JP2009209742A - Multiple injection hole fuel injection nozzle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that fuel easily adheres on a flat surface part and a large quantity of carbon piles up by auxiliary spray from an auxiliary injection hole in a multiple injection hole fuel injection nozzle which has a plurality of main injection holes provided around the single auxiliary injection hole provided at an injection part of a nozzle body and which has the auxiliary injection hole oppositely arranged roughly perpendicularly to a flat surface part of a projecting body formed at a roughly center part of a cavity constructing a combustion chamber at a piston top part. <P>SOLUTION: Injection hole diameter d2 of the auxiliary injection hole 25 is formed smaller than injection hole diameter d1 of the main injection holes 6 and an injection hole length adjusting structure making injection hole length L21 of the auxiliary injection hole 25 shorter than injection hole length L1 of the main injection hole 6 is provided. The injection hole length adjusting structure is constructed by forming a horizontal lower surface 20b which is a removal surface on an opening outside 25a of the auxiliary injection hole 25. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multi-injection fuel injection nozzle used in a direct-injection diesel engine, and more particularly, to a multi-injection fuel injection nozzle in which auxiliary injection ports are arranged to be opposed to each other at a substantially right angle to a flat portion of a projecting body formed in a combustion chamber at the top of a piston. About.

  2. Description of the Related Art Conventionally, in a direct injection diesel engine in which fuel is directly injected into a combustion chamber to cause natural combustion, a cavity is provided at the top of the piston so that the combustion chamber is formed between the inner surface of the cylinder and the lower surface of the cylinder head. In addition, by arranging the injection port of the injection portion of the fuel injection nozzle so as to face the cavity, the air flow of the swirl or the like is actively used, and the spray injected from the fuel injection nozzle is The fuel was diffused toward the wall surface, and the fuel was sufficiently mixed with air to burn efficiently.

  In particular, by providing a plurality of spray holes in the injection unit to increase the number of sprays, the fuel is diffused over a wide range to increase the efficiency of air utilization, and a projection having a flat part is provided in the approximate center of the cavity. A small-diameter nozzle (hereinafter referred to as an “auxiliary nozzle”) is disposed at the lower end of the injection section so as to face the plane section at a substantially right angle so that the air in the cavity immediately below the fuel injection nozzle is effectively used. There are known multi-injection fuel injection nozzles of opposed arrangement that improve the fuel efficiency and reduce the smoke emitted during engine operation.

Here, FIG. 5 is a partial cross-sectional side view of the front portion of such a conventional multi-injection fuel injection nozzle, and FIG. 6 is also the vicinity of the combustion chamber, showing the spraying state by the conventional multi-injection fuel injection nozzle. FIG.
As shown in FIGS. 5 and 6, a hemispherical injection part 3 is formed in the lower part of the nozzle body 2 of the multi-injection fuel injection nozzle 1, and the injection hole length L <b> 2 and the injection hole diameter are provided at the lower end of the injection part 3. A small diameter auxiliary injection hole 5 of d2 is formed, and a plurality of large diameter injection holes (hereinafter referred to as “main injection holes”) 6 having the injection hole length L1 and the injection hole diameter d1 are formed around the auxiliary injection hole 5. Has been. Furthermore, the nozzle length L2 is equal to the nozzle length L1, and the nozzle diameter d2 is set smaller than the nozzle diameter d1.

  The multi-injection fuel injection nozzle 1 is fitted to the cylinder head 8 so that the nozzle axis 7 is disposed coaxially with a cylinder center line 18 of a cylinder (not shown) that houses the piston 9. The main injection port 6 and the auxiliary injection port 5 of the injection unit 3 face the inside of the combustion chamber 4 from the lower surface 8 a of the cylinder head 8.

  The combustion chamber 4 is formed between a lower surface 8a of the cylinder head 8, an inner surface of a cylinder (not shown), and a cavity 10 in which a top portion 9a of the piston 9 is processed into a concave shape. In the center, the protrusion 11 bulges upward, and a substantially flat flat surface portion 11a is formed on the upper portion of the protrusion 11, and the auxiliary injection hole 5 is provided with respect to the flat surface portion 11a. The auxiliary nozzle center line 12 is disposed so as to be substantially orthogonal.

  In the above-described configuration, the fuel injected from the plurality of main nozzles 6 is directed toward the inner wall 10a of the cavity 10 that is obliquely downward while spreading as a main spray 16 on the center line 13 of the main nozzle. Further, the fuel injected from the auxiliary nozzle 5 advances toward the flat surface portion 11a below while spreading as a supplementary spray 15 on the center line 12 of the auxiliary nozzle. As a result, the number of sprays is increased, and air existing in the space immediately below the multi-injection fuel injection nozzle 1 reduced by the projection 11 is sufficiently mixed with the fuel by the auxiliary spray 15 and burned. To improve the efficiency of air use.

