so as to have an inner peripheral surface shape that is elongated along the flow direction of the air flowing inside the intake duct 4. That is, as shown in FIG. 3, when viewed from the duct radial direction (see FIG. 3A), the upstream side (through hole side) is round and the downstream side is tapered into a spindle shape. The length L of the recessed portion 4 along the length is about four times the through-hole diameter d1, and the width W of the recessed portion 4 in the direction perpendicular to the flow direction is slightly wider than the diameter d1 of the through-hole 3, and in the circumferential direction of the duct When viewed along (see FIG. 3B), the recessed depth H of the recessed portion 4 is slightly larger than the diameter d <b> 1 of the through hole 3. Moreover, the cross-sectional shape of the recessed part seen from the direction along the center axis | shaft of an air intake duct is a shape which protruded toward the duct outer side in semicircle shape (refer FIG.3 (c)). That is, the three-dimensional shape of the recessed portion 4 has a predetermined shape from the basic shape surface 23 of the duct by forming a substantially flat surface in which the through hole is to be provided in the upstream portion 41 with respect to the portion having the maximum recessed depth. In the downstream portion 42, a recessed portion is formed in a semi-cylindrical surface substantially parallel to the through hole center line m, and the recessed depth and width of the recessed portion gradually increase toward the downstream side. The shape is reduced.

A through hole 3 is opened in the upstream portion 41 of the recessed portion 4. In the present embodiment, the through hole 3 is oriented in such a direction that the through hole central axis m faces the upstream side of the ventilation duct as it goes to the outside of the duct, and the central axis m is about 20 degrees from the duct central axis (or the duct basic shape). It is provided to make an angle of. The downstream portion 42 of the recessed portion 4 is formed to have a semi-cylindrical surface that is substantially parallel to the central axis of the through hole 3.

The through hole 3 provided so as to penetrate the duct wall in the upstream portion of the recessed portion 4 is a circular through hole in this embodiment, and the through hole 3 allows the internal space of the duct body 2 and the external space to be formed. Communicate with each other. By providing the through hole 3, air column resonance generated in an intake system connected with a series of ducts can be prevented or suppressed. The through hole 3 is effective in the axial direction of the duct for preventing and suppressing air column resonance. It is provided at a position and a size (preferably about 3 mm to 18 mm in diameter, 10 mm in this embodiment), and functions as a so-called tuning hole.

When intake is performed through the intake duct 1, as a main air flow path, air is sucked from the funnel portion 21, flows through the duct internal space, and flows downstream through the duct mouth portion 22. In the present invention, the intake duct 1 is used in such a manner that the static pressure inside the duct becomes negative with respect to the atmospheric pressure outside the duct, that is, the air is sucked. As air is sucked into the intake system from the main flow path of the intake duct 1, the air is secondarily sucked from the through hole 3, and merges with the main flow sucked from the funnel 21 to be downstream. Air will flow through.

There is no restriction | limiting in particular as a material which comprises the intake duct 1, The various material which can form such a duct can be used. For example, thermoplastic synthetic resins such as polypropylene resin, polyamide resin, and polyethylene resin, relatively hard synthetic resins such as thermosetting synthetic resins, relatively soft elastomers such as rubber and thermoplastic elastomers, aluminum and iron, etc. The metal material can be illustrated. Especially, since a duct member can be efficiently shape | molded by the blow molding method or the injection molding method, synthetic resin materials, such as a thermoplastic resin, rubber | gum, and a thermoplastic elastomer, can be used preferably.

The intake duct 1 can be manufactured by a known method. For example, in the intake duct 1 of the present embodiment, the duct body 2 in which the recessed portion 4 is integrally formed is formed by a known blow molding method, and the funnel portion 21, the mouth portion 22, and the through hole 3 are opened. Thus, the intake duct 1 can be obtained. The through hole 3 may be processed by drilling, or the portion that becomes the through hole 3 may be blow molded into a so-called discard bag shape, and the discard bag portion may be cut after blow molding to open the through hole 3. Good.

