JPH0574686B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a diesel engine, and particularly in a diesel engine having a sub-combustion chamber such as a swirl combustion chamber or a pre-combustion chamber, combustion during low load such as idling. This invention relates to a diesel engine that can slow down the pressure increase rate in the cylinder, thereby significantly reducing noise and vibration.

[Prior Art] FIG. 10 shows a diesel engine equipped with a swirl combustion chamber as an example of an auxiliary combustion chamber, in which a swirl combustion chamber 2 is defined within a cylinder head 1. As shown in FIG. This combustion chamber 2 is communicated with a cylinder chamber 3 formed in a cylinder block (not shown), and generates a vortex S of compressed air flowing in due to the upward movement of the piston. Further, the combustion chamber 2 is provided with a combustion injection nozzle 4 for injecting fuel F into the chamber. The fuel F injected from the injection nozzle 4 is accelerated to become a mixture by the vortex S.
The heat of compression ignites and burns it.

By the way, in the case of a diesel engine, if the ignition delay period is long, the fuel injected during the ignition delay period becomes a premixture, creating a high energy state in the combustion chamber 2 as a whole, and generating a large number of flame kernels. At the same time, combustion progresses all at once (explosively). Such rapid combustion increases the rate of pressure rise in the cylinder chamber 3 and generates large pressure waves, which impact the piston, cylinder wall, etc. and generate noise and vibration, especially Immediately after the engine is started, when the engine is idling and the cooling water temperature is low, the temperature of the entire engine is also low, so the ignitability of the fuel itself is poor and this tendency is noticeable, which is not a pleasant experience.

In view of these circumstances, the applicant of the present application proposed a "vortex chamber for diesel engines" as shown in FIG. 11 (Japanese Utility Model Publication No. 82432/1983). In the present invention, instead of the injection nozzle 4 having a single nozzle 5 as shown in FIG. 10, the combustion chamber 2 has a main nozzle 6 and a sub-nozzle branching from this to perform a small amount of preliminary injection. 7 (so-called "pistou nozzle") 8 is provided. The sub-nozzle 7 faces the glow plug 9, and injects the fuel F before fuel injection from the main nozzle 6, and also causes the fuel F to collide with the glow plug 9 to atomize the fuel, so that the fuel can be atomized at an early stage. Achieve ignition.

[Problems to be solved by the invention] By the way, as proposed above, in order to reduce noise and prevent the generation of unburned fuel, ignition can be achieved by promoting atomization/vaporization of the injected fuel and mixture vaporization by vortex flow. By shortening the delay period, the ignition performance throughout the combustion chamber 2 can be improved, and considerable improvements in noise performance and the like can be achieved. However, if only ignitability is pursued, there is a concern that rapid combustion may not be sufficiently suppressed and the noise performance will deteriorate because a large amount of fuel is vaporized and premixed even within the shortened ignition delay period.

Therefore, the present invention was devised to provide a diesel engine that can shorten the ignition delay period, slowly vaporize the injected fuel, slow its combustion, and significantly reduce noise and vibration. It is something.

As a conventional technique for achieving slow combustion, there is Japanese Utility Model Application Publication No. 59-88218. However, in this proposal, a recess is formed in the heat shield of the fuel injection nozzle, which is insufficient to cause the fuel injected from the sub-nozzle to contribute to slow combustion.
That is, even if the fuel injected from the auxiliary nozzle temporarily stays in the recess, it may peel off without flowing into the auxiliary combustion chamber due to the level difference with the inner wall of the auxiliary combustion chamber, and there is a risk of rapid evaporation and combustion. The present invention ensures slow combustion after early ignition.

[Means for Solving the Problems] The present invention provides an injection nozzle having a main injection port in a passage communicating with a sub-combustion chamber, and the injection nozzle has a sub-injection port branched from the main injection port that continues to the wall of the sub-combustion chamber. A fuel retention part is formed facing the inner wall of the passage, and a part of the injected fuel is scattered and the remaining part is deposited on the inner wall of the passage. It is designed to make it easier to understand.

[Operation] With the above configuration, fuel is injected from the sub-nozzle during idling or under low load, and collides with the fuel retention portion on the inner wall of the passage. A part of the fuel is atomized and atomized and scattered into the sub-combustion chamber, while the remaining fuel adheres to the fuel retention area and then flows to the wall of the sub-combustion chamber to form a liquid film. The scattered fuel causes early ignition, and the fuel that gradually vaporizes from the inner wall of the combustion chamber causes slow combustion.

