JPH0335488B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention distributes intake air from one horizontal carburetor approximately equally to each cylinder in an in-line three-cylinder internal combustion engine, and provides a strong The present invention relates to an intake device that forms an intake swirl.

[Conventional technology]

When distributing intake air from one carburetor to each cylinder in an in-line three-cylinder internal combustion engine, the lengths of the three intake passages from the carburetor to the intake port for each cylinder cannot be made equal. In the distribution to each cylinder, uneven distribution is more likely to occur than in the case of an even number of cylinders, and the intake swirl in each cylinder is also reduced.

Therefore, the applicant of this application filed an earlier patent application (Japanese Patent Application No. 1983-
No. 206211, Japanese Patent Application Laid-Open No. 60-98127), when the intake air from one vertical carburetor is distributed to each cylinder of an in-line three-cylinder internal combustion engine via an intake manifold, It branches into a single intake passage to the first cylinder and a common intake passage to the second and third cylinders, and further divides the common intake passage into an intake passage to the second cylinder and an intake passage to the third cylinder. We proposed an intake system with two branches.

The intake device of this prior art is for a vertical carburetor, and the intake air from the vertical carburetor collides with the bottom surface of the gathering part in the intake manifold and is directed from a downward vertical direction to a horizontal direction. As a result, the atomization of the fuel is promoted and the uneven flow of the flow is corrected, resulting in an average flow at each location.
While offset from the center of the cylinder to the third cylinder side, the axis of the common intake passage is located between the center of the second cylinder and the center of the third cylinder, and the axis of the gathering part is set to the axis of the common intake passage. and the axis of the first cylinder intake passage is aligned with the axis of the common intake passage across the axis of the gathering portion. By making the cylinder substantially symmetrical, intake air can be distributed substantially equally to each of the three cylinders, and a strong intake swirl can be formed in each cylinder.

[Problem that the invention seeks to solve]

However, when a horizontal carburetor is applied to the intake manifold in the intake device of this prior art in place of the vertical carburetor, the direction change at the gathering part is not possible as in the case of the vertical carburetor. Therefore, the intake air from the horizontal carburetor flows straight in the axial direction within the collecting section, and it is not possible to promote fuel atomization and equalize the flow in the collecting section. With this configuration, both the intake air to the second cylinder and the intake air to the third cylinder flow continuously through the common intake passage for the second and third cylinders, so that the intake air to the engine is reduced. In a low-load/low-speed range where the amount of fuel is small, the fuel flowing along the inner wall surface of the collecting portion tends to drift toward the common intake passage for the second and third cylinders.

In other words, when a horizontal carburetor is applied to the intake system of the prior art, the performance of distributing the intake air to each cylinder will decrease in the low load/low rotation range of the engine, improving the intake swirl and improving the distribution performance. Therefore, it was not possible to simultaneously achieve the improvement of

The present invention solves the problems described above when a horizontal carburetor is applied to the intake device in the prior art.

[Means for solving problems]

For this reason, the present invention provides an in-line three-cylinder internal combustion engine in which a collecting part in an intake manifold is oriented horizontally and a horizontal carburetor is connected thereto, and a single intake passage from the collecting part in the intake manifold to a first cylinder; The common intake passage is branched into a common intake passage to the second cylinder and the third cylinder, and the common intake passage is further branched into an intake passage to the second cylinder and an intake passage to the third cylinder. While the collecting part is offset from the center of the second cylinder to the third cylinder side, the axis of the common intake passage is located between the center of the second cylinder and the center of the third cylinder, and the axis of the collecting part is offset from the center of the second cylinder to the center of the third cylinder. The axis of the first cylinder intake passage is oriented toward the second and first cylinders, and the axis of the first cylinder intake passage is oriented toward the common intake passage with the axis of the gathering portion in between. In the intake device that is substantially symmetrical to the axis of the intake passage, the valve axis of the throttle valve in the horizontal carburetor is substantially perpendicular to the axis of the gathering portion and is oriented substantially horizontally; is located at an appropriate height lower than the common intake passage for the second and third cylinders when viewed from the side.

[Action/effect of the invention]

In this way, by configuring the intake passage for the first cylinder to be located at an appropriate height lower than the common intake passage for the second and third cylinders when viewed from the side, the engine can be operated at low loads and low engine speeds. To correct the tendency for fuel flowing along the inner bottom surface of a gathering part in the area to flow more easily toward the common intake passage, with difficulty flowing toward the common intake passage, and more flow toward the first cylinder intake passage. This makes it possible to ensure approximately equal distribution of intake air to each cylinder in the low engine load and low rotation range.

