JPS5979032A - Direct-injection type diesel engine - Google Patents

Abstract

PURPOSE:To prevent generation of noises due to ignition lag and to reduce generation of hydrocarbon, by forming a combustion chamber by forming a recess in the top surface of a piston and forming a projection by projecting the central part of the bottom of said recess upward. CONSTITUTION:A combustion chamber 4 is formed by forming a recess in the top surface 2 of a piston 1 and forming a projection 3 by projecting the central part of the bottom of said recess upward. Fuel is injected from main injection holes 13 toward the side wall 7 of the recess, and the atomized fuel is mixed with compressed air by the function of swirl produced in the combustion chamber 4. Here, since the inner wall surface 11 is located at a fairly small distance from a subsidiary injection hole 14 and fuel ejected onto the inner wall surface 11 is scattered after collision to the same, fuel is atomized into fine particles and vaporized instaneously. During the above while, the piston is raised to a position corresponding to a crank angle C and the temperature of air is raised to the ignition temperature. Since the above while, i.e., the ignition lag T1 is lessened, pressure rise in the cylinder is made smooth, so that production of noises can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention is capable of preventing as much as possible the generation of noise associated with ignition delay tl17c in a direct injection diesel engine. The present invention relates to a direct injection diesel engine that can reduce generation.

[Technical background of the invention and its problems]

Generally, in a direct injection diesel engine (hereinafter referred to as a direct injection diesel engine), fuel is directly injected from an injection nozzle into a combustion chamber when the piston reaches top dead center. At this time, in order to mix the fuel and compressed air sufficiently,
The combustion chamber is configured to create a vortex of compressed air in the combustion chamber. That is, as shown in FIG.
is depressed into a hollow shape t1, and the approximate center of the bottom of the depression protrudes upward to form a protrusion 3, thereby forming a toroidal combustion chamber 4 (hereinafter simply referred to as a combustion chamber). When the piston 1 rises to compress the air in the cylinder 5,
A vortex is generated within the combustion chamber 4, and fuel is injected through the injection nozzle 6 into the area where the vortex is generated, so that the compressed air and fuel can be sufficiently mixed.

By the way, since a direct injection diesel engine has a high rate of increase in cylinder pressure, the ignition delay n is generally large. When the ignition delay is very large, the engine will not operate smoothly and will be noisy. In other words, almost all of the 2 tons of fuel injected during the ignition delay n accumulates and burns at once, and the sudden rise in pressure accompanying this rapid combustion creates a pressure wave, which collides with the cylinder wall. This will generate sound. Ignition delay f′
In order to shorten L, increasing the compression ratio can be considered, but if the cylinder pressure is high, it becomes difficult to atomize the fuel, and there is a problem that hydrocarbons due to unburned or incomplete combustion will increase as a component in the exhaust gas. be. Furthermore, since the stroke volume of the cylinder increases for a constant amount of shaft effective work, the shaft average effective pressure decreases, resulting in an inevitable reduction in shaft torque and shaft horsepower.

In addition, in the conventional combustion chamber, as shown in FIG. 2, fuel is injected toward the side wall surface 7 of the combustion chamber 4, and the particle size of the sprayed fuel decreases after colliding with the side wall surface 7. , ignition delay 'n,'
i It is not effective enough to solve the problem. That is, before the fuel injected from the injection nozzle reaches the side wall surface 1, ignition has already been completed, and the momentum of the sprayed fuel colliding with the side wall surface γ has already been attenuated. However, the particle size is not sufficiently reduced.

[Purpose of the invention]

The present invention has been devised in view of the above problems and to effectively solve them.

SUMMARY OF THE INVENTION An object of the present invention is to provide a direct injection diesel engine that can prevent the generation of noise caused by delayed ignition and can completely reduce the generation of hydrocarbons.

[Embodiments of the invention]

A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

In the direct injection diesel engine according to the present invention, as shown in FIG. A combustion chamber 4 is formed.

An injection nozzle 6 is provided above the combustion chamber 4 and is inserted into a nozzle hole 9 of a cylinder head 8. The lower end of the nozzle hole 9 is chamfered so that its diameter gradually increases downwardly from the diameter of the tip 10 of the injection nozzle 6. Therefore, a chamber 12 is formed around the tip 10 of the injection nozzle 6, which has the chamfered surface as the inner wall 11, encloses the injection nozzle 6, and is open facing the combustion chamber 4.

