JP3341653B2 - Abnormal noise reduction structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for reducing abnormal noise in an intake air, for example, a structure for reducing abnormal noise generated from an integrated structure of an intake manifold and a surge tank of an automobile (hereinafter referred to as an intake manifold surge tank).

[0002]

2. Description of the Related Art When a throttle valve is suddenly opened in an automobile, a high-frequency noise called "shu" is generated from a portion of an intake manifold surge tank. This abnormal noise occurs regardless of whether the intake manifold surge tank is made of resin or aluminum. Especially, a loud noise is generated in the intake manifold surge tank made of resin. Conventionally, a structure in which a wire mesh is disposed between a throttle valve and an engine combustion chamber has been proposed as a countermeasure against backfire from the engine, although it is not a countermeasure against abnormal noise (for example, Japanese Utility Model Laid-Open No.
-107838).

[0003]

In recent years, the intake manifold surge tank has tended to be made of resin in order to reduce the weight and thereby improve fuel efficiency. In particular, the noise of the intake manifold surge tank made of resin has become a problem. Have been doing. A structure in which a wire mesh is disposed between the throttle valve and the engine combustion chamber as a countermeasure against backfire is also effective in reducing abnormal noise, but has another problem of increasing passage resistance. An object of the present invention is to provide an abnormal noise reduction structure capable of reducing abnormal noise from an intake manifold surge tank. However, it is assumed that the ventilation resistance is not increased unacceptably.

[0004]

The present invention to achieve the above object is as follows. (1) When a net is arranged downstream and near the throttle valve and the passage wall immediately downstream of the net is made of resin, the net portion of the net to which the intake air passing through the side on which the throttle valve falls down on the upstream side hits. The direction of the intake noise is directed toward the direction in which the intake air passing through the net portion is separated from the inner wall surface of the passage wall immediately downstream of the net. (2) When a net is arranged downstream and near the throttle valve, and the passage wall immediately downstream of the net is made of metal, the net portion of the net to which the intake air passing through the side on which the throttle valve falls down on the upstream side is applied. Is directed toward the inner wall surface of the passage wall immediately downstream of the net. (3) The intake noise reduction structure according to (1) or (2), wherein the net is disposed on a half cross section of the cross section of the passage on the side where the throttle valve falls to the upstream side. (4) The net includes a cylindrical portion having an axis parallel to the passage axis and a plurality of circumferentially divided flange portions extending radially outward from an upstream end of the cylindrical portion, and the direction is set to the direction. The abnormal noise reduction structure for intake air according to (1) or (2), wherein an eye provided with is formed on the flange portion. (5) a cylindrical portion having the axis parallel to the passage axis, a circumferentially continuous flange extending radially outward from an upstream end of the cylindrical portion, and a throttle extending upstream from the cylindrical portion; (1) The intake noise reduction structure according to (1) or (2), wherein the valve comprises a semi-cylindrical portion formed on a half circumference on the side where the valve falls to the upstream side, and the eye having the orientation is formed on the flange portion. . (6) Intake noise reduction according to (1) or (2), wherein the net is arranged in two outer regions when the passage cross section is divided into three regions by two straight lines parallel to the rotation axis of the throttle valve. Construction. (7) The intake abnormal noise reduction structure according to (1) or (2), wherein the net is arranged in an outer peripheral side region when a cross section of the passage is divided into two regions by a circle having a smaller diameter than the passage diameter. (8) The intake abnormal noise reduction structure according to (1) or (2), wherein the net is disposed on a half cross section of the passage cross section opposite to the side on which the throttle valve falls to the upstream side. (9) The air intake system according to (1) or (2), wherein the net is arranged on the entire cross-section of the passage and the size of the eyes is increased so as to suppress an increase in passage resistance. Sound reduction structure.