However, if the nozzle length L2 and the nozzle diameter d2 of the auxiliary nozzle 5 are inappropriate, the penetration force of the auxiliary spray 15 becomes strong and the spray length S2 becomes long, and the fuel constituting the auxiliary spray 15 is Before it is sufficiently atomized, it collides with the flat surface portion 11a and adheres to the collision surface. As a technology for preventing such fuel adhesion, the spray angle of the auxiliary spray is increased by setting the ratio of the nozzle hole length to the nozzle hole diameter at the auxiliary nozzle hole to be equal to or less than the ratio of the nozzle hole length to the nozzle hole diameter at the main nozzle. A technique for reducing the penetration force and shortening the spray length is known (for example, see Patent Document 1).
JP 2004-204808 A

  However, in the above technique, the auxiliary nozzle is the lower nozzle of the upper and lower nozzle arrays formed in the nozzle body, and the auxiliary spray injected from the auxiliary nozzle is also the inner wall of the cavity, like the main spray. It travels diagonally and collides. On the other hand, in the case of the opposed injection type multi-injection fuel injection nozzle 1 according to the present invention, the auxiliary spray 15 injected from the auxiliary injection port 5 collides at a substantially right angle toward the flat surface portion 11a of the projection 11. The adhesion force of the fuel to the collision surface is stronger, and for this reason, in the multi-injection fuel injection nozzle 1, the spray length S2 varies even a little and the tip of the auxiliary spray 15 is flat. When contacting the portion 11a, the fuel easily adheres to the flat portion 11a and a large amount of carbon is deposited.

  Here, as in the above technique, even if only the ratio of the nozzle length L to the nozzle diameter d (hereinafter simply referred to as “shape factor”) L / d is adjusted, if the nozzle diameter is too large, the spray angle In addition to the effect of alleviating the penetration force due to expansion, the effect of enhancing the penetration force due to the increase in mass accompanying the increase in the amount of spray is also achieved, and it is possible to reliably reduce the spray length to a length where the spray does not contact the inner wall of the cavity difficult. In particular, when fuel is injected substantially vertically downward as in the auxiliary injection nozzle 5 of the multi-injection fuel injection nozzle 1 described above, the effect of enhancing the penetration force by increasing the spray amount through the increase in mass is remarkable.

  Therefore, even if the above technique is applied, the fuel adhesion force to the flat surface portion 11a is strong as in the conventional multi-injection fuel injection nozzle 1, and the effect of enhancing the penetration force by increasing the spray amount is significant. If the amount of spray increases due to slight fluctuations due to the pulsation of the supplied fuel pressure or the like, the tip of the auxiliary spray 15 comes into contact with the flat surface portion 11a located in the immediate vicinity, and fuel easily flows into the flat surface portion 11a. There is a problem that engine performance is remarkably lowered due to frequent deposition of black smoke at low load and white smoke immediately after starting.

  As a result of intensive studies to solve the above-described problems, the present inventors have found that the shape factor L2 / d2 of the auxiliary injection nozzle 5 is used to prevent the fuel from adhering to the flat portion 11a in the opposed injection type multi injection nozzle fuel injection nozzle 1. It has been found that the adjustment of the nozzle length L2 after forming the nozzle diameter d2 smaller is much more effective than the above adjustment.

That is, according to claim 1, a single auxiliary injection port is provided in the injection part of the nozzle body, a plurality of main injection ports are provided around the auxiliary injection port, and the auxiliary injection port is a cavity that forms a combustion chamber at the top of the piston. In the multi-injection fuel injection nozzle disposed substantially perpendicular to the flat portion of the projecting body formed at substantially the center of the auxiliary nozzle, the auxiliary nozzle has a nozzle diameter smaller than the nozzle diameter of the main nozzle, and the auxiliary nozzle A nozzle length adjustment structure is provided that sets the nozzle hole length of the nozzle hole to be shorter than the nozzle hole length of the main nozzle hole.
According to a second aspect of the present invention, the nozzle hole length adjusting structure is formed by forming a deletion surface outside the opening of the auxiliary nozzle hole.
According to a third aspect of the present invention, the ratio of the nozzle hole length to the nozzle hole diameter at the auxiliary nozzle hole and the ratio of the nozzle hole length to the nozzle hole diameter at the main nozzle hole are set substantially the same by the nozzle hole length adjusting structure.

