JP2653571B2 - Combustion chamber of direct injection diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a combustion chamber of direct-injection diesel engine for achieving simultaneous reduction of smoke and nitrogen oxides (NO _X).

[0002]

At present, reduction of smoke and NO _X in the diesel engine is an important issue, and various proposals have been made in the improvement of the exhaust gas recirculation method (EGR) and combustion method towards the reduction I have.

The EGR includes an external EGR for recirculating a part of the exhaust gas upstream of the intake valve, and an internal EGR for reserving a part of the exhaust gas in the engine to perform an EGR operation.
The external EGR has durability and reliability problems such as deterioration of fuel efficiency, increase of smoke, corrosion of the EGR device due to exhaust gas, or deterioration of function. The internal EGR has a system in which the gas stored in the exhaust system flows backward through the intake valve or the exhaust valve into the cylinder, and a chamber for storing the exhaust gas in a place other than the cylinder is used to enter and exit the exhaust gas. In the former case, the exhaust gas replaces part of the intake air, leading to a reduction in maximum output and durability.The latter problem in which the intake air amount decreases little but requires significant engine remodeling have.

Further, from the viewpoint of the combustion system, in the case of low-pressure injection, which is widely used at present, the spray is ignited in the vicinity of the nozzle and then proceeds while being entirely surrounded by a flame. At the same time, it burns while involving the burned gas generated by itself, so a high temperature part and an oxygen deficient part are formed at the center of the spray, which is a factor of smoke generation,
It is said that the burning of burned gas acts as a negative factor. Therefore, in order to reduce smoke, it is necessary to mix fuel and air quickly, and a method of improving the air utilization rate by swirling, squishing, etc. has been adopted. since mixing speed also increases, the increase of premixed combustion increases the initial combustion of the heat generation rate has a contradictory problem that causes an increase in NO _X, which is difficult to simultaneously reduce the smoke and NO _X ing.

[0005] In order to solve the above-mentioned problem, there has been proposed 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. This will be described with reference to FIG.
Reference numeral 1 denotes a piston, 2 denotes a piston ring, 3 denotes a cylinder liner, 4 denotes a gasket, 5 denotes a cylinder head, 6 denotes a fuel injection valve having a nozzle 7, and a combustion chamber 9 is formed at the top of the piston 1. When the piston 1 rises and reaches the vicinity of the top dead center, the fuel spray F injected from the nozzle 7 ignites at once at the wall surface 10, and then the flame H flows into the combustion chamber 9.
It expands toward the center, and the center remains as a non-combustible area until the end of injection. That is, the spray F travels while sufficiently entraining fresh air A on the non-combustible area side near the center of the combustion chamber 9 until it reaches the wall surface 10, and collides with the wall surface 10 while introducing burned gas on the wall surface 10 side. Follow the combustion path of For high-pressure injection, in combination with the injection timing delays catch fire since greatly delayed injection timing, it is possible to simultaneously reduce the smoke and NO _X compared to the low-pressure injection.

[0006]

However, since the high-pressure injection has a higher spray energy than the low-pressure injection, the spread of the flame H toward the center of the combustion chamber 9 by the injection energy is suppressed. Therefore, the spray F is applied to the nozzle 7
The smoke is greatly reduced because the fresh air A is always introduced on the side, but since the amount of air introduced until ignition is large and the burned gas is less involved, it ignites at once at the wall as described above,
Compared with the same injection timing is a problem that inevitably becomes large generation amount of NO _X.

The present invention has been made to solve the above-mentioned problem, and only by changing the structure of the combustion chamber, can smoke and NO
It is an object of the present invention to provide a combustion chamber of a direct injection diesel engine capable of simultaneously and significantly reducing _X.

[0008]

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 9 having a recess 11 ; a fuel injection valve 6 provided in a cylinder head 5; a plurality of injection holes provided in a nozzle 7 of the fuel injection valve; br /> is formed on the bottom surface of the counter to the combustion chamber, the projecting member 12 which is adapted piston forms a narrow gap between the nozzle 7 when it reaches the vicinity of top dead center increases, projecting the member facing the bottom surface and the upper portion of the combustion chamber and a recirculation passage 15 formed so as to communicate, a ring passage for each nozzle hole of the nozzle
And the fuel F from the injection hole is supplied to the circulation passage 1.
5 so as to spray toward a substantially middle portion of the upper opening 15a.
It is characterized by having done. 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.

