JPH10252476A - Combustion method of direct injection type diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a delay in the ignition of main injection and reduce noise and NOx by jetting part of fuel of a total injection amount primarily at the middle time of a compression process, evaporating and diffusing it to prepare lean and uniform pre-air fuel mixture, igniting it in the vicinity of a compression top dead center by itself, and jetting it in the vicinity of a top dead center mainly. SOLUTION: High pressure fuel is supplied to an injection nozzle for main injection 1 from a fuel pump for main injection 11 and to an injection nozzle for pilot 2 from a fuel pump for pilot injection 12, respectively, and a small amount of fuel is jetted 5 from the injection nozzle for pilot 2 toward a specific pre-air fuel mixture formation region 4 in a combustion chamber 3 at the middle time of a compression process. Here, lean and uniform pre-air fuel mixture 6 is generated by evaporating fuel. A temperature of this air fuel mixture 6 is increased up to a high temperature by the compression, and the air fuel mixture 6 is ignited in the vicinity of a top dead center by itself to form a pilot flame 7. Main injection 8 is done by the injection nozzle for main injection 1 in the vicinity of self-ignition timing to perform the diffusion combustion without delay of the ignition by the pilot flame 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion method for converting a diesel engine employing a sub-chamber combustion mechanism into a highly efficient direct injection diesel engine in terms of noise reduction.

[0002]

2. Description of the Related Art Conventionally, a technique relating to pilot injection, which is a technique for performing a primary injection of a part of fuel of a total injection amount in a middle stage of a compression stroke, has been known. For example, the technique is described in Japanese Patent Application Laid-Open No. 5-141243. However, in the case of the conventional pilot injection, 1
The pilot injection is performed at a position of about 0 to 30 °. In this case, since the directions of the pilot injection and the main injection match, the combustion area of the pilot ignition becomes oxygen deficient,
Furthermore, since the main injection is performed in that portion, there is a problem that soot is generated. In addition, since pilot injection causes ignition at an equivalence ratio, a large amount of NOx
There was a problem that occurs. It is also known to use a normal compression premixed self-ignition combustion system, that is, a method of injecting all the fuel in the middle stage of the compression stroke, completely evaporating and mixing, and self-ignition. But also in this case,
Unless the fuel is totally diluted, NOx increases, so that a large amount of fuel cannot be injected, resulting in a problem that the output is low. In addition, there is a problem that unburned HC increases because a complete premixed gas is generated. In addition, there are fumigation (technique for pilot ignition of premixed intake air) and VIGOM method (old technology for pilot ignition of intake stroke injection) for injection prior to main injection. Since the unburned HC deteriorated, it was not used in the actual machine.

[0003]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned disadvantages of the prior art. According to the present invention, by making the pilot injection a lean premixture, oxygen is left in the pilot combustion and the deterioration of soot due to lack of oxygen, which is a drawback of the pilot injection, is usually solved. Further, in normal pilot injection, NOx is generated by the ignition of the pilot injection itself. However, when a premixed pilot is used, NOx is generated due to lean combustion of the pilot injection.
The occurrence can be suppressed. Further, as compared with the case where the full-quantity premixed self-ignition is performed, the main injection has the same combustion form as the conventional diesel combustion, so that high output and low THC can be realized. The main object is to reduce the ignition delay of main injection and achieve low noise and low NOx by pilot ignition without deteriorating soot performance or NOx.

[0004]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. In the first aspect, in the middle stage of the compression stroke, a part of the fuel of the total injection amount is primary injected (hereinafter, pilot injection).
And evaporate and diffuse in a limited area within the combustion chamber,
A lean homogeneous premixture is generated in the limited region, self-ignition is performed near the compression top dead center, and main injection is performed near the top dead center.

According to a second aspect of the present invention, there is provided the direct injection type diesel engine combustion method according to the first aspect, wherein a plurality of single or multiple injection hole nozzles are provided, one of which is a pilot and one is for main injection, and pilot injection is performed. Is injected into a specific area provided in the combustion chamber, and the main injection is injected into an adjacent combustion chamber area other than the pilot combustion area.

According to a third aspect of the present invention, in the combustion method for a direct injection type diesel engine according to the second aspect, a cylindrical projection is provided at the center of the combustion chamber, and an annular groove is provided on an outer periphery thereof, and this area is defined as a pilot combustion area. The shape of the combustion chamber and the main injection are caused to collide with the flat portion at the tip of the projection and diffuse.