Since this invention was comprised as mentioned above, there exists an effect shown below.
That is, according to claim 1, a single auxiliary injection port is provided in the injection part of the nozzle body, a plurality of main injection ports are provided around the auxiliary injection port, and the auxiliary injection port is a cavity that forms a combustion chamber at the top of the piston. In the multi-injection fuel injection nozzle disposed substantially perpendicular to the flat portion of the projecting body formed at substantially the center of the auxiliary nozzle, the auxiliary nozzle has a nozzle diameter smaller than the nozzle diameter of the main nozzle, and the auxiliary nozzle Since the nozzle hole length adjustment structure is set to set the nozzle hole length shorter than the nozzle hole length of the main nozzle hole, the main nozzle hole is formed with a larger nozzle diameter to increase the spray amount, and While maintaining the penetrating force strongly, the auxiliary nozzle has a small nozzle diameter to prevent the penetrating force from being increased by increasing the spray amount, and then shortening the nozzle length and widening the spray angle to reduce the penetrating force. Full relaxation It can, by shortening the spray length of the auxiliary spray fuel is atomized before striking the flat surface portion, it is possible to reliably prevent the fuel from adhering to the flat surface portion. As a result, even in the multi-hole fuel injection nozzle of the opposed arrangement type, the air in the cavity immediately below the multi-hole fuel injection nozzle is effectively used to generate black smoke at low load and white smoke immediately after starting. It is possible to improve engine performance by suppressing it.
According to a second aspect of the present invention, since the nozzle hole length adjusting structure is formed by forming a deletion surface outside the opening of the auxiliary nozzle, the outer surface of the auxiliary nozzle is spaced apart from the flat surface by forming the deletion surface. This makes it difficult to contact the tip portion of the auxiliary spray with the portion, thereby further suppressing fuel adhesion to the flat portion, and further improving engine performance.
In claim 3, since the ratio of the nozzle hole length to the nozzle hole diameter in the auxiliary nozzle hole and the ratio of the nozzle hole length to the nozzle hole diameter in the main nozzle hole are set substantially the same by the nozzle hole length adjusting structure, the auxiliary nozzle hole The nozzle length is too long and the spray angle is narrowed, the penetration force is increased and the spray length of the auxiliary spray is increased, or the nozzle length of the auxiliary nozzle is too short and the member thickness near the auxiliary nozzle is reduced. Thus, it is possible to reliably prevent deterioration of the durability of the entire multi-injection fuel injection nozzle due to a decrease in strength such as pressure resistance and heat resistance, and to ensure good engine performance and nozzle durability.

Next, embodiments of the invention will be described.
FIG. 1 is a partial cross-sectional side view of a front portion of a multi-injection fuel injection nozzle according to the present invention, FIG. 2 is an enlarged view of the same, and FIG. 3 shows the state of spraying by the multi-injection fuel injection nozzle according to the present invention. FIG. 4 is an explanatory view showing the influence of the shape factor of the auxiliary injection hole on the black smoke density at low load. The embodiment of the multi-injection fuel injection nozzle to which the present invention is applied has been described with reference to FIGS. 1 to 4. The same reference numerals are used for the same parts and dimensions as those of the conventional examples of FIGS. 5 and 6 described above. Is attached.

First, the multi-injection fuel injection nozzle 21 according to the present invention will be described with reference to FIGS.
Similarly to the multi-hole fuel injection nozzle 1 described above, the multi-hole fuel injection nozzle 21 is also attached to the cylinder head 8 so that the nozzle axis 7 is disposed coaxially with a cylinder center line 18 of a cylinder (not shown). It is inserted. Further, an injection portion 20 according to the present invention is formed below the multi-injection fuel injection nozzle 21, and the injection portion 20 faces the inside of the combustion chamber 4 from the lower surface 8 a of the cylinder head 8.

  A spherical sac hole 14 is formed inside the injection unit 20, and a spherical center 19 of the sack hole 14 is located on the nozzle axis 7. A conical lower end 17 a of a valve body 17 that can slide up and down projects from the sack hole 14, and the lower end 17 a is formed so as to be seated on a valve seat 22 a in the nozzle body 22. . Further, a fuel supply path 23 is formed between the inner peripheral side surface of the nozzle body 22 and the outer peripheral side surface of the valve body 17.

  In such a configuration, at the start of fuel injection, a high-pressure fuel is supplied to the fuel supply path 23 from a fuel injection pump (not shown), and then a gap between the lower end 17a of the valve body 17 and the valve seat 22a. The gas flows into the sack hole 14 through 23 a and is injected into the cavity 10 constituting the combustion chamber 4 from the later-described injection holes 6 and 25 formed in the injection unit 20.

  At the end of fuel injection, an electromagnetic valve or the like is operated based on a control signal from a control device (not shown), and the valve body 17 is lowered by an actuator such as a hydraulic piston to shut off the gap 23a. The fuel supply to the inside 14 is stopped, and the fuel injection into the cavity 10 from the nozzle holes 6 and 25 is stopped.

  Next, the structure of the injection unit 20 and the nozzle holes 6 and 25 according to the present invention will be described with reference to FIGS.

  As shown in FIGS. 1 to 3, the injection unit 20 is provided by horizontally cutting and removing the lower half of the hemispherical injection unit 3 of the multi-injection fuel injection nozzle 1. In the hemispherical side surface 20a at the upper part of the injection unit 20, the spherical center 24 substantially coincides with the spherical center 19 of the sack hole 14, and the plurality of main injection holes 6 are opened in the hemispherical side surface 20a. . On the other hand, the horizontal lower surface 20b at the lower part of the injection unit 20 is formed at a substantially right angle to the nozzle shaft center 7, and a single auxiliary injection hole 25 is opened at the approximate center of the horizontal lower surface 20b in plan view. .

  The plurality of main nozzle holes 6 are arranged at equal intervals in the circumferential direction on the same circumference centered on the nozzle axis 7