JP2022161279A - Intake system for internal combustion engine - Google Patents

Abstract

To provide an intake system capable of reducing a difference between an intake amount detected by an air flow meter and an intake amount actually sucked to an internal combustion engine.SOLUTION: An intake system for an internal combustion engine includes an intake passage 13 that supplies intake air to the internal combustion engine and in which an air flow meter detecting a flow rate of the intake air is disposed. An intake adjustment part 29 for adjusting a flow of intake air is disposed at a position on the downstream side in the intake air flowing direction of the air flow meter in the intake passage 13. The intake adjustment part 29 includes an adjustment passage 38 through which intake air passes. A cross sectional area at a downstream end in the intake air flowing direction in the adjustment passage 38 is set smaller than that at an upstream end in the intake air flowing direction in the adjustment passage 38.SELECTED DRAWING: Figure 4

Description

The present invention relates to an intake system for an internal combustion engine having an intake passage in which an airflow meter for detecting the flow rate of intake air is arranged.

In general, an air flow meter for measuring the flow rate of air supplied to an internal combustion engine is arranged in an intake passage that supplies air (intake) to an internal combustion engine such as an automobile in order to determine the amount of fuel injection to the internal combustion engine. ing. However, since the amount of air taken in by the internal combustion engine is not constant, the flow velocity of the air flowing through the intake passage fluctuates, causing a reverse flow of air in the intake passage.

When backflow of air occurs in the intake passage, the backflowing air is also detected by the airflow meter, resulting in a difference between the amount of air detected by the airflow meter and the amount of air actually taken into the internal combustion engine. . For this reason, conventionally, an air flow rate measuring device as disclosed in Patent Document 1, for example, has been proposed. Such an air flow measuring device includes a body having a main air passage through which air supplied to an internal combustion engine flows, a sub air passage formed in the main air passage and through which part of the air flowing in the main air passage flows, a sub air a detection unit that is arranged in the passage and detects the flow rate of air flowing through the secondary air passage.

The secondary air passage has a first passage having an inlet opening surface that opens substantially perpendicular to the air flow of the main air passage, and an outlet opening surface that opens substantially parallel to the air flow of the main air passage. It is configured in an L shape by communicating with the second passage provided. By arranging the detection portion in the first passage, when a backflow of air occurs in the main air passage, the backflow of air is made difficult to be detected by the detection portion.

JP-A-10-9921

By the way, the air flow measuring device as described above has a structure in which the detection unit is simply arranged in the first passage in the L-shaped auxiliary air passage. Therefore, depending on the situation, there is a risk that the backflow of air generated in the main air passage may enter the sub air passage from the outlet opening surface of the second passage to some extent.

Therefore, it is not sufficient to make it difficult for the detection unit to detect the backflow of air generated in the main air passage. That is, when backflow of air occurs in the main air passage, it is difficult for the backflowing air to be detected by the detection unit, thereby reducing the difference between the amount of air detected by the detection unit and the amount of air actually taken in by the internal combustion engine. However, there is still room for improvement.

Means for solving the above problems and their effects will be described below.
An intake device for an internal combustion engine that solves the above problems is an intake device for an internal combustion engine that supplies intake air to the internal combustion engine and includes an intake passage in which an airflow meter for detecting the flow rate of the intake air is disposed, wherein the intake passage An intake air adjusting section for adjusting the flow of the intake air is arranged at a position downstream of the airflow meter in the flow direction of the intake air, and the intake air adjusting section has an adjustment passage through which the intake air passes. The gist is that a cross-sectional area of a downstream end of the adjustment passage in the flow direction of the intake air is smaller than a cross-sectional area of an upstream end of the adjustment passage in the flow direction of the intake air.

According to this configuration, the degree of ease with which intake air flows into the adjustment passage from the downstream side is smaller than the degree of ease with which intake air flows into the adjustment passage from the upstream side. Therefore, when intake air flows backward from the internal combustion engine side toward the airflow meter side in the intake passage, the intake air adjusting section can prevent the reversed intake air from being detected by the airflow meter. Therefore, the difference between the amount of intake air detected by the airflow meter and the amount of intake air actually drawn into the internal combustion engine can be reduced.

