JPS59134322A - Direct-injection type diesel engine - Google Patents

Abstract

PURPOSE:To shorten time for an ignition delay as well as to prevent the occurrence of noise to the smallest possible extent, by forming an almost conical body-form projecting part in a sinking part of the head top surface of a piston, while making both main and auxiliary nozzle holes of an injection front toward a specified direction. CONSTITUTION:In this combustion chamber 4, its head top surface 2 is sunk in a hollow form, while a projecting part 3 is formed at almost the central part of a bottom surface 7 of this sinking part. A main nozzle hole 11 of a multihole type injection nozzle 6 is installed position fronting on the side wall of the combustion chamber 4. An auxiliary nozzle hole 12 being smaller in diameter than that of the main nozzle hole 11 is made to front toward a direction nearly along a side wall incline of the projecting part 8. Doing like this, time for an ignition delay is shortened as well as the combustion required for fuel or fuel-air mixture can be made to slow down, thus the occurrence of noise can be prevented remarkably to the smallest possible extent.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a direct injection diesel engine, and in particular to a direct injection diesel engine that can prevent noise generation due to rapid combustion of fuel in a combustion chamber as much as possible. This relates to a type diesel engine.

[Technical drawbacks of the invention and its problems]

Generally, in a direct injection easel engine, fuel is injected directly from the injection nozzle into the combustion chamber when the piston reaches top dead center. At this time, what about fuel and compressed air? To ensure sufficient mixing, VC@ is used to create a vortex of compressed air in the combustion chamber. That is, as shown in Figure 1,
The top part 2 of the piston 1 is sunken into a hollow shape n1, and the approximate center of the chin of the sunken part protrudes upward to form a projection part 3, thereby forming a combustion chamber 4. Piston 1 is pulling 5
When the air in the combustion chamber 4 rises to be completely compressed, a vortex of compressed air is generated within the combustion chamber 4, and fuel is injected through the injection nozzle 6 into the area where this vortex is generated, so that the compressed air and fuel are sufficiently mixed. Can be mixed.

By the way, in direct injection diesel engines, the evaporated fuel mixture that forms in the combustion chamber from the start of fuel injection to its ignition is rapidly combusted at the same time as ignition, so the rate of increase in cylinder pressure is high. , the maximum cylinder pressure also tends to increase.

The rapid increase in cylinder pressure accompanying this rapid combustion generates pressure waves within the cylinder, and these pressure waves collide with cylinder walls and the like, producing loud noise.

In general, direct injection diesel engines have good fuel efficiency, but have problems such as high noise and a lot of smoke exhaust, and it is especially desirable to improve the above-mentioned noise.

[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 reduce the ignition delay t''L and slow the combustion of fuel or fuel mixture, thereby preventing noise as much as possible.

[Embodiments of the invention]

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

FIG. 2 completely shows the combustion chamber 4 and the multi-hole injection nozzle 6 (hereinafter simply referred to as an injection nozzle) provided facing the nVC according to the present invention.

The combustion chamber 4 is constructed by recessing the top surface 2 of the piston 1 into a hollow shape, and forming an upwardly projecting protrusion 3 approximately in the center of the bottom 1 of the recess.

The protrusion 3 is formed into a conical shape whose horizontal cross-sectional area gradually decreases in the direction of protrusion, and its side wall 8 is configured to form a slope.

Above the combustion chamber 4 and the projection 3, an injection nozzle 6 is provided facing the combustion chamber 4 and the projection 3. The nozzle tip portion 91C at the tip of the injection nozzle 6 has two main nozzles 11 for injecting fuel toward the side wall 10 of the combustion chamber 4, and a main nozzle 11 that faces the slope of the side wall 8 of the protrusion 3 in a direction that is substantially clean. Sub-nozzle 12 that fully injects fuel
are formed in two places. Further, as shown in FIG. 5, the diameter d2 of the sub-nozzle 12 is equal to the diameter d2 of the main nozzle 11.
1, and are configured to control each other's spout amounts. Furthermore, FIG. 3 shows the entire distribution of the fuel f' injected into the combustion chamber 4, but it is injected from the main nozzle 11 in the direction of arrow A, and from the auxiliary nozzle 12 in the direction of arrow B. The main injection ports 11 and the sub-I mass ports 12 are arranged at positions 90 degrees apart from each other so that the fuel is distributed almost evenly within the combustion chamber 4, and the main nozzle ports 11 and the sub-I mass ports 12 are arranged at positions 180 degrees opposite each other. The location of the spout is well set.

Next, the operation of the present invention will be explained.