As described above, according to the present invention, when air is taken into each cylinder of a three-cylinder internal combustion engine using a horizontal carburetor, the distribution of air in the low load and low rotation range of the engine can be improved. Swirl and equal distribution of intake air to each cylinder can be ensured over the entire operating range of the engine, which has the effect of improving output and reducing output torque fluctuations and vibrations.

〔Example〕

Hereinafter, embodiments of the present invention will be explained with reference to the drawings. In the drawings, 1 indicates the first cylinder A1, the second cylinder A1,
It shows an in-line three-cylinder internal combustion engine in which the second and third cylinders A3 are arranged in the direction of the crankshaft (not shown),
The internal combustion engine 1 has an axis 2 of the cylinder bore in each cylinder when viewed from the direction of the clamp shaft.
are installed so as to be inclined at an appropriate angle (θ) with respect to the horizontal line 3, and the cylinder head 4 of the internal combustion engine 1 has intake ports 5 for each of the cylinders A1, A2, and A3 on the side surface 4a that is the upper surface side. ，
6 and 7 are open.

8 indicates each cylinder A1, A in the internal combustion engine 1.
2, shows the intake manifold for A3, the collecting part 8a of the intake manifold 8 is horizontally oriented, and the horizontal carburetor 9 is installed in this collecting part 8a.
The throttle valve 9a is mounted so that its valve shaft 9b is substantially perpendicular to the axis 10 of the gathering portion 8a and is oriented substantially horizontally.

Gathering portion 8a in the intake manifold 8
, a single intake passage 8b to the first cylinder A1, and a common intake passage 8 to the second cylinder A2 and third cylinder A3.
c, and furthermore, the common intake passage 8c is divided into
It branches into an intake passage 8d to the second cylinder A2 and an intake passage 8c to the third cylinder A3, and the intake passage 8b for the first cylinder is connected to the intake port 5 in the first cylinder A1.
Then, the second cylinder intake passage 8d is connected to the intake port 6 of the second cylinder A2, and the third cylinder intake passage 8e is connected to the intake port 7 of the third cylinder A3.

In this case, the gathering portion 8a in the intake manifold 8 is located in the second cylinder A in a plan view.
The common intake passage 8b is located at a position offset by an appropriate distance (e) from the center line O2 of the second cylinder A3 toward the third cylinder A3, and the axis 11 of the common intake passage 8b is located between the center line O2 of the second cylinder A2 and the third cylinder A3 in plan view. The axis 10 of the collecting portion 8a is oriented toward the second cylinder A2 and the center line O3 of the cylinder A3, while the axis 10 of the collecting portion 8a is further aligned with the second cylinder A2 and It is directed toward the portion 13 shifted toward the first cylinder A1 side, and furthermore, the first
The axis 14 of the cylinder intake passage 8b is substantially symmetrical to the axis 11 of the common intake passage 8b across the axis 10 of the gathering portion 8a in plan view.

Note that the internal combustion engine 1 has a horizontal plane 15 when viewed from a direction perpendicular to its crankshaft.
It is inclined by an appropriate angle (α) so that the first cylinder A1 side is slightly higher than the third cylinder A3 side. Further, the intake ports 5, 6, 7 to which the intake passages 8b, 8d, 8e in the intake manifold 8 are connected are connected to the respective cylinders A1, A2, A3.
The air-fuel mixture from each of the intake ports 5, 6, and 7 is configured tangentially to form a swirl in each cylinder as shown by arrow a. Furthermore, the inner diameter D1 of the gathering portion 8a in the intake manifold 8 is smaller than the throttle bore inner diameter D0 (the inner diameter of the portion where the throttle valve 9a is provided) in the carburetor 9, and each intake passage 8b, 8
The inner diameter D2 of the connecting portions d and 8e to the intake ports 5, 6, and 7 is also smaller than the throttle bore inner diameter D0 of the carburetor 9, and the intake manifold 8
The inner diameters of other portions of the carburetor 9 are equal to or larger than the throttle bore inner diameter D0 of the carburetor 9.

The axis 1 of the first cylinder intake passage 8b
4 and the axis 11 of the common intake passage 8c, when viewed from the side, the axis 14 of the first cylinder intake passage 8b is located below the axis 10 of the gathering portion 8a, and the axis 11 of the common intake passage 8c is located below. By configuring the first cylinder intake passage 8b to be located at the top, the first cylinder intake passage 8b becomes a common intake passage 8 for the second cylinder A2 and the third cylinder A3 in a side view.
The structure is such that it is located at an appropriate height h lower than c.