1 is a schematic cross-sectional view of an intake device that supplies intake air to an internal combustion engine in a first embodiment; FIG. FIG. 3 is a perspective view showing a state of the intake adjusting portion of the same intake device when viewed from the upstream side; The perspective view which shows the state when the intake air adjustment part of the same air intake device is seen from a downstream. 4-4 line arrow sectional view of FIG. FIG. 5 is an enlarged view enlarging a part of FIG. 4; FIG. 4 is an enlarged perspective view showing a part of the air intake adjustment unit when viewed from the downstream side; The perspective view which shows the state when the intake adjusting part of the intake device in 2nd Embodiment is seen from an upstream. FIG. 8 is an enlarged view enlarging a part of FIG. 7; The perspective view which shows the state when the intake air adjustment part of the same air intake device is seen from a downstream. The enlarged view which expanded a part of FIG. FIG. 7 is a cross-sectional view taken along line 11-11 of FIG. FIG. 12 is an enlarged view enlarging a part of FIG. 11;

(First embodiment)
A first embodiment of an intake device for an internal combustion engine will be described below with reference to the drawings.
As shown in FIG. 1, an intake system 12 of an internal combustion engine 11 of a vehicle includes an intake passage 13 for supplying intake air to the internal combustion engine 11 of, for example, a multi-cylinder. The intake passage 13 is formed by an air cleaner 14, an air cleaner hose 15, a throttle body 16, and an intake manifold 17 which are arranged in order from upstream to downstream in the flow direction of intake air. In the following description, the upstream side and the downstream side of the intake passage 13 in the flow direction of the intake air are simply referred to as the upstream side and the downstream side.

The air cleaner 14 comprises a bottomed box-like case 19 having an upper opening 18, a lidded box-like cap 21 having a lower opening 20, and a filter element 22 provided between these openings 18 and 20. It has A side wall 23 of the case 19 is provided with a cylindrical inlet duct 24 that communicates between the inside and outside of the case 19 and introduces intake air into the case 19 so as to protrude outward.

A side wall 25 of the cap 21 is provided with a cylindrical outlet duct 26 that communicates between the inside and the outside of the cap 21 and guides the intake air toward the internal combustion engine 11 side. The filter element 22 filters the intake air flowing from the case 19 into the cap 21 to remove foreign matter such as dust contained in the intake air.

A mounting hole (not shown) is formed through the outlet duct 26 at an intermediate position. An air flow meter 27 for detecting the flow rate of intake air flowing through the outlet duct 26 from the upstream side to the downstream side is inserted through the mounting hole (not shown) from the outside of the outlet duct 26 and mounted. That is, an air flow meter 27 is arranged in the intake passage 13 to detect the flow rate of the intake air. The airflow meter 27 is electrically connected to the control unit 28 of the vehicle.

The airflow meter 27 is composed of, for example, a thermal flow sensor. This thermal type flow sensor detects the amount of heat carried away by the flow of intake air from a heating resistor being heated, and outputs a higher voltage as the flow rate of intake air increases as the amount of heat carried away increases. An intake adjusting portion 29 that adjusts the flow of intake air in the intake passage 13 is attached to the downstream end of the outlet duct 26 .

That is, at a position downstream of the airflow meter 27 in the intake passage 13 , an intake air adjusting section 29 that adjusts the flow of intake air in the intake passage 13 is arranged. The air intake adjusting portion 29 has a substantially disc shape as a whole and has a size substantially equal to the cross section of the air intake passage 13 in the outlet duct 26 . That is, the outer diameter of the air intake adjusting portion 29 is approximately the same as the inner diameter of the outlet duct 26 .

The air cleaner hose 15 is composed of a flexible bellows tube. The air cleaner hose 15 connects the downstream end of the outlet duct 26 and the upstream end of the throttle body 16 . The throttle body 16 has therein a throttle valve 30 that adjusts the amount of intake air supplied to the internal combustion engine 11 .

The intake manifold 17 has an upstream end connected to a downstream end of the throttle body 16 , and a downstream end branched into a plurality of branches and connected to a plurality of intake ports 31 of the internal combustion engine 11 . The intake manifold 17 has a surge tank 32 , and evenly distributes and supplies the intake air flowing from the upstream side to the plurality of intake ports 31 of the internal combustion engine 11 .

Each intake port 31 is provided with an injector 33 that injects fuel. Each injector 33 is electrically connected to the control unit 28 of the vehicle and controlled by the control unit 28 . The controller 28 causes each injector 33 to inject fuel in an amount corresponding to the flow rate of the intake air detected by the airflow meter 27 .

