JPH0368213B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an intake port structure for an engine that is provided with a plurality of intake valves facing a combustion chamber.

(Prior Art) As is well known, by strengthening the flow of the air-fuel mixture taken into the combustion chamber by swirling, the combustion speed is increased and knocking is suppressed.

Conventionally, the two intake ports facing the combustion chamber are both straight-shaped, and the diameters of the two intake valves that open and close are made different, so that the amount of air-fuel mixture from one intake port is larger than the other. Some devices actively generate the above-mentioned swirl based on the difference in momentum (see Japanese Patent Publication No. 156408/1983).

However, in the above-mentioned conventional technology, since the diameters of the intake valves are different, the number of types of intake valves increases and the number of parts increases. Therefore, manufacturability is poor.

(Object of the invention) This invention was made in order to solve the above-mentioned conventional problems, and without causing an increase in the number of parts,
It is an object of the present invention to provide an intake port structure for an engine that generates the swirl and suppresses knocking.

(Structure of the Invention) In order to achieve the above object, the present invention first makes the area of the opening to the combustion chamber the same in a plurality of straight-shaped intake ports through which the intake valve opens and closes. In addition, the narrowest part in the middle of the intake port that forms one of the two openings that are farthest from the center of the cylinder bore is smaller than the narrowest part in the middle of the intake port that forms the other opening. is forming.

According to this invention, since the opening areas of all intake ports are the same, the shapes of all intake valves are the same.
The dimensions can be made the same. Therefore, the number of parts does not increase. Also, the two openings furthest from the center of the cylinder bore try to generate swirls in opposite directions that cancel each other out.
Since the narrowest part of one of the intake ports is formed to be smaller than the narrowest part of the intake port forming the other opening, a difference occurs in the amount of air-fuel mixture sucked into the combustion chamber from the intake port. Therefore, swirl is effectively generated and knocking can be suppressed.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1, 1 is a cylinder, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5 is an intake pipe, 6 is an exhaust valve, 7 is an exhaust port, and 8 is a carburetor.

9, 9 are intake valves;
As shown in FIG. 2, the two intake ports 5A and 5B, both of which are straight ports, are opened and closed. The intake ports 5A and 5B are the combustion chamber 4
The areas of the openings 10 are the same. A narrowest portion 5a is formed in the middle of one intake port 5A, the cross-sectional area of which is reduced. This narrowest part 5a
may be narrowed in any shape with respect to the cross-sectional area of the intake port 5A, but in the case of this embodiment, the narrowest portion 5a is formed concentrically with respect to the intake port 5A having a circular cross section. are doing.

In the above configuration, the air-fuel mixture formed in the carburetor 8 of FIG. 1 is separated from the intake pipe 5 of FIG. 4 will be introduced. here,
Since the intake port 5A is provided with the narrowest portion 5a, the amount of air-fuel mixture introduced into the combustion chamber 4 from the intake port 5A is smaller than that of the intake port 5B. Therefore, the size of the swirl to be generated in the air-fuel mixture introduced from the intake port 5A is
The arrow SA indicates the intake port 5B, whereas the arrow SB indicates the intake port 5B. Therefore, an intake swirl as shown by arrow S is generated from the difference between both SA and SB, improving combustion efficiency and suppressing knocking.

Furthermore, in order to generate the intake swirl as described above, the present invention employs a simple structure in which the narrowest portion 5a is formed in the middle of one intake port 5A. For this reason, the shape of the intake valves 9, 9,
The dimensions can be made the same, and there is no reduction in manufacturability due to an increase in the number of parts as in the conventional case.

The first embodiment described above is for a case where the number of intake ports is two, but a case where the number of intake ports is three or more will be described below.

In FIG. 3 showing the second embodiment of the invention, intake ports 5A, 5B, and 5C have openings 1
The areas of 0A, 10B, and 10C are all the same. The openings 10A and 10B are the most distant from the center 11 of the cylinder bore 1a, and a narrowest portion 5a having an elliptical cross section is provided in the middle of the intake port 5A forming one of the openings 10A.
Note that the other configurations are similar to those of the first embodiment, and the same components are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In the above configuration, the air-fuel mixture introduced from the intake port 5C is sucked toward the center 11, so that no swirl occurs. Further, the amount of air-fuel mixture introduced from the intake port 5B is larger than that of the intake port 5A since the intake port 5A has the narrowest portion 5a. Therefore, the swirl S is generated in the same way as in the first embodiment.

(Effects of the Invention) As explained above, according to the present invention, the difference in the amount of air-fuel mixture taken into the combustion chamber from the straight-shaped intake port, that is, the difference in the momentum of the air-fuel mixture, As a result, swirl is generated and knocking can be effectively suppressed. Moreover, because the means for achieving this is a simple structure in which the narrowest part of one intake port is formed smaller than the narrowest part of the other intake port, manufacturability is reduced due to an increase in the number of parts as in the past. There is no invitation.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the invention, and FIG. 2 is a schematic plan view of the embodiment. FIG. 3 is a schematic plan view showing a second embodiment of the invention. 4... Combustion chamber, 5A, 5B, 5C... Intake port,
5a... Narrowest part, 9... Intake valve, 10, 10A,
10B, 10C...Opening, 1a...Cylinder bore, 1
1...Center.

Claims (1)

[Claims] 1. In an engine intake port structure having a plurality of intake valves facing the combustion chamber of the engine, the areas of the openings into the combustion chamber of the plurality of straight-shaped intake ports through which the intake valves open and close are all the same, and , the narrowest part in the middle of the intake port forming one of the two openings furthest from the center of the cylinder bore is smaller than the narrowest part in the middle of the intake port forming the other opening. The engine intake port structure is characterized by the following: