JPS628630B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for an in-line three-cylinder internal combustion engine, which distributes the air-fuel mixture from one carburetor to each cylinder at a substantially equal air-fuel ratio. .

In order to distribute the air-fuel mixture from one carburetor to each cylinder in an in-line three-cylinder engine, three intake passages are established from the collecting pipe section _B4 where the carburetor A is attached, as shown in Figures 1 and 2. B ₁ , B ₂ , B ₃ for each cylinder of engine C
An intake manifold B is used which branches symmetrically or approximately symmetrically toward C ₁ , C ₂ , and C ₃ in plan view. In this case, the first
The intake passages B ₁ and B ₃ leading to the cylinder C ₁ and the third cylinder C ₃ are bilaterally symmetrical or approximately symmetrical, and their curves and lengths are equal, and the flow conditions within the passages are also approximately equal. The air-fuel mixture can be distributed approximately equally to the cylinders and the third cylinder, but the intake passage _B2 for the second cylinder _C2 between them is in a straight line with the collecting pipe part _B4 and is short in length. The air-fuel mixture from the collecting pipe part _B4 easily flows into the cylinder intake passage _B2 , and the liquid fuel flowing down the inner bottom surface of the pipe collects at the inner bottom of the collecting pipe part, and the inner bottom of the collecting pipe part is dense. This rich mixture and liquid fuel mainly flow in the direction of the intake passage _B2 for the second cylinder, so that the air-fuel ratio of the intake mixture for the second cylinder _C2 is the same as that of the intake mixture for other cylinders. The air-fuel ratio becomes richer than the air-fuel ratio, and the air-fuel mixture cannot be distributed under conditions where the air-fuel ratio is approximately equal for each cylinder, resulting in uneven combustion in each cylinder. In particular, if the carburetor attached to the collecting pipe section _B4 is a horizontal carburetor, more fuel from the various nozzles of the horizontal carburetor will collect at the inner bottom of the collecting pipe section. The tendency for the mixture to become richer in the two cylinders was further increased.

In the intake manifold of such a three-cylinder engine, the present invention provides a bent portion in the shape of a medium-high mountain with an appropriate height in the intake passage for the second cylinder, where the intake air mixture tends to become rich, and at the same time, the bent portion is A bypass passage is provided that communicates the inner bottom of the passage before the bending part with the inside of the passage after the bending part, and the liquid fuel and rich mixture at the inner bottom of the collecting pipe part are regulated to an appropriate amount by the bypass passage. By guiding the air to two cylinders, the air-fuel ratio of the air-fuel mixture to each cylinder is made uniform.

To explain the drawings of the embodiment below, the intake manifold B is bilaterally symmetrical or approximately symmetrical in plan view.
From the collecting pipe section B ₄ to which the carburetor A is attached, 3
When branching the intake passages B ₁ , B ₂ , B ₃ to the intake ports C ₁ ′, C ₂ ′, C ₃ ′ in each cylinder C ₁ , C ₂ , C ₃ of the cylinder engine C, the first cylinder The intake passage B ₁ and the intake passage B ₃ for the third cylinder are branched horizontally outward in plan view, and each intake port remains substantially horizontal.
While connected to C ₁ ′ and C ₃ ′, the second cylinder intake passage B ₂
is branched in a straight line with the collecting pipe portion B ₄ in a plan view and diagonally upward in a side view, and then bent to the same or approximately the same height position as the intake passages B ₁ and B ₃ for the first and third cylinders. and its intake port
By connecting to C ₂ ′, a medium-high mountain-shaped bent portion B _{2 ′} of an appropriate height H is provided in the middle of the intake passage B 2 from the intake passages B ₁ and B ₃ for the first and third cylinders.

and a thick portion on the lower surface of the bent portion B ₂ ′.
B ₂ '' is provided with a bypass passage B ₂ of an appropriate diameter that communicates between the inner bottom part B _{4 ′} of the collecting pipe part B ₄ before the bent part B ₂ ′ and the inside of the passage after the bent part B _{2 ′} . It is made by drilling.

With this configuration, the inner bottom of the collecting pipe section _B4
The liquid fuel and rich mixture in B ₄ ′ flow into the second cylinder C 2 through the second cylinder intake passage B _{2 ′} in an amount regulated by the bypass passage B ₂ , while
This regulation of the bypass passage B ₂ also causes the flow of liquid fuel and rich air-fuel mixture toward the intake passages B ₁ and B ₃ for the first and third cylinders, so the distribution of the air-fuel mixture to each cylinder is approximately averaged. It will be done.

The distribution ratio of liquid fuel and rich air-fuel mixture to the second cylinder side and the first and third cylinder sides can be arbitrarily set according to the bypass passage diameter according to the characteristics of the engine. It is noted that the middle-to-taka mountain-shaped bent part in the intake passage for the second cylinder may be provided in the middle of the intake passage for the second cylinder, instead of being provided at the branch part to the collecting pipe part _B4 as in the above embodiment. Needless to say.

As described above, according to the present invention, since the air-fuel mixture from the carburetor can be distributed to each cylinder at a substantially equal air-fuel ratio in an in-line three-cylinder engine, combustion in each cylinder can be made substantially uniform. This has the effect of improving the quietness and output of a three-cylinder engine.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the conventional device, FIG. 2 is a side view of FIG. 1, FIG. 3 is a plan view of the device according to the embodiment of the present invention, FIG. 4 is a side view of FIG. 3, and FIG. Figure 3 -
FIG. 3 is an enlarged cross-sectional view. A... Carburetor, B... Intake manifold, C...
…Engine, C ₁ , C ₂ , C ₃ … Cylinder, C ₁ ′, C ₂ ′, C ₃ ′…
...Intake port, B ₄ ...Collecting pipe section, B ₁ , B ₂ , B ₃ ...
...Intake passage, B ₂ ′...Bending section, B ₂ ...Bypass passage.

Claims (1)

[Claims] 1. In an intake manifold in which three intake passages are branched in a bilaterally symmetrical or substantially bilaterally symmetrical manner in a plan view from a collecting pipe section to which a carburetor is attached to each cylinder of an in-line three-cylinder engine, each of the intake passages Of these, the intake passage for the second cylinder is provided with a bent part in the shape of a medium-high mountain, and the bent part is provided with a bypass passage that communicates the inner bottom of the passage before the bent part with the inside of the passage after the bent part. An intake system for an internal combustion engine characterized by: