JP2003120245A - Intake device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily prevent dirt around an opening/closing shaft of a throttle valve due to an oil droplet of blowby gas without reducing a degree of freedom in a layout, in an intake device for an internal combustion engine having a blowby gas circulating structure and a down flow type intake passage. SOLUTION: A discharge opening of the blowby gas is arranged to an upstream side of the throttle valve in the down flow type intake passage. Between the throttle valve of the intake passage and the discharge opening of the blowby gas, in order to introduce droplets to a part in which the throttle valve moves downward at opening of the valve, a circular stepped part is provided which is arranged to an intake passage wall and is inclined downward at is upper surface corresponding to the part. Accordingly, the droplets such as oil droplets are introduced to a position which does not interfere the opening/closing shaft of the throttle valve with simple structure, thereby eliminating a fear of contamination of the opening/closing shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for an internal combustion engine having a blowby gas discharge port upstream of a throttle valve in a downflow type intake passage.

[0002]

2. Description of the Related Art Conventionally, a structure has been well known in which an intake passage is connected to an oil pan, a cylinder head and the like to recirculate blow-by gas. This blow-by gas recirculation structure is applied to an internal combustion engine having a downflow type intake passage that hangs from upstream to downstream of intake air, and the blow-by gas discharge port to the intake passage is located upstream of the throttle body, that is, above. When it is arranged in such a manner, droplets of oil or the like contained in the blow-by gas are transmitted along the inner wall surface of the intake passage and adhere to the throttle valve in the throttle body, particularly the opening / closing shaft and the bearing, which causes a problem such as slowing the operation. is there.

For example, in Japanese Unexamined Patent Publication No. 10-77913, a blow-by gas passage is formed in an annular shape along the outer periphery of the main intake passage, and the blow-by gas passage spirals in the flow direction of the main intake passage. The structure formed in the above is disclosed. This publication discloses a structure in which a blow-by gas discharge port is formed on the downstream side of the throttle valve, that is, since the blow-by gas does not pass through the throttle valve, the throttle valve is not contaminated.

[0004]

However, since the throttle body is usually provided in the vicinity of the surge tank of the intake manifold, the structure in which the blow-by gas discharge port is provided between the surge tank and the throttle body is There is a problem in that the degree of freedom in layout is reduced because the position is limited. Further, in the structure disclosed in the above publication, it is necessary to integrally form the annular recirculation gas passage on the outer periphery of the main intake passage, which complicates the formation and further reduces the layout flexibility.

The present invention has been devised in order to solve the above-mentioned problems of the prior art. In the intake system of an internal combustion engine having a blow-by gas recirculation structure and a downflow type intake passage, a layout is provided. An object of the present invention is to easily prevent stains around the opening / closing axis of a throttle valve due to oil drops of blow-by gas without lowering the degree of freedom.

[0006]

In order to achieve the above-mentioned object, according to the present invention, an intake device for an internal combustion engine having a blowby gas discharge port 8a upstream of a throttle valve 5 in a downflow type intake passage. In order to guide the liquid droplets between the throttle valve 5 and the blow-by gas discharge port 8a of the intake passage toward a portion (position C) that moves downward when the throttle valve 5 is opened. An annular step portion 11 is provided on the wall of the intake passage and has an upper surface inclined toward the portion (position C). As a result, droplets such as oil droplets are guided to a portion (C) that does not interfere with the opening / closing shaft 5a of the throttle valve 5 with a simple structure, and flow down below the throttle valve 5 when the throttle valve 5 is opened. In particular, an annular recess 10 is formed in the intake passage, the diameter of which gradually increases from the upper side to the lower side,
By forming the annular stepped portion 11 at the lower end thereof, it is possible to prevent the intake air flow from being disturbed. Further, since the annular step portion 11 is integrally formed with the air flow tube 6 in the air flow tube 6 that connects the air cleaner 7 and the throttle body including the throttle valve 5, the shape of the intake passage wall is devised. The guide structure can be realized by simply doing so, and the manufacturing becomes easy.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a front perspective view of an in-line four-cylinder engine as an internal combustion engine to which the present invention is applied, and FIG. 2 is a side sectional view around a throttle valve in an intake passage of the engine of FIG. On the front surface of this engine, an intake manifold 2 connected to an intake port provided in the cylinder head 1, and a surge tank 3 connected to an intake upstream end of the intake manifold 2 and arranged below the intake manifold 2
And the surge tank 3 is connected to an intake inlet opening on the upper surface of the right end in the figure, and a throttle body 4 having a throttle valve 5 inside, and one end is connected to an upper end of the throttle body 4, that is, an intake upstream end. And an air flow tube 6 having the other end connected to an air cleaner 7. The air flow tube 6 extends substantially horizontally from the air cleaner 7 and hangs downward at an intermediate portion to reach the throttle body 4. The portion 6a of the airflow tube 6 that hangs downward and the throttle body 4
Is a downflow type intake passage. The other end of a breather tube 8 having one end connected to a breather tank (not shown) is connected to the vicinity of the intake air outlet of the air cleaner 7 so as to recirculate the blow-by gas, and a blow-by gas discharge port 8a opens to the intake passage ( (Fig. 4). The air cleaner 7 is connected to an outside air introduction port (not shown) via another air flow tube 9.