Next, the configuration of the intake air adjusting section 29 will be described in detail.
As shown in FIGS. 2 and 3 , the air intake adjustment unit 29 includes a first annular plate-shaped frame 34 , a plurality of annular plate-shaped fins 35 arranged inside the first frame 34 , and a center A plurality of strip-shaped second frames 37 extending radially from the portion 36 and connected to the first frame 34 are provided. A plurality (eight in this example) of the second frames 37 are arranged at regular intervals in the circumferential direction and connected to each other at the central portion 36 .

A plurality of (ten in this example) fin portions 35 are arranged at regular intervals in the radial direction between the first frame 34 and the central portion 36 . That is, the outer diameters of the plurality of fin portions 35 gradually increase toward the outer side in the radial direction. Each fin portion 35 penetrates all the second frames 37 in the circumferential direction. A plurality of annularly extending adjustment passages 38 through which intake air passes are formed between the fin portions 35 in the radial direction. That is, the intake air adjusting section 29 has a plurality of adjusting passages 38 through which the intake air passes.

As shown in FIGS. 4 to 6, each fin portion 35 of the intake air adjusting portion 29 is inclined so that the downstream side is closer to the central axis J of the air intake adjusting portion 29 than the upstream side. At the upstream end portion of each fin portion 35, a bent portion 39 is formed by bending the upstream end portion radially outward into a U-shape in a cross-sectional view. In the air intake adjustment portion 29, the adjustment passage 38 is formed between the bent portion 39 of the fin portion 35 and the upstream end portion of another fin portion 35 adjacent to the bent portion 39 of the fin portion 35 on the outer side in the radial direction. It is

The cross-sectional area of the downstream end of each adjustment passage 38 in the intake air flow direction is smaller than the cross-sectional area of the upstream end of each adjustment passage 38 in the intake air flow direction. That is, the cross-sectional area of each adjustment passage 38 gradually decreases from the upstream end to the downstream end. Each adjustment passage 38 extends in a direction that intersects the direction in which the central axis J of the intake adjustment portion 29 extends, which is the direction in which the intake passage 13 extends.

Each adjustment passage 38 extends radially outward from the direction in which the central axis J of the intake adjustment portion 29 extends. The U-shaped surface in cross section inside the bent portion 39 of each fin portion 35 receives the reverse flow of intake air flowing through the intake passage 13 from the downstream side to the upstream side, and directs the reverse flow of intake air from the upstream side to the downstream side. A conversion section 40 is provided to convert the forward flow of intake air.

Next, the operation of the intake air adjusting section 29 during operation of the internal combustion engine 11 will be described.
As shown in FIG. 1, when the internal combustion engine 11 is operated, intake air flows through the intake passage 13 from the upstream side (the side of the air cleaner 14) toward the downstream side (the side of the internal combustion engine 11) due to the generation of negative pressure in the intake pipe. . At this time, the intake air flowing through the intake passage 13 from upstream to downstream is supplied to the internal combustion engine 11 after being detected by the airflow meter 27 .

However, in the internal combustion engine 11, intake air is intermittently drawn into the combustion chamber 42 by opening and closing the intake valve 41, so the intake air flowing through the intake passage 13 pulsates. That is, in the intake passage 13, a forward flow of intake air flowing from the upstream side to the downstream side and a reverse flow of intake air flowing from the downstream side to the upstream side alternately occur. Therefore, the airflow meter 27 detects not only the forward flow of intake air but also the reverse flow of intake air. Therefore, there is a difference between the amount of intake air detected by the airflow meter 27 and the amount of intake air actually drawn into the combustion chamber 42 of the internal combustion engine 11 .

In this regard, in the intake device 12 of the present embodiment, an intake adjusting section 29 that adjusts the flow of intake air in the intake passage 13 is arranged at a position downstream of the airflow meter 27 in the intake passage 13 . In this case, as shown in FIGS. 4 and 5, each adjusting passage 38 of the intake air adjusting portion 29 has a cross-sectional area that gradually decreases from the upstream end to the downstream end, and also extends in a direction that intersects the

That is, each adjustment passage 38 of the intake air adjusting portion 29 is structured such that the forward flow of intake air flowing through the intake passage 13 easily enters, but the reverse flow of intake air flowing through the intake passage 13 hardly enters. Therefore, the degree of easiness with which the reverse flow of intake air flows into each adjustment passage 38 from the downstream side is smaller than the degree of susceptibility of the forward flow of intake air into each adjustment passage 38 from the upstream side.

