JP2021102953A - diesel engine - Google Patents

Abstract

To provide a diesel engine capable of suppressing generation of black smoke and deterioration of fuel economy and reducing noise by performing multi-stage injections.SOLUTION: A diesel engine 1 comprises: a fuel injection nozzle 30 having a large-diameter hole 32 in a central portion and small-diameter holes 33, 34 that are arranged at positions on both sides of the large-diameter hole and have a diameter smaller than the diameter of the large-diameter hole 32; and a mouth piece 50 having nozzle holes that provide communication between a main combustion chamber 10 and a subsidiary combustion chamber 20 and include a main nozzle hole 51, subsidiary nozzle holes 52, 52 arranged at positions on both sides of the main nozzle hole 51, and auxiliary nozzle holes 53, 53 arranged at positions on both sides of the subsidiary nozzle holes. In an intake stroke in a range across the bottom dead center T1 of the intake stroke, where a cylinder internal pressure is 10 MPa or less, a pilot injection 100 of fuel is performed from the fuel injection nozzle 30 toward the mouth piece 50 via the subsidiary combustion chamber 20.SELECTED DRAWING: Figure 5

Description

The present invention relates to a sub-chamber type diesel engine that injects fuel into a sub-combustion chamber (also referred to as a sub-chamber) provided in a cylinder head.

In medium- and large-sized diesel engines, a direct injection system (DI combustion system) is combined with a high-pressure fuel injection common rail system (CRS) as a combustion system. In a high-pressure fuel injection common rail diesel engine, noise is reduced by injecting fuel in multiple stages.

Patent Document 1 discloses a sub-chamber type diesel engine. The sub-chamber type diesel engine can easily obtain a stable combustion state as compared with the direct injection type diesel engine. The sub-chamber type diesel engine has a main combustion chamber and a sub-combustion chamber provided at a position eccentric with respect to the main combustion chamber, and is used as, for example, a small industrial diesel engine. The main combustion chamber and the sub-combustion chamber are connected to each other through the injection holes. The combustion airflow is ejected from the sub-combustion chamber into the main combustion chamber through the injection hole. In the sub-chamber type diesel engine, the generation of PM (particulate matter) is suppressed by reviewing the shape of the recess formed on the ceiling wall of the piston.

Japanese Unexamined Patent Publication No. 2019-113008

By the way, in a small industrial diesel engine, for example, a small diesel engine having a small bore diameter of 75 mm or less, when fuel is injected in multiple stages at high pressure, the fuel spray collides with the wall surface of the combustion chamber, that is, penetration occurs. appear. For this reason, the mixture of the fuel injection and the intake air becomes incomplete, and the deterioration of combustion causes an increase in black smoke and a deterioration in fuel efficiency. Therefore, it has been difficult to reduce noise by using multi-stage fuel injection for a small industrial diesel engine.

The present invention has been made to solve the above problems, and to provide a diesel engine capable of suppressing the generation of black smoke and deterioration of fuel efficiency and reducing noise by performing multi-stage injection. The purpose.

The problem is a diesel engine in which a main combustion chamber and an auxiliary combustion chamber provided at a position eccentric from the main combustion chamber communicate with each other, and a large-diameter hole arranged in a central portion and the above-mentioned problem. A fuel injection nozzle having small-diameter holes arranged at positions on both sides of the large-diameter hole and having a diameter smaller than the diameter of the large-diameter hole, and a nozzle for communicating the main combustion chamber and the sub-combustion chamber. A mouthpiece having the nozzle including a main nozzle, sub-injections arranged at positions on both sides of the main nozzle, and auxiliary nozzles arranged at positions on both sides of the sub-injection. In the intake process in which the cylinder internal pressure is 10 MPa or less with the bottom dead point of the intake process in between, pilot injection of fuel is performed from the fuel injection nozzle toward the mouthpiece via the auxiliary combustion chamber. This is solved by the diesel engine according to the present invention.