According to a fourth aspect of the present invention, there is provided the direct injection type diesel engine combustion method according to the first aspect, wherein a single injection hole nozzle or a multi injection hole nozzle is provided, and at the time of pilot injection, direct injection is performed into the pilot combustion region. At the time of the main injection, it collides with a part of the side wall of the combustion chamber of the piston to diffuse the spray into an area adjacent to the pilot combustion area.

According to a fifth aspect of the present invention, in the combustion method for a direct-injection diesel engine according to the fourth aspect, a cylindrical projection is provided at the center of the combustion chamber, and an injection nozzle is provided immediately above the cylindrical projection. It has an annular groove on the outer circumference, and at the time of pilot injection, the distance between the injection nozzle and the columnar projection is made larger than the distance that the injected fuel is atomized to diffuse the spray into the annular groove area, The distance between the injection nozzle and the columnar projection near the point is made smaller than the distance at which the injected fuel is atomized, so that the main injection collides with the flat part of the projection tip in a liquid column state that does not split, and the annular groove Is diffused into the combustion chamber close to.

According to a sixth aspect of the present invention, in the combustion method of the direct injection type diesel engine according to the fifth aspect, the tip of the cylindrical projection is partially conical in the case of using a multi-injection nozzle.

According to a seventh aspect of the present invention, in the combustion method for a direct injection type diesel engine according to the fifth aspect, when a multi-injection nozzle is used, the vicinity of the center of the tip of the columnar projection is flattened, and the vicinity of the outer periphery is arcuate. It has a concave shape.

According to an eighth aspect of the present invention, there is provided the direct injection type diesel engine combustion method according to the third aspect, further comprising one hole nozzle and another throttle nozzle, wherein the throttle nozzle is a pilot and the other hose nozzle is mainly used. It is for injection.

According to a ninth aspect, in the combustion method for a direct injection diesel engine according to the first aspect, the pilot combustion region is surrounded by a material having high heat insulation.

According to a tenth aspect of the present invention, there is provided the direct injection diesel engine combustion method according to the second aspect, further comprising one hole nozzle and another throttle nozzle, wherein the hole nozzle is a pilot and the other slot nozzle is mainly used. This is for injection.

[0014]

Next, an embodiment of the present invention will be described. FIG. 1 is a diagram illustrating the effect of pilot injection in a diesel engine with respect to changes in in-cylinder pressure, FIG. 2 is a diagram illustrating the problem of pilot injection in a diesel engine,
FIG. 3 is a view showing the structure of the pilot injection according to the first embodiment of the present invention, FIG. 4 is a conceptual diagram of the operation of the pilot injection according to the first embodiment of the present invention, and FIG. FIG. 6 is a conceptual diagram of the operation of the present invention according to claim 3, FIG. 7 is a conceptual diagram of the operation of the present invention according to claim 4, and FIG. 9 is a conceptual diagram of the operation of the present invention of claim 5, FIG. 10 is a conceptual diagram of the operation of the present invention of claim 6, FIG. 11 is a conceptual diagram of the operation of the present invention of claim 7,
FIG. 12 is a conceptual view of the operation of the present invention according to claim 8, FIG. 13 is a structural view of the present invention according to claim 9, and FIG. 14 is a drawing showing the change of the compression ratio and the in-cylinder temperature of the present invention according to claim 10. 15 is claim 9
FIG. 16 is a diagram showing a compression ratio and a volume distribution in a cylinder according to the present invention. FIG.

FIG. 1 shows the in-cylinder pressure of the diesel engine according to the first aspect of the present invention. The combustion noise of a diesel engine has a strong relationship with the rate of increase of the in-cylinder pressure, and the higher the rate of rise, the greater the noise. In the case of normal main injection only diesel combustion, as shown by A in FIG. 1, the injected fuel ignites after a certain ignition delay, but during this period, the premixed fuel having a concentration that facilitates combustion is used. A large amount of air is generated and burns at once (premixed combustion). Therefore, the in-cylinder pressure rise rate increases. As shown in B in the figure, when performing the pilot injection, a small amount of fuel evaporates first and ignites, so that the ignition delay of the main injection becomes small. Therefore, the ratio of rapid premix combustion becomes small, and the in-cylinder pressure rise rate becomes small.

