JP3096149B2 - Combustion chamber of heat shield engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber of a heat shield engine for improving the combustion state of an engine having a sub-chamber and a combustion chamber having a heat shield structure.

[0002]

2. Description of the Related Art In recent years, heat-shielding materials capable of withstanding high temperatures, such as ceramics, and having low thermal conductivity have been used in the combustion chambers and related parts of engines to enable high-temperature operation without cooling. Engines are being developed. This type of heat-shielding engine has the advantages that the weight of the engine itself is reduced because the cooling device is not required, and that the thermal efficiency is excellent and energy is saved.

[0003]

In the heat-shielding engine using the above-mentioned ceramics, since the wall temperature of the combustion chamber is high and exceeds 700 C, the drawn air is overheated and expanded. When the superheated air in this state is compressed, the fuel is injected at the end of the compression stroke at 200 ° C. to 300 ° C. as compared with an engine equipped with a normal cooling device.
When the temperature becomes high and fuel is injected into the high-temperature air, there is a problem that the mixture of the fuel and the air is poor and combustion is not sufficiently performed.

The present invention has been made in view of such a problem, and an object of the present invention is to improve a communication flow path between a sub-chamber and a main combustion chamber arranged at the upper center of a cylinder having a main combustion chamber. It is another object of the present invention to provide a combustion chamber of a heat shield engine which promotes mixing of fuel and air to obtain a good combustion state.

In order to achieve the above object, according to the first aspect of the present invention, in a combustion chamber of a heat-shielding engine having a heat-shielding structure having a sub-chamber, a sub-chamber provided at the upper center of a cylinder head. A piston connected to a piston head and a body by a coupling ring and reciprocally fitted into the cylinder liner, and penetrates into the opening of the sub chamber near the top dead center of the piston, A disk-shaped protrusion provided on the piston head for closing the opening, a plurality of narrow grooves which are inclined downward and are cut radially at the lower end of the inner wall of the opening of the sub-chamber, and the narrow grooves A plurality of sub-chambers-a narrow communication flow passage formed between the main combustion chamber and a plurality of sub-chambers formed by a concave groove on the outer peripheral upper edge of the projection that is inclined in the same direction as the narrow groove and is engraved in the radial direction at the corresponding portion. Provided with a combustion chamber of a heat shield engine characterized by having It is. In the invention according to claim 2 of the present application, in the invention according to claim 1, the opening of the sub-chamber is closed within a range of 10 degrees to 20 degrees in crank angle, and the combustion of the heat shield engine is performed. Provide room. In the invention according to claim 3 of the present application, in the invention according to claim 1, the communication flow path is 5 to 2 times smaller than the opening of the sub chamber.
A combustion chamber of a heat shield engine characterized by being about 0%.

[0006]

A projection for closing the opening of the sub-chamber is provided on the upper surface of the piston, and a narrow groove and a concave groove are formed at the lower end of the opening of the sub-chamber and the projection of the piston so as to cut off respective corners, thereby providing a narrow communication flow. In the initial stage of combustion, combustion with little generation of nitrogen oxides is performed in the sub-chamber closed by the projections, and then the flame is sharply blown out from the sub-chamber through the communication flow passage into the main combustion chamber, and , And sufficiently mixed with the vortex of fresh air to perform good combustion.

[0007]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a combustion chamber of a heat shield engine according to the present invention, and FIG. 2 is an explanatory view showing a combustion state in a main combustion chamber.

In these drawings, reference numeral 1 denotes a sub-chamber serving as a sub-combustion chamber, which is connected to the upper center of the head portion 21 of the cylinder 2 and is opened in the lower piston direction. The head portion 21 is made of a ceramic having high strength and heat resistance. An injection nozzle 11 is inserted into the ceiling of the sub-chamber 1 and performs fuel injection at the end of the compression stroke.

Reference numeral 3 denotes a piston, and a piston head 31 and a body 3 made of ceramics having high strength and capable of withstanding high temperatures.
2 and these parts are connected to each other by a coupling ring 33. A disk-shaped projection 311 is formed on the upper surface of the piston head 31 and corresponds to the opening of the sub-chamber 1 and is closed at the top dead center position. The opening is closed between 10 degrees and 20 degrees. At the lower end of the inner wall of the opening, narrow grooves 12 inclined downward at four places are cut radially, and further, the upper peripheral edge of the projection 311 on the upper part of the piston 3 has an oblique corresponding to the narrow grooves 12. Recessed grooves 31a are engraved, and these grooves serve as communication passages between the sub-chamber 1 and the main combustion chamber, and the communication passages are formed at 5 to 20% of the opening. . Reference numeral 34 denotes a piston ring attached to the body 32 of the piston 3 for maintaining airtightness with the inner wall of the cylinder liner 22 and scraping off oil when the piston 1 reciprocates.

