JPH04159419A - Structure of combustion chamber of engine - Google Patents

Abstract

PURPOSE:To improve combustibility by protruding and forming a mask from the wall of a combustion chamber on the cylinder head side to peripheral wall sections of port up to the vicinity of virtual lines which connect each central point of suction air side ports and a suction air center port in the structure of the combustion chamber of an engine of suction air three valve type. CONSTITUTION:An ignition plug hole 3 is opened at the center of a combustion chamber 2 of pent roof type of a cylinder head 1. In the system in which a suction air center port 4 is formed on the suction air side of the cylinder head 1 and suction air side ports 5, 6 are formed on the right and left, when a virtual line which connects centers a, b of each suction air port 4, 5 is alpha and a virtual line which connects centers a, c of each suction air port 4, 6 is beta, a mask 9 is protruded and formed from a wall 2a of the combustion chamber on the cylinder head 1 side to peripheral wall sections 4a to 6a of port of each suction air port 4 to 6 up to the vicinity of each virtual line, alpha, beta. Consequently, tumble component in the reverse direction which is produced in the initial period of opening of suction air valve in particular cannot be produced by the mask 9, and tumble in the forward direction only can be produced to improve combustibility.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention is applicable to engines such as five-valve engines in which three intake valves and two exhaust valves are arranged for a single cylinder, for example. Regarding the combustion chamber structure.

(Prior Art) Conventionally, as a multi-valve engine of the above-mentioned example, there is a structure described in, for example, Japanese Patent Application Laid-open No. 58-113512.

That is, 3 intake valves for a single cylinder and 2
This is a 5-valve engine with multiple exhaust valves installed to increase engine output.

By the way, in order to improve combustibility in the above-mentioned five-valve engine, it is necessary to generate a vertical swirl flow (tumble) in which the intake air flowing into the combustion chamber from the intake port swirls in a plane parallel to the cylinder axis. Combustibility can be improved by directional flow of intake air in the pipe.

However, in the above five-valve engine, when only the two intake side valves open, or when only the intake center valve opens, there is relatively little interference between the intake flows;
While it is possible to generate a forward tumble well, if the three intake valves are opened at the same time, a tumble in the opposite direction that cancels out the tumble in the forward direction is generated due to the interference of the intake air flows with each other, so it is not enough. There was a problem that it was not possible to improve the combustibility.

Therefore, the present applicant attempted to investigate various causes of the generation of reverse tumble, and found that the above-mentioned reverse tumble occurs on the intake side port surrounding wall, especially in the early stages of opening of the intake valve when the lift amount of the intake side valve is small. It was found that this was generated due to the gap between the intake center boat and the surrounding wall of the intake center boat.

(Object of the invention) This invention provides a unique squish area,
In particular, by masking the reverse tumble component generated at the initial stage of intake valve opening and generating only the forward component tumble, the forward tumble from the time of low intake valve lift is strengthened and the combustibility is improved. It is an object of the present invention to provide a combustion chamber structure for an engine that can improve the combustion chamber structure of the engine and can effectively prevent fuel from adhering to the wall surface.

(Structure of the Invention) The present invention provides a combustion chamber structure for an intake three-valve type engine in which intake side boats are provided on the left and right sides of an intake center port, and the intake side boats, which connect the center points of the intake center boats, are provided. The combustion chamber structure of the engine is characterized in that the squish area is extended by forming a mask protruding from the combustion chamber wall on the cylinder head side to the boat peripheral wall to a position near the imaginary line.

(Effects of the Invention) According to the present invention, the mask is formed to protrude from the combustion chamber wall on the cylinder head side to the boat peripheral wall part to the above-mentioned predetermined position to extend the squish area, so especially at the initial stage of opening of the intake valve. The tumble component in the backward direction to be generated can be made impossible to generate by using the above-described mask, and only the tumble component in the forward direction can be generated.

As a result, the forward tumble of the intake valve from the time of low lift is strengthened, and the combustibility can be improved.

In addition, by extending the squish area as described above, the intake air flow flowing from the wall surface of the combustion chamber to the center of the combustion chamber has the effect of effectively preventing fuel from adhering to the wall surface of the combustion chamber.