[0005] Analysis of the flow of intake air when the throttle valve was opened in a state where a butterfly type throttle valve was disposed in a pipe having a circular cross section and no net was disposed, revealed the following. The flow passing through the side where the throttle valve falls to the upstream side has a greater influence on the turbulent flow formation than the flow passing through the side where the throttle valve falls to the downstream side. The flow passing through the side where the throttle valve falls to the upstream side concentrates toward the center in plan view, while the flow passing through the side where the throttle valve falls to the downstream side spreads out in plan view. The flow passing through the side where the throttle valve falls to the upstream side causes first turbulence when passing through the gap between the throttle valve and the pipe wall. The second flow collides with the flow, and then flows obliquely downward and collides with the flow that has passed the side on which the throttle valve falls to the downstream side, thereby generating a third turbulence. In the flow disturbance generating section, high-frequency pressure fluctuation occurs, which vibrates the passage wall and is radiated as abnormal noise.

In the intake noise reduction structure of (1) to (9), a net is disposed downstream and near the throttle valve to lower the level of the first turbulence and to reduce the flow concentrated toward the center. The second and third disturbances are eliminated by making it less likely to occur. This reduces abnormal noise generated in the intake manifold surge tank when the throttle valve is opened. In the above (1), when the passage wall immediately downstream of the net is made of resin, the direction of the eye of the net portion hit by the air passing through the side of the net where the throttle valve falls to the upstream side is changed to the air passing through the net portion. The direction away from the inner wall of the passage wall just downstream of the net,
After the first turbulence has passed through the net, the first turbulence is directed to the vertical center of the passage, does not follow the passage wall surface, and makes it difficult to vibrate the passage wall downstream of the net. As a result, even with a resin wall having a lower rigidity than a metal, the radiation noise is reduced by about 3 dB. In the above (2), when the passage wall immediately downstream of the net is made of metal, the direction of the eye of the net portion to which the air passing through the side of the net passing through the side where the throttle valve falls down is changed to the direction of the air passing through the net portion. Is directed toward the passage wall immediately downstream of the net, so that after the first turbulence has passed through the net, the first turbulence hits the passage wall surface and is attenuated, thereby weakening the second and third turbulence. Since the metal passage wall has high rigidity, it does not easily vibrate even if the first turbulent flow is applied after passing through the net. Since the effect of weakening the second and third disturbances and reducing the generation of abnormal noise is greater than the effect of increasing the abnormal noise by applying the flow with the first disturbance dropped after passing through the net, Abnormal noise is reduced.

The above (3) to (9) show examples of the arrangement of nets. In the above (3) to (8), since the net is provided only in a part of the passage cross section, the resistance of the passage does not significantly increase, and both the suppression of the increase in the passage resistance and the suppression of the abnormal noise are satisfied. . In the above (9), the net is provided on the entire cross section of the passage, but since the size of the passage is not so large as to significantly increase the resistance of the passage, both the suppression of the increase in the passage resistance and the suppression of the abnormal noise are satisfied. Is done.

[0008]

FIG. 1 shows a first embodiment of the present invention, FIG. 2 shows a second embodiment of the present invention, and FIG.
FIG. 4 shows a third embodiment of the present invention, FIG. 4 shows a fourth embodiment of the present invention, FIG. 5 shows a fifth embodiment of the present invention, and FIG. FIG. 7 shows a sixth embodiment of the present invention, FIG. 8 shows an eighth embodiment of the present invention, and FIG. 9 shows a ninth embodiment of the present invention. ing. In the drawings, structural parts common to all embodiments of the present invention are denoted by the same reference numerals throughout all embodiments of the present invention.