[0009]

In the present invention, as shown in FIG. 1B, for example, when fuel F collides with the wall surface 10 and ignites at once,
The flame H that has reached the bottom of the combustion chamber 9 is sucked by the spray energy of the fuel F injected from the nozzle 7 and is introduced into the spray as the burned gas G through the recirculation passage 15 of the projecting member 12.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a combustion chamber of a direct injection diesel engine according to the present invention, in which (A) and (B) are sectional views and (C) is a plan view, respectively. 1 is a piston, 2 is a piston ring, 3 is a cylinder liner, 4 is a gasket, 5
Is a cylinder head, 6 is a fuel injection valve 9 having a nozzle 7
Denotes a combustion chamber, 10 denotes a wall surface, and on the top of the piston 1,
A cylindrical recess 11 is formed. This depression 11
A projecting member 12 is fixed to the piston 1 by a bolt 13 at the center of the bottom surface so that a narrow gap is formed between the projecting member 12 and the nozzle 7 when the piston 1 rises and reaches near the top dead center. Make up. Further, the projecting member 12, return passage 15 is provided which opens into the bottom surface and the upper portion of the combustion chamber 9. The recirculation passage 15 is provided at each injection hole of the nozzle 7.
The fuel (F) from each injection hole of the nozzle 7 is provided by the number (6 in the figure) facing each other .
Injection is performed toward a substantially intermediate portion of the upper opening 15a . The shape and number of the return passages 15 are not limited to the embodiment shown in FIG.

The operation of the present invention having the above configuration will be described. As shown in FIG. 1A, when the piston 1 rises and reaches near the top dead center, the fuel F is injected from the nozzle 7 along the upper surface of the protruding member 12. At this time, since the gap between the protruding member 12 and the nozzle 7 is small, the introduction of fresh air into the spray is suppressed. As shown in FIG. 2B, when the fuel F collides with the wall surface 10 and ignites, the flame H that has reached the bottom of the combustion chamber 9 is sucked by the spray energy of the fuel F injected from the nozzle 7 and the projecting member. The burned gas G is introduced into the spray through the 12 return passages 15. Therefore, in the spray period, since the entrainment of burnt gas G into the spray is promoted, it is possible to simultaneously and significantly reduce the smoke and NO _X in combination with high-pressure injection.

In the above embodiment, the projecting member 1
Although 2 is fixed to the piston 1 by the bolt 13 , the protruding member 12 may be formed integrally with the piston 1 .

[0013]

As is apparent from the above description, according to the present invention, at the beginning of combustion, the distance between the projecting member and the nozzle is reduced.
The small gap minimizes the introduction of fresh air into the spray,
When it collides with the wall and ignites, the flame goes to the bottom of the combustion chamber
Is the spray energy of the fuel injected from each nozzle hole
Into each spray through each return passage
Introduced as burned gas and therefore during each spray period
High pressure injection and
Simultaneously and significantly smoke and NO _X in combination
Can be reduced .

[Brief description of the drawings]

FIG. 1 shows one embodiment of a combustion chamber of a direct injection diesel engine of the present invention, wherein (A) and (B) are sectional views showing a combustion stroke, and (C) is a plan view .

2A and 2B show a combustion chamber of a conventional direct injection diesel engine, in which FIG. 2A is a cross-sectional view and FIG . 2B is a plan view .

[Explanation of symbols]

1 ... piston, 3 ... cylinder, 5 ... cylinder head, 6
... fuel injection valve 7 ... nozzle, 9 ... combustion chamber, 10 ... wall surface, 11 ... recess
12 Projecting member 15 Recirculation passage , 15a Upper opening, F Fuel

Continuation of the front page (72) Inventor Kinji Tsujimura 2530 Karma, Tsukuba-shi, Ibaraki Inside the Japan Automobile Research Institute Inside the New Combustion System Laboratory Co., Ltd. (56) References JP-A-3-43620 (JP, A) 61-160227 (JP, U)

Claims (1)

(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
If, formed on the bottom surface of the combustion chamber opposite the nozzle, Pi
When the stone rises and reaches near the top dead center,
A projecting member which is adapted to form a narrow gap, projecting et provided a bottom and top of the combustion chamber in the member so as to communicate
And a return passage, which is provided for each injection hole of the nozzle.
And the fuel from the nozzle hole
A combustion chamber for a direct injection diesel engine, wherein the fuel is injected toward a substantially intermediate portion of an upper opening of a road .