In the conventional pilot injection, both pilot and main injection are performed near the compression top. Therefore, in the conventional pilot injection type diesel engine, as shown in FIG. 2, since the main injection comes after the pilot injection ignites near the compression top dead center, oxygen depletion of the main injection occurs and soot generally deteriorates. Will occur. Further, since the flame of the pilot injection itself becomes a high-temperature flame, NOx is generated. The present invention is configured as shown in FIG. High-pressure fuel is supplied from the main injection fuel pump 11 to the main injection nozzle 1 and from a pilot injection fuel pump 12 to the pilot injection nozzle 2. FIG.
As shown in the figure, in the middle stage of the compression stroke, the fuel is sprayed as pilot injection 5 which is a small amount of injection from the pilot injection nozzle 2 and is injected toward a specific premixed gas forming region 4 in the combustion chamber 3 where it evaporates. , A uniform premixed gas 6 is generated. At this time, the concentration of the premixed gas 6 is a lean mixture such that NOx is sufficiently reduced. This air-fuel mixture is compressed to a high temperature, self-ignites near top dead center, and becomes a pilot flame 7 (FIG. 4).

Because of the self-ignition of the lean premixed gas, this flame hardly generates NOx or soot. Further, near this self-ignition timing, the main injection 8 is performed from the main injection injection nozzle 1, and the pilot flame 7 in which the premixed gas 6 self-ignites.
Thus, diffusion combustion with a small ignition delay can be performed. Since the pilot flame 7 in the present invention is lean, there is residual oxygen, so that there is no deterioration in soot unlike the conventional pilot combustion, and it is possible to achieve both low noise and low smoke. Heretofore, no method has been invented to eliminate the ignition delay so as to minimize soot deterioration. The present invention can fundamentally change the combustion system of a direct injection diesel engine.

Referring to FIG. 5, the second aspect of the present invention will be described. The invention according to claim 2 has a plurality of single or multiple injection hole nozzles, one of which is a pilot injection nozzle 2.
The other is a main injection injection nozzle 1, pilot injection is performed into a premixed gas forming region 4 provided in the combustion chamber 3, and main injection is performed in the adjacent combustion chamber 3 other than the pilot combustion region. It is configured to inject into the area.
As shown in FIG. 5, one of the two injection nozzles is a pilot injection nozzle 1 and the other is a main injection nozzle 2. The pilot injection is injected into a limited area in the combustion chamber, evaporates and mixes as in claim 1, self-ignites to become a pilot flame 7, and the main injection is performed from a nozzle.
The main injection by the main injection injection nozzle 1 is injected into a region near the region inside the combustion chamber 3 other than the region. Accordingly, the main injection 8 is not sent directly to the pilot flame 7, and soot deterioration due to lack of oxygen in the main injection is reduced.

Next, a third aspect of the present invention will be described with reference to FIG. According to the third aspect of the present invention, the combustion chamber 3 has a columnar projection A in the center thereof, and an annular groove 14 is formed on the outer periphery thereof. , The main injection is made to collide with the flat portion of the tip of the columnar projection A and diffuse. As a result, the main injection 8 is diffused widely by using the collision diffusion to the columnar projection A, the amount of wall adhesion is reduced, and both soot and blue and white smoke can be reduced.

As shown in FIG. 6, the main injection nozzle 1
Of the two injection nozzles of the pilot injection nozzle 2 and
One is a pilot injection nozzle 2 and the other is a pilot injection nozzle 2. A cylindrical projection A is provided near the center of the combustion chamber 3, and an annular groove 14 is provided on the outer periphery of the cylindrical projection A. Alternatively, the pilot injection 5 injected above the annular groove 14 is injected into the annular groove 14, becomes a premixed gas 6 that is vaporized and mixed in the same manner as in claim 1, and then becomes a pilot flame 7 that has self-ignited, The main injection 8 is performed from the main injection nozzle 1. The main jet 8 is jetted from above the columnar projection A and the annular groove 14 and collides with the flat top of the columnar projection A and diffuses. By this diffusion, the diffusion of the main injection 8 is promoted, soot performance is improved,
The main injection 8 can be arranged in an area in contact with the area of the pilot flame 7.

Next, a fourth aspect of the present invention will be described with reference to FIG. The invention of claim 4 has one single nozzle or a multi-hole hole nozzle 9, during pilot injection, direct injection is performed in the pilot combustion area, and at the main injection timing, a part of the combustion chamber side wall of the piston is provided. It impinges and spreads the spray in an area adjacent to the pilot combustion area. FIG.
As shown in the figure, a single nozzle or a multi-hole hole nozzle 9 is provided in the cylinder. In the vicinity of the center of the combustion chamber 3, there is provided a premixed gas forming region 4 which is a moon-shaped depression. At the time of the pilot injection, the piston is far away, and at this time, the pilot injection 5 is performed toward the premixed gas formation region 4. After the premixed gas 6 is formed by the evaporative mixing and self-ignites to become the pilot flame 7, the main injection 8 is performed. This main injection 8
Since the piston is approaching the hole nozzle 9 at the time, the spray collides with the wall surface other than the premixed gas formation region 4 constituted by the circular dent, and is diffused so as to cover the same. This makes it possible to perform two injections with one valve of the single nozzle or the multiple nozzles of the hole nozzle 9 and to automatically arrange the main injection in a region in contact with the region of the pilot flame 7. The same effect as described above can be obtained.
Other items are the same as those of the first aspect.

Next, a fifth aspect of the present invention will be described with reference to FIGS. The invention according to claim 5 has a cylindrical projection A at the center of the combustion chamber 3, a single nozzle or a multi-hole hole nozzle 9 immediately above the cylindrical projection A, and an annular groove 14 on the outer circumference of the cylinder.
In the case of the pilot injection 5, the distance between the single nozzle or multi-hole hole nozzle 9 and the cylindrical projection A is made larger than the distance that the injected fuel is atomized, and the spray is formed in the annular groove 14. At the same time, the distance between the injection nozzle 9 and the cylindrical projection A near the compression top dead center is made smaller than the distance that the injected fuel is atomized. The collision is made to collide with the flat portion at the tip of the columnar projection A and diffuse into the combustion chamber 3 close to the annular groove 14.

FIG. 8 shows a process in which the injected fuel splits, and is in a liquid column state up to a certain distance (spray split length). The present invention uses this phenomenon. As shown in FIG. 9, a cylindrical projection A is provided near the center of the combustion chamber 3, and an annular groove 14 is provided on an outer peripheral portion of the cylindrical projection A. A single nozzle or a multi-hole hole nozzle 9 is arranged above the columnar projection A. At the time of pilot injection 5, since there is a distance between the piston and the nozzle,
The injected pilot injection 5 is sufficiently atomized. Therefore, the protrusions are separated along the outer periphery and guided to 14. In the same manner as in the first aspect, the premixed gas 6 is evaporated and mixed, and then self-ignited to become a pilot flame 7, and the main injection 8 is performed from the injection nozzle 9. At this main injection timing, since the upper surface of the cylindrical projection A approaches the injection nozzle 9, the main injection 8 collides with the cylindrical projection A before atomization. Therefore, the columnar projection A
Collide and diffuse at the flat top of By this diffusion, atomization and diffusion of the main injection 8 are promoted, soot performance is improved, and the main injection 8 can be automatically arranged in a region in contact with the region of the pilot flame 7. In addition, the adhesion of the spray to the wall is small, and blue smoke can be reduced.

Next, the sixth aspect of the present invention will be described with reference to FIGS. According to the invention of claim 6, when the multi-hole nozzle is used, the distal end of the columnar projection A is partially conical. The main structure is the same as in FIG. FIG.
As shown at 0, the tip of a cylindrical projection A provided near the center of the combustion chamber is formed into a conical shape, and the main injection 8 is caused to collide with the conical surface. When it collides with a flat surface,
As shown in the drawing of (a), a gap is formed between the diffused sprays, and the air utilization rate decreases. On the other hand, when colliding with the conical surface as in the present invention, the spray is diffused at a wide angle due to the curved surface shape, and the gap between the sprays is reduced as shown in the drawing of FIG. As a result, the air utilization rate of the main injection 8 is improved, and soot performance is improved.

Next, the seventh aspect of the present invention will be described with reference to FIGS. The invention according to claim 7 is characterized in that, when a multi-hole nozzle is used, the vicinity of the center of the tip of the cylindrical projection is flattened,
The vicinity of the outer periphery is formed in an arc-shaped hollow shape. The main structure is the same as in FIG. As shown in FIG. 11, the tip of the columnar projection A provided near the center of the combustion chamber has a planar shape 13 near the center, and the outer peripheral portion has an arc-shaped concave shape 1.
5 is assumed. The main injection 8 is started near the compression top dead center, and initially collides with the plane shape 13 near the center. In the late stage of the injection, the piston descends, the distance between the injection valve and the projection increases, and the collision point moves closer to the outer periphery of the projection.
Therefore, the collision point shifts from the planar shape 13 to the arc-shaped hollow shape 15, and the spray is diffused upward along the arc. The initial diffusion spray is close to the pilot flame 7, the ignition delay is shortened, and combustion starts. Subsequent spray is diffused toward unused air above, so that the air utilization rate in the cylinder axial direction is increased, and soot performance is improved. In addition, the effect of pilot ignition can be used effectively.

Next, an eighth aspect of the present invention will be described with reference to FIGS. The invention of claim 8 has one hole nozzle and another throttle nozzle, wherein the throttle nozzle is used as a pilot and the other hose nozzle is used for main injection. FIG. 12 shows a structure according to the eighth aspect of the present invention. The main structure is the same as in FIG. 6, and the pilot injection nozzle 2 is a throttle valve as shown in the figure. As shown in the figure, the spray from the throttle valve is atomized from the point when it comes out of the nozzle and has a hollow cone shape (megaphone shape).
Therefore, the fuel spray can be evenly arranged over the entire premixed gas formation region for pilot combustion without touching the protrusion at the center of the combustion chamber. As a result, it is possible to promote uniformization of the pilot combustion premixed gas, to improve the stability of the self-ignition timing, and to reduce the NOx and soot reduction of the pilot flame. The other operation principle is the same as that of the third aspect.

Next, the ninth aspect of the present invention will be described with reference to FIGS. According to a ninth aspect of the present invention, the pilot combustion region is surrounded by a material C having a high heat insulating property. FIG. 13 shows the structure. The main structure is the same as in FIG. The wall of the combustion chamber 3 surrounding the annular groove 14, which is a region in which the pilot injection is diffused by evaporation to form a uniform lean premixed gas, is made of a material C having a high heat insulating property such as ceramics. FIG. 14 shows the change over time of the compression ratio and the in-cylinder temperature. In the case of a normal metal material (A), heat escapes from the high-temperature compressed air during compression (heat loss). When the temperature falls below the self-ignition temperature, ignition stops. On the other hand, when the compression ratio is increased to increase the temperature to the ignition temperature, as shown in FIG. 15, since the dead volume such as the top clearance is constant, it is necessary to reduce the combustion chamber volume. There is less air in the combustion chamber. In general, the amount of air in the combustion chamber has a deep relationship with soot performance. Therefore, a high compression ratio is disadvantageous in soot performance. Therefore, in the present invention, the premixed pilot region is insulated with the material C having a high heat insulating property, and the heat loss in that portion is reduced.
As shown in FIG. 3, a local high-temperature region is formed in the combustion chamber, and stable pilot auto-ignition is performed without increasing the compression ratio. If the wall temperature is high when the main injection collides, a boiling phenomenon (film boiling / transition boiling) occurs at that point, and atomization is promoted.

Next, the tenth aspect of the present invention will be described with reference to FIG. The invention of claim 10 has one hole nozzle and another throttle nozzle, wherein the hole nozzle is used as a pilot and the other slot nozzle is used for main injection. FIG. 16 shows a structure according to the tenth aspect of the present invention. The concept of combustion is the same as that of the second aspect of the invention, but a throttle nozzle having high diffusivity is used for the main injection nozzle 1 for performing main injection, and the shape of the combustion chamber is close to the spray shape of main injection. At the same time, a premixed gas formation region 4, which is a pilot combustion region, is provided near the center of the combustion chamber. The fuel injected from the pilot injection nozzle 2 in the middle stage of compression evaporates and mixes in the center of the combustion chamber, and self-ignites near the top dead center to become the pilot flame 7. The main injection seal is jetted from the main injection injection nozzle 1 so as to be in contact therewith. Since the spray has a cone shape as shown in the figure, the combustion chamber also has a shape close to the spray shape in order to effectively use air. Immediately after the injection, the main injection comes in contact with the pilot flame at the position 16 and starts combustion with a short ignition delay.