A structure common to all embodiments of the present invention will be described with reference to FIGS. The noise reduction structure according to the embodiment of the present invention comprises a throttle valve 2 disposed in an intake passage of an automobile engine, an intake manifold surge tank 3 downstream of the throttle valve 2, and a net 1 disposed immediately downstream of the throttle valve 2. The intake air flows through the gap between the throttle valve 2 and the passage wall 8 to the intake manifold surge tank 3, and further flows into the engine cylinder.
The throttle valve 2 is arranged in a throttle body 4 usually made of metal. The throttle valve 2 is composed of a butterfly type valve, and is turned around a rotation axis to open and close a passage. When the throttle valve 2 is opened, one side (upper side in the illustrated example) of the rotation axis of the throttle valve 2 falls toward the upstream side, and the other side (lower side in the illustrated example) falls toward the downstream side.

[0010] The intake manifold surge tank 3 comprises:
An intake manifold 5 and a surge tank 6 are provided. In the example of FIG. 1, the intake manifold surge tank 3 is made of resin, and is connected to the throttle body 4 with the net 1 interposed therebetween. When the intake manifold surge tank 3 is made of resin, the intake manifold section 5 and the surge tank 6 are integrally formed. However, intake manifold surge tank 3 may be made of metal (for example, aluminum).

As shown in FIG. 2, a metal spacer 7 may be interposed between the intake manifold surge tank 3 made of resin or metal and the throttle body 4 made of metal. In this case, the net 1 is sandwiched and arranged between the throttle body 4 and the spacer 7.

In both cases of FIGS. 1 and 2, the net 1
At least, the throttle valve 2 is disposed at a position where the intake air flowing through the gap between the passage wall 8 and the portion that falls to the upstream side when the valve is opened hits.

The operation of the above structure will be described. As a result of flow analysis, it was found that the flow A flowing through the gap between the passage wall 8 and the portion of the throttle valve 2 that falls on the upstream side when the valve was opened had a significant effect on the generation of abnormal noise. When the net 1 is not provided (conventionally), the flow A flowing through the gap between the passage wall 8 and the portion of the throttle valve 2 that falls to the upstream side when the valve is opened has the first turbulence when passing through the throttle valve portion. It is formed and brought to the center side of the pipe in plan view, the left and right flows are concentrated to form a second turbulence there, heading obliquely downward therefrom, and falling to the downstream side of the throttle valve 2 when the valve is opened. Colliding with the flow B flowing through the gap between the
To form disturbances. The turbulence of the flow causes a high-frequency pressure fluctuation, which causes the passage wall 8 to vibrate, generating abnormal noise. Particularly when the passage wall 8 is made of resin, the noise is large.

In the present invention, since the net 1 is provided, the first
Of the disturbance, the level of the disturbance in the downstream portion of the net 1 is reduced. Although the turbulence of the portion upstream of the net 1 remains as it is, the passage wall of the portion upstream of the net 1 is the throttle body itself and is made of metal, so that it does not easily vibrate and does not pose a problem in generating abnormal noise. In addition, the second and third disturbances are reduced or eliminated by reducing or eliminating the first disturbance. Thus, by providing the net 1 at a portion of the throttle valve 2 where the flow A flowing through the gap between the portion that falls to the upstream side when the valve is opened and the passage wall 8 hits, the first, second, and second 3, the vibration of the passage wall and the generation of abnormal noise can be suppressed.

Next, the structure and operation unique to each embodiment of the present invention will be described. In the first embodiment of the present invention, as shown in FIG. 1, the net 1 is arranged downstream and near the throttle valve 2, and the passage wall 8 immediately downstream of the net 1 is made of resin. In this case, the throttle valve 2 of the net 1
The direction of the eyes of the net portion hit by the intake air A passing through the side that falls to the upstream side when opened is the direction in which the intake air passing through the net portion is directed away from the inner wall surface 8a of the passage wall immediately downstream of the net 1. Have been. The net 1 having the eyes of the net 1 oriented, for example, pulls a plate (for example, a metal plate) having a number of parallel slits formed in a direction perpendicular to the slits to open the slits (at this time, automatically (The opening of the slit is twisted to give direction to the eyes). This kind of net 1 is called expanded metal.

