JPH0331892B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to an intake passage for an internal combustion engine, and more particularly to an improvement in the shape of an intake port of a multi-valve reciprocating internal combustion engine having a plurality of intake valves per cylinder.

(Prior Art) Internal combustion engines with two intake valves per cylinder are being adopted in general passenger cars for the purpose of improving intake efficiency and output characteristics, but when high-speed performance is not particularly required, In consideration of costs, it has been considered to use only one exhaust valve, and therefore some engines have a three-valve type engine configuration with three intake and exhaust valves in total.

One example of this type of three-valve engine is the one shown in FIG.

As shown in the figure, two intake valves 3A and 3 having approximately the same diameter are installed in the combustion chamber 2 of the cylinder head 1.
B, and a so-called Siamese-shaped suction port 4 having corresponding passage portions 4A and 4B branched from the middle is formed.

By the way, the two intake valves 3A and 3B like this
In a configuration in which the engines are arranged in parallel and only one exhaust valve is provided, if the spark plug is placed in the center of the combustion chamber 2 with emphasis on combustion efficiency only, the effective diameter of the exhaust valve will not be sufficient. Therefore, as shown in the figure, the exhaust valve 5 and the spark plug 6 are arranged in parallel with each other, that is, the exhaust valve 5 is arranged in front of one intake valve 3A, and the spark plug 6 is arranged in front of the other intake valve 3B. become. (For known examples of three-valve engines, see Japanese Patent Laid-Open Nos. 59-93926, 105925, etc.) (Problems to be Solved by the Invention) However, according to the above valve arrangement, the ignition plug 6
is also located approximately on the extension of one of the branch passages 4B of the intake port 4, so during low-temperature operation when the fuel in the intake air is supplied in a substantially liquid state, the electrode part of the ignition plug 6 is located in the port branch passage. It will be exposed to the liquid fuel that has flowed into the combustion chamber section 2 via the section 4B. Therefore, at low temperatures, discharge is inhibited by so-called fog, resulting in poor startability, resulting in the problem that stable idling and drivability are difficult to obtain even after starting.

This invention was made with the aim of solving such conventional problems.

(Means for solving the problem) In order to achieve the above object, the present invention focuses on the fact that most of the liquid fuel flows along the lower wall surface of the intake passage and the intake port, and as described above, At least two intake valves and at least one exhaust valve are provided per cylinder, and an intake port having a passage section branching from the middle corresponding to each of the two intake valves is formed, and at least one branching port is formed. In an internal combustion engine in which an ignition plug is arranged in front of a passage and an exhaust valve is arranged in front of another branch passage, an upwardly sloped part is provided in the middle of the branch passage facing the ignition plug, and the exhaust valve is The middle portion of the other branch passage portion was formed at a lower level than the ascending slope portion.

(Function) According to the above configuration, the fuel that enters the intake port in a liquid state at low temperature attempts to branch to each branch passage along the lower part of the port, but the branch passage on the ignition plug side has an upward slope along the way. In addition, the part of the branch passage on the exhaust valve side that corresponds to the upward slope part is at a lower level, in other words, the branch passage on the exhaust valve side is connected from the branch passage on the ignition plug side to the branch passage on the exhaust valve side. Since the slope slopes downward toward , most of the liquid fuel is forced toward the exhaust valve side branch passage.

Furthermore, even if a certain amount of liquid fuel were to proceed through the ignition plug side branch passage, since this branch passage has an upward slope in the middle, the portion immediately before reaching the combustion chamber would almost follow the intake valve stem. Since the fuel flow descends on a steep slope, by changing its direction along this steep slope, the fuel flow, which is mainly composed of vertical velocity components, will not proceed toward the spark plug after entering the combustion chamber.

Therefore, the spark plug can exhibit stable ignition performance without being exposed to liquid fuel.

Next, embodiments of the present invention will be described based on the drawings. Note that substantially the same parts as in FIG. 5 are designated by the same reference numerals.

(Example) In FIG. 1, 10 is an intake manifold;
11 is an intake port that introduces the intake air flow from the intake manifold 10 into the engine combustion chamber 2; 11A is a branch passage that branches from the middle of the intake port 11 and reaches the first intake valve 3A for the exhaust valve 5; , 11B is a branch passage section leading to the second intake valve 3B for the ignition plug 6.