[Embodiment] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, a vortex combustion chamber 2 is defined as a sub-combustion chamber within the cylinder head 1, and a vortex S of compressed air is generated in the combustion chamber 2. A cylindrical passage 11 is formed on one side of the combustion chamber 2 so as to be close to the ejection end 10a of the sub-nozzle 10, and facing into the combustion chamber 2. A fuel injection nozzle 12 for injecting fuel into the combustion chamber 2 is provided inside the passage 11 . This injection nozzle 12 has a nozzle body 13 forming its outer shell attached to a cylindrical attachment hole 14 communicating with the passage 11 via a heat shield 15.
The combustion chamber side wall 13a is engaged with a folded annular claw portion 15a of the heat shield 15. The heat shield 15 is configured to isolate the nozzle body 13 from the hot cylinder head 1 and prevent heat transfer.

A fuel supply hole 16 through which fuel is fed under pressure from the fuel pump is formed inside the nozzle body 13, and this supply hole 16 has a conical valve seat surface 17 whose diameter is gradually reduced toward the combustion chamber 2 side. It communicates with a main nozzle 18 formed to inject fuel into the combustion chamber 2 through the main nozzle 18 . Further, in the middle of the valve seat surface 17, a relatively small-diameter sub-nozzle port 10 is formed branching from the main nozzle port 18 and extending outward in the radial direction of the nozzle body 13. In the nozzle body 13 formed in this way, a needle valve 19 is provided extending from the supply passage hole 16 side to the main nozzle port 18 .

The needle valve 19 mainly includes a shaft-shaped first valve body part 19a for opening and closing the main nozzle 18, and a cone-shaped second valve body part 19b for opening and closing the supply hole 16. There is. The needle valve 19 is configured to be reciprocated by an operating mechanism (not shown) in accordance with the crank angle and with a considerable lift amount depending on the load condition.
The first valve body portion 19a requires less fuel than the needle valve 19.
When the amount of lift is small, that is, when idling or under low load, the main nozzle 18 is inserted to a depth that can maintain the main nozzle 18 in a closed state. On the other hand, the second valve body portion 19b is seated on the steam valve seat surface 17 along its circumferential direction in a substantially linear contact state, and opens and closes the supply passage hole 16 by constantly following the reciprocating movement of the needle valve 19. It is composed of

The inlet side of the sub-nozzle 10 is formed between the valve seat surface 17 and the second valve body portion 19b, and fuel is supplied from the supply hole 16 even when the main nozzle 18 is closed. . When the amount of injected fuel is small, such as during idling, the configuration is such that fuel is injected only from this auxiliary nozzle 10.

As shown in the figure, the sub-nozzle 10 configured in this manner has an ejection end 10a that directs the fuel F injected therefrom along the combustion chamber wall 20 in the downstream direction of the vortex S generated within the combustion chamber 2. The opening is opened facing the inner wall 21 of the passage 11 formed in close proximity to the passage 11 so as to allow water to flow therethrough. In particular, in the present invention, the sub-nozzle 1
Part of the fuel F that is injected from the sub-nozzle 10 and collides with the inner wall 21 of the passage facing the passage ₂₁ is atomized by the momentum of the collision, is scattered inward of the combustion chamber 2, and is converted into a mixture by the vortex S. A fuel retention section 22 is configured to cause most (remaining part) of the fuel F to immediately collide and adhere to the combustion chamber wall 20 in the form of a liquid film L, and to suppress vaporization and mixture vaporization caused by the vortex S. It is formed. That is, early ignition is achieved with the part _F1 of the fuel that collides with the inner wall 21 of the passage, atomizes and scatters, and is mixed and vaporized by the vortex S, and the combustion that follows ignition is caused to form a liquid film along the inner wall 20 of the combustion chamber. It is slowed down by the flowing fuel F. Specifically, the fuel retention part 22 is formed by carving uneven grooves on the inner wall 21 of the passage, and the fuel retention part 22 is formed by carving uneven grooves on the inner wall 21 of the passage.
At the same time, part of the fuel F ₁ is scattered from the passage 11 to the combustion chamber 2 side.

More specific embodiments of the fuel retention section 22 are shown in FIGS. 2 to 7.

The one shown in Fig. 2 has a plurality of unevenness along the circumferential direction of the cylindrical inner wall 21 of the passage, and grooves are formed in multiple stages in the axial direction of the passage 11. It is made up of screw threads arranged in a spiral pattern.

The one shown in FIG. 3 is formed by disposing trapezoidal threads in place of the triangular threads in FIG. 2. These have excellent workability.