Next, the operation of this embodiment constructed as described above will be described. In the compression stroke, the piston 3 rises in accordance with the rotation of the crankshaft to compress the air inside the cylinder 2, and at the end of the compression stroke, The generated air flows into the sub-chamber 1 as a vortex and mixes with the fuel injected from the injection nozzle 11, and the air-fuel mixture is ignited by the heat of compression to start combustion.

This combustion gas explosively expands and tries to flow out of the sub chamber 1 into the main combustion chamber.
Is closed by the projection 311 on the upper surface of the piston during the predetermined crank angle at the top dead center position, the fuel is stopped inside the sub-chamber 1 and burns in an extremely rich mixture state, and the combustion is performed with a large equivalent ratio. The formation of nitrogen oxides is suppressed by air.

The four communication channels formed by the narrow groove 12 and the concave groove 31a delay the outflow of the combustion flame to the outside due to the pores, so that the unburned rich air-fuel mixture inside the sub-chamber 1 is removed. As shown in FIG. 2, the combustion gas contained blows out strongly to reach the peripheral wall of the cylinder 2 through the communication flow path and mixes with external air as shown in FIG. Abrupt combustion is performed by mixing with the fresh air vortex in the direction of arrow A.

Although the present invention has been described with reference to the above-described embodiments, various modifications can be made within the scope of the present invention, and these modifications are not excluded from the scope of the present invention.

[0015]

According to the present invention as in the above embodiment,
A sub-chamber is provided in the upper center of the cylinder in the heat shield engine, and a projection is provided on the upper surface of the piston near the top dead center position to close the opening of the sub-chamber. Since there is no throttling loss, the lower end of the opening of the sub-chamber and the projection of the piston are cut out at the respective corners during combustion, and the cut-out direction is the same as the vertical movement direction of the piston when viewed from the side. Since a narrow communication flow path between the sub chamber and the main combustion chamber is provided by a plurality of narrow grooves and a concave groove on the outer peripheral edge of the projection formed in the same direction as the narrow grooves, the initial combustion is closed. The combustion of the fuel in the sub-chamber with a high equivalence ratio suppresses the production of nitrogen oxides and promotes the production of an air-fuel mixture.
The effect is obtained that the penetration of the flame blown out from the narrow communication channel into the main combustion chamber reaches the peripheral wall of the cylinder, mixes with fresh air, and prompt combustion takes place.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a combustion chamber of a heat shield engine according to the present invention.

FIG. 2 is an explanatory diagram showing a combustion state in a main combustion chamber of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Subchamber 2 ... Cylinder 3 ... Piston 11 ... Narrow groove 21 ... Head part 31 ... Piston head 31a ... Concave groove 311 ... Projection

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI F02F 3/00 302 F02F 3/00 302A 3/28 3/28 B (58) Investigated field (Int.Cl. ⁷ , DB name ) F02B 19/04 F02B 19/16 F02B 19/18 F02F 1/24 F02F 3/00 302 F02F 3/28

Claims (3)

(57) [Claims] In a combustion chamber of a heat shield engine having a sub-chamber and a heat-shielding structure, a sub-chamber provided at the upper center of a cylinder head is connected to a piston head and a body by a connecting ring, and a cylinder liner is provided. A piston inserted reciprocally into the piston, a disc-shaped protrusion provided on the piston head that penetrates into the opening of the sub-chamber near the top dead center position of the piston, and closes the opening. A plurality of narrow grooves which are inclined downward and are radially cut at the lower end of the inner wall of the opening of the sub-chamber; A combustion chamber for a heat shield engine, comprising: a plurality of sub-chambers formed by the provided outer peripheral upper edge concave grooves and a narrow communication flow path between the main combustion chamber. 2. The method according to claim 1, wherein the opening of the sub-chamber is closed at a crank angle of 10 to 20 degrees.
The combustion chamber of the heat shield engine described. 3. The combustion chamber of a heat shield engine according to claim 1, wherein said communication flow path is about 5 to 20% of the opening of the sub-chamber.