Therefore, when intake air flows backward from the internal combustion engine 11 side toward the airflow meter 27 side in the intake passage 13, the intake air adjusting section 29 detects that the reversed intake air flows to the airflow meter 27 and is detected by the airflow meter 27. Suppressed. Therefore, the difference between the amount of intake air detected by the airflow meter 27 and the amount of intake air actually taken into the internal combustion engine 11 is reduced.

As shown in FIG. 5 , each fin portion 35 of the intake air adjusting portion 29 is formed with a converting portion 40 having a U-shaped cross section so as to be adjacent to the adjusting passage 38 . Therefore, when backflowing intake air hits each converting portion 40 of the intake air adjusting portion 29, the backflowing intake air hitting the corresponding converting portion 40 travels along the converting portion 40 as indicated by the two-dot chain line arrow in FIG. It turns and is converted into forward intake air. Therefore, it becomes even more difficult for the reverse intake air in the intake passage 13 to enter the adjusting passages 38 of the intake air adjusting portion 29 .

Further, when the intake air in the intake passage 13 switches from the reverse flow to the forward flow, the forward flow of intake air (indicated by the solid arrow in FIG. 5) that has passed through each adjustment passage 38 hits the converting portion 40 described above and makes a U-turn. (indicated by the double-dashed arrow in FIG. 5). As a result, the forward flow of intake air is suppressed, so that the fluctuation width (fluctuation width) of the forward flow of the entire intake air flowing through the intake passage 13 is reduced. As a result, the air flow meter 27 can detect the flow rate of forward intake air with improved accuracy.

According to the first embodiment described in detail above, the following effects are exhibited.
(1-1) The intake system 12 supplies intake air to the internal combustion engine 11 and includes an intake passage 13 in which an air flow meter 27 for detecting the flow rate of the intake air is arranged. At a position downstream of the air flow meter 27 in the intake passage 13 in the flow direction of the intake air, an intake air adjusting section 29 for adjusting the flow of the intake air is arranged. The intake air adjusting section 29 has an adjusting passage 38 through which the intake air passes. The cross-sectional area of the downstream end of the adjustment passage 38 in the flow direction of the intake air is smaller than the cross-sectional area of the upstream end of the adjustment passage 38 in the flow direction of the intake air.

According to this configuration, the degree of ease with which intake air flows into the adjustment passage 38 from the downstream side can be made smaller than the degree with which intake air flows into the adjustment passage 38 from the upstream side. Therefore, when intake air flows backward in the intake passage 13 from the internal combustion engine 11 side toward the airflow meter 27 side, the intake air adjusting section 29 can prevent the backflowing intake air from being detected by the airflow meter 27 . Therefore, the difference between the amount of intake air detected by the airflow meter 27 and the amount of intake air actually drawn into the internal combustion engine 11 can be reduced.

(1-2) In the intake device 12, the intake air adjustment unit 29 receives a reverse flow of intake air that flows from the downstream side to the upstream side in the intake passage 13, and receives the reverse flow of intake air that flows from the upstream side to the downstream side. It has a conversion unit 40 that converts to the intake air.

According to this configuration, part of the reverse-flowing intake air flowing through the intake passage 13 can be converted into forward-flowing intake air by the conversion unit 40 , so that the reverse-flowing intake air can be suppressed from entering the adjustment passage 38 .
(1-3) In the intake device 12, the adjustment passage 38 extends in a direction intersecting the direction in which the intake passage 13 extends.

According to this configuration, it is possible to further suppress entry of the intake air flowing backward through the intake passage 13 into the adjustment passage 38 .
(Second embodiment)
Next, a second embodiment of an intake device for an internal combustion engine will be described with reference to the drawings.

As shown in FIGS. 1, 7 and 9, the intake device 50 of the second embodiment is obtained by changing the intake adjusting section 29 to an intake adjusting section 51 in the intake device 12 of the first embodiment. In the second embodiment, only points different from the first embodiment will be described, and descriptions overlapping with the first embodiment will be omitted.

As shown in FIGS. 7 and 8, the intake air adjusting portion 51 has a disk shape of the same size as the air intake adjusting portion 29 of the first embodiment, and has an annular plate-like first frame on the periphery. 52. A plurality of adjustment passages 53 having a regular hexagonal shape when viewed from the upstream side are formed through the entire region of the intake air adjusting portion 51 inside the first frame 52 . When the intake air adjusting portion 51 is viewed from the upstream side, the plurality of adjusting passages 53 are arranged regularly in a zigzag pattern without gaps.

