JPH0583733B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a swirl combustion chamber type diesel engine,
Especially when idling or under low load, the vortex flow can suppress the generation of HC, etc. as much as possible, slow down its combustion, and keep the rate of pressure rise inside the cylinder low, which can significantly reduce noise and vibration. Regarding combustion chamber type diesel engines.

[Prior Art] Generally, a swirl combustion chamber type diesel engine has a swirl combustion chamber 2 in a cylinder head 1, as shown in FIG.
are divided into sections. 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 fuel injection nozzle 4 for injecting fuel F into the chamber. The mixture vaporization of the fuel F injected from the injection nozzle 4 is promoted by the vortex S, and is ignited and combusted by the heat of compression.

[Problems to be Solved by the Invention] Conventionally, in order to reduce noise and prevent the generation of unburned fuel, injected fuel has been atomized and
Promote mixture vaporization by vaporization and vortex flow, and
Although the overall ignitability has been improved, if only the ignitability is pursued, the air-fuel mixture in the combustion chamber 2 will be in a high energy state as a whole, and combustion will proceed at once with the generation of a large number of flame kernels. 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 It is not a pleasant experience when idling or the like.

In view of these circumstances, the inventor of the present application has considered a swirl combustion chamber type diesel engine as shown in FIG. Instead of the injection nozzle 4 having a single injection port 5 as shown in FIG. 1, the combustion chamber 2 has a main injection port 6;
An injection nozzle 8 having one sub-nozzle 7 branched from this is provided. This injection nozzle 8 is designed to inject fuel F only from the sub-nozzle 7 by reciprocating the needle valve 9 with the main nozzle 6 closed when a small amount of fuel is sufficient, such as when idling or under low load. It is composed of The sub-nozzle 7 is on the downstream side in the flow direction of the vortex S and is located in the combustion chamber 2.
It is made to face the inner wall 10 of. Then, the fuel F injected from the sub-nozzle 7 is deposited on the inner wall 10 as a liquid film L, and the fuel scattered around it is mixed and vaporized by the vortex S, thereby starting from a flame kernel while preventing ignition delay. The idea is to propagate the combustion slowly and achieve slow combustion.

However, even with this proposal, due to the shape of the combustion chamber 2,
It is conceivable that the sub-nozzle 7 and the inner wall 10 are separated and the amount of fuel that gets caught up in the vortex S and vaporizes/mixtures until the fuel F reaches the inner wall 10 is large, and rapid combustion is sufficiently suppressed. I'm worried that it won't be possible.

The present invention was devised in view of the above-mentioned problems, and an object of the present invention is to suppress the generation of HC etc. as much as possible while injecting fuel vapor during idling and low load. To provide a vortex combustion chamber type diesel engine which allows slow combustion and slow combustion to greatly reduce noise and vibration.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method in which a fuel injection nozzle including a main nozzle and a sub-nozzle is attached to the nozzle through a heat shield so as to face the vortex combustion chamber. attached to the hole, the fuel injection nozzle is
The main nozzle is closed and only the auxiliary nozzle is opened during low load including when the engine is idling. A guide surface is formed so as to be smoothly continuous with the indoor wall surface and further tangentially connected to the sub-nozzle, and the fuel injected from the sub-nozzle is directed into a thin liquid film along the guide surface and the wall surface of the swirl combustion chamber. In a vortex combustion chamber type diesel engine that allows slow combustion to occur, the sub-nozzle may be formed in a plurality of sub-nozzles in parallel along the guide surface or A slit-like shape having a predetermined width is formed by communicating between a plurality of sub-nozzles arranged in parallel.

[Function] According to the above configuration, during idling and under low load, the fuel is flowed from the sub-nozzle along the inner wall of the combustion chamber via the guide surface so as to form a thin liquid film in the downstream direction of the vortex flow. By slowly vaporizing the fuel from the inner wall and burning it slowly, the rate of pressure rise in the cylinder chamber can be kept low, and noise and vibrations during idling and low load can be significantly reduced.

