JPH0120293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the improvement of a swirl chamber type diesel engine, and more specifically, a plurality of nozzles are provided to communicate the swirl chamber and the main chamber, and a main chamber is provided at the top of the piston. This invention relates to improvement of a swirl chamber type diesel engine with a cavity formed therein.

(Prior art) The swirl chamber type is known as a combustion chamber type suitable for high-speed diesel engines, but in order to further improve its combustion properties, multiple nozzles are provided to communicate the swirl chamber and the main chamber. A similar method has been proposed (for example, see Utility Model Application No. 174721/1983).

To explain this with reference to FIG. 3, the vortex chamber 1 is formed between an engine cylinder head 2 and a mouthpiece 3 fitted from the bottom surface of the engine cylinder head. It communicates with the main room 6.

The main nozzle 4 has an opening on the swirl chamber 1 side opening in the tangential direction of the swirl chamber 1, and an opening on the main chamber 6 side opening slightly toward the center of the cylinder. A gas jet is ejected toward the center of the main chamber 6. On the other hand, the small-diameter sub-nozzle 5 opens along the injection direction of the fuel injection valve 7 facing the swirl chamber 1, so that a part of the injected fuel flows out into the main chamber 6 during the ignition delay. I have to.

According to such a combustion chamber, not only the vortex chamber 1 but also the main chamber 6 in which gas flows gently through the sub-nozzle 5
Since fuel is supplied to both chambers and combustion proceeds in both chambers, the maximum combustion temperature is suppressed compared to when the entire amount of injected fuel is supplied only to swirl chamber 1 and combusted, resulting in the generation of NOx, which is a harmful substance. It is known that the amount decreases.

On the other hand, in order to improve the air utilization efficiency in the main chamber, a diffusion section 13 consisting of a recess is provided at the top of the piston, and a groove-shaped trench section 16 whose one end is connected to this diffusion section 13 and the other end is connected to the nozzle. A main chamber cavity 12 is formed.

That is, the fuel ignited in the vortex chamber 1 near the compression top dead center of the engine becomes a flame (combustion gas) and is ejected and diffused into the diffusion section 13, where it is combusted while taking in fresh air within the diffusion section 13. proceed.

Therefore, the utilization rate of air in the main chamber 6 is improved, and smoke that tends to occur in the initial stage of combustion can be reduced.

(Problems to be Solved by the Invention) Incidentally, the trench portion 16 serves to guide the flame from the main nozzle 4 and the auxiliary nozzle 5 to the diffusion portion 13 and to maintain the strength of the flame flow in the diffusion portion 13 to an appropriate level. Therefore, the groove of the trench portion 16 is shallow and formed generally flat with respect to the piston top portion 11.

In such a shallow trench portion 16, since there is little air available, the vaporization of the sprayed fuel supplied through the sub-nozzle 5 during the ignition delay cannot be promoted, and therefore the air-fuel mixture is not formed sufficiently.

Therefore, if the air-fuel mixture is not sufficiently vaporized, good combustion cannot be expected, and there is a fear that smoke may be generated due to incomplete combustion. In other words, it is still insufficient for the sub-nozzle 5 to perform its function of distributing a portion of the fuel to the main chamber 6 for gentle combustion.

In addition, if a high compression ratio is adopted, fuel efficiency will be good, but on the other hand, vibration and noise will be increased, so there is a tendency to lower the compression ratio. Become. At such a low compression ratio, the penetration force of the spray originally injected at high pressure increases due to the decrease in combustion chamber pressure, and the spray fuel adheres mainly to the groove wall surface of the trench portion 16 located on the extension line of the central axis of the sub-nozzle. It also happens.

For this reason, if the fuel adhering to the groove wall surface burns afterburning, it is thought that the generation of smoke will be further promoted due to insufficient oxygen.

SUMMARY OF THE INVENTION An object of the present invention is to provide a diesel engine that secures air in a trench portion to promote vaporization of a portion of fuel supplied from a sub-nozzle, and also prevents sprayed fuel from adhering to the groove wall surface of the trench portion. .

(Means for Solving the Problems) The present invention provides a swirl chamber facing the fuel injection valve in the engine cylinder head, and combines the swirl chamber and the main chamber in the injection direction of the fuel injection valve in addition to the main nozzle. A main chamber cavity is provided at the top of the piston, and is composed of a diffusion section that is a concave portion, and a groove-shaped trench section that is connected to the diffusion section and has one end extending to the lower surface of the main nozzle. This assumes a swirl chamber type diesel engine.

In the present invention, the bottom surface of the trench portion is formed to be inclined toward the main nozzle, and the deepest part of the inclination is located on an extension of the central axis of the sub-nozzle.

(Function) In this way, since sufficient air is secured in the trench portion for some of the fuel supplied from the sub-nozzle, it is easy to atomize the sprayed fuel, that is, to form a mixture. After that, it harmonizes with the flame that flows in and burns well. In other words, the function of the sub-nozzle is fully exhibited.

In addition, since the distance from the sub-nozzle to the bottom of the trench increases, even if the penetration force of the spray increases under conditions such as high altitudes, the sprayed fuel will not adhere to the trench wall and will be dispersed and atomized. This will be promoted.

(Embodiment) FIG. 1 is a longitudinal sectional view showing the relationship between the main chamber and the swirl chamber in an embodiment of the present invention, and FIG. 2 is a plan view of the top of the piston in the same embodiment.

This embodiment is applied to a vortex chamber formed into a flat cylindrical shape in order to improve the directionality of the vortex flow in the vortex chamber.