With respect to the operation of the first embodiment of the present invention, the first turbulence is reduced when the intake air that passes through the side of the net 1 that falls to the upstream side when the throttle valve 2 is opened hits the net 1, but the first turbulence is reduced. Because it does not disappear, net 1
The flow after passing through still has a first turbulence of reduced level. When the flow having the first turbulence after passing through the net flows along the resin-made passage wall 8 having relatively low rigidity, the passage wall 8 is vibrated, which causes abnormal noise. In the first embodiment, since the flow is directed in a direction away from the inner wall surface 8a of the passage wall depending on the direction of the eyes of the net 1, it is difficult to vibrate the passage wall 8, and it is difficult to generate abnormal noise. As a result of the test, it was found that the noise was about 3% when the net 1 with the eyes was provided than when the net without the eyes was provided.
Decibel fell.

In the second embodiment of the present invention, as shown in FIG. 2, a net 1 is arranged downstream and near the throttle valve 2, and a passage wall 8 immediately downstream of the net 1 is made of metal (for example, aluminum). Is the case. In this case, the direction of the eyes of the net portion of the net 1 to which the intake air A that has passed on the side where the throttle valve 2 falls to the upstream side when the throttle valve 2 is opened hits the air passing through the net portion, The direction is directed toward the inner wall surface 8a.

With respect to the operation of the second embodiment of the present invention, the first turbulence is reduced when the intake air passing through the side of the net 1 that falls on the upstream side when the throttle valve 2 is opened hits the net 1, but the first turbulence is reduced. Because it does not disappear, net 1
The flow after passing through still has a first turbulence of reduced level. Even if the first turbulent flow after passing through the net flows along the passage wall 8, in the case of the metal passage wall 8 having high rigidity, the passage wall 8 is hard to vibrate, so that abnormal noise is hardly generated. Rather, by flowing along the passage wall 8, the first turbulence is attenuated, so that the second and third turbulences are reduced and the effect of reducing abnormal noise is greater. Therefore, in the second embodiment of the present invention,
According to the direction of the eyes of the net 1, the flow passing through the net 1 is directed to the inner wall surface 8a of the passage wall to attenuate the first turbulence,
The noise was reduced.

In the third embodiment of the present invention, as shown in FIG. 3, in the intake passage of FIG. 1 or FIG.
In the cross section of the passage, the throttle valve 2 is provided on a half section on the side that falls to the upstream side when opened. The direction of the eyes of the net 1 described in the first and second embodiments is set in the net 1.

Regarding the operation of the third embodiment of the present invention, since the net 1 is provided only in a part of the passage cross section, the increase in flow resistance due to the provision of the net 1 is relatively slight. . Further, since the net 1 is provided on the side that falls to the upstream side when the throttle valve 2 is opened, the effect of preventing abnormal noise is large. Therefore, both suppression of increase in flow resistance and suppression of abnormal noise are satisfied.

In the fourth embodiment of the present invention, as shown in FIG. 4, in the intake passage of FIG. 1 or FIG.
A cylindrical portion 1a having an axis parallel to the passage axis, and a cylindrical portion 1a
And a plurality of circumferentially divided flange portions 1b extending radially outward from an upstream end of the flange portion 1b. The direction of the eyes of the net 1 described in the first and second embodiments is set to the flange portion 1b. Desirably, of the flange portion 1b, the side of the flange portion 1b that falls on the upstream side when the throttle valve 2 is opened. It is set in the part in the half section.

Regarding the operation of the fourth embodiment of the present invention, since the net 1 is provided only in a part of the passage cross section, the increase in flow resistance due to the provision of the net 1 is relatively slight. . Further, since the net portion directed toward the eyes is provided on at least the side of the flange portion 1b that falls to the upstream side when the throttle valve 2 is opened,
Great noise prevention effect. Also, since there is a cylindrical portion 1a,
The flow passing through the net flange portion 1b passes through the cylindrical portion 1a, the second and third disturbances are suppressed, and the noise is further suppressed. Therefore, both suppression of increase in flow resistance and suppression of abnormal noise are satisfied.