According to the diesel engine according to the present invention, since the pilot injection of fuel is performed in a state where the cylinder internal pressure is as low as 10 MPa or less, the internal pressure of the sub-combustion chamber communicating with the main combustion chamber of the cylinder is also low. Therefore, the fuel spray is less likely to collide with the inner wall surface of the sub-combustion chamber, and the injected fuel is less likely to adhere to the inner wall surface of the sub-combustion chamber. Therefore, it is possible to improve combustion and suppress the generation of black smoke and the deterioration of fuel efficiency. Further, the pilot injection (preceding injection) of the fuel is performed in the sub-combustion chamber prior to the main injection (main injection). Therefore, the temperature of the combustion chamber including the sub-combustion chamber and the main combustion chamber becomes high before the main injection. This makes it easier for the fuel injected during the main injection to burn, and it is possible to prevent the fuel injected during the main injection from adhering to the inner wall surface of the sub-combustion chamber. Therefore, multi-stage injection of low-pressure fuel is possible, and noise can be reduced. As a result, it is possible to suppress the generation of black smoke and the deterioration of fuel efficiency, and to reduce noise by performing multi-stage injection.

In the diesel engine according to the present invention, preferably, the pilot injection of the fuel is performed only from the large-diameter hole of the fuel injection nozzle.
According to the diesel engine according to the present invention, the pilot injection of low pressure fuel is performed only through the large diameter holes. As a result, low-pressure fuel spraying can be smoothly performed on the sub-combustion chamber, and it is possible to further suppress the fuel injected during pilot injection from adhering to the inner wall surface of the sub-combustion chamber.

In the diesel engine according to the present invention, the main injection of the fuel is further performed in a state of the cylinder internal pressure higher than the cylinder internal pressure at the time of the pilot injection, and the main injection of the fuel is the fuel. It is characterized in that it is performed from both the large-diameter hole of the injection nozzle and the small-diameter hole of the fuel injection nozzle.
According to the diesel engine according to the present invention, the main injection of high-pressure fuel is performed from both the large-diameter hole of the fuel injection nozzle and the small-diameter hole of the fuel injection nozzle. As a result, high-pressure fuel spraying can be efficiently and smoothly performed on the sub-combustion chamber by using both the large-diameter hole and the small-diameter hole.

In the diesel engine according to the present invention, preferably, in the main injection of the fuel, the injection of the fuel from the small-diameter hole is performed toward the auxiliary injection port of the mouthpiece.
According to the diesel engine according to the present invention, it is possible to suppress the generation of penetration in the sub-combustion chamber at the time of main injection, that is, the fuel injected at the time of main injection collides with the inner wall surface of the sub-combustion chamber.

According to the present invention, it is possible to provide a diesel engine capable of suppressing the generation of black smoke and deterioration of fuel efficiency and reducing noise by performing multi-stage injection.

It is sectional drawing which shows the vicinity of the main combustion chamber and the sub-combustion chamber of the diesel engine which concerns on embodiment of this invention. It is an enlarged sectional view showing the vicinity of the sub-combustion chamber of this embodiment in an enlarged manner. It is a figure which shows the structural example of the injection part of the fuel injection nozzle of this embodiment. It is a bottom view which shows the structural example of the base of this embodiment. It is a graph which shows the change example of the pressure between the pilot injection and the main injection with respect to the crank angle of the diesel engine which concerns on this embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
Since the embodiments described below are suitable specific examples of the present invention, various technically preferable limitations are added, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these aspects. Further, in each drawing, the same components are designated by the same reference numerals, and detailed description thereof will be omitted as appropriate.

(Structural example of diesel engine 1)
FIG. 1 is a cross-sectional view showing the vicinity of a main combustion chamber and a sub-combustion chamber of a diesel engine according to an embodiment of the present invention.
The diesel engine 1 shown in FIG. 1 is a so-called sub-chamber type diesel engine, and has a main combustion chamber 10 and a sub-combustion chamber 20. The diesel engine 1 shown in FIG. 1 is also referred to as an E-TVCS (vortex chamber flow type) combustion type diesel engine. The diesel engine 1 is, for example, a small IDI (Indirect Injection) combustion type diesel engine having a bore diameter of 75 mm or less. The diesel engine 1 is mounted on, for example, a construction machine, an agricultural machine, a lawn mower, or the like. However, the type of equipment on which the diesel engine 1 is mounted is not particularly limited.

