JPH0754604Y2 - Intake device in a three-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an in-line three-cylinder internal combustion engine in which cylinders are arranged in a substantially straight line, and an intake air-fuel mixture from one carburetor is supplied to each cylinder. The present invention relates to an intake device for distributing to.

[Conventional technology]

Generally, when distributing an intake air-fuel mixture from one carburetor to each cylinder, an intake manifold is used in which a distribution passage to each cylinder is branched from a collecting portion to which the carburetor is attached. As is well known, when this intake manifold is applied to the three-cylinder internal combustion engine, the distribution passage for the cylinder in the center among the distribution passages in the intake manifold is substantially perpendicular to the cylinder row in plan view. However, since the distribution passages for the two cylinders on both sides have a form inclining in a V shape from the collecting portion toward the cylinders on both sides in a plan view, the intake air-fuel mixture from the carburetor and the fuel propagating through the wall surface are: There is a tendency that more fuel flows toward the center cylinder, and that the fuel atomizability for the center cylinder is worse than that for the other two cylinders. Than it is.

Therefore, Japanese Utility Model Laid-Open No. 55-108262 discloses the prior art.
By providing a groove on the inner wall surface of the inlet hole from the carburetor to the collecting portion of the intake manifold so as to surround the inlet hole, the distribution of the intake air-fuel mixture and the fuel to each cylinder and the atomization property of the fuel can be improved. Propose to improve.

[Problems to be solved by the device]

However, as in this prior art, by providing a groove on the inner wall surface of the inlet hole from the carburetor to the collecting portion in the intake manifold so as to surround the inlet hole, the intake gas mixture from the carburetor is In the portion (1), the flow forms such that it is once expanded and then throttled again, so that the flow resistance of the intake air-fuel mixture is remarkably large and the output is reduced.

Further, since this type of intake manifold is manufactured by casting, the inner wall surface of the inlet hole to the collecting portion is
Forming the groove so as to surround the inlet hole significantly complicates the shape of the core mold for forming the inside of the intake manifold during casting, and significantly increases the cost required for casting the intake manifold. It was

It is an object of the present invention to provide an intake system for a three-cylinder internal combustion engine that solves these problems all at once.

[Means for Solving the Problems]

In order to achieve this object, the present invention provides an intake manifold for a three-cylinder internal combustion engine, which includes a collecting portion to which a carburetor is attached and three distribution passages extending from the collecting portion toward each of the three cylinders. In the above, a bulge portion is formed on the ceiling surface at the entrance portion from the gathering portion to the central distribution passage among the distribution passages, and the bulge portion is formed so as to enlarge the cross-sectional area at the inlet portion. The bulged portions are formed on both the left and right inner side surfaces of the portion so as to reduce the inner width dimension of the bulge portion.

[Function and effect of device]

According to this structure, when the intake air-fuel mixture flowing from the carburetor into the collecting portion and the fuel propagating through the inner wall surface are distributed to the distribution passages, the intake air distributed to the central distribution passage among the distribution passages. A part of the air-fuel mixture flows into the central distribution passage with a small flow resistance through the bulge formed on the ceiling surface at the entrance to the central distribution passage, while the fuel flowing along the inner wall surface Part of the gas will also flow into the bulge, where atomization will be promoted and then into the central distribution passage.

In this case, the flow of the intake air-fuel mixture and the fuel flowing into the central distribution passage via the bulge portion is restricted by the ridges provided on the left and right inner side surfaces of the bulge portion. Therefore, it is possible to set the intake air-fuel mixture and fuel amounts to the central distribution passage so as not to be larger than the intake air-fuel mixture and fuel amounts to the other two distribution passages.
By setting the width dimension between the both raised portions, it can be achieved without increasing the flow resistance of the intake air-fuel mixture to the central distribution passage.

Therefore, according to the present invention, the intake air-fuel mixture flowing from the carburetor into the collecting portion and the fuel propagating through the inner wall surface are distributed substantially equally to the three distribution passages branched from the collecting portion.
This can be achieved reliably without increasing the flow resistance of the intake air, and consequently, reducing the output of the internal combustion engine.
It is possible to surely prevent the fuel atomization property of the central distribution passage of the respective distribution passages from being worse than the fuel atomization properties of the other two distribution passages.