In addition, the method of manufacturing the intake duct 1 is not limited to the blow molding method, and can be performed by an injection molding method. In particular, when the accuracy of the inner peripheral surface shape of the duct is required, the injection molding method may be used. preferable. The recessed portion 4 is not necessarily formed integrally with the duct body portion 2 at the same time. The duct body portion 2 and the recessed portion 4 are manufactured separately as in a second embodiment to be described later, and are bonded and integrated later. You may make it.

The effect of the ventilation duct of this invention is demonstrated.
In the present invention, the recessed portion 4 in which the through hole 3 is provided does not hinder the function of the through hole itself, so that the through hole exhibits the effect originally expected. The effect of improving the acoustic characteristics of the system is exerted, and the air column resonance of the duct system is prevented and suppressed, and the noise propagating through the duct is radiated to the outside and the noise propagating to the funnel side can be reduced.

Further, in the intake duct 1 of the present invention, the through-hole 3 is provided in the upstream side portion of the recessed portion 4 provided in an elongated shape along the flow direction, so that the ventilation resistance when air is sucked by the intake system is provided. Can be reduced.
First, the air flow inside the duct in the conventional intake duct in which the recessed portion 4 is not provided will be described. As shown in FIG. 4, the flow from the through hole merges with the main flow flowing from the left side of the drawing. In the downstream area of the through hole, a stagnation region or vortex is generated, and the flow from the vortex, stagnation, or through hole compresses the main flow path in the duct, increasing the airflow resistance. End up.

In the intake duct 1 according to the present invention, the through hole 3 is provided in the upstream portion of the recessed portion 4, whereby the air is sucked from the through hole 3 into the space in the downstream portion of the recessed portion 4 provided in an elongated shape. As shown in FIG. 5, the flow of air is induced and the generation of vortices and stagnation regions due to the flow from the through hole 4 is prevented or suppressed, and the flow from the through hole is ducted in the downstream region of the through hole. It is prevented from entering the inside greatly, and flows along the duct wall. Therefore, the degree to which the flow path of the main flow in the duct is compressed by the flow from the through hole is alleviated, and the deterioration of the ventilation resistance is suppressed.

In order to obtain such a ventilation resistance reduction effect, as described above, it is preferable that the recessed portion 4 is provided in an elongated shape along the flow direction. However, the shape of the recessed portion 4 is in the flow direction of the duct. It is not limited to the elongate shape along, but the space by the recessed part 4 is formed in the downstream side of the through hole 3 so that the air flow sucked from the through hole can be guided in the downstream direction of the air flow in the duct. It only has to be formed. Therefore, the length (L) in the duct length direction of the recessed portion 4 is larger than the size (d1) of the through hole when viewed in a cross section in a plane including the duct central axis as shown in FIG. If the concave portion 4 is formed and the through hole 3 is provided in the upstream portion of the concave portion, the airflow resistance reducing effect of the present invention can be obtained.

Below, in order to acquire such a ventilation resistance reduction effect, the shape of a recessed part and a through-hole especially preferable is demonstrated.

The recessed portion 4 is formed such that the length L of the recessed portion 4 is 1.5 times or more, more preferably 2 times or more, with respect to the size of the through hole in the cross section in the plane including the duct central axis. It is preferable.

The recess depth H and the width W of the recess 4 are set to a width and depth sufficient to provide the through hole 3 in the upstream portion of the recess. On the other hand, if the depth and width of the recessed portion is extremely larger than the size of the through hole 3, the layout space around the duct is used unnecessarily, and the effect of improving the ventilation resistance is reduced. The penetration depth and width are preferably the same or slightly larger than the representative dimension of the through hole and not more than three times the representative dimension of the through hole.

As shown in FIG. 3B, the shape of the downstream portion 42 of the recessed portion 4 is such that the opening direction of the through hole (direction of the central axis m) and the inner peripheral surface of the recessed portion downstream side portion are substantially parallel. If it is provided, the flow sucked from the through hole 3 flows along the inner peripheral surface of the recessed portion without peeling off, which is particularly effective for reducing the airflow resistance. Even when the opening direction of the through hole (in the direction of the central axis m) and the inner peripheral surface of the recessed portion downstream side portion make an angle with each other, the angle should be 45 degrees or less, more preferably 30 degrees or less. It is preferable.