(Example) An embodiment of the present invention will be described in detail below based on the drawings.

The drawings show the combustion chamber structure of a five-valve engine. In FIGS. 1 and 2, when the cylinder head is viewed from the piston side, a spark plug hole 3 is located approximately in the middle of the pent-roof type combustion chamber 2 of the cylinder head 1. Open this spark plug hole 3
The spark plug is arranged so that the plug gap is located on the combustion chamber 2 side.

Further, an intake center port 4 is formed on the intake side of the above-mentioned cylinder head 1 and communicates with the combustion chamber 2 as appropriate, and this intake center port 4 is provided with an intake center valve that is opened and closed by a valve mechanism. There is.

Furthermore, combustion chambers 2 are located on the left and right sides of the above-mentioned intake center port 4.
The left and right intake side boats 5 and 6 are respectively provided with intake side valves that are opened and closed by valve operating mechanisms.

On the other hand, two exhaust ports 7.8 are formed on the exhaust side of the cylinder head 1, which communicate with the combustion chamber 2 as appropriate, and each of these exhaust ports 7.8 is provided with an exhaust valve that is opened and closed by a valve mechanism. They are respectively arranged to form a 5-valve engine with 3 intake valves and 2 exhaust valves.

By the way, the virtual line connecting the center a of the intake center bolt 4 and the center of the intake side boat 5 on one side is α, and the center a of the intake center port 4 and the center C of the intake side boat 6 on the other side is α. When the connecting imaginary line is β, each of these imaginary lines α
, up to a position near β, the combustion chamber wall 2 on the cylinder head 1 side
From a to the boat peripheral wall portions 4a, 5 of each intake port 4, 5.6
A mask 9 is formed to protrude from a and 5a to extend a squish area 10 (shown with hatching in FIG. 1 for convenience of explanation).

The above-mentioned mask 9 protrudes toward the cylinder 11 (see Fig. 3) formed in the cylinder block by a predetermined height H so as not to interfere with the top dead center of the piston, and this height H is set by the following formula. Ru.

H≧DX0.15 However, D is the throat diameter 0.15 is the experimentally determined value (4th (see figure).

In addition, as shown in FIG. 4 above, when H/D is less than 0.15, tumbles in the opposite direction tend to be generated, and when H/D is 0.
．． The data shown is experimentally determined to indicate that forward tumbles are generated when the value is 15 or more.

In this way, an imaginary line α connects each center point S, a, and c of the intake side port 5.6 and the intake center port 4.

Combustion chamber wall 2 on the cylinder head 1 side to a position near β
The mask 9 is formed protruding from the port peripheral wall portions 4a, 5a, and 6g from a to extend the squish area 10, and the height H of the mask 9 is set to 0.15D or more. The generated backward tumble component e (see FIG. 3) can be made impossible to generate by the mask 9 described above, and only the forward direction component tumble d (see FIG. 3) can be generated.

As a result, the forward tumble of the intake valve from the time of low lift is strengthened, and the combustibility of the five-valve engine can be improved.

In addition, since the squish area 10 is extended as described above, the intake air flow flowing from the wall surface of the combustion chamber 2 to the center of the combustion chamber 2 has the effect of effectively preventing fuel from adhering to the wall surface of the combustion chamber 2. be.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention. Fig. 1 shows the structure of the combustion chamber of the engine as the cylinder head is viewed from the piston side, Fig. 2 is a perspective view of the same, and Fig. 3 shows a forward tumble. FIG. 4 is a schematic perspective view showing tumble and reverse tumble, and FIG. 4 is a characteristic diagram. 1... Cylinder head 2... Combustion chamber 2a... Combustion chamber wall 4... Intake center port 5.6... Intake side ports 4a, 5a, 6a... Port peripheral wall portion 9... Mask 10... Squish areas a, b, c... Center points α, β... Virtual line Figure 3 0.15 - Misery%

Claims (1)

[Claims] (1) A combustion chamber structure of a three-valve intake engine in which intake side ports are provided on the left and right sides of an intake center port, up to a position near the imaginary line connecting the center points of the intake side ports and the intake center port. An engine combustion chamber structure in which a mask is formed protruding from the combustion chamber wall on the cylinder head side to the port peripheral wall to extend the squish area.