The diesel engine 1 has a cylinder block 2 and a cylinder head 3. A cylinder 4 is provided inside the cylinder block 2. The piston 5 is arranged in the cylinder 4 and can reciprocate along the cylinder central axis P. The cylinder 4 has a main combustion chamber 10 at the top. The cylinder head 3 is assembled on the cylinder block 2. An auxiliary combustion chamber 20 is provided inside the cylinder head 3. The sub-combustion chamber 20 is also referred to as a sub-chamber, a vortex chamber, a vortex chamber, or the like.

As shown in FIG. 1, the fuel injection nozzle 30 is attached to the cylinder head 3. The injection portion 31 of the fuel injection nozzle 30 is arranged so as to face the inside of the sub-combustion chamber 20, and is exposed in the internal space of the sub-combustion chamber 20 from above to diagonally downward. The main combustion chamber 10 in the cylinder 4 is connected to the sub-combustion chamber 20 via a base 50. The base 50 has multiple nozzles 40 through which the combustion airflow G passes. The multiple nozzle 40 of the present embodiment is an example of the "port" of the present invention. The main combustion chamber 10 communicates with the sub-combustion chamber 20 through the multiple nozzles 40 of the base 50. The multiple nozzles 40 are provided at locations eccentric with respect to the main combustion chamber 10. The multiple nozzles 40 are formed, for example, diagonally downward along the substantially tangential direction of the inner peripheral surface of the sub-combustion chamber 20.

(Structural example of sub-combustion chamber 20)
FIG. 2 is an enlarged cross-sectional view showing the vicinity of the sub-combustion chamber of the present embodiment in an enlarged manner.
As shown in FIG. 2, the internal space of the sub-combustion chamber 20 is substantially elliptical or circular when viewed in the vertical cross section. The mounting hole 48 is formed in the cylinder head 3 at a position eccentric from the cylinder central axis P toward the cylinder peripheral wall side. The base 50 is held in a state of being housed in the mounting hole 48. The base 50 is also called a chamber or the like, and forms a lower half portion of the internal space of the sub-combustion chamber 20. The mounting hole 48 has a large-diameter opening 56 and a small-diameter body accommodating portion 57 in this order from the cylinder head bottom surface 6A side toward the fuel injection nozzle 30 side. The large-diameter opening 56 accommodates the bottom 59 of the base 50. The body portion 60 of the base 50 is accommodated in the body portion accommodating portion 57. The glow plugs arranged in the sub-combustion chamber 20 are not shown.

The base 50 shown in FIG. 2 is a stepped columnar metal fitting having a columnar body portion 60 and a bottom portion 59. The outer diameter of the bottom portion 59 is larger than the outer diameter of the body portion 60. The body 60 has a substantially hemispherical recess 61 for forming the lower half of the internal space of the sub-combustion chamber 20. The bottom 59 has multiple nozzles 40. The multi-injection port 40 is formed in the inner bottom portion of the recess 61, and connects the inner peripheral surface 61A of the recess 61 and the main combustion chamber 10. That is, the multi-injection port 40 communicates the main combustion chamber 10 and the sub-combustion chamber 20. When the base 50 is assembled to the cylinder head 3, it is formed by the upper half of the internal space of the auxiliary combustion chamber 20 formed by the inner peripheral surface 58A of the cavity 58 and the inner peripheral surface 61A of the recess 61. The lower half of the internal space of the sub-combustion chamber 20 is substantially flush with each other. As described above, the internal space of the sub-combustion chamber 20 is formed by the cavity 58 and the recess 61.