The structure shown in FIGS. 4 and 5 has a plurality of unevenness arranged along the axial direction of the passage 11, and grooves are formed in multiple stages in the circumferential direction of the passage inner wall 21, and is configured for so-called spline teeth. This is what I did. In this embodiment, since the grooves can be formed deeply, the adhesion of fuel can be promoted, the generation of premixture can be suppressed, and the noise performance can be improved.

In what is shown in FIG. 6, a plurality of holes 23 are bored radially outward from a cylindrical inner wall 21 of a passage, and these holes 23 form uneven grooves. Such a fuel retention section 22 may be constructed by separately manufacturing a sleeve 24 in which a hole 23 is formed and installing this sleeve 24 inside the passage 11.

The one shown in FIG. 7 has a cylindrical porous material 25, such as a ceramic material, disposed inside the passage 11 to form uneven grooves.

Ceramic material has excellent heat resistance, etc.
It is suitable for use in 2. This embodiment does not require groove molding, so productivity is good, and substantially the same functions can be achieved in any of the embodiments.

On the other hand, the ejection end 10a of the auxiliary nozzle 10 is formed to have a small diameter, so that the particle size of the ejected fuel is reduced so that the liquid film L is easily evaporated. That is, by turning the fuel into a liquid film and flowing the liquid film L downstream of the vortex S, it is possible to suppress the vaporization and mixture vaporization of the fuel. The liquid film L
By making the fuel thinner and the particle size finer, it supplements the vaporization of the fuel and achieves slow combustion while suppressing the deterioration of HC, etc. by maintaining a balance between the two.

Incidentally, as shown in FIG. 1, 26 is a glow plug for improving the startability of the engine. Generally, it is extended to float inward of the combustion chamber 2 in order to collide and heat the injected fuel, but in this embodiment, it is placed in the combustion chamber in the downstream direction of the vortex S in order to bring it into contact with the liquid film L. It is installed along the wall 20. With this configuration, the durability of the glow plug 26 can be improved without being exposed to high pressure and high heat during normal operation after startup.

Next, we will discuss the effect.

As shown in FIG. 1, when idling or under low load, the needle valve 19 reciprocates and the second valve body 1
9b opens and closes the fuel supply hole 16 to supply fuel, but the first valve body portion 19a maintains the main injection port 18 in a closed state, and fuel is injected only from the sub injection port 10. Immediately after being injected, the injected fuel F collides with the fuel retention portion 22 of the passage inner wall 21, causing some
F ₁ is atomized and atomized and scattered into the combustion chamber 2, and most of the fuel F forms a wide thin liquid film L on the combustion chamber wall 20 in a predetermined angle range. At this time, the fuel retention portion 22 effectively adheres and retains the injected fuel through its uneven grooves and flows it from the passage 11 to the combustion chamber wall 20, and also scatters a portion of the fuel _F1 toward the combustion chamber 2 side. Since most of the fuel F flowing onto the combustion chamber wall 20 is on the downstream side of the vortex S, that is, in the same direction as the vortex S, the liquid film L is caused to flow into the combustion chamber by the vortex S of the high-temperature compressed air. Peeling off from the wall 20 can be suppressed as much as possible. However, vaporization and mixture vaporization of the fuel are not prevented at all, and since the diameter of the sub-nozzle 10 is small, the particle size itself is relatively small, and the liquid film L is also evaporated because it flows in a thin film over a wide area. It is becoming easier to do so. Therefore, as described above, the ignition point A occurs early due to the air-fuel mixture of the fuel F ₁ partially scattered in the combustion chamber 2, and as combustion starts, the fuel gradually vaporizes from the combustion chamber wall 20. It will be burned and undergo a slow combustion process. As a result, as shown in Fig. 8, whereas conventionally, due to the ignition delay _T2 , the entire cylinder chamber was in a high energy state and combustion proceeded explosively (indicated by the broken line B in the figure). In the present invention, ignitability is maintained by a portion of the fuel F ₁ that collides with the fuel retention portion 22 of the passage inner wall 21 and is scattered, and early ignition is achieved (indicated by T ₁ in the figure). Most of the fuel is deposited on the combustion chamber wall 2 as a liquid film L.
Since combustion is performed by gradual vaporization from zero, the rate of pressure increase in the cylinder chamber 3 can be kept low without reducing the average effective pressure in the cylinder, as shown by solid line A, and noise and vibration can be significantly reduced. can be reduced to In the figure, P is the injection period of the sub-nozzle 10 during low load such as idling.

FIG. 9 shows the measurement results of noise for each engine cooling water temperature. In the figure, × and ◯ indicate respective measured values for the conventional example and the preferred embodiment of the present invention shown in FIG. 10, respectively. According to the present invention, it has been demonstrated that superior noise performance can be exhibited compared to conventional examples.

