JPH0196421A - Combustion chamber of diesel engine - Google Patents

Abstract

PURPOSE:To utilize air in respective sections in combustion chamber sufficiently over the entire operating zone of an engine by providing a plurality of recesses opening in oval onto the inner circumferential face of the combustion chamber. CONSTITUTION:Shapes of reflection faces of fuel spray ejected through respective ejection ports are differentiated by forming four recesses 6 opening in oval shape formed with curved faces or approximately curved faces onto the inner circumferential face of a combustion chamber 2 arranged on the top face of a piston 1. Consequently, air flow entered into the recess 6 flows out in all directions along the profile of the opening. As a result, a three-dimensional complex air flow is produced in the combustion chamber 2 to double swirl suppression effect under high rotary speed region of engine, while air even in the bottom and the central section can be utilized sufficiently, resulting in a good combustion over the entire operating zone.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a combustion chamber of a diesel engine in which fuel is injected and supplied toward the inner peripheral surface of the combustion chamber recessed in the top surface of a piston. It is.

<Prior Art> Conventional combustion chambers of this type of diesel engine are as described in Japanese Patent Publication No. 4Q-1AAIN, Japanese Patent Publication No. 51-42249, or U.S. Patent No. 3,302,627. Some combustion chambers have a plurality of recesses or protrusions on the inner circumferential surface of the combustion chamber to improve combustion efficiency.

These combustion chambers suppress the velocity of the swirling flow (hereinafter referred to as swirl) of the intake air within the combustion chamber, especially in the high-speed rotation range of the engine, by using recesses or protrusions provided on the peripheral surface of the combustion chamber. The aim is to improve combustion efficiency over a wide range of operating ranges by actively utilizing the small vortices created by the provision of a combustion engine to promote mixing of air and fuel.

<Problems to be Solved by the Invention> However, in the past, only a rectangular opening recess or a columnar protrusion was provided, so the effect of suppressing the swirl speed and the small vortex flow caused by the recess or protrusion were poor. The generation area is limited to a two-dimensional range within a plane parallel to the top surface of the piston. Therefore, there is a problem in that the air at the bottom and center of the combustion chamber, where these influences are difficult to reach, cannot be fully utilized, and there is a limit to how much combustion efficiency can be improved.

The present invention has been made to solve these conventional problems, and aims to further improve combustion efficiency by fully utilizing the air in each part of the combustion chamber in all operating ranges of the engine.

Means for Solving the Problems> In order to achieve the above object, the present invention has a combustion chamber recessed in the top surface of the piston, and the combustion chamber is provided at the tip of the fuel injection nozzle attached to the cylinder head. In a diesel engine that injects fuel toward the inner peripheral surface of the combustion chamber, a plurality of recesses opening in an oval or elliptical shape are provided in the inner peripheral surface of the combustion chamber.

Effect> Since the recess opening in an oval or elliptical shape is thus provided on the inner peripheral surface of the combustion chamber, the airflow that enters the recess flows out in all directions along the shape of the opening. Therefore, a three-dimensional complex air flow is generated within the combustion chamber, which doubles the swirl suppression effect in the high-speed rotation range of the engine, and also makes full use of the air at the bottom and center of the combustion chamber. This allows for good combustion in all operating ranges of the engine.

<Example> Examples of the present invention will be described in detail below based on the drawings.

A throttle 4 is provided around the entire opening of a combustion chamber 2 provided on the top surface of a piston l that reciprocates within a cylinder (not shown).

Further, a diesel engine is constructed by providing a conical projection 5 on the bottom surface of the combustion chamber 2, and attaching a hole-type fuel injection nozzle 3, which has five nozzles equally spaced at the tip, to a cylinder head (not shown). There is.

Furthermore, by forming four concave portions 6 having an elliptical opening formed by a curved surface or a surface approximating a curved surface at equal intervals on the inner circumferential surface of the combustion chamber 2, the fuel spray 7 injected from each nozzle is prevented. The shape of the reflecting surface (collision surface) is different for each.

In this embodiment, the number of recesses 6 is one less than the number of nozzles in the fuel injection nozzle 3, but conversely, the number of recesses 6 may be one more than the number of nozzles. Although it is desirable to vary the shape (reflection condition) of the reflecting surface of the fuel injection n7 from each nozzle by varying the number of concave portions 6, the number of nozzles and concave portions 6 may be the same.

In the diesel engine configured in this manner, as the engine operates, the combustion chamber 2 is filled with air having a swirl speed proportional to the engine rotational speed, and the air flows from the nozzle of the fuel injection nozzle 3 to the inner periphery of the combustion chamber 2. Fuel is injected towards the surface. At this time, since the recess 6 is provided on the inner peripheral surface of the combustion chamber 2, the swirl speed is appropriately suppressed by contact with the recess 6. In addition, as a result of the air flowing into the recess 6 flowing out along the opening shape (elliptical shape), the combustion chamber 2
Inside, airflow is generated in all directions.

On the other hand, since the shape of the inner peripheral surface with which the fuel spray 7 collides is different, various different reflection states (collision states) occur.

Therefore, even if the diffusion state of the fuel spray 7 changes depending on the operating conditions of the engine, air-fuel mixtures with various properties are generated within the combustion chamber 2.

Therefore, an air-fuel mixture with properties suitable for ignition exists somewhere in the combustion chamber 2, and the ignition delay is shortened.

Furthermore, even after ignition, the mixing condition in the combustion chamber 2 is good, so the combustion engine can be relatively short, and as a result, the N
It is possible to obtain an ideal combustion state with less generation of exhaust gas components such as Ox and excellent fuel consumption.

In the embodiment, the throttle 4 is provided around the entire circumference of the opening of the combustion chamber 2, but the intended purpose can also be achieved even if the present invention is applied to an oven chamber type combustion chamber that does not have the throttle 4. .

Furthermore, the same holds true for a flat dish type combustion chamber in which the conical protrusion 5 is not provided at the bottom, and the same holds true even if the opening shape of the recess 6 is made into an ellipse or a shape similar to an ellipse.

(Effects of the Invention) As explained above, according to the present invention, a concave portion opening in an oval or elliptical shape is provided on the inner circumferential surface of the combustion chamber to induce airflow in multiple directions within the combustion chamber, while creating a swirl. Since the engine is configured to moderate the speed, it is possible to improve the mixing state of fuel and air.Therefore, the generation of exhaust gas components such as nitrogen is small in any operating range of the engine.
Ideal combustion with excellent fuel consumption can be performed.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a piston equipped with an embodiment of a combustion chamber according to the present invention, and FIG. 2 is a sectional view taken along line AA in FIG. 1... Piston 2... Combustion chamber 3... Fuel injection nozzle 4... Opening throttle 5... Bottom protrusion 6... Recess 7... Fuel injection

Claims (1)

[Claims] In a diesel engine in which a combustion chamber is recessed in the top surface of the piston, and fuel is injected and supplied from a nozzle provided at the tip of a fuel injection nozzle toward the inner circumferential surface of the combustion chamber, an oval or elliptical shape is used. A combustion chamber for a diesel engine, characterized in that a plurality of recesses opening into the combustion chamber are provided on an inner circumferential surface of the combustion chamber.