As shown in FIG. 2, the sub-combustion chamber 20 is provided at a position eccentric with respect to the main combustion chamber 10. The main combustion chamber 10 and the sub-combustion chamber 20 are connected to each other so that the combustion airflow G can pass between the main combustion chamber 10 and the sub-combustion chamber 20 through the multi-injection port 40. The combustion airflow G in the sub-combustion chamber 20 is ejected from the sub-combustion chamber 20 into the main combustion chamber 10 through the multiple nozzles 40. Here, the multi-injection port 40 is formed so as to be inclined obliquely toward the center side of the main combustion chamber 10. Therefore, the combustion airflow G ejected from the multi-injection port 40 is obliquely blown to, for example, the top surface 5A of the piston 5 near the top dead center.

(Injection portion 31 of the fuel injection nozzle 30)
Next, a configuration example of the injection unit 31 of the fuel injection nozzle 30 shown in FIG. 2 will be described with reference to FIG.
FIG. 3 is a diagram showing a structural example of the injection portion of the fuel injection nozzle of the present embodiment.
The injection portion 31 of the fuel injection nozzle 30 shown in FIG. 3 has a large-diameter hole 32 in the central portion and small-diameter holes 33 and 34 arranged at positions on both sides of the large-diameter hole 32. The range of the ratio between the diameter of the large-diameter hole 32 and the diameter of the small-diameter holes 33 and 34 is preferably about 1.1 to 2. The number of holes provided in the injection unit 31 is not limited to three, and may be four or more.

(Cap 50)
Further, a structural example of the base 50 shown in FIG. 2 will be described with reference to FIG.
FIG. 4 is a bottom view showing a structural example of the base of the present embodiment.
The base 50 has the multiple nozzles 40 shown in FIG. The multiple nozzles 40 of the base 50 include a main nozzle 51, sub-ports 52 and 52 arranged at positions on both sides of the main nozzle 51, and auxiliary nozzles 53 and 53 arranged at positions on both sides of the sub-ports 52 and 52. Have. The multi-injection port 40 is formed so as to be inclined with respect to the cylinder central axis P shown in FIG. 1 along a substantially tangential direction of the inner peripheral surface of the sub-combustion chamber 20 shown in FIG. When the piston 5 compresses the main combustion chamber 10, the air entering the sub-combustion chamber 20 generates a vortex in the sub-combustion chamber 20.

The main nozzle 51 is formed substantially in the center of the bottom 59 of the base 50. The sub nozzles 52 and 52 have an opening area smaller than the opening area of the main nozzle 51, and are formed continuously with the main nozzle 51 at the left and right positions of the main nozzle 51. The auxiliary nozzles 53, 53 have an opening area smaller than the opening area of the sub nozzles 52, 52, and are formed at positions on the left and right of the sub nozzles 52, 52 apart from the main nozzle 51 and the sub nozzles 52, 52. There is. The main nozzle 51, the sub-ports 52, 52, and the auxiliary nozzles 53, 53 are inclined so as to be directed from the sub-combustion chamber 20 toward the central portion of the main combustion chamber 10, that is, as shown by the combustion airflow G in FIG. It is formed.

(Example of operation of multi-stage injection in diesel engine 1)
Next, an operation example of multi-stage injection in the diesel engine 1 according to the present embodiment will be described with reference to FIG.
FIG. 5 is a graph showing an example of changes in pressure between pilot injection and main injection with respect to the crank angle of the diesel engine according to the present embodiment.
The multi-stage fuel injection includes a low pressure pilot injection 100 and a high pressure main injection 200. The graph shown in FIG. 5 shows how the pilot injection 100 is performed at the bottom dead center T1 of the piston and the main injection 200 is performed at the top dead center T2.

<Fuel pilot injection 100>
First, the fuel pilot injection 100 will be described. In the fuel pilot injection 100, in the intake process in the range where the cylinder internal pressure is 10 MPa or less with the bottom dead center T1 of the intake process in between, only from the large-diameter hole 32 of the injection portion 31 of the fuel injection nozzle 30 shown in FIG. Fuel is injected in the direction of the combustion airflow G shown in FIG. That is, the fuel injection nozzle 30 performs low-pressure injection of 10 MPa or less in the pilot injection 100. The fuel spray by the pilot injection 100 smoothly passes through the main injection port 51 of the base 50 and enters the cylinder 4 shown in FIG.