The tip 10 of the injection nozzle 6 has a plurality of main injection ports 13 for injecting fuel toward the side wall surface 7 of the combustion chamber 4, and a plurality of main injection ports 13 for injecting fuel toward the VC toward the inner wall 11 surface of the chamber 12. A sub-nozzle 14 is also provided. The diameter of the sub-nozzle 14 is set smaller than that of the main nozzle 13, and the two are configured to control each other's ejection amounts.

The effect of the present invention will be explained to the company.

FIG. 5 is a graph comparing the ignition combustion process of the direct injection diesel engine according to the present invention with that of a conventional engine. In the figure, the vertical axis represents the cylinder pressure and the needle valve lift, i.e.
The opening and closing of the injection nozzle 6 are shown, with needle valve lift 0 representing an open state and S representing a closed state. The horizontal axis indicates the crank angle, and D indicates the top dead center position.

The piston 1 rises according to the compression stroke, and the pressure inside the cylinder also rises accordingly. At this time, inside the combustion chamber 4,
Compressed air forms a vortex.

When the piston 1 rises to the position of the crank angle A, the injection nozzle 6 opens, and the fuel flows into the combustion chamber 4 as shown in FIG.
Inject inside. The main injection port 13 injects toward the side wall surface 7vC, and the vortex generated within the combustion chamber 4 mixes compressed air and atomized fuel. From the sub-nozzle 14, the chamber 12
The liquid is injected toward the inner wall 11 of the This inner wall 11 is located at a sufficiently close distance from the sub-nozzle 14, and the fuel sprayed by this f'LK has a strong force, and after colliding with the inner wall 11, it scatters, forming a group of fine droplets and instantaneously. vaporizes into

In FIG. 4, during this period, the piston 1 has risen to the crank angle C, the pressure inside the cylinder has increased, and the temperature of the compressed air has reached the ignition temperature. This period is the ignition delay, and according to the present invention, it is TI. In the figure, To is the ignition delay n according to the conventional example, and the crank angle requires time from A to E.

The period between A and B is the fuel injection time.

By reducing the ignition delay, the increase in cylinder pressure becomes smoother, and therefore noise can be significantly reduced.

Furthermore, the vaporization of the atomized fuel injected from the main nozzle 13 is accelerated before it reaches the side wall surface 7 due to its early ignition. 7
The rate at which this happens will be reduced. Therefore, generation of hydrocarbons due to incomplete combustion or unburned combustion is also reduced.

〔Effect of the invention〕

As is clear from the above explanation, the present invention provides the following excellent effects.

1. The ignition delay nf can be shortened as much as possible, and the generation of noise caused by the ignition delay can be reduced.

2. By promoting the vaporization of the fuel injected into the combustion chamber, the total amount of hydrocarbons contained in the exhaust gas can be reduced.

3. Since the compression ratio does not increase, the entire axial average effective pressure can be maintained.

4. The structure is simple and can be easily adopted.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of a direct injection diesel engine, Figure 2
The figure is an ltl sectional view showing a conventional fuel injection situation, FIG. 3 is a side sectional view showing a fuel injection situation in an embodiment of the present invention, and FIG. FIG. 2 is a graph diagram comparing the entire combustion process. In the figure, 1 is a piston, 2 is a top surface, 4 is a combustion chamber, 6 is an injection nozzle, 8 is a cylinder head, 10 is a tip of the injection nozzle, 12 is a chamber, and 11 is its inner wall. Patent Applicant Isuso Jidosha Co., Ltd. Agent Patent Attorney Nobuo Kinutani Figure 1 Figure 2 @ Figure 3

Claims (1)

[Claims] It has a hollow toroidal combustion chamber on the top surface of the piston to generate a vortex flow of compressed air, and has a multi-hole injection nozzle supported on the cylinder head facing the combustion chamber. In the direct injection diesel engine, a chamber is formed in the cylinder head, the diameter of which is expanded from the tip of the injection nozzle, and which is open facing the combustion chamber, and all of the fuel impinges on the inner wall of the chamber. A direct injection diesel engine, characterized in that the injection nozzle is provided with a sub-nozzle for atomization.