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

As shown in FIG. 3, reference numeral 2 denotes a vortex combustion chamber defined within the cylinder head 1. In this combustion chamber 2, a vortex S of compressed air is generated, and at the same time a vortex S is generated for injecting fuel into the chamber. Fuel injection nozzle 11
is provided. This injection nozzle 11 has a nozzle body 12 that forms an outer shell of the injection nozzle 11 and a heat shield 1 that is connected to a cylindrical mounting hole 13 that communicates with the inside of the combustion chamber 2.
It is attached via 4. A fuel supply hole 15 is formed inside the nozzle body 12, as shown in FIG. 4, through which fuel is fed under pressure from the fuel pump. It communicates with a main injection port 6 formed to inject fuel into the combustion chamber 2 via a shaped valve seat surface 16 . Also, in the middle of the valve seat surface 16, there are
As shown in the figure, a plurality of relatively small-diameter sub-nozzle ports 17 are formed branching from the main nozzle port 6 and radially outward of the nozzle body 12 at predetermined intervals. In the nozzle body 12 formed in this way, a needle valve 9 is provided extending from the supply hole 15 side to the main nozzle port 6. The needle valve 9 mainly includes a shaft-shaped first valve body part 9a for opening and closing the main nozzle 6, and a cone-shaped second valve body part 9b for opening and closing the supply hole 15. .
The needle valve 9 is configured to be reciprocated by an operating mechanism (not shown) in accordance with the crank angle and in accordance with the load condition. When the required fuel is small and the amount of movement of the needle valve 9 is small, the first valve body portion 9a
That is, it is inserted into the main nozzle 6 at a depth that allows the main nozzle 6 to be maintained in a closed state during idling or under low load.
On the other hand, the second valve body portion 9b is configured to sit on the valve seat surface 16 in a substantially linear contact with the valve seat surface 16 along its circumferential direction, and to open and close the supply hole 15 by always following the reciprocating movement of the needle valve 9. be done.

The sub-nozzle 17... has its inlet side facing these valve seat surfaces 16.
and the second valve body portion 9b, and communicates with a gap C through which fuel is supplied from the supply hole 15 even when the main injection port 6 is closed. When the amount of injected fuel is small, such as when idling, this sub-nozzle 1
The configuration is such that fuel injection is performed only from 7....

The combustion chamber 2 of the sub-nozzle 17 configured in this way
As shown in FIGS. 3, 4, and 5, the side-facing ejection ends 17a... They are arranged in parallel at intervals and configured to inject fuel over as wide a range as possible.
In particular, in the present invention, these jetting ends 17a...
is formed so as to face the inner wall 10 in the downstream direction of the vortex S generated in the combustion chamber 2, and causes the injected fuel F to flow along the inner wall 10 as a thin liquid film L, The configuration is such that vaporization and mixture vaporization due to the vortex S are suppressed. Furthermore, these ejection ends 17a are formed to have a small diameter, so that the particle size of the injected fuel is reduced so that the liquid film L is easily evaporated. That is, by converting the fuel into a liquid film and causing the liquid film L to flow downstream of the vortex S, it is possible to suppress the vaporization and mixture vaporization of the fuel, but if the evaporation of the fuel is significantly impaired, unburned matter will be left behind after combustion. Therefore, by making the liquid film L thinner and the particle size smaller, we can compensate for the vaporization of the fuel, and by achieving a balance between these two, we can achieve slow combustion while suppressing the increase in HC, etc. That is.

The sub-nozzle 17 configured in this manner and the inner wall 10
A guide surface 18 is formed between these surfaces without interruption to form a series of surfaces, and on which the fuel F injected from the sub-nozzle ports 17 immediately adheres to form a liquid film L and flow toward the inner wall 10. is intervened. That is, a part of the inner wall 10 is extended to the sub-nozzle ports 17 by the guide surface 18. In this embodiment, as shown in FIGS. 4, 5, and 6, the combustion chamber side outer wall 12a of the nozzle body 12
The nozzle body 12 is raised along the formation direction of the combustion chamber wall 10 and smoothly connected to the combustion chamber wall 10.
It expands in the circumferential direction and is formed by a fan-like pyramidal surface,
The fuel F injected from the plurality of sub-nozzles 17 in a radial direction is caused to collide and adhere, thereby forming a thin liquid film L over a wide range on the inner wall 10. Further, a portion of the fuel _F1 is directly scattered into the combustion chamber 2 by the force of the injection, is atomized and vaporized, and is used for ignition.