[0029]

As described above, the present invention has the following advantages. In the first aspect of the present invention, in the middle stage of the compression stroke, a part of the fuel in the total injection amount is subjected to primary injection (hereinafter, pilot injection), and is vaporized and diffused in a limited region in the combustion chamber, thereby producing a lean uniform premix. Gas is generated, self-ignition near compression top dead center, and main injection is performed near top dead center.By premixing pilot injection, oxygen is left in pilot combustion, which is a drawback of normal pilot injection. It was possible to eliminate the deterioration of soot due to the lack of oxygen. In normal pilot injection, NOx is generated by the ignition of the pilot injection itself. However, if a premixed pilot is used, NOx generation can be suppressed by lean combustion of the pilot injection. Further, as compared with the case where the full-quantity premixed self-ignition is performed, the main injection has the same combustion form as the conventional diesel combustion, so that high output and low THC can be realized. The main object is to reduce the ignition delay of main injection and achieve low noise and low NOx by pilot ignition without deteriorating soot performance or NOx.

According to a second aspect of the present invention, there is provided the direct injection diesel engine combustion method according to the first aspect, wherein a plurality of single or multiple injection hole nozzles are provided, one of which is used as a pilot and one is used for main injection. The pilot injection is performed in a specific region provided in the combustion chamber, and the main injection is performed in a region close to the pilot flame by injecting the fuel into an adjacent combustion chamber region other than the pilot combustion region. Thus, it is possible to prevent the soot performance from deteriorating while keeping the effect of reducing the ignition delay.

According to the third aspect of the present invention, the main injection is diffused widely by using the collision diffusion to the projection,
By reducing the amount of adhesion to the wall, both soot and blue-white smoke could be reduced.

With the configuration as described in claim 4, the same effect as that of the invention in claim 2 can be obtained with one nozzle.

According to the fifth aspect, the positional relationship between the injection nozzle and the piston changes with time, so that the effect of reducing soot and blue and white smoke can be obtained with a single nozzle in the same manner as in the third aspect. It was able to be constituted so that it could be done.

According to the sixth aspect of the present invention, the soot performance can be improved by enhancing the horizontal diffusion of the main injection.

According to the seventh aspect of the invention, during the injection period of the main injection, as the piston moves down, the impinging spray can be diffused upward, whereby oxygen can be used effectively and soot is reduced. I was able to do it.

According to the eighth aspect of the present invention, the throttle valve having high spray diffusibility is used for pilot injection, fuel is uniformly distributed in the pilot region, uniformization of the premixed air for pilot combustion is promoted, and self ignition timing This has made it possible to improve the stabilization of the fuel cell and to reduce the NOx and soot reduction of the pilot flame.

In the first aspect of the present invention, the pilot injection has a low NOx and low soot concentration by forming a lean homogeneous mixture. However, because of the leanness, it is necessary to set a considerably high temperature for self-ignition. . In order to create a high-temperature field, it is general to increase the compression ratio. However, the higher the compression ratio, the higher the NOx of the main combustion and the smaller the amount of air (volume ratio) in the combustion chamber ( Top clearance volume is constant). This causes deterioration of soot performance. Therefore, it is ideal to raise the temperature only in the region where the premixed compression ignition is performed. In the ninth aspect of the present invention, the deterioration of soot performance can be prevented.

According to a tenth aspect of the present invention, in addition to the second aspect, the diffusion of the main injection in the combustion chamber is increased, soot and NOx generated in the main combustion are reduced, and the main injection adheres to the wall of the combustion chamber. By making it harder, blue and white smoke could be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the effect of pilot injection in a diesel engine with respect to a change in in-cylinder pressure.

FIG. 2 is a view showing a problem of pilot injection in a diesel engine.

FIG. 3 is a drawing showing a structure of a pilot injection according to the present invention of claim 1;

FIG. 4 is an operation conceptual diagram of the pilot injection according to the first embodiment of the present invention.