First, the fuel injected into the combustion chamber 4 is distributed as shown in FIG. 3, and at this time, a vortex of compressed air is generated in the direction of arrow C. A part of the fuel injected by the main nozzle 11 in the direction of arrow A is distributed along the side wall 10 of the combustion chamber 4 as a liquid film 13. form, and the rest are bottom 7 VC? =A liquid film is completely formed as shown in distribution 14. This is to actively form a fuel gold liquid film and completely suppress its evaporation. Therefore, the diameter d1 of the main nozzle 11 is set relatively large.

On the other hand, the fuel injected from the sub-nozzle 12 in the direction of arrow B flows almost on the slope of the side wall 8 of the protrusion 3, so there is no stale collision, and a V liquid film is formed as shown in the distribution 15. do. However, since the diameter d2 of the sub-nozzle 12 is set to be small, the fuel that is injected into droplets has a small particle size and is relatively easy to evaporate, and the side wall 8. Near the slope, it becomes partially atomized, making it easier to ignite.

Inside the combustion chamber 4, most of the fuel is almost evenly distributed in the form of a liquid film, and its evaporation is suppressed, but it is heated by the side wall 10 or the bottom 7 of the combustion chamber 4, albeit slowly. n will evaporate. The distribution 16 shows the entire distribution of fuel vapor just before ignition, and the ignition point 11il''l is the point where the fuel injected from the sub-nozzle 12 is atomized near the slope of the side wall 8 of the crab protrusion 13.

The ignition and combustion process of a direct injection diesel engine without fuel injection as described above is compared with that of a conventional engine, and is shown in FIG. In the figure, the vertical axis indicates the cylinder internal pressure and the needle valve lift, that is, the opening and closing of the injection nozzle. A needle valve lift of 0 indicates an open state, and S indicates a closed state. The horizontal axis indicates the crank rotation angle, and γ indicates the entire top dead center position.

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

When the piston 1 rises to the position of the crank rotation angle α, the injection nozzle 6 opens and fuel is injected into the combustion chamber 4 as shown in FIG. A part of the fuel injected from the small-diameter sub-nozzle 12 becomes small droplets, evaporates instantly, and ignites. In Fig. 4, the piston 1 rises to the crank rotation angle β during this time. , the pressure inside the cylinder increases and the temperature of the compressed air reaches the ignition temperature. This period is the ignition delay n, which according to the present invention is T1. In the figure, To is the ignition delay according to the conventional example, and the crank rotation angle requires time from α to δ. Injection nozzle 6 between α and ε
is the fuel injection time when it is open.

After ignition, it enters a combustion state, but because the fuel evaporates slowly,
The rate of increase in the cylinder pressure is low, and the maximum pressure in the seven rings is also kept low, allowing for gentle combustion to proceed and noise to be kept low.

In the figure, the broken line indicates the combustion process according to the conventional example.

〔Effect of the invention〕

As is clear from the above description, the present invention exhibits the following excellent effects.

(1) When the ignition delay n is completely shortened, the combustion of the VC fuel or the fuel mixture can be completely slowed down, and therefore, the generation of noise can be prevented as much as possible.

(2) The structure is simple and can be easily adopted.

[Brief explanation of drawings]

FIG. 11 is a schematic configuration diagram of a direct injection diesel engine, FIG. 2 is a side sectional view showing the fuel injection state in an embodiment of the present invention, and FIG. 3 is a diagram showing the fuel distribution state in an embodiment of the present invention. A plan view, FIG. 4 is a graph comparing the ignition/combustion process between an embodiment of the present invention and a conventional example, and FIG. 5 is a side sectional view showing the nozzle tip portion of an injection nozzle in an embodiment of the present invention. It is. In the figure, 1 is the piston, 2 is the top surface of the piston, 3 is the protrusion,
4 is a combustion chamber, 6 is an injection nozzle, 8 is a side wall of a protrusion, 10
1 is a side wall of the combustion chamber, 11 is a main nozzle, and 12 is a sub-nozzle. Fig. 2 Fig. 3 ct 1s'; rs” 'y Kula) ZEI wind angle A[

Claims (1)

[Claims] Compressed air swirl? In order to achieve this, a combustion chamber is formed in which the top of the piston is depressed into a hollow shape, and a protrusion is formed approximately at the bottom of the depression, and a multi-hole injection nozzle is provided facing the combustion chamber. In the direct injection diesel engine, the protrusion is formed into a substantially conical shape whose cross section gradually decreases along the protrusion direction 1c, and the main injection nozzle of the multi-hole injection nozzle is located in the combustion chamber. Is it provided facing the side wall, and is a sub-nozzle with a smaller diameter than the main nozzle also provided so as to face the slope of the side wall of the protrusion? Features a direct injection diesel engine.