In the downstream portion 42 of the recessed portion 4, the gradient of the recessed portion downstream portion with respect to the duct wall basic shape surface is 1/1 so that the recessed amount of the recessed portion gradually decreases toward the downstream side. It is preferable to make it less than or equal to ½, so that the downstream portion 42 of the recessed portion is directed to the downstream side so that the recessed amount of the recessed portion gradually decreases. By doing so, the area of the stagnation and vortex generated downstream of the through hole can be reduced, and the ventilation resistance can be effectively reduced.

In addition, it is preferable that the boundary portion between the downstream portion 42 of the recessed portion and the basic shape 23 of the duct is also connected to form a smoothly continuous curved surface by adding R or the like. Further, when viewed in a cross section along the main flow, when the cross section of the downstream portion of the recess is convex toward the inside of the duct (for example, as in the second embodiment shown in FIG. 9), The inner peripheral surface of the downstream portion of the recessed portion can be smoothly connected to the basic shape 23 of the duct, which is particularly effective for reducing the ventilation resistance.

In addition, the position where the through hole 3 is provided in the upstream portion of the recessed portion is set so that the through hole 3 is as close as possible to the deepest portion of the recessed portion (the portion where the recessed depth is maximum). It is preferable in terms of reduction. By doing so, the air flow flowing from the through hole flows along the inner peripheral surface of the recessed portion, and the separation of the air flow flowing from the through hole is prevented, and the stagnation and vortex generated downstream of the through hole are prevented. It is possible to reduce the area and effectively reduce the ventilation resistance.

Moreover, it is preferable to provide the through hole 3 in the recessed portion 4 so as to be as upstream as possible in the duct flow direction. The closer the through hole is to the upstream side, the more effectively the internal space of the recessed portion on the downstream side of the through hole becomes. The airflow resistance can be effectively suppressed by working and deflecting the flow sucked from the through hole 3.

The direction of opening of the through hole 3, that is, the direction of the central axis m may be a direction parallel to the radial direction of the duct as in the embodiment described later, but the flow from the through hole 3 is as much as possible with the main flow in the duct. Inclined toward the upstream side of the flow with respect to the duct radial direction of the ventilation duct 1 so as to be close to parallel, that is, in the direction toward the upstream side of the duct flow as the through-hole central axis m goes to the outside of the duct. It is preferable to be provided. In particular, the inclination of the through hole is determined so that the angle γ between the through hole central axis m and the duct central axis (or the duct basic shape surface) is 0 degrees (parallel) to 80 degrees, more preferably 0 degrees to 60 degrees. It is preferable to do.

Therefore, in the upstream portion 41 of the recessed portion 4, the angle α at which the recessed portion 4 rises from the basic shape surface 23 of the duct body is preferably 10 ° to 90 ° at the boundary α between the basic shape surface and the recessed portion. Is preferably 30 to 90 degrees. By providing the upstream portion 41 so as to rise from the duct basic shape surface 23, the through hole 3 opened in the recessed portion upstream portion 41 extends in a direction along the flow direction of the main flow flowing through the inside of the ventilation duct 1. As a result of being opened, the flow flowing from the through hole becomes easy to flow in the direction along the main flow, which is advantageous in reducing the ventilation resistance.

The result of verifying the ventilation resistance suppressing effect of the present invention by numerical fluid simulation will be described. The numerical fluid simulation was performed for a duct shape similar to the intake duct 1 shown in FIG. The specific dimensions of the intake duct are as follows: the overall length of the duct is 450 mm, the cross-sectional shape of the duct main body is an oval shape with a major axis of 40 mm and a minor axis of 26 mm (equivalent to a circular cross section with a diameter of 36 mm). It is the intake duct expanded in the shape of an ellipse. The overall shape of the intake duct is a straight tubular duct. A recessed portion is provided at a position 200 mm from the downstream end portion of the duct, and a through hole 3 having a diameter of 10 mm is provided in the upstream portion of the recessed portion. The specific dimensions of the recessed portion shape are a recessed depth of 12.6 mm, an inner surface width of 12 mm, and a length of about 46 mm. The opening direction of the through hole is a direction that forms an angle of 20 degrees with the duct center axis. The shape of the downstream portion of the entrance is formed in a semi-cylindrical shape substantially parallel to the through-hole central axis. (Hereinafter referred to as “Example 1 with an angle of 20 degrees”)

Similarly, the simulation was performed for the intake duct in which the shape of the recessed portion was similarly determined by setting the angle γ formed by the opening direction of the through hole and the central axis of the duct to 30 degrees, 40 degrees,. Called Example 1 in Angle "). In Example 1 in which these angles are changed, the shape of the downstream portion of the recessed portion is a semi-cylindrical surface substantially parallel to the central axis m of the through hole, and the length of the recessed portion is an angle in the opening direction of the through hole. Has changed in response to.

