JP2561761B2 - Direct injection diesel engine - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a direct injection diesel engine,
Towards the reduction of smoke and NO _X exhaust gas recirculation method (EGR), water injection, the improvement various proposals combustion system have been made. Among them, EGR has problems of durability and reliability such as deterioration of fuel consumption, increase of smoke, corrosion of EGR device due to exhaust gas, or deterioration of function. Further, water injection has problems such as rust in the combustion chamber, oil dilution, and large water consumption.

From the viewpoint of the combustion system, in the case of low pressure injection which is widely used at present, after the spray is ignited in the vicinity of the nozzle, it progresses while being entirely wrapped in flame. At this time, the spray is air. At the same time, it burns while energizing the burnt gas generated by itself, so a high temperature part and an oxygen deficient part are formed in the center of the spray, which becomes a cause 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 methods such as swirl and squish are used to improve the air utilization rate. Since the mixing speed also increases, there is a contradictory problem that the heat generation rate in the early stage of combustion increases due to the increase in premixed combustion, leading to an increase in NO _X , which makes it difficult to reduce smoke and NO _X simultaneously. ing.

In order to solve the above problems, a system has been proposed in which a high pressure injection, a small injection hole diameter nozzle, a shallow dish combustion chamber and a low swirl are combined. To explain this by Figure 8,
31 is a piston, 32 is a piston ring, 33 is a cylinder liner, 34 is a gasket, 35 is a cylinder head,
Reference numeral 36 denotes a fuel injection valve having a nozzle 37, and a combustion chamber 39 is formed at the top of the piston 31. When the piston 31 rises and reaches the vicinity of the top dead center, the spray F of the fuel injected from the nozzle 37 ignites at once on the wall surface 40, and then the flame H expands toward the center of the combustion chamber 39.
The center remains as a non-combustible area until the end of injection. That is,
The spray F proceeds until it reaches the wall surface 40 while sufficiently entraining the fresh air A on the non-combustible region side near the center of the combustion chamber 39, and on the wall surface 40 side, the burned gas is introduced and the spray F collides with the wall surface 40. Follow the combustion path. 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.

[0005]

However, since the high-pressure injection has larger spray energy than the low-pressure injection, the flame H is suppressed from spreading toward the center of the combustion chamber 39 due to the injection energy. Therefore, since the spray F always introduces the fresh air A on the nozzle 37 side, the smoke is greatly reduced, but since the amount of air introduced until ignition is large and the amount of burned gas entrainment is small, as described above, all at once on the wall surface. Nothing happens if you ignite and compare at the same injection timing.
There is a problem that the generation amount of _X increases.

Further , in EGR, the actual development number 62-10
According to Japanese Patent No. 1057, fuel injection is performed near the top dead center of the piston.
A method of injecting exhaust gas toward the part is known,
It is difficult to reliably guide the exhaust gas to the fuel injection section.
Together, the problem of adversely affecting the flow of fuel spray
Have

[0007] The present invention has been made to solve the above problems, and an object thereof is to provide a direct injection diesel engine capable of simultaneously and significantly reduce the smoke and NO _X.

[0008]

To this end, the present invention is claimed.
The direct injection diesel engine according to Item 1 is a cylinder blower.
Lock 1, piston 2 and cylinder head 3, and fix
A combustion chamber 4 having a recess formed at the top of the cylinder 2;
Provided Daheddo 3, and the main injection nozzle 5a for injecting fuel into the combustion chamber, the secondary injection nozzle 6a for injecting a portion of the exhaust gas, is formed inside the piston 2, sub injection Bruno
Introducing exhaust gas from the slur 6a into the vicinity of the main injection nozzle 5a
And a gas passage 19 for injecting a part of the exhaust gas before and after starting fuel injection and in the latter period of combustion.

The invention according to claim 2 is the same as claim 1.
In the direct injection diesel engine mounted on the
A plurality of projecting walls 23 facing the main injection nozzle 5a are provided on the upper surface.
The fuel spray passage 23a is formed in an annular shape , and the fuel spray passage 23a is formed between the protruding walls 23.
It is characterized in that it is formed, and further,
The described invention includes a cylinder block 1, a piston 2 and
A recess is formed at the top of the cylinder head 3 and the piston 2.
Installed in the combustion chamber 4 and the cylinder head 3
Main injection nozzle 5a for injecting fuel into the combustion chamber, and exhaust gas
The sub-injection nozzle 6a for injecting a part of the gas,
It is formed on the upper surface so as to face the main injection nozzle 5a and
Exhaust gas from the injection nozzle 6a near the main injection nozzle 5a
Before the start of fuel injection.
Injecting a portion of the exhaust gas after and late in combustion
It is characterized by the following. It should be noted that the numbers added to the above-mentioned configurations are for comparison with the drawings in order to facilitate understanding of the present invention, and the configurations of the present invention are not limited thereby.