In the fifth embodiment of the present invention, as shown in FIG. 5, in the intake passage of FIG. 1 or FIG.
A cylindrical portion 1c having an axis parallel to the passage axis, and a cylindrical portion 1c
A circumferentially continuous flange portion 1d extending radially outward from the upstream end of the throttle valve, a semi-cylindrical portion 1e formed on a half circumference extending from the cylindrical portion 1c to the upstream side and on which the throttle valve 2 falls down on the upstream side; Consists of The direction of the eyes of the net 1 described in the first and second embodiments is set to the flange portion 1d. Desirably, of the flange portion 1d, the side of the flange portion 1d that falls on the upstream side when the throttle valve 2 is opened. It is set in the part in the half section.

Regarding the operation of the fifth embodiment of the present invention, since the net 1 is provided only in a part of the passage cross section, the increase in flow resistance due to the provision of the net 1 is relatively small. . Further, since the net portion directed toward the eyes is provided on at least the side of the flange portion 1d which falls to the upstream side when the throttle valve 2 is opened,
Great noise prevention effect. Also, since there is a cylindrical portion 1c,
The flow passing through the net flange portion 1b passes through the cylindrical portion 1a, the second and third disturbances are suppressed, and the noise is further suppressed. Further, the provision of the semi-cylindrical portion 1e further reduces the first disturbance. Therefore, both suppression of increase in flow resistance and suppression of abnormal noise are satisfied.

In the sixth embodiment of the present invention, as shown in FIG. 6, in the intake passage of FIG. 1 or FIG.
The passage is disposed in two outer regions when the cross section of the passage is divided into three regions by two straight lines parallel to the rotation axis of the throttle valve. The direction of the eyes of the net 1 described in the first and second embodiments is set in the net 1 in the region where the throttle valve 2 falls to the upstream side when the throttle valve 2 is opened.

In the operation of the sixth embodiment of the present invention, since the net 1 is provided only in a part of the passage cross section, the increase in flow resistance due to the provision of the net 1 is relatively slight. . In addition, since the direction of the eyes of the net 1 is set to the net 1 that falls on the upstream side when the throttle valve 2 is opened, the effect of preventing abnormal noise is large. Therefore,
Both suppression of increase in flow resistance and suppression of abnormal noise are satisfied.

In the seventh embodiment of the present invention, as shown in FIG. 7, in the intake passage of FIG. 1 or FIG.
The passage is arranged in an outer peripheral region when the cross section of the passage is divided into two regions by a circle having a smaller diameter than the passage diameter. The direction of the eyes of the net 1 described in the first and second embodiments is set in at least a portion of the net 1 on the side where the throttle valve 2 falls to the upstream side when the throttle valve 2 is opened.

Regarding the operation of the seventh embodiment of the present invention, since the net 1 is provided only in part of the passage cross section, the increase in flow resistance due to the provision of the net 1 is relatively slight. . Further, since the direction of the eyes of the net 1 is set at least on the side that falls on the upstream side when the throttle valve 2 is opened, the effect of preventing abnormal noise is large. Therefore, both suppression of increase in flow resistance and suppression of abnormal noise are satisfied.

In the eighth embodiment of the present invention, as shown in FIG. 8, in the intake passage of FIG. 1 or FIG.
The throttle valve is disposed in a half cross section of the passage cross section opposite to the side on which the throttle valve falls to the upstream side. Net 1
The direction of the eyes of the net 1 described in the first and second embodiments, particularly the second embodiment, is set.