In addition, although the basic shape of the duct and the shape of the through hole are the same, an intake duct in which a through hole is directly opened on the surface of the basic shape of the duct without a recessed portion and the through hole is opened in the radial direction of the duct. A comparative shape was obtained (Comparative Example 1).
The basic shape of the duct was the same, and an intake duct without a through hole was used as a comparative shape without a through hole (Comparative Example 2). For these comparative examples, the numerical fluid simulation was performed in the same manner to determine the ventilation resistance.

For the intake ducts of the present embodiment and comparative example of the above shape, a numerical fluid simulation was performed so that the amount of air sucked from the downstream end portion of the duct was 48 liters / second, and the duct wall surface at the downstream end portion of the duct was used. The static pressure (differential pressure with respect to atmospheric pressure) was obtained and the ventilation resistance was evaluated. According to the analysis results, in Example 1 with an angle of 20 degrees, the airflow resistance was 1824.5 Pa, and in the intake duct of Comparative Example 1 in which the through hole was provided without providing the recessed portion, the airflow resistance was 1985.6 Pa. The ventilation resistance was reduced by 8.1%. Further, the ventilation resistance in Comparative Example 2 without a through hole is 1838.7 Pa, and Example 1 with an angle of 20 degrees can reduce the ventilation resistance as compared with the intake duct without the through hole (Comparative Example 2). FIG. 8 shows a simulation result including Example 1 in each angle where the angle γ is changed to 30 degrees, 40 degrees,..., 80 degrees. In each example, a normal through hole is provided in the ventilation duct. Compared with Comparative Example 1, the ventilation resistance can be reduced. When the angle γ between the through hole center line and the duct center line is 60 degrees or less, the airflow resistance is reduced as compared with the intake duct comparative example 2 without the through hole, and the intake duct without the through hole (comparison) Compared to Example 2), it can be seen that the intake duct is excellent in both acoustic characteristics and ventilation characteristics.

FIGS. 6 and 7 show visualization of the flow in the duct calculated by the numerical fluid simulation. FIG. 6 and FIG. 7 show streamlines of the flow from the through holes in the examples and comparative examples of the present invention, and both show the streamlines seen in a cross section along the duct central axis. FIG. 6 shows the flow lines of the flow from the through hole in Comparative Example 1, and the airflow sucked from the through hole peels off from the duct wall and enters the inside of the duct to inhibit the flow through the inside of the duct. The state of doing is shown. FIG. 7 shows streamlines from the through hole in Example 1 at an angle of 40 degrees. The air flow sucked from the through hole flows along the inner peripheral surface of the downstream portion of the recessed portion, and the flow separation occurs. It is shown that the main flow that is suppressed and smoothly merges with the main flow flowing through the inside of the duct is not narrowed.

The fine arrows in the figure indicate the direction of the velocity component in the main cross section of the velocity vector of the flow at each point, and the flow velocity decreases as the color becomes lighter, as in the flow velocity scale shown on the right side of the figure. It is high. That is, in Comparative Example 1 in FIG. 6, a stagnation region with a low flow velocity is observed in the downstream portion of the through hole. On the other hand, in Example 1 of the present invention shown in FIG. 7, it can be confirmed that a stagnation region does not occur even in the downstream portion of the through hole and the flow is smooth.

The present invention is not limited to the above embodiment, and can be implemented with various modifications. Other embodiments of the present invention will be described below. However, in the following description, portions different from the above embodiment will be mainly described, and the same portions will be denoted by the same reference numerals and description thereof will be omitted. To do.