The two branch passage sections 11A and 11B branch symmetrically from each other's branch point 12 on a plane, but when viewed from the side, the branch passage section 11A on the exhaust valve 5 side branches out as shown in FIG. The branch passage section 11B on the side of the spark plug 6 has its bottom surface connected to the inlet section 1.
3 to near the branch point 12 becomes an upward slope section 15, and the downstream side of the branch point 12 is steeply sloped and its center line is approximately at the intake valve stem 1.
The fuel chamber part 2 has a directionality close to vertical along 6.
It is open to

Based on such an intake port shape, among the liquid fuel that has flowed into the intake port 11 along the bottom surface of the intake manifold 10, the fuel that is flowing toward the ignition plug side branch passage section 11B is directed toward the upward slope section. At 15, its momentum in the advancing direction is reduced, and at the same time, it is urged by gravity toward the exhaust valve side branch passage section 11A located at a lower position. Therefore, most of the liquid fuel is introduced into the exhaust valve side branch passage section 11A.

Furthermore, if liquid fuel enters the spark plug side branch passage section 11B, this fuel changes its direction in a substantially vertical direction together with the intake air flow and enters the combustion chamber section 2 and the cylinder.

Therefore, the liquid fuel does not come into direct contact with the ignition point 6, and stable ignition performance can be guaranteed.

Needless to say, the atomized or vaporized fuel flows into the two branch passages 11A and 1 along with the intake air.
The flow is evenly divided into 1B and enters the cylinder.

FIG. 3 shows another embodiment of the invention. This is the branch passage portions 11A and 11B of the suction port 11.
The side shape of is the same as that in FIG. 2, but in plan view, the port inlet portion 13 is offset toward the exhaust valve 5 side as shown in the figure, and the intake manifold 10 and the exhaust valve side branch passage portion 11A are formed. It is arranged in almost a straight line. Thereby, the liquid fuel from the intake manifold 10 can be introduced exclusively into the exhaust valve side branch passage section 11A by utilizing its inertia, and the amount of liquid fuel entering the ignition plug side branch passage section 11B can be further reduced. Can be reduced.

Furthermore, in each of the above embodiments, a step as shown in FIGS. 4A and B is formed along the lower edge of the opening of the ignition plug side branch passage section 11B (section C in FIG. 3) when viewed from the port inlet section 13. By forming the attached portion 18 or the groove 19, it is possible to more reliably suppress the liquid fuel that tends to flow along the port bottom surface to the spark plug side branch passage portion 11B.

(Effects of the Invention) As described above, according to the present invention, liquid fuel is prevented from flowing into the branch passage section of the intake port facing the spark plug, thereby avoiding the liquid fuel from directly adhering to the spark plug. As a result, the ignition performance of the ignition plug can be maintained at a good level. Therefore, the startability of the multi-valve internal combustion engine at low temperatures and the driving performance after guidance can be improved, and deterioration in fuel efficiency and exhaust composition caused by poor ignition or irregular combustion can be avoided.

[Brief explanation of drawings]

FIG. 1 is a bottom view of an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line A--A. FIG. 3 is a bottom view of another embodiment, and FIGS. 4A and 4B are sectional views showing an example of the shape of the portion along the line BB. FIG. 5 is a bottom view of the conventional example. 1...Cylinder head, 2...Combustion chamber part, 3
A, 3B... Intake valve, 4, 11... Intake port,
4A, 4B, 11A, 11B... Branch passage section of the suction port, 5... Exhaust valve, 6... Spark plug, 15...
...Uphill slope section.

Claims (1)

[Claims] At least two intake valves and at least one exhaust valve are provided per cylinder, and an intake port having a passage part branching from the middle corresponding to each intake valve is formed, and at least one branch passage part. In an internal combustion engine in which an ignition plug is disposed in front of the ignition plug and an exhaust valve is disposed in front of another branch passage, an ascending slope part is provided in the middle of the branch passage facing the ignition plug, and the other side facing the exhaust valve is An intake system for an internal combustion engine, characterized in that an intermediate portion of the branch passage portion is formed at a lower level than the upward slope portion.