[0010]

In the present invention, EGR is performed before and after the start of fuel injection.
When the gas is injected, as shown in FIG. 2, the EGR gas E
Is introduced into the fuel spray F portion near the main injection nozzle 5a,
Since the EGR gas E is entrained in the fuel spray F together with the fresh air, premixed combustion is suppressed and NO _X is reduced.
When the EGR gas is injected in the latter stage of combustion, the EGR gas E is introduced into the combustion flame portion as shown in FIG.
Due to the kinetic energy of the gas, the mixing of the fuel and air in the combustion chamber 4 further progresses, combustion becomes active, and the unburned smoke is reduced. Therefore, the EGR gas is injected both before and after the start of fuel injection and in the latter stage of combustion. By doing, NO
Both _X and smoke can be reduced.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views for explaining the concept of a direct injection diesel engine of the present invention, FIG. 1 is an overall configuration diagram, FIG. 2 is a configuration of a combustion chamber portion, FIG. A is a plan view, and FIG. Is a sectional view, FIG. 3 is a diagram for explaining the gas injection timing,
FIG. 4 is a plan view for explaining the operation.

In FIG. 1, a diesel engine includes a cylinder block 1, a piston 2 and a cylinder head 3.
The piston 2 is provided with a combustion chamber 4 in which a recess is formed at the top. The cylinder head 3 is provided with a main injection valve 5 for injecting light oil fuel and a sub injection valve 6 for injecting a part of exhaust gas (hereinafter referred to as EGR gas). An EGR valve 9 is provided in the exhaust pipe 7 of the engine, components such as smoke are removed from the EGR gas by a trap filter 10, and the EGR gas is pressurized by a pressurizing pump 11 and injected from the auxiliary injection valve 6 into the combustion chamber 4. It Further, hydraulic oil is supplied to the sub injection valve 6 by a hydraulic oil pump 12 driven by an engine, and opening / closing of the sub injection valve 6 is controlled. Light oil fuel is supplied to the main injection valve 5 from the fuel pump 13 and injected into the combustion chamber 4. Signals of the engine speed, the engine load, and the crank angle are input to the electronic control unit 15, and arithmetic processing is performed on the basis of these input signals.
A valve opening signal is output to the GR valve 9 and a gas injection timing signal is output to the hydraulic oil pump 12.

In FIG. 2, the cylinder head 3 is provided with a main injection valve 5 and a sub injection valve 6 each having a main injection nozzle 5a and a sub injection nozzle 6a, and an intake valve 16 and an exhaust valve 17. ing. The injection direction of the sub injection nozzle 6a is such that the EGR gas E is supplied to the main injection nozzle 5a.
It is set to inject directly under

The operation of the present invention having the above configuration will be described. The electronic control unit 15 outputs a valve opening signal to the EGR valve 9 and a gas injection timing signal to the hydraulic oil pump 12 based on the crank angle signal, and as shown in FIG. EGR gas is injected into the combustion chamber 4 from the sub-injection nozzle 6a before and after the start and in the latter stage of combustion.

When the EGR gas is injected before and after the start of fuel injection, the EGR gas E is injected into the fuel spray F portion near the main injection nozzle 5a as shown in FIG.
Since the GR gas E is caught in the fuel spray F, premixed combustion is suppressed and NO _X is reduced. In the latter half of combustion, E
When the GR gas is injected, the EGR gas E is injected into the combustion flame portion as shown in FIG. 4, and the kinetic energy of the EGR gas further advances the mixing of the fuel and air in the combustion chamber 4, Combustion becomes active, and smoke that remains unburned is reduced. Therefore, by injecting the EGR gas both before and after the start of fuel injection and in the latter stage of combustion, both NO _X and smoke can be reduced.

5 to 8 show each embodiment of the present invention. The same components as those shown in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

In the embodiment of FIG. 5, the exhaust gas from the sub injection nozzle 6a is introduced into the piston 2 inside the main injection nozzle 5a.
The gas passage 19 for injecting the gas is formed in the vicinity of, and the EGR gas E injected from the sub injection nozzle 6a is introduced directly below the main injection nozzle 5a.

In the embodiment of FIG. 6, the sub-injection nozzle 6
a is arranged on the outer peripheral side of the piston 2 to form gas passages 20, 21 and 22 from the outer peripheral upper part of the piston 2 toward the central part, and the EGR gas E injected from the sub injection nozzle 6a is supplied to the main injection nozzle 5a. It is configured to be installed immediately below. Further, a plurality of projecting walls 23 are formed in an annular shape on the bottom surface of the combustion chamber 4 of the piston 2 so as to face the main injection nozzle 5a, and a fuel spray passage 23a is formed between the projecting walls 23 to generate EGR gas.
The projecting wall 23 is maintained in the vicinity of the main injection nozzle 5a so that it can be introduced into the fuel spray F more effectively.