In the pilot injection 100, the fuel injection into the cylinder 4 is performed at atmospheric pressure or lower, so that the combustion spray spreads smoothly into the main combustion chamber 10 in the cylinder 4. As a result, the generation of penetration is suppressed and the mixing of the fuel spray and the intake air is promoted. That is, since the pilot injection 100 is performed in a state where the internal pressure of the cylinder 4 shown in FIG. 1 is as low as 10 MPa or less, the internal pressure of the sub-combustion chamber 20 communicating with the main combustion chamber 10 of the cylinder 4 is also low. Therefore, the fuel spray is unlikely to collide with the inner wall surface of the auxiliary combustion chamber 20. Therefore, the fuel is unlikely to adhere to the inner wall surface of the auxiliary combustion chamber 20. Therefore, it is possible to improve combustion and suppress the generation of black smoke and the deterioration of fuel efficiency.

<Main injection of fuel 200>
Next, the fuel main injection 200 will be described. In the fuel pilot injection 100 described above, fuel is injected only from the large-diameter hole 32 of the injection portion 31 of the fuel injection nozzle 30 shown in FIG. 3 in a state where the internal pressure of the cylinder 4 is as low as 10 MPa or less. On the other hand, in the fuel main injection 200, when the piston 5 of FIG. 1 reaches the top dead center T2 shown in FIG. 5, the fuel is fueled from all the holes of the injection portion 31 of the fuel injection nozzle 30 shown in FIG. Is injected. That is, in the fuel main injection 200, in the high pressure state when the piston 5 reaches the top dead center T2, the large-diameter hole 32 and the small-diameter hole 33 of the injection portion 31 of the fuel injection nozzle 30 shown in FIG. Fuel is injected from all the holes with 34 toward the sub-combustion chamber 20. As described above, the fuel injection nozzle 30 performs high-pressure injection at the main injection 200 with a cylinder pressure higher than the cylinder internal pressure at the time of the pilot injection 100. At this time, the fuel injection from the small-diameter holes 33 and 34 is performed so as to be directed toward the auxiliary nozzles 53 and 53 of the base 50, that is, toward the fuel spray X shown in FIG. As a result, it is possible to prevent the generation of penetration, that is, the fuel spray from colliding with the inner wall surface of the auxiliary combustion chamber 20.

According to the diesel engine 1 according to the present embodiment, since the pilot injection 100 of the fuel is performed in a state where the internal pressure of the cylinder 4 is as low as 10 MPa or less, the sub-combustion chamber 20 communicating with the main combustion chamber 10 of the cylinder 4 The internal pressure is also low. Therefore, the fuel spray is less likely to collide with the inner wall surface of the sub-combustion chamber 20, and the injected fuel is less likely to adhere to the inner wall surface of the sub-combustion chamber 20. Therefore, it is possible to improve combustion and suppress the generation of black smoke and the deterioration of fuel efficiency. Further, the fuel pilot injection (preceding injection) 100 is performed in the sub-combustion chamber 20 prior to the main injection (main injection) 200. Therefore, the temperature of the combustion chamber including the sub-combustion chamber 20 and the main combustion chamber 10 becomes high before the main injection 200. This makes it easier for the fuel injected at the time of the main injection 200 to burn, and it is possible to prevent the fuel injected at the time of the main injection 200 from adhering to the inner wall surface of the sub-combustion chamber 20. Therefore, multi-stage injection of low-pressure fuel is possible, and noise can be reduced. As a result, it is possible to suppress the generation of black smoke and the deterioration of fuel efficiency, and to reduce noise by performing multi-stage injection.

Further, the low-pressure fuel pilot injection 100 is performed only through the large-diameter hole 32 of the fuel injection nozzle 30. As a result, low-pressure fuel spraying can be smoothly performed on the sub-combustion chamber 20, and the fuel injected at the time of pilot injection 100 can be further suppressed from adhering to the inner wall surface of the sub-combustion chamber 20. it can.