As shown in FIGS. 11 and 12 , the cross-sectional area of the downstream end of each adjustment passage 53 in the flow direction of intake air is smaller than the cross-sectional area of the upstream end of each adjustment passage 53 in the flow direction of intake air. That is, the cross-sectional area of each adjustment passage 53 gradually decreases from the upstream end to the downstream end. Each adjustment passage 53 extends in the direction in which the central axis K of the intake adjustment portion 51 extends, which is the direction in which the intake passage 13 extends.

As shown in FIGS. 9 and 10, a plurality of band-shaped second frames 55 extending radially from the central portion 54 and connected to the first frame 52 are provided on the downstream side of the intake air adjusting portion 51 . . A plurality of (eight in this example) second frames 55 are arranged at equal intervals in the circumferential direction and are connected to each other at the central portion 54 .

A plurality of (six in this example) recesses 56 are provided around each adjustment passage 53 that opens downstream in the air intake adjustment portion 51 so as to surround each adjustment passage 53 . Each recess 56 is arranged adjacent to the adjustment passage 53 and has a substantially triangular shape when viewed from the downstream side of the intake air adjustment portion 51 . Each recess 56 opens downstream in the direction of flow of intake air in the intake passage 13 .

Next, the operation of the intake air adjusting section 51 during operation of the internal combustion engine 11 will be described.
As shown in FIG. 1, when the internal combustion engine 11 is operated, intake air flows through the intake passage 13 from the upstream side (the side of the air cleaner 14) toward the downstream side (the side of the internal combustion engine 11) due to the generation of negative pressure in the intake pipe. . At this time, the intake air flowing through the intake passage 13 from upstream to downstream is supplied to the internal combustion engine 11 after being detected by the airflow meter 27 .

However, in the internal combustion engine 11, intake air is intermittently drawn into the combustion chamber 42 by opening and closing the intake valve 41, so the intake air flowing through the intake passage 13 pulsates. That is, in the intake passage 13, a forward flow of intake air flowing from the upstream side to the downstream side and a reverse flow of intake air flowing from the downstream side to the upstream side alternately occur. Therefore, the airflow meter 27 detects not only the forward flow of intake air but also the reverse flow of intake air. Therefore, there is a difference between the amount of intake air detected by the airflow meter 27 and the amount of intake air actually drawn into the combustion chamber 42 of the internal combustion engine 11 .

In this regard, in the intake device 50 of the present embodiment, an intake adjusting section 51 that adjusts the flow of intake air in the intake passage 13 is arranged at a position downstream of the airflow meter 27 in the intake passage 13 . In this case, as shown in FIGS. 11 and 12, the cross-sectional area of each adjustment passage 53 of the intake air adjustment portion 51 gradually decreases from the upstream end to the downstream end.

That is, each adjusting passage 53 of the intake air adjusting portion 51 has a structure in which the forward flow of intake air flowing through the intake passage 13 easily enters, but the reverse flow of intake air flowing through the intake passage 13 does not easily enter. Therefore, the degree of easiness of reverse flow of intake air flowing into each adjustment passage 53 from the downstream side is lower than the degree of susceptibility of forward flow of intake air flowing into each adjustment passage 53 from the upstream side.

Therefore, when intake air flows backward from the internal combustion engine 11 side toward the airflow meter 27 side in the intake passage 13, the intake air adjusting section 51 detects that the reversed intake air flows to the airflow meter 27 and is detected by the airflow meter 27. Suppressed. Therefore, the difference between the amount of intake air detected by the airflow meter 27 and the amount of intake air actually taken into the internal combustion engine 11 is reduced.

Further, as shown in FIG. 12 , recesses 56 that open downstream in the flow direction of intake air in the intake passage 13 are formed on the downstream side of the intake air adjusting portion 51 so as to be adjacent to the adjusting passage 53 . Therefore, when a part of the reverse flow of intake air flowing through the intake passage 13 flows into each recess 56 of the intake air adjusting portion 51, the reverse flow of intake air indicated by the two-dot chain line arrow in FIG. A vortex is generated by

Then, a part of the backflow of intake air generated near the opening of each recess 56 prevents the backflow of intake air flowing through the intake passage 13 from entering each adjustment passage 53 . Therefore, the reverse flow of intake air flowing through the intake passage 13 is further suppressed from entering the adjusting passages 53 . It should be noted that the forward intake air flows smoothly toward the downstream side through each adjustment passage 53 as indicated by the solid line arrows in FIG. 12 .