Note that 14 is a cylindrical heat shield for isolating the nozzle body 12 from the high-temperature cylinder head 1 to prevent heat transfer. In this embodiment, since one side of the nozzle body 12 is continuous with the inner wall 10 as the guide surface 18, that part is not folded back, and the remaining part is folded back toward the main nozzle 6 side.

Next, the operation of the present invention will be described.

As shown in FIGS. 3 and 4, when idling or under low load, the needle valve 9 reciprocates and the second valve body portion 9b opens and closes the fuel supply hole 15, thereby opening and closing the gap C.
Although fuel is supplied to the sub-nozzles 17, the first valve body portion 9a maintains the main nozzle 6 in a closed state, and fuel is injected from each sub-nozzle 17. The fuel F is supplied to the sub-nozzle 17...
An inner wall 10 with a part F ₁ including a guide surface 18 with an aperture of
It is scattered nearby and becomes a mixture, and most of it immediately travels along the guide surface 18 to form a thin liquid film L over a wide area on the inner wall 10. At this time, since the direction in which the liquid film L is formed is on the downstream side of the vortex S, that is, in the same direction as the flow direction of the vortex S, it is possible to prevent the liquid film L from being peeled off from the inner wall 10 by the vortex S of high-temperature compressed air. can be suppressed. However, vaporization of the fuel is not prevented at all, and because the sub-nozzles 17 are small in diameter and are provided in a wide range, the particle size itself is relatively small, and the fuel flows in a thin film over a wide range, so the liquid film L itself is in a state where it easily evaporates. Therefore, the flame kernel A is generated by the fuel F ₁ scattered near the inner wall 10 as described above, and combustion is started, and the inner wall 1
The fuel that is vaporized sequentially from zero is combusted and follows a slow combustion process, but since the fuel is vaporized smoothly, the generation of HC and the like can also be suppressed. That is, the present invention maintains ignitability with the fuel F ₁ partially mixed and vaporized by the vortex S, and prevents ignition delay, while providing most of the fuel to slow combustion. By suppressing the pressure rise rate of the fuel to significantly reduce noise and vibration, and by making the fuel finer and thinner, it promotes vaporization and makes it easier to generate through slow combustion.
This is in harmony with efforts to reduce HC, etc.

In addition, as shown by the two-dot chain line in Fig. 5, the sub-nozzle 1
7... may be connected to form a slit 19 having a predetermined width along the inner wall 10 of the combustion chamber 2, and the slit 19 may constitute a sub-nozzle. In this case, although fuel particle refinement is slightly impaired, clogging due to carbon or the like can be prevented, and the reliability of the injection nozzle 11 can be improved.

In addition, during normal operation to high-load operation, combustion is performed in a state in which the main injection port 6 is opened by the needle valve 9 and mixture vaporization by the vortex S is promoted. At this time, a portion of the fuel F is also injected from the auxiliary nozzles 17, 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 this embodiment, since the guide surface 18 is integrally formed on the nozzle body 12 in which the sub-nozzle ports 17 are formed, the sub-nozzle ports 17 can be bored along the guide surface 18 during manufacturing. In this case, the connecting portion between the sub-nozzle ports 17 and the guide surface 18, which requires the most precision, can be precisely and smoothly processed.

Incidentally, the fuel injection nozzle 11 adopted in this proposal is as follows:
Although it is similar to a so-called "pintoe nozzle" that performs preliminary injection before injecting fuel from the main nozzle 6 in order to improve ignition performance, its operation and effect are completely different. While the pinto nozzle has the function of making its sub-nozzle face the upstream side of the vortex and injecting fuel in advance before injection from the main nozzle to promote the mixture vaporization and improve ignitability, the pinto nozzle is adopted in the present invention. The sub-nozzles 17 of the nozzles 11 function for fuel injection during idling, etc., and form a liquid film L of fuel along the inner wall 10 on the downstream side of the vortex S to suppress mixture vaporization.

