JPS6046264B2 - Internal combustion engine intake system - 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 a mixture from a horizontal carburetor to each cylinder at a substantially equal air-fuel ratio.

In order to distribute the air-fuel mixture from the horizontal carburetor to each cylinder in an in-line three-cylinder engine, three intake passages B, 1, , B
.

, B are branched toward each cylinder Cl, Co, and Ca of the engine C in a symmetrical or substantially symmetrical manner in plan view. In this case, if vaporizer A is vertical, the mixed focus will flow down once and then change direction horizontally at the collecting pipe section, so at that time the flow velocity will be reduced and the flow will flow in a specific direction. This tendency is corrected, and since the air-fuel mixture tends to flow along the pipe wall, the air-fuel mixture does not concentrate particularly in the central intake passage, and the amount distributed to each intake passage can be kept almost constant. . However, when the carburetor A is horizontal as shown, the air-fuel mixture moves straight in the horizontal direction, so the amount supplied to the central intake passage C2 increases and flows to each cylinder Cl, Co, and Co. In addition, in the case of a horizontal carburetor, the fuel density in the lower part of the flowing mixture tends to be high, so this rich mixture concentrates in the second cylinder. As a result, the air-fuel ratio of the intake air-fuel mixture for the second cylinder C2 becomes richer than the air-fuel ratio of the intake air-fuel mixture for the other cylinders, and the air-fuel mixture is maintained in a state where the air-fuel ratios are approximately equal for each cylinder. The fuel cannot be distributed, resulting in uneven combustion in each cylinder.

As a means to deal with this problem, for example,
No. 642 [publication] In distributing the mixture to a three-cylinder engine, the mixture passage from the collecting pipe section is once branched to the left and right, and
A configuration has been disclosed in which a passage is further branched from the left and right passages to a central cylinder, and a container for guiding the air-fuel mixture is provided in the left and right passages.
In such a configuration, the structure of the manifold becomes complicated and casting is difficult, and if the mixture passage has many branch parts as in this publication, resistance will increase when the flow velocity of the mixture changes. There was a problem in that the amount distributed to each cylinder could not be made appropriate due to flow inertia.

The present invention provides an intake manifold for a three-tube engine using such a horizontal carburetor, in which the intake passage for the second cylinder, where the intake air mixture tends to become rich, and the other intake passages for the first and second cylinders are connected. By providing a height difference in the vertical direction between the intake pipes, the rich air-fuel mixture and liquid fuel at the inner bottom of the collecting pipe portion flow approximately equally to each intake passage, thereby solving the above problem.

In this case, the following embodiments are available for providing a height difference in the vertical direction between the intake passage for the second cylinder and the intake passages for the first and third cylinders. As a first embodiment, as shown in FIGS. 3 and 4, a horizontal carburetor A is attached to a collecting pipe m? in an intake manifold B that is bilaterally symmetrical or approximately bilaterally symmetrical in plan view. , each cylinder Cl,C of the three-cylinder engine C
2, In branching the intake passages Bl, B2, and 8 to the intake boats C/, C2″, and C3″ in C3, the intake passage B1 for the first cylinder and the intake passage B3 for the third cylinder are horizontal in side view. In plan view, the second cylinder intake passage B2 branches horizontally outward and is symmetrical or approximately symmetrical; however, in plan view, the second cylinder intake passage B2 is in line with the collecting pipe portion B4, and in side view, it branches diagonally upward. Therefore, a chevron-shaped bend m2'' with an appropriate height H is provided from the intake passages for the first and third cylinders, B1 and B2, on the way to the intake passage for the second cylinder, and the intake passage for the second cylinder 8 is connected to the first and third cylinders. It is set higher than the intake passages Bl and B3 for the third cylinder.

As a second embodiment, as shown in FIG. 5, FIG. 6, and FIG.
2. Among the intake boats C1″, C2″, and C3″ of C3,
The intake boat C2'' for the second cylinder is provided at an appropriate dimension H'' higher than the intake boats C1'', C2'', and C3'' for the first and third cylinders, and is symmetrical or approximately symmetrical in plan view. The first and third intake passages Bl and B2 branch from the collecting pipe part B4 in the intake manifold B.
The cylinder intake passage Bi9B3 and the collecting pipe m are at approximately the same horizontal height).
By making the cylinder intake passage B2 higher than the collecting pipe M and connecting it to the intake boat C2'', the second cylinder intake passage B2 is made higher than the first and third cylinder intake passages B1 and B3. do.