According to the second embodiment described in detail above, in addition to the effects described in (1-1) above, the following effects are exhibited.
(2-1) In the intake device 12, the intake adjustment portion 51 has a recess 56 that opens downstream in the direction of flow of intake air in the intake passage 13, and the recess 56 is arranged adjacent to the adjustment passage 53. It is

According to this configuration, when part of the backflow of intake air flowing through the intake passage 13 flows into the recess 56 , a vortex is generated by the backflow of intake air in the recess 56 . This vortex prevents the reverse flow of intake air flowing through the intake passage 13 from entering each adjustment passage 53 .

(Change example)
Each of the above embodiments can be implemented with the following modifications. Moreover, each of the above-described embodiments and the following modified examples can be implemented in combination with each other within a technically consistent range.

- In the first embodiment, each adjusting passage 38 of the intake adjusting portion 29 may extend in the direction in which the intake passage 13 extends.
- In the first embodiment, the bending portion 39 and the converting portion 40 in each fin portion 35 of the intake air adjusting portion 29 may be omitted.

- In 2nd Embodiment, the recessed part 56 of the intake air adjustment part 51 may be abbreviate|omitted.
- In the second embodiment, the number of recesses 56 of the air intake adjustment unit 51 may be changed as appropriate.
- In the second embodiment, the shape of each recessed portion 56 when viewed from the downstream side of the intake air adjusting portion 51 is not limited to a triangular shape, and may be a polygonal shape other than a triangular shape, a circular shape, an elliptical shape, or the like. .

- In the second embodiment, the number of adjustment passages 53 of the intake air adjustment unit 51 may be changed as appropriate.
- In the second embodiment, the shape of each adjustment passage 53 when viewed from the upstream side of the air intake adjustment portion 51 is not limited to a regular hexagon, but may be a polygonal shape other than a regular hexagon, a circular shape, an elliptical shape, or the like. may

- In the first and second embodiments, the air intake adjusting portions 29 and 51 may be formed integrally with the outlet duct 26 .

DESCRIPTION OF SYMBOLS 11... Internal combustion engine 12, 50... Air intake device 13... Air intake passage 14... Air cleaner 15... Air cleaner hose 16... Throttle body 17... Intake manifold 18, 20... Opening 19... Case 21... Cap 22... Filter element 23, 25... Side wall 24 Inlet duct 26 Outlet duct 27 Air flow meter 28 Control section 29, 51 Intake adjusting section 30 Throttle valve 31 Intake port 32 Surge tank 33 Injector 34, 52 First frame 35 Fin section 36, 54...Center part 37,55...Second frame 38,53...Adjustment passage 39...Bend part 40...Conversion part 41...Intake valve 42...Combustion chamber 56...Recess part J, K...Center axis line

Claims (4)

An intake device for an internal combustion engine, comprising an intake passage for supplying intake air to an internal combustion engine and in which an airflow meter for detecting the flow rate of the intake air is disposed,
an intake adjusting unit for adjusting the flow of the intake air is arranged at a position downstream of the air flow meter in the intake passage in the flow direction of the intake air;
The intake air adjustment unit has an adjustment passage through which the intake air passes,
An intake system for an internal combustion engine, wherein a cross-sectional area of a downstream end of the adjustment passage in the flow direction of the intake air is smaller than a cross-sectional area of an upstream end of the adjustment passage in the flow direction of the intake air. The intake air adjustment section receives the reverse flow of intake air flowing through the intake passage from the downstream side to the upstream side in the flow direction of the intake air, and directs the reverse flow of the intake air from the upstream side to the downstream side in the flow direction of the intake air. 2. An intake system for an internal combustion engine according to claim 1, further comprising a converting portion for converting the forward flow of intake air. 3. An intake system for an internal combustion engine according to claim 1, wherein said adjustment passage extends in a direction crossing the direction in which said intake passage extends. The intake air adjusting section has a recess opening downstream in the direction of flow of the intake air in the intake passage,
2. An intake system for an internal combustion engine according to claim 1, wherein said recess is arranged adjacent to said adjustment passage.

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