Further, the main injection 200 of the high-pressure fuel is performed from both the large-diameter holes 32 of the fuel injection nozzle 30 and the small-diameter holes 33 and 34 of the fuel injection nozzle 30. As a result, high-pressure fuel spraying can be efficiently and smoothly performed on the sub-combustion chamber 20 by using both the large-diameter holes 32 and the small-diameter holes 33 and 34.

Further, in the main injection 200, the fuel injection from the small diameter holes 33 and 34 is performed toward the auxiliary injection ports 53 and 53 of the base 50. As a result, it is possible to prevent the generation of penetration, that is, the fuel spray from colliding with the inner wall surface of the auxiliary combustion chamber 20.

Further, the drive loss of the fuel injection pump of the diesel engine 1 can be reduced, the fuel consumption can be improved, and the noise and vibration can be reduced. Further, it is possible to realize the clean exhaust gas at low cost and to provide the diesel engine 1 having a small amount of _{CO 2 emission.} As a result, the diesel engine 1 according to the present invention has the potential to comply with the European minicar Euro5 regulations. Further, the amount of fuel adhering to the cylinder 4 can be reduced, and the dilution of the fuel can be suppressed.

The embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of claims. The configuration of the above embodiment may be partially omitted or may be arbitrarily combined so as to be different from the above. For example, the arrangement positions, the number of settings, and the shapes of the large-diameter holes 32 and the small-diameter holes 33, 34 of the injection portion 31 of the fuel injection nozzle 30 shown in FIG. 3 are not limited to the illustrated examples. Further, the arrangement positions, the number of settings, and the shapes of the main nozzle 51, the sub nozzles 52, 52, and the auxiliary nozzles 53, 53 of the multiple nozzle 40 of the base 50 shown in FIG. 4 are not limited to the illustrated examples. Absent.

1: Diesel engine, 2: Cylinder block, 3: Cylinder head, 4: Cylinder, 5: Piston, 5A: Top surface, 6A: Cylinder head bottom surface, 10: Main combustion chamber, 20: Sub-combustion chamber, 30: Fuel injection Nozzle, 31: Injection part, 32: Large diameter hole, 33, 34: Small diameter hole, 40: Multiple nozzles, 48: Mounting hole, 50: Base, 51: Main nozzle, 52: Secondary nozzle, 53: Auxiliary nozzle , 56: Opening, 57: Body accommodation, 58: Cavity, 58A: Inner circumference, 59: Bottom, 60: Body, 61: Recess, 61A: Inner circumference, 100: Piston injection, 200: Main injection, G: Combustion airflow, P: Cylinder center axis, T1: Bottom dead center, T2: Top dead center, X: Fuel spray

Claims (4)

A diesel engine in which the main combustion chamber and the sub-combustion chamber provided at a location eccentric from the main combustion chamber communicate with each other.
A fuel injection nozzle having a large-diameter hole arranged in a central portion and a small-diameter hole arranged at positions on both sides of the large-diameter hole and having a diameter smaller than the diameter of the large-diameter hole.
A nozzle that connects the main combustion chamber and the sub-combustion chamber, the main nozzle, the sub-ports arranged at both sides of the main nozzle, and the auxiliary nozzles arranged at both sides of the sub-combustion. With a mouthpiece having the nozzle, including
With
In the intake process in which the cylinder internal pressure is 10 MPa or less across the bottom dead center of the intake process, fuel pilot injection is performed from the fuel injection nozzle toward the mouthpiece via the auxiliary combustion chamber. Diesel engine. The diesel engine according to claim 1, wherein the pilot injection of the fuel is performed only from the large-diameter hole of the fuel injection nozzle. The main injection of the fuel is further performed in the state of the cylinder internal pressure higher than the cylinder internal pressure at the time of the pilot injection.
The diesel according to claim 1 or 2, wherein the main injection of the fuel is performed from both the large-diameter hole of the fuel injection nozzle and the small-diameter hole of the fuel injection nozzle. engine. The diesel engine according to claim 3, wherein in the main injection of the fuel, the injection of the fuel from the small-diameter hole is performed toward the auxiliary injection port of the mouthpiece.

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