Regarding the operation of the eighth embodiment of the present invention, since the net 1 is provided only in a part of the passage cross section, the increase in flow resistance due to the provision of the net 1 is relatively slight. . Further, since the direction of the eyes is set in the net 1, the effect of preventing abnormal noise is increased. In particular, when the passage wall in FIG. 2 is made of metal, the net 1 is provided immediately before the portion where the third disturbance occurs, thereby suppressing the third disturbance and attenuating the flow toward the passage wall. By doing so, the abnormal noise prevention effect is increased. Therefore, both suppression of increase in flow resistance and suppression of abnormal noise are satisfied.

In the ninth embodiment of the present invention, as shown in FIG. 9, in the intake passage of FIG. 1 or FIG.
It is located in the entire cross section of the passage. Further, the size of the eyes is set large enough to suppress an increase in passage resistance. Further, the direction of the eyes described in the first and second embodiments is set at least in the portion of the net 1 that falls on the upstream side when the throttle valve 2 is opened.

In the operation of the ninth embodiment of the present invention, since the size of the mesh of the net 1 is set so as to suppress the increase in the passage resistance, the increase in the flow resistance due to the provision of the net 1 is relatively small. It is. Further, since the direction of the eyes of the net 1 is set at least on the side of the net 1 that falls on the upstream side when the throttle valve 2 is opened, the noise prevention effect is increased. Therefore, both suppression of increase in flow resistance and suppression of abnormal noise are satisfied.

[0033]

According to the noise reduction structure of the first aspect, when the passage wall immediately downstream of the net is made of resin, the net portion of the net to which the intake air passing through the side on which the throttle valve falls down on the upstream side hits. Is directed in a direction away from the inner wall surface of the passage wall immediately downstream of the net, so that the flow having the first turbulence is in the vertical center of the passage after passing the net. As a result, it is difficult to vibrate the passage wall downstream of the net. Thereby, even with a resin wall having a lower rigidity than a metal, abnormal noise can be reduced. Further, the level of the first turbulence is lowered, and the flow concentrated toward the center is less likely to occur, thereby reducing the second and third turbulences and further reducing abnormal noise. According to the abnormal noise reduction structure of claim 2, when the passage wall immediately downstream of the net is made of metal, the direction of the eye of the net portion to which the intake air that passes through the side of the net that passes through the side where the throttle valve falls down on the upstream side is directed. Since the intake air passing through the net portion was directed to the passage wall immediately downstream of the net, the first
After passing through the net, the disturbance hits the passage wall and is attenuated,
Reduce the second and third disturbances. Since the metal passage wall has high rigidity, it does not easily vibrate even if the first turbulent flow is applied after passing through the net. Since the effect of weakening the second and third disturbances and reducing the generation of abnormal noise is greater than the effect of increasing the abnormal noise by applying the flow with the first disturbance dropped after passing through the net, The abnormal noise can be reduced. According to the abnormal noise reduction structure of the third aspect, since the net is only a part of the cross section of the passage, both the abnormal noise reduction effect and the passage resistance increase suppressing effect of the first or second aspect can be satisfied. According to the abnormal noise reduction structure of the fourth aspect, in addition to the effect equivalent to the effect of the third aspect, the second and third disturbances can be more effectively suppressed because the net has a cylindrical portion, The noise reduction effect can be increased. According to the abnormal noise reduction structure of claim 5, according to claim 4,
In addition to the effect similar to the effect described above, since the net has a semi-cylindrical portion, the first disturbance can be suppressed more effectively, and the noise reduction effect can be increased. According to the noise reducing structure of the sixth aspect, since the net is only a part of the cross section of the passage, both the abnormal noise reducing effect and the passage resistance increase suppressing effect of the first or second aspect can be satisfied. According to the noise reduction structure of the seventh aspect, since the net is only located in a part of the passage cross section, both the noise reduction effect and the passage resistance increase suppression effect of the first or second aspect can be satisfied. According to the noise reduction structure of the eighth aspect, since the net is only located on a part of the passage cross section, both the noise reduction effect and the passage resistance increase suppression effect of the second aspect can be satisfied. According to the noise reducing structure of the ninth aspect, the size of the mesh of the net is set to such an extent that the resistance increase can be suppressed, so that both the abnormal noise reducing effect and the passage resistance increase suppressing effect of the first or second aspect can be satisfied.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an abnormal noise reduction structure according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of an abnormal noise reduction structure according to a second embodiment of the present invention.