In the embodiment of FIG. 7, the top of the piston 2 is
Further forming a recess 25 on the upper surface of the recess formed in parts, so as to face the depressions viewed portion 25 to the main injection nozzle 5a
In this way, the EGR gas E is injected into the recess 25 through the fuel spray F so that the EGR gas is evenly distributed in the fuel spray. In this embodiment, the piston 2
EGR gas is directly under the main injection nozzle 5a by simple processing.
Can be introduced into.

In each of the above-described embodiments, the EGR gas is injected into the combustion chamber 4 from the sub-injection nozzle 6a before and after the start of fuel injection and in the latter stage of combustion, but NO _X and smoke are the engine load and the rotational speed. Therefore, if these are detected and the injection timing of the EGR gas is determined, NO _X and smoke can be further reduced.

[0021]

As is apparent from the above description, according to the present invention, in the case of high-pressure injection, the EGR gas is directly secured in this incombustible region by utilizing the characteristic that the vicinity of the nozzle during fuel injection remains as the incombustible region. When adopting a structure that can be introduced into
EGR both before and after the start of fuel injection and in the latter half of combustion
By injecting gas, when needed, when needed
That the EGR gas is introduced in an appropriate amount and in a required place.
Bets can be, low NO _X and smoke simultaneously and significantly
Can be reduced.

[Brief description of drawings]

FIG. 1 illustrates the concept of a direct injection diesel engine of the present invention.
It is the whole block diagram for clarifying.

FIG. 2 is a plan view and FIG. B is a sectional view showing a structure of a combustion chamber portion .

Figure der for explaining the gas injection timing of the present invention; FIG
It

FIG. 4 is a plan view for explaining the operation of the present invention .

5 is a cross-sectional view showing one embodiment of the present invention.

6 shows another embodiment of the present invention, FIG. A is a plan view and FIG. B is a sectional view .

FIG. 7 is a sectional view showing another embodiment of the present invention .

FIG. 8 shows an example of a conventional direct injection diesel engine,
FIG. A is a sectional view and FIG. B is a plan view.

[Explanation of symbols]

1 ... Cylinder block , 2 ... Piston, 3 ... To cylinder
Dot, 4 ... Combustion chamber, 5a ... Main injection nozzle, 6a ... Sub injection nozzle 19, 20, 21, 22 ... Gas passage, 23 ... Projecting wall, 23a ... Fuel spray passage, 25 ... Recess, F ... Fuel spray , E ... EGR gas

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kinji Tsujimura, Inventor 2530, Kuma, Tsukuba, Ibaraki Pref., Japan Automobile Research Institute, Inc., New Combustion Systems Laboratory, Inc. (72) Masaaki Takiguchi, 2530, Kuma, Tsukuba, Ibaraki Japan Automobile Research Institute Co., Ltd. New Combustion System Research Institute Co., Ltd. (56) Reference JP-A-3-279660 (JP, A) JP-A-59-85471 (JP, A) Actual Kaihei 3-95062 (JP, U) Actual Open 62-101057 (JP, U) Actual open 56-65150 (JP, U)

Claims (3)

(57) [Claims] 1. A cylinder block, a piston and a cylinder.
Dha head and combustion chamber with a recess at the top of the piston
A main injection nozzle provided in the cylinder head for injecting fuel into the combustion chamber , a sub injection nozzle for injecting a part of exhaust gas, and a sub injection nozzle formed inside the piston.
Introduce exhaust gas from the injection nozzle near the main injection nozzle
Direct injection diesel engine, characterized in that a gas passage of the order, to inject a portion of the exhaust gas to the fuel injection start longitudinal and combustion late. Wherein opposite the main injection nozzle on the upper surface of the piston to form a plurality of projecting walls annularly direct injection of claim 1 wherein the forming the fuel spray passage between projecting Dekabe Type diesel engine. 3. A cylinder block, a piston and a cylinder.
Dha head and combustion chamber with a recess at the top of the piston
And is provided in the cylinder head to supply fuel to the combustion chamber.
A main injection nozzle that injects into the interior and injects part of the exhaust gas
On the upper surface of the recess and the main injection nozzle.
Exhaust gas from the auxiliary injection nozzle that is formed to face
And a recess for introducing the gas near the main injection nozzle.
Well, before and after the start of fuel injection and in the latter half of combustion, the exhaust gas
A direct injection diesel engine characterized by injecting a part .