Moreover, the present invention has a configuration in which a bulge portion is provided at the entrance ceiling portion from the gathering portion to the central distribution passage, and ridge portions are provided on both left and right inner side surfaces of the bulge portion. Since the core mold in the case of casting is not complicated as in the prior art, the cost required for casting the intake manifold can be significantly reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In the drawings, reference character A indicates a first cylinder A1, a second cylinder A2, and a third cylinder.
A3 shows an in-line three-cylinder internal combustion engine in which A3 are arranged in a straight line, and a side surface of the internal combustion engine A is an intake air-fuel mixture from a dual-type carburetor 1 having a primary 1a and a secondary 1b. Is connected to each of the cylinders A1, A2, A3 by a cast intake manifold 2.

The intake manifold 2 is provided with the carburetor 1, and is provided with an inlet portion 3a for the intake air-fuel mixture from the carburetor 1, and a collector portion 3 from the collector portion 3 to the cylinders A1, A2, A3. It is composed of three distribution passages 7, 8 and 9 that branch to extend substantially horizontally and horizontally toward the intake ports 4, 5 and 6.

In this case, the distribution passage 8 for the central second cylinder A2 among the distribution passages 7, 8, 9 is substantially perpendicular to the cylinder row in plan view, but the first cylinder A1 and the third cylinder A3 Both of the distribution passages 7 and 9 for the cylinders are inclined in a V shape from the collecting portion 3 toward the cylinders A1 and A3 on both sides in a plan view.

Then, on the ceiling surface at the entrance of the distribution passages 7, 8, 9 from the gathering portion 3 to the central distribution passage 8, there is a bulge portion 10 having an enlarged cross-sectional area at the entrance. The width dimension of the bulge portion 10 is narrowed from the width dimension (W1) substantially equal to the inner diameter of the central distribution passage 8 to each of the left and right inner side surfaces of the bulge portion 10 ( The ridges 11 and 12 that have been reduced to W2) are integrally formed.

In such a structure, when the intake air-fuel mixture flowing from the carburetor 1 into the collecting portion 3 and the fuel propagating through the inner wall surface are distributed to the distribution passages 7, 8 and 9 in the collecting portion 3, A part of the intake air-fuel mixture distributed to the central distribution passage 8 among the passages 7, 8 and 9 has a bulge portion formed on the ceiling surface at the inlet thereof as shown by a dotted arrow B in FIG. While flowing into the central distribution passage 8 with a low flow resistance via 10, a part of the fuel traveling along the inner wall surface also flows into the bulging portion 10, where atomization is promoted. After that, it will flow into the central distribution passage.

On the other hand, the flow of the intake air-fuel mixture and the fuel flowing into the central distribution passage 10 through the bulge portion 10 is restricted by the ridges 11 and 12 provided on the left and right inner side surfaces of the bulge portion 10. Therefore, the intake air-fuel mixture and fuel amount to the central distribution passage 8 should be set so as not to be larger than the intake air-fuel mixture and fuel amount to the other two distribution passages 7 and 9. However, by setting the width dimension (W2) between the both raised portions 11 and 12, it is possible to surely achieve without increasing the flow resistance of the intake air-fuel mixture to the central distribution passage 8.

[Brief description of drawings]

1 is a plan view, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is an enlarged view of a main part in FIG. 2, and FIG. 3 is a sectional view taken along line IV-IV of FIG. 3, FIG. 5 is a sectional view taken along line VV of FIG. 3, and FIG. 6 is a sectional view taken along line VI-VI of FIG. A ... Internal combustion engine, A1, A2, A3 ... Cylinder, 1 ... Vaporizer, 2
...... Intake manifold, 3 ...... Collector, 3a …… Inlet hole,
4,5,6 …… Intake ports, 7,8,9 …… Distribution passages, 10 …… Bulging parts, 11,12 …… Raised parts.

Claims (1)

[Scope of utility model registration request] 1. An intake manifold for a three-cylinder internal combustion engine, comprising: a collecting portion to which a carburetor is attached, and three distribution passages extending from the collecting portion toward each of three cylinders.
A bulge portion is formed on the ceiling surface at the entrance portion from the gathering portion to the central distribution passage of each of the distribution passages, and a bulge portion is formed so as to increase the cross-sectional area of the inlet portion. An intake system for a three-cylinder internal combustion engine, characterized in that a raised portion is formed on each of the left and right inner side surfaces so as to reduce the inner width dimension of the bulge portion.