FIG. 9 shows another embodiment of the through hole and the recessed portion. In the present embodiment, the through hole 5 is an oval hole having a long diameter in the circumferential direction of the duct, and the recessed portion 6 is formed by replacing the recessed member 61 formed separately from the duct body 2 with the duct body 2. It is formed by bonding and integration so as to cover the opening hole provided in the duct wall. A step portion corresponding to the thickness of the duct wall is provided at the peripheral edge portion of the recessed member 61 so that the inner peripheral surface of the recessed portion 6 and the duct basic shape surface 23 are smoothly connected. . Further, the length along the flow direction of the recessed portion 6 is made larger than the size of the surface including the duct center line of the through hole 5 (that is, the length corresponding to the minor axis of the ellipse). About 3 times.

The shape of the upstream portion of the recessed portion 6 is slightly wider than the through hole 5 and rises at an angle of about 60 degrees with respect to the basic shape surface of the duct wall, and the downstream portion of the recessed portion 6 has a major recessed depth. When viewed in a cross section along the flow direction (FIG. 9B), the depth of the recessed portion gradually decreases toward the downstream, and the shape gradually approaches the duct basic shape surface. That is, the downstream portion of the recessed portion 6 has a shape that is convex toward the inside of the duct as seen in a cross section along the main flow direction.

Also in the present embodiment, the flow from the through hole is guided along the inner peripheral surface of the recessed portion, and the air flow inside the duct is disturbed by the flow flowing from the through hole 5 to prevent or suppress the airflow resistance. Is done. In particular, in the present embodiment, the downstream portion of the recessed portion 6 has a convex shape toward the inside of the duct. Therefore, the downstream portion of the recessed portion is smoothly connected to the basic shape surface of the ventilation duct, and the ventilation resistance The suppression effect is high.

FIG. 10 shows another embodiment regarding the shape of the recessed portion and the shape of the through hole. FIG. 10 shows only a cross section along the duct center line near the recessed portion. The shape of the downstream portion of the recessed portion 7 is not limited to a shape in which the recessed amount gradually decreases toward the downstream side as in the embodiment shown in FIG. 3 or FIG. As shown in b), the amount of recess in the downstream portion of the recess 7 is substantially constant over the main portion of the recess, and the recess suddenly decreases in the most downstream portion of the recess. Also good. Even in such an embodiment, the internal space of the recessed portion 7 exists on the downstream side of the through hole 5, and the flow of air sucked from the through hole 5 is deflected to the downstream side of the ventilation duct, The ventilation resistance of the duct is reduced.

In the present embodiment, the through hole 5 may be provided inclined toward the upstream side of the duct as shown in FIG. 10A, or in the radial direction of the duct as shown in FIG. It may be provided substantially in parallel. In addition, the reduction effect of ventilation resistance is higher when the through hole 5 is inclined toward the upstream side of the duct.

A numerical fluid simulation corresponding to the embodiment of FIG. 10 was performed. For the duct basic shape similar to that of the first embodiment already described, a recessed portion (width 12 mm, length 28.6 mm, recessed depth 7 mm) as shown in FIG. 10 is provided. 10), a through hole having a diameter of 10 mm is provided in a direction in which the angle γ with respect to the duct center line is 70 degrees (hereinafter referred to as “Example 2 with an angle of 70 degrees”), and as shown in FIG. As a result of calculation for an example in which a through hole is provided in parallel with the radial direction of the duct (hereinafter referred to as “execution separation 2 at an angle of 90 degrees”), the ventilation resistance is 1870.2 Pa for Example 2 at an angle of 70 degrees. As for Example 2 with an angle of 90 degrees, a result that the ventilation resistance was 1885.3 Pa was obtained. This result is shown in the graph of FIG. 8 together with the result of Example 1. In any of the examples, the ventilation resistance is reduced as compared with Comparative Example 1 in which a through hole is simply provided. The flow lines of the flow passing through the through holes obtained as a result of the simulation are shown in FIG. 12 for Example 2 at an angle of 70 degrees and in FIG. 13 for Example 2 at an angle of 90 degrees.

As described above, the present invention can be implemented even if the shape of the through hole or the shape of the recessed portion is changed, and for the purpose of reducing the manufacturing efficiency, the ventilation resistance, or for other purposes. The shape of the through hole and the recessed portion can be changed.

