JP2653556B2 - Combustion chamber of direct injection diesel 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 direct injection diesel engine for reducing smoke and nitrogen oxides.

[0002]

2. Description of the Related Art At present, reduction of smoke and nitrogen oxides is an important issue in a diesel engine, and various proposals have been made to reduce the smoke and nitrogen oxides in the exhaust gas recirculation method (EGR) and the improvement of a combustion system. ing. EGR
There are problems with durability and reliability, such as deterioration of fuel efficiency and smoke, corrosion of the EGR device due to exhaust gas, or deterioration of functions.

[0003] Also, from the viewpoint of the combustion method, in the case of low-pressure injection, the spray proceeds after being ignited near the nozzle and entirely wrapped in a flame. Since the gas is burned while entrained, a high-temperature portion and an oxygen-deficient portion are formed at the central portion of the spray, which causes soot generation, and the entrainment of burned gas is said to act as a negative factor. Further, in order to quickly mix fuel and air, a method of improving air utilization rate and reducing soot by swirl, squish, etc. is adopted, but this also increases the fuel and air mixing speed during the ignition delay. For,
The heat generation rate in the initial stage of combustion increases due to the increase in premixed combustion,
There is a problem that an increase in nitrogen oxides is caused.

[0004] In order to solve the above-mentioned problem, there is known a system in which a high-pressure injection, a small injection hole diameter nozzle, a shallow dish combustion chamber, and a low swirl are combined. In this case, after igniting at once at the wall surface, the flame expands slowly toward the center of the cavity, and the central portion remains as a non-combustible region until the end of the injection. In other words, the spray proceeds while sufficiently entraining air in the non-combustible area near the center of the cavity until it reaches the wall, and on the wall, it follows a two-stage combustion path that collides with the wall while introducing burned gas, and the low-pressure injection And smoke and nitrogen oxides can be reduced.

[0005]

However, the conventional high-pressure injection system has a problem that the amount of air introduced before ignition is large, so that the generation of nitrogen oxides increases. Due to the cylindrical shape, the amount of burned gas introduced into the spray after ignition is small, and the generation of nitrogen oxides is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a combustion chamber of a direct injection diesel engine capable of reducing smoke and nitrogen oxides by improving the structure of the combustion chamber. With the goal.

[0007]

For this purpose, the combustion chamber of the direct injection diesel engine according to the present invention is provided at the top of the piston 1.
A combustion chamber 7 which is formed with a recess, a fuel injection valve 6 disposed in the cylinder head 8, the fuel injection valve
A plurality of injection holes provided in the nozzle 6a, and a piston formed on the bottom surface of the combustion chamber facing the nozzle of the fuel injection valve ;
Rises and reaches the top dead center.
A protruding portion 9 for forming such a gap 10 and a recess 12a formed at the base of the wall of the combustion chamber.
And a plurality of protrusions 12 having a curved surface shape, and injecting fuel from the plurality of injection holes between the plurality of protrusions 12 . The numbers added to the above configuration are for comparison with the drawings to facilitate understanding of the present invention, and the configuration of the present invention is not limited by this.

[0008]

In the present invention, as shown in FIGS. 1 and 2, for example, when the piston 1 rises and reaches near the top dead center, the fuel flows from the nozzle 6a along the protruding portion 9 and substantially in the middle of each protruding portion 12. The fuel is injected toward the wall, collides with the wall surface 11 and ignites. At this time, since the gap 10 between the protruding portion 9 and the cylinder head 5 is small, the introduction of air into the spray can be suppressed, and the initial combustion can be suppressed. The introduction of A is promoted, and the presence of the depression 12a of the projection 12 suppresses the spread of the combustion flame and promotes the entrainment of the burned gas G. Therefore, it is possible to reduce the amount of nitrogen oxides while suppressing smoke. Can be planned.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show one embodiment of a combustion chamber of a direct injection diesel engine according to the present invention, wherein (A) is a plan view and (B) is a cross-sectional view. 1 is a piston, 2 is a piston ring, 3 is a cylinder liner, 4 is a gasket,
Reference numeral 5 denotes a cylinder head, 6 denotes a fuel injection valve having a nozzle 6a, and a combustion chamber 7 having a recess is formed at the top of the piston 1. The combustion chamber 7 formed in the piston 1 has a protruding portion 9 formed on the bottom surface thereof in opposition to the nozzle 6a. It is configured such that a slight gap 10 is formed. The projection 9a shown by a dotted line shows a conventional example. Also, on the wall surface 11 around the combustion chamber 7, curved protrusions 12 having a depression 12a at the root thereof are formed at equal intervals. The protrusions 12 are provided by the number of injection holes (six in the figure) of the nozzle 6a, and inject the fuel F from the nozzle 6a toward a substantially intermediate portion of each of the protrusions 12.