When the intake passage for the second cylinder is made higher than the intake passage for the first and third cylinders as in the first and second embodiments,
The liquid fuel and rich mixture at the inner bottom of the collecting pipe section are
While it becomes difficult for the air to flow into the intake passage for the second cylinder, more flow flows into the intake passage for the first and third cylinders, and
Since the flow resistance of the air-fuel mixture in the cylinder intake passages is greater than when the air-fuel mixture is in a straight line, the distribution of the air-fuel mixture to each cylinder is averaged, and the air-fuel ratio can be made approximately equal.

In addition, as a third embodiment, FIGS. 8, 9 and 10
As shown in the figure, among the intake boats C1'', C2'', and C3'' of each cylinder that open on the side of the three-cylinder engine C, the intake boat C2'' for the second cylinder is replaced with the intake boat C2'' for the first and third cylinders. Each intake passage Bl, B2, B3 branches from the collecting pipe part B4 in the intake manifold B, which is bilaterally opposite or approximately bilaterally symmetrical in plan view, and is opened at an appropriate dimension H'''' higher than C1'', C3''. Among them, the intake passage B2 for the second cylinder is at approximately the same horizontal height as the collecting pipe section B).
'', the intake passages Bl, B3 for the first and third cylinders are lowered than the collecting pipe part B4, and the intake boats C1'', C3'' are respectively lowered.
By connecting to the intake passages Bl and B1 for the first and third cylinders, respectively, the entire passage to the intake passage Bl for the first and third cylinders is made lower than the intake passage B2 for the second cylinder, and according to this embodiment, the liquid level at the inner bottom of the collecting pipe portion While a large amount of fuel and rich air-fuel mixture flows in the direction of the low-height intake passages for the first and third cylinders, the amount of flow into the intake passages for the second cylinder decreases accordingly.
The air-fuel ratio of the intake air mixture to each cylinder is averaged. In addition, by combining the second embodiment and the third embodiment,
The collecting pipe portion may be installed at an intermediate height between the second cylinder intake boat and the first and third cylinder intake boats. If it is not possible to increase the height difference between the intake boat for the first cylinder and the intake boats for the first and third cylinders, the first embodiment can be combined with this, and the height difference between the intake boats for the first and third cylinders can be increased. It is sufficient to provide a mountain-shaped mid-high bend.

In this case, in either example, the central intake passage B2 must be located above the left and right intake passages Bl, B2. As described above, according to the present invention, although the configuration is extremely simple by simply providing a height difference between each intake passage in the intake manifold, the air-fuel mixture from one carburetor for each cylinder in a three-cylinder engine can be reduced. Since the fuel can be reliably distributed and supplied under the same air-fuel ratio, combustion in each cylinder can be made substantially uniform, which has the effect of improving the quietness and output of a three-cylinder engine.

Moreover, since the present invention has an extremely simple structure, it can be manufactured at low cost, and the air-fuel mixture that has been traveling straight is distributed and guided in the vertical direction by the height difference provided in each intake passage, and is directly directed to each intake passage. Since the air-fuel mixture is guided by the air-fuel mixture, it can be distributed uniformly to each cylinder regardless of the air-fuel mixture flow velocity.
Furthermore, since the air-fuel mixture as a whole is guided horizontally and the intake resistance is small, acceleration response is not deteriorated.

[Brief explanation of the drawing]

Figure 1 is a plan view of the conventional device, Figure 2 is a side view of Figure 1,
FIG. 3 is a plan view of the device according to the first embodiment of the present invention, and FIG.
Figure 5 is a side view of the device according to the second embodiment of the present invention;
Fig. 6 is a partially cutaway side view of Fig. 5, and Fig. 7 is a partially cutaway side view of Fig. 6.
-■ A cross-sectional view, FIG. 8 is a plan view of the device according to the third embodiment of the present invention, FIG. 9 is a side view of FIG. 8, and FIG. 10 is a line XX in FIG. 9.
FIG. A... Carburetor, B... Intake manifold, C... Engine, Cl, C2, C3...
・Cylinder, C1″, C2′, C3″・・・Intake boat, B,・・・Collecting pipe part, Bl, B2, P)3・
...Intake passage.

Claims (1)

[Claims] 1. An intake manifold for distributing the air-fuel mixture from a horizontal carburetor to each cylinder of an in-line three-cylinder engine is connected to a collecting pipe section attached to the horizontal carburetor and from the collecting pipe section in a manner that is symmetrical or approximately horizontal in plan view. In an intake system for an internal combustion engine, the intake manifold is configured to have three intake passages that branch symmetrically and are attached to each cylinder, and is configured to guide the air-fuel mixture from the carburetor along a substantially horizontal direction. The second cylinder intake passage in the center and the first cylinder intake passage on both left and right sides
An intake system for an internal combustion engine, characterized in that a height difference is provided in the vertical direction between the intake passage and the third cylinder intake passage so that the central intake passage is located on the upper side.