In the description of the above embodiment, the duct body 2 has an elliptical cross-sectional shape, and the intake duct 1 has a substantially linear shape. However, the present invention is not limited thereto, and the duct cross-sectional shape. The shape can be a circle, an ellipse, an ellipse, a rectangle, a polygon, or the like. Further, the duct may be bent in the length direction. Further, the ventilation duct may be a tube that is expanded or contracted in a tapered shape.

In FIG. 11, the perspective view of other embodiment of the ventilation duct of this invention is shown. In the present embodiment, the recessed portions 4 and 4 having the same shape as that of the first embodiment shown in FIG. 3 and the through holes 3 and 3 provided in the upstream portion of each recessed portion are arranged in the circumferential direction of the duct. The recessed portions 4 and 4 are continuously provided at the same position so as to be aligned along the flow direction of the duct. Also in the present embodiment, as already described, it is possible to effectively prevent the flow sucked from the through hole 3 from compressing the main flow flowing inside the duct and increasing the airflow resistance. When a plurality of through holes and recessed portions are provided, if they are provided at positions overlapping in the circumferential direction of the duct as in this embodiment, the flow sucked from the upstream through hole is sucked from the downstream through hole. It is particularly effective to effectively merge the flows and reduce the duct resistance.

In the description of the above embodiment, the through hole 3 and the through hole 5 are described as being through holes opened to the outside of the air intake duct. However, for the purpose of further improving the duct silencing performance and other purposes. It is also possible to carry out by modifying the structure outside the through hole.
In the practice of the present invention, the purpose of providing the through hole in the duct wall is not limited to the purpose of improving the acoustic characteristics of the duct such as a so-called tuning hole, and can be various purposes.

In the description of the above embodiment, the embodiment in which the present invention is applied to the intake duct used in the intake system of the internal combustion engine for automobiles has been described. However, as is clear from the above description, the implementation of the present invention has been described. However, the present invention is not limited to this, and can be implemented in a ventilation duct generally used in a duct system used in a form of sucking air by the duct system. That is, a duct for sucking air supplied to a household fuel cell, a ventilation duct for guiding cooling air for cooling a secondary battery of an electric vehicle, and an air conditioner for guiding air sucked by an air conditioner such as an air conditioner. The ventilation duct of the present invention can be used for a duct or the like.

The ventilation duct of the present invention can be used for an intake system of an internal combustion engine or a fuel cell, a duct system such as a battery cooling system or an air conditioning system. The ventilation duct of the present invention can suppress an increase in ventilation resistance when a through hole is provided in the duct wall, and has high industrial utility value.

DESCRIPTION OF SYMBOLS 1 Intake (air ventilation) duct 2 Duct main body 3 Through-hole 4 Recessed part 41 Recessed part upstream part 42 Recessed part downstream part 5 Through-holes 6 and 7 Recessed part

Claims (4)

A ventilation duct for configuring a ventilation path for sucking air,
The ventilation duct is provided with a recessed portion where the inner peripheral surface of the duct wall is recessed toward the outside of the duct rather than the basic shape of the duct wall,
A through hole is provided in the upstream portion of the recess so that air can flow from the outside of the duct to the inside of the duct through the duct wall,
A ventilation duct characterized in that the length of the recessed portion in the direction along the flow in the duct is made longer than the size of the through hole in a cross section on the plane including the central axis of the ventilation duct. While the through hole is provided to be inclined upstream with respect to the radial direction of the duct,
In the cross section in the plane including the central axis of the ventilation duct, the downstream portion of the recessed portion is made substantially parallel to the direction of the through hole, and the recessed portion is formed so that the recessed amount decreases toward the downstream side. The ventilation duct according to claim 1, characterized in that: 3. The cross section in a plane including the central axis of the ventilation duct is formed so that the downstream portion of the recessed portion is convex toward the inside of the duct, and is smoothly connected to the basic shape of the ventilation duct. Ventilation duct as described in. The ventilation duct according to claim 2, wherein a through-hole is provided in a direction in which an angle with the duct central axis is 0 degrees to 60 degrees.