FIG. 3 is a schematic front view of a net portion of a noise reduction structure according to a third embodiment of the present invention.

FIG. 4 is a schematic front view of a net portion of a noise reduction structure according to a fourth embodiment of the present invention.

FIG. 5 is a schematic front view of a net portion of an abnormal noise reduction structure according to a fifth embodiment of the present invention.

FIG. 6 is a schematic front view of a net portion of an abnormal noise reduction structure according to a sixth embodiment of the present invention.

FIG. 7 is a schematic front view of a net portion of an abnormal noise reduction structure according to a seventh embodiment of the present invention.

FIG. 8 is a schematic front view of a net portion of an abnormal noise reduction structure according to an eighth embodiment of the present invention.

FIG. 9 is a schematic front view of a net portion of a noise reduction structure according to a ninth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Net 2 Throttle valve 3 Intake manifold surge tank 4 Throttle body 5 Intake manifold part 6 Surge tank 7 Spacer 8 Passage wall

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI F02M 35/10 301L (58) Investigated field (Int.Cl. ⁷ , DB name) F02M 35/10 F02M 35/12 F16L 55 / 02 F02D 9/10

Claims (9)

(57) [Claims] 1. A net portion is disposed downstream of and near a throttle valve, and when a passage wall immediately downstream of the net is made of resin, a net portion of the net to which intake air passing through the side on which the throttle valve falls to the upstream side hits. The abnormal noise reduction structure of claim 1, wherein the direction of the eyes is directed to the direction in which the intake air passing through the net portion is separated from the inner wall surface of the passage wall immediately downstream of the net. 2. A net portion disposed downstream of and adjacent to a throttle valve, wherein a portion of the net to which intake air passes passes through a side on which the throttle valve falls to the upstream side when the passage wall immediately downstream of the net is made of metal. The abnormal noise reduction structure of claim 1, wherein the direction of the eyes is such that the air passing through the net portion is directed toward the inner wall surface of the passage wall immediately downstream of the net. 3. The intake abnormal noise reduction structure according to claim 1, wherein the net is disposed on a half cross section of the passage cross section on the side where the throttle valve falls to the upstream side. 4. The net comprises: a cylindrical portion having an axis parallel to the passage axis; and a plurality of circumferentially divided flange portions extending radially outward from an upstream end of the cylindrical portion;
The intake noise reduction structure according to claim 1 or 2, wherein the oriented eyes are formed on the flange portion. 5. A net having a cylindrical portion having an axis parallel to a passage axis, a circumferentially extending flange extending radially outward from an upstream end of the cylindrical portion, and an upstream from the cylindrical portion. 3. The abnormal noise of the intake air according to claim 1 or 2, wherein the extended throttle valve comprises a semi-cylindrical portion formed on a half circumference on a side which falls on the upstream side, and the eye having the orientation is formed on the flange portion. Reduction structure. 6. The net according to claim 1, wherein the net is disposed in two outer regions when the passage cross section is divided into three regions by two straight lines parallel to the rotation axis of the throttle valve.
Above intake abnormal noise reduction structure. 7. The intake abnormal noise reduction structure according to claim 1, wherein the net is arranged in an outer peripheral side region when a cross section of the passage is divided into two regions by a circle having a smaller diameter than the passage diameter. 8. The intake noise reduction structure according to claim 1, wherein the net is arranged on a half cross section of the cross section of the passage opposite to the side where the throttle valve falls to the upstream side. 9. The net according to claim 1, wherein the net is arranged on the entire cross section of the passage and the size of the eye is increased so as to suppress an increase in the passage resistance. Abnormal intake noise reduction structure.