FIG. 5 is a drawing showing the concept of the operation of the pilot injection according to the present invention of claim 2;

FIG. 6 is an operation conceptual diagram of the present invention of claim 3;

FIG. 7 is an operation conceptual diagram of the present invention according to claim 4;

FIG. 8 is a drawing showing the development process of the spray according to the invention of claim 5;

FIG. 9 is an operation conceptual diagram of the present invention according to claim 5;

FIG. 10 is an operation conceptual diagram of the present invention according to claim 6;

FIG. 11 is an operation conceptual diagram of the present invention according to claim 7;

FIG. 12 is an operation conceptual diagram of the present invention according to claim 8;

FIG. 13 is a structural view of the present invention according to claim 9;

FIG. 14 is a drawing showing changes in the compression ratio and the in-cylinder temperature of the present invention according to claim 10;

FIG. 15 is a view showing a compression ratio and a volume distribution in a cylinder according to the ninth aspect of the present invention.

FIG. 16 is a conceptual diagram showing the structure and operation of the present invention according to claim 10;

[Description of Signs] A Columnar projection C Material with high heat insulation property 1 Main injection nozzle 2 Pilot injection nozzle 3 Combustion chamber 4 Premixed gas formation region 5 Pilot injection 6 Premixed gas 7 Pilot flame 8 Main injection 9 Single Hole nozzle with orifices or multiple orifices 13 Planar shape 15 Arc-shaped hollow shape

Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 41/38 F02D 41/38 B 41/40 41/40 D F02F 3/26 F02F 3/26 A F02M 61/08 F02M 61/08 H 61 / 14 310 61/14 310D 310U 61/18 320 61/18 320Z 360 360J 63/00 63/00 M

Claims (10)

[Claims] In the middle stage of a compression stroke, a part of fuel of a total injection amount is pilot-injected and vaporized and diffused in a limited region in a combustion chamber, and a lean homogeneous premixed gas in the limited region. A self-ignition near compression top dead center, and a main injection near top dead center. 2. The method for combustion of a direct injection diesel engine according to claim 1, comprising a plurality of single or multiple injection hole nozzles, one of which is used for pilot and one for main injection. A direct injection diesel engine combustion method characterized by injecting into a specific region provided in the combustion chamber, and injecting the main injection into an adjacent combustion chamber region other than the pilot combustion region. 3. A combustion method for a direct-injection diesel engine according to claim 2, wherein the combustion chamber has a cylindrical projection in the center of the combustion chamber, an annular groove on the outer periphery thereof, and this area is used as a pilot combustion area. A direct injection diesel engine, wherein the main injection collides with a flat portion at the tip of the projection and diffuses the main injection. 4. The direct injection diesel engine combustion method according to claim 1, further comprising a single injection hole nozzle or a multi-injection hole nozzle. The present invention relates to a direct injection type diesel engine combustion method, comprising colliding with a part of a side wall of a combustion chamber of a piston and diffusing spray into an area adjacent to a pilot combustion area. 5. The method for combustion of a direct injection diesel engine according to claim 4, further comprising a cylindrical projection at the center of the combustion chamber, an injection nozzle immediately above the cylindrical projection, and an annular groove on the outer periphery of the cylindrical projection. At the time of pilot injection, the distance between the injection nozzle and the columnar protrusion is made larger than the distance at which the injected fuel is atomized, and the spray is diffused into the annular groove region. The distance between the injection nozzle and the columnar projection is made smaller than the distance at which the injected fuel is atomized, and the main injection collides with the flat part at the tip of the projection in a liquid column state that does not split, causing combustion near the annular groove. A combustion method for a direct-injection diesel engine, characterized by being diffused indoors. 6. The direct injection diesel engine according to claim 5, wherein the tip of the cylindrical projection has a partially conical shape in the case of using a multi-injection nozzle. Engine combustion method. 7. The method for combustion of a direct injection diesel engine according to claim 5, wherein when using a multi-injection nozzle, the center of the tip of the cylindrical projection is flattened, and the outer circumference is formed in an arcuate concave shape. A combustion method for a direct injection diesel engine, characterized in that: 8. A combustion method for a direct-injection diesel engine according to claim 3, comprising one hole nozzle and another throttle nozzle, wherein the throttle nozzle is used as a pilot and the other hose nozzle is used for main injection. A combustion method for a direct injection diesel engine, characterized in that: 9. The combustion method for a direct-injection diesel engine according to claim 1, wherein the pilot combustion region is surrounded by a material having high heat insulation. 10. The method for combustion of a direct injection diesel engine according to claim 2, further comprising one hole nozzle and another throttle nozzle, wherein the hole nozzle is a pilot,
A direct injection diesel engine combustion method, wherein the other throttle nozzle is used for main injection.