The operation of the present invention having the above configuration will be described. As shown in FIG. 1, when the piston 1 rises and reaches near the top dead center, the fuel F flows from the nozzle 6a to the protrusion 9
Is injected toward a substantially intermediate portion of each projection 12, and collides with the wall surface 11 to ignite. At this time, since the gap 10 between the projecting portion 9 and the cylinder head 5 is small, the introduction of air into the spray is suppressed, and the initial combustion is suppressed, so that the nitrogen oxides can be reduced. As shown in FIG. 2, when the fuel ignites at once at the wall surface 11, the fresh air A
Is promoted, and the presence of the depressions 12a of the projections 12 suppresses the spread of the combustion flame and promotes the entrainment of the burned gas G, thereby suppressing smoke and reducing nitrogen oxides. Can be planned.

FIG. 3 shows another embodiment of the present invention. The same components as those in the embodiment of FIG. In this embodiment, the protrusion 9 is further raised, and a fuel passage 9b is formed in the upper surface of the protrusion 9 in a radial direction to suppress the introduction of air into the spray to suppress the initial combustion, thereby reducing nitrogen oxides. Is to be further planned.

[0012]

According to the present invention as described in the foregoing, the formed combustion chamber so as to have a recess at the top of the piston, and a fuel injection valve disposed in the cylinder head, fuel
A plurality of injection holes provided in a nozzle of the injection valve, and a plurality of injection holes formed in a bottom surface of the combustion chamber facing the nozzle of the fuel injection valve ;
When the ton rises and reaches the top dead center, between the cylinder head
A protrusion which is adapted to form a slight gap is formed on the wall surface of the combustion chamber, the curved surface shape having a depression in its root
A plurality of projections, and a front between the plurality of projections.
By injecting fuel from multiple injection holes, the introduction of air was suppressed at the beginning of combustion, and the structure of the combustion chamber was improved after ignition to promote the introduction of burned gas. Can be reduced. In particular, the fuel consumption is less deteriorated than EGR, the durability and reliability of parts are excellent, and the cost can be reduced without requiring any special device or modification.

[Brief description of the drawings]

[1] shows one embodiment of a combustion chamber of a direct injection diesel engine of the present invention, (A) is a plan view, (B) is a sectional view der
You.

FIG. 2 is a diagram for explaining the operation of FIG . 1;
Is a plan view, and (B) is a sectional view.

FIG. 3 shows the combustion chamber of the direct injection diesel engine of the present invention.
Shows another embodiment, (A) is a plan view, (B) is a sectional view,
(C) is a sectional view taken along line CC in (A) .

[Explanation of symbols]

1 ... piston, 5 ... cylinder head, 6 ... fuel injection valve,
6a: nozzle, 7: combustion chamber, 9: protrusion, 11: wall surface,
12, 13, 15, 16 ... protrusion, 12a ... depression.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-149314 (JP, A) JP-A-53-134105 (JP, A) JP-A-63-162925 (JP, A) JP-A-2- 245418 (JP, A) Japanese Utility Model 1-134730 (JP, U) Japanese Utility Model 62-122129 (JP, U) Japanese Utility Model 56-127326 (JP, U) Japanese Utility Model 59-194530 (JP, U) Japanese Utility Model Hei 1-127931 (JP, U) Japanese Utility Model Hei 3-10033 (JP, U)

Claims (2)

(57) [Claims] A combustion chamber formed to have a recess at the top of a piston, a fuel injection valve disposed in a cylinder head, and a plurality of fuel injection valves provided in a nozzle of the fuel injection valve. Orifice
And on the bottom surface of the combustion chamber facing the nozzle of the fuel injection valve.
When the piston rises and reaches top dead center,
And a protrusion formed to form a slight gap between the combustion chamber and the head, and a recess formed at the base of the wall of the combustion chamber.
A plurality of protrusions having a curved surface shape having a curved surface , wherein fuel from the plurality of injection holes is injected between the plurality of protrusions. . 2. A fuel passage is formed radially on an upper surface of the projection.
Combustion chamber of direct-injection diesel engine according to claim 1, wherein the form has.