The intake air from the horizontal carburetor 9 flows straight through the gathering portion 8a and passes through the first cylinder intake passage 8b.
and a common intake passage 8c.
The intake air at point c is further divided into a second cylinder intake passage 8d and a third cylinder intake passage 8e, and flows into each cylinder.

In this case, the valve shaft 9b of the throttle valve 9a in the horizontal carburetor 9 is substantially perpendicular to the axis 10 of the collecting portion 8a and is oriented substantially horizontally;
is located at a position offset by an appropriate distance e from the center line O2 of the second cylinder A2 toward the third cylinder A3 in plan view, and is aligned with the axis 1 of the common intake passage 8b.
1 is a portion 1 between the center line O2 of the second cylinder A2 and the center line O3 of the third cylinder A3 in plan view.
2, and furthermore, the gathering portion 8a
The axis 10 of the second cylinder A2 and the first
The axis 14 of the first cylinder intake passage 8b is oriented toward the portion 13 shifted toward the cylinder A1 side, and in addition, the axis 14 of the first cylinder intake passage 8b is aligned with the common intake passage 8b across the axis 10 of the gathering portion 8a in a plan view. axis 1 of
1, the intake air from the horizontal carburetor 9 can be distributed approximately equally to each intake passage 8b, 8d, 8e, and in turn to each cylinder A1, A2, A3. Intake passages 8b, 8d, 8
Since the length of e is the shortest and the flow resistance is small, a strong swirl can be formed in each cylinder A1, A2, and A3.

However, in the low load/low rotation range of the engine, the amount of intake air is small, so the mixing of the fuel within the collecting part 8a is poor, and a considerable amount of fuel flows along the inner bottom surface of the collecting part 8a. , in the common intake passage 8c,
Since both the intake air to the second cylinder A2 and the intake air to the third cylinder A3 flow continuously, with the configuration as described above, the fuel flowing along the inner bottom surface of the gathering portion 8a flows through the common intake passage. 8b, but as mentioned above, the first cylinder intake passage 8b
In a side view, the second cylinder A2 and the third cylinder A
3, the fuel flowing along the inner bottom surface of the gathering portion 8a in the low load/low rotation range of the engine is located at an appropriate height h lower than the common intake passage 8c for the common intake passage 8c. Since it is difficult for the air to flow toward the first cylinder intake passage 8b and more likely to flow toward the first cylinder intake passage 8b, it is possible to correct the tendency for a large amount to flow toward the common intake passage 8c.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a partially cutaway plan view, FIG. 2 is a partially cutaway side view of FIG. 1, FIG. 3 is a cross-sectional view of FIG. 2, and FIG. is a - sectional view of FIG. 1... Internal combustion engine, A1... First cylinder, A2...
2nd cylinder, A3...Third cylinder, 5, 6, 7...Intake port, 8...Intake manifold, 8a...Collection part, 8b...Intake passage for first cylinder, 8c...Common intake passage, 8d...Intake passage for second cylinder, 8e
...Intake passage for third cylinder, 9 ...Horizontal carburetor, 9
a... Throttle valve, 9b... Valve shaft of the throttle valve, 10... Axis of the collecting portion, 11... Axis of the common intake passage, 14... Axis of the intake passage for the first cylinder.

Claims (1)

[Claims] 1. A collecting part in the intake manifold of an in-line three-cylinder internal combustion engine is oriented horizontally and a horizontal carburetor is connected to it, and a single intake passage from the collecting part in the intake manifold to the first cylinder, and a single intake passage from the collecting part in the intake manifold to the first cylinder, and The common intake passage is further branched into an intake passage to the second cylinder and an intake passage to the third cylinder. While offset from the center of the cylinder to the third cylinder side, the axis of the common intake passage is located between the center of the second cylinder and the center of the third cylinder, and the axis of the gathering part is set to the axis of the common intake passage. and the axis of the first cylinder intake passage is aligned with the axis of the common intake passage across the axis of the gathering portion. In the substantially symmetrical intake device, the valve shaft of the throttle valve in the horizontal carburetor is substantially perpendicular to the axis of the gathering portion and is oriented substantially horizontally, and the intake passage for the first cylinder is arranged in a side view. An intake system for a three-cylinder internal combustion engine, characterized in that the intake system is located at an appropriate height lower than a common intake passage for a second cylinder and a third cylinder.