FIG. 3 taken along line III-III of FIG.
As shown in FIG. 2, the intake passage gradually expands in diameter to form an annular recess 10 at the inner wall of the downwardly depending portion 6a of the air flow tube 6, that is, at a position above the throttle body 4 in the intake passage. Has been done. An annular stepped portion 11 serving as a droplet guide structure is formed at the lower end of the annular recessed portion 10. The upper surface of the annular step portion 11 is inclined obliquely downward from a position B opposite to the position A corresponding to the position C above which the throttle valve 5 moves downward when the valve is opened. The annular step portion 11 is formed integrally with the air flow tube 6.

With this structure, as shown in FIGS. 2 and 3, when a droplet of oil or the like flows along the inner wall of the air flow tube 6, it is guided to the position A by the annular step portion 11 and the throttle valve therebelow. It will flow to position C of 5. As described above, this position C is the farthest position from the opening / closing shaft 5a, and there is no concern that it will adhere to the opening / closing shaft 5a.
Further, since the position C is a position where the throttle valve 5 moves downward when the throttle valve 5 is opened, the throttle valve 5 opens to flow further downward, which also hinders opening and closing of the throttle valve 5. There is no such thing. Further, by gradually expanding the diameter of the intake passage from the upstream side of the annular stepped portion 11 to form the annular recessed portion 10, even if the annular stepped portion 11 is formed at the lower end of the annular recessed portion and the diameter is reduced, the intake flow is less likely to be disturbed. ing.

FIG. 5 shows a modified example of the above embodiment.
2 is the same as that of FIG. 2, and the same parts as those of FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted. In this configuration, the annular recess 9 is not formed in the airflow tube 6, and the inward flange-shaped annular step portion 12 is integrally molded with the airflow tube 6. The other structure is the same as that of the above embodiment.

[0012]

As is apparent from the above description, according to the intake system for an internal combustion engine of the present invention, a blow-by gas discharge port is provided upstream of the throttle valve in the downflow type intake passage, Between the throttle valve of the passage and the blow-by gas discharge port, a liquid droplet is guided to a portion that moves downward when the throttle valve is opened. Since the upper surface has the annular step portion that inclines downward, there is no fear that the opening / closing shaft of the throttle valve and the bearing will be contaminated by droplets such as oil droplets with a simple structure. Especially, the intake passage is prevented from being disturbed by gradually expanding the diameter of the intake passage from the upper side to the lower side of the annular stepped portion to form the annular recessed portion and the annular stepped portion at the lower end thereof. Furthermore,
Since the annular step is integrally formed in the air flow tube that connects the air cleaner and the throttle body with the throttle valve, the guide structure can be realized simply by devising the shape of the intake passage wall, and the manufacturing is easier. become.

[Brief description of drawings]

FIG. 1 is a front perspective view of an in-line four-cylinder engine as an internal combustion engine to which the present invention is applied.

FIG. 2 is a side sectional view around a throttle valve in an intake passage of the engine of FIG.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a cross-sectional view showing a connecting portion of a breather tube to an air cleaner.

FIG. 5 is a sectional view similar to FIG. 2 showing a modified example of the above embodiment.

[Explanation of symbols]

2 intake manifold 4 Throttle body 5 Throttle valve 5a Opening / closing axis 6 Air flow tube 6a Hanging part 7 Air cleaner 8 Blow-by gas reflux pipe 10 annular recess 11, 12 annular step

Claims (3)

[Claims] 1. An intake system for an internal combustion engine, comprising an outlet for blow-by gas upstream of a throttle valve in a down-flow type intake passage, wherein the throttle valve and the blow-by gas outlet in the intake passage are provided. An annular step portion is provided in the intake passage wall and has an upper surface inclined downward corresponding to the portion so as to guide the droplet toward the portion that moves downward when the throttle valve is opened. An intake device for an internal combustion engine, comprising: 2. The intake passage has an annular recess whose diameter gradually increases from the upper side to the lower side, and the annular step is formed at the lower end of the annular recess. An intake system for an internal combustion engine according to item 1. 3. The method according to claim 1, wherein the annular step portion is integrally formed with an air flow tube in an air flow tube connecting the air cleaner and the throttle body including the throttle valve. An intake system for an internal combustion engine according to item 1.