[Modification example]

FIG. 7 shows a modification of the above embodiment. As shown in the figure, a heat shield 14 is employed as the guide surface 18 in this example. That is, the combustion chamber side outer wall 12a of the nozzle body 12
The folded piece 14a of the heat shield 14, which is folded back to cover the auxiliary nozzle 17... and the combustion chamber wall 10, is extended and smoothly formed, and serves as a guide surface 18 to guide the fuel to the inner wall 10. It is configured to do so.

In the example shown in FIG. 8, the guide surface 18 that is integrally formed with the nozzle body 12 is formed all around the outer wall 12a of the nozzle body 12 on the combustion chamber side. This is advantageous in that it requires fewer processing steps than forming the surface 18 only around the auxiliary nozzle 17. However, since the area around the main nozzle 6 becomes narrow, carbon adhesion is a concern, and the above embodiment may be better in terms of reliability.

These modified embodiments also provide the same effects as those of the above embodiments.

〔Effect of the invention〕

In summary, the present invention exhibits the following excellent effects.

(1) The sub-nozzles provided to inject fuel during idling, low load, etc. are placed along the inner wall of the combustion chamber in the downstream direction of the vortex, and the fuel injected from these sub-nozzles is immediately directed along the inner wall. Since a liquid film is formed by flowing the mixture, vaporization and mixture vaporization can be suppressed to achieve sequentially slow combustion, and noise and vibration can be significantly reduced.

(2) A plurality of sub-nozzles with small diameters are formed along the wall of the combustion chamber so that the injected fuel flows as a thin liquid film with fine particles as wide as possible, so that the liquid film itself is Evaporation can be promoted and HC, etc. generated due to slow combustion can be reduced as much as possible.

(3) The mixture necessary for ignition can be obtained by the fuel injected from the sub-nozzle and vaporized near the inner wall, and ignition delay will not be caused.

(4) The structure is simple and can be easily adopted.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing a conventional example, Fig. 2 is a side sectional view showing a studied embodiment, Fig. 3 is a side sectional view showing a preferred embodiment of the present invention, and Fig. 4 is a side sectional view showing a preferred embodiment of the present invention. An enlarged sectional view of the main part in the figure, Figure 5 is - of Figure 4.
6 is a sectional view taken along the - line in FIG. 5, FIG. 7 is a side sectional view showing a modified embodiment, and FIG. 8 is a modified example of the guide surface provided integrally with the nozzle body. FIG. In the figure, 1 is the cylinder head, 2 is the swirl combustion chamber,
6 is a main injection port, 10 is an inner wall of the combustion chamber, 11 is an injection nozzle, 17 is a sub injection port, 17a is an injection end thereof, 19 is a slit, F is a fuel, and S is a vortex flow.

Claims (1)

[Claims] 1 A fuel injection nozzle 11 having a main nozzle 6 and a sub-nozzle 17 is attached to a nozzle mounting hole facing the vortex combustion chamber 2 through a heat shield 14, and the fuel injection nozzle 11 When loaded, the main nozzle 6 is closed and only the auxiliary nozzle 17 is opened. A guide surface 18 is formed so as to be smoothly continuous with the sub-nozzle 10 and further tangentially connected to the sub-nozzle, so that the fuel injected from the sub-nozzle 17 is guided along the guide surface 18 and the wall surface 10 of the swirl combustion chamber. In a swirl combustion chamber type diesel engine in which the liquid flows to form a thin liquid film to perform slow combustion, a plurality of sub-nozzles 17 are formed in parallel along the guide surface 18, or A swirl combustion chamber type diesel engine characterized in that a plurality of sub-nozzles arranged in parallel along a guide surface 18 are formed in a slit shape having a predetermined width by communicating with each other.