Note that the fuel F flowing into the combustion chamber wall 20 is a thin film and fine particles, and deterioration of HC and the like can also be suppressed.

In addition, during normal operation to high-load operation, the main injection port 18 is opened by the needle valve 19, and combustion is performed in a state where mixture vaporization by the vortex particles S is promoted. At this time, a portion of the fuel F is also injected from the auxiliary nozzle 10, and a portion of the total amount of injected fuel is subjected to slow combustion, making it possible to reduce noise more than when all the fuel is mixed and vaporized.

Furthermore, in the present invention, the passage inner wall 21 facing the combustion chamber 2 and the ejection end 10a are close to each other,
It is possible to prevent the fuel F from being drawn into the vortex S until the collision occurs, and from this aspect as well, rapid combustion can be prevented.

Incidentally, the fuel injection nozzle 12 employed in the present invention
In order to improve ignition performance, the so-called "pinto" is used to conduct a preliminary injection before injecting fuel from the main nozzle.
The pinto nozzle has its sub-nozzle facing upstream of the vortex, and injects fuel before injection from the main nozzle to vaporize the mixture. On the other hand, the sub-nozzle 10 of the nozzle 12 employed in the present invention functions for fuel injection during idling, etc. Along the line, a liquid film L of fuel is formed to suppress mixture vaporization.

In the above embodiment, one sub-nozzle 10 is formed, but a plurality of sub-nozzles 10 may be formed.

Further, the fuel retention section 22 is not limited to the above embodiment, and may be any structure as long as it facilitates the attachment of fuel.

Further, in the above embodiment, the overflow combustion chamber was used as an example of the sub-combustion chamber, but the present invention can also be applied to a diesel engine equipped with a pre-combustion chamber.

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

A fuel retention section is provided on the inner wall of the passageway facing the sub-nozzle, in which a part of the injected fuel is scattered and the remaining part is deposited, and the attached fuel is configured to flow in a liquid film form along the wall of the sub-combustion chamber and sequentially vaporize. The scattered fuel causes early ignition, and the liquid film formed on the inner wall of the sub-combustion chamber ensures slow combustion, resulting in a significant reduction in noise and vibration.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing a preferred embodiment of the present invention, Fig. 2 is a side sectional view showing a specific embodiment of the fuel retention section, and Fig. 3 is a side sectional view showing another specific embodiment. , FIG. 4 is a side sectional view showing still another specific embodiment, FIG. 5 is a sectional view taken along the - line in FIG. 4, and FIG.
The figure is a side cross-sectional view showing still another specific embodiment.
The figure is a side sectional view showing still another specific embodiment, No. 8
The figure is a graph comparing the combustion process of the present invention and the conventional example, Figure 9 is a graph showing the noise measurement values at each engine cooling water temperature of the present invention and the conventional example, and Figures 10 and 11 are the conventional example. FIG. In the figure, 2 is a swirl combustion chamber exemplified as a sub-combustion chamber, 10 is a sub-nozzle, 11 is a passage, 21 is an inner wall thereof, 12 is an injection nozzle, 18 is a main nozzle, and 22 is a fuel retention part.

Claims (1)

[Scope of Claims] 1. An injection nozzle having a main injection port is provided in a passage communicating with the sub-combustion chamber, and the injection nozzle has a sub-injection port branched from the main injection port facing the inner wall of the passage that continues to the wall of the sub-combustion chamber. A fuel retention part is provided on the inner wall of the passageway to scatter a part of the injected fuel and the remaining part is attached, and the attached fuel is made to flow in a liquid film along the inner wall of the sub-combustion chamber and to be sequentially vaporized. A diesel engine that is characterized by: 2. The diesel engine according to claim 1, wherein the fuel retention portion is constituted by uneven grooves formed in the inner wall of the steam passage. 3. The diesel engine according to claim 2, wherein a plurality of the uneven grooves are arranged along the circumferential direction of the passage, and are formed in multiple stages in the axial direction of the passage. 4. The diesel engine according to claims 2 to 3, wherein the uneven groove is spirally arranged along the circumferential direction of the passage, and is formed in multiple stages in the axial direction of the passage. . 5. The diesel engine according to claim 2, wherein a plurality of the uneven grooves are arranged along the axial direction of the passage, and are formed in multiple stages in the circumferential direction of the passage. 6. The diesel engine according to claim 2, wherein the uneven groove is formed by a plurality of holes bored radially outward in the passage. 7. The diesel engine according to claim 2, wherein the uneven groove is formed of a cylindrical porous material disposed inside the passage. 8. The diesel engine according to claim 7, wherein the porous material is molded from a ceramic material.