That is, the right cylindrical surface 1A in which the main nozzle 4 is opened
and two substantially parallel side planes (not shown) that are orthogonal to the central axis of the right cylindrical surface 1A, forming a vortex chamber 1.

Further, the positions of the fuel injection valve 7 and the sub-nozzle 5A are regulated in order to promote atomization of the spray that reaches the sub-nozzle 5A under high altitude conditions.

That is, the intersection E between the center axis of the fuel injection valve 7 and the wall surface of the swirl chamber is located closer to the main injection port 4 than the center axis of the swirl chamber, the distance between the fuel injection valve 7 and the sub injection port 5A is expanded, and the fuel injection valve The central axis of No. 7 and the central axis of the sub-nozzle 5A intersect within the swirl chamber 1 (the intersection is designated as D). Furthermore, in this embodiment, the intersection point D is located downstream of the intersection point F between the center axis of the fuel injection valve 7 and the center axis of the swirl chamber.

On the other hand, the top portion 11 of the piston includes diffusion portions 13A and 14A, each consisting of a pair of circular recesses located below the intake and exhaust valves and having a diameter larger than that of both valves, and both diffusion portions 13A and 14A. A groove-shaped trench portion 16A is formed which is connected to the main nozzle 4 and has one end extending to the lower surface of the main nozzle 4 (see FIG. 2).

In this way, the diffusion parts 13A, 14A and the trench part 1
A main chamber cavity 12A consisting of 6A is formed, and in the present invention, the groove bottom surface 17 of this trench portion 16A is the deepest on the side extending to the lower surface of the main nozzle 4.
It is formed to be inclined so that it becomes shallower from the deepest part 18 toward the connecting part 15 and has the same depth as the step of the connecting part 15 at the connecting part 15.

Further, the deepest inclined portion 18 is located on an extension of the central axis of the sub-nozzle 5A.

In addition, 2 is a cylinder head, 3 is a mouthpiece, 8 is a glow plug, and 10 is a piston.

To explain the effect of the above configuration, during the compression process, the forced flow that flows into the swirl chamber 1 through the main nozzle 4 flows tangentially into the right cylindrical surface 1A to form a swirl A. , is guided by a lateral plane substantially perpendicular to the center of rotation to maintain strong directionality, and therefore maintains a sufficient vortex state even under the influence of counterflow from the sub-nozzle 5A. That is, the atomized fuel injected from the fuel injection valve 7 hits the glow plug 8 due to this vortex flow A and falls approximately vertically along the direction of the vortex flow, but because of the ignition delay, part of the spray B becomes atomized while Also passes through the sub-nozzle 5A.

In the trench portion 16A into which a portion of the fuel flows, the groove bottom surface facing the extension of the center axis of the sub-nozzle, that is, the opening of the sub-nozzle 5A, is deepest, so that sufficient air is secured to vaporize the sprayed fuel. ,
Fuel spray uses this air to form a good mixture.

The air-fuel mixture thus formed blends with the flames flowing through the main nozzle 4 and the auxiliary nozzle 5A and burns, providing a good connection to the subsequent combustion in the main chamber. Note that the flame flow in the main chamber cavity 12A is indicated by C.

Therefore, the original function of the sub-nozzle 5A, which supplies part of the fuel to the main chamber to achieve gentle combustion, is promoted, improving combustion in the main chamber and reducing smoke.

In addition, the groove bottom surface 17 facing the sub-nozzle 5A becomes deeper, and as the distance from the sub-nozzle 5A increases, the dispersion and atomization of the spray are promoted. Because it does not stick as a center, HC due to fuel adhesion
This does not result in an increase in smoke or afterburning.

(Effects of the Invention) The present invention makes it possible to utilize air in the trench by forming the bottom surface of the trench so as to be inclined toward the nozzle, and by locating the deepest part of the inclination on an extension of the central axis of the sub-nozzle. Since the fuel efficiency has been improved, it is possible to achieve a reduction in the amount of smoke generated due to improved combustion.

Furthermore, since atomization is promoted by increasing the distance between the sub-nozzle and the bottom of the trench, an increase in HC and smoke can be prevented even under high-altitude conditions.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a combustion chamber according to an embodiment of the present invention, and FIG. 2 is a plan view of the top of a piston of the same embodiment. FIG. 3 is a longitudinal sectional view of a conventional combustion chamber. 1... Vortex chamber, 2... Cylinder head, 4... Main nozzle, 5A... Sub-nozzle, 6... Main chamber, 7... Fuel injection valve,
DESCRIPTION OF SYMBOLS 11... Piston top part, 12A... Main chamber cavity, 13A, 14A... Diffusion part, 15... Connection part, 1
6A...Trench portion, 17...Groove bottom surface, 18...Deepest inclined part.

Claims (1)

[Claims] 1. A swirl chamber facing the fuel injection valve is provided in the engine cylinder head, and the swirl chamber and the main chamber are communicated through a sub-nozzle opening in the injection direction of the fuel injection valve in addition to the main nozzle, and In a swirl chamber type diesel engine in which a main chamber cavity is formed at the top of the piston, consisting of a diffusion part consisting of a concave part and a groove-shaped trench part connected to the diffusion part and having one end extending to the lower surface of the main nozzle, the groove of the trench part A swirl chamber type diesel engine characterized in that the bottom surface is inclined toward the main nozzle, and the deepest part of the inclination is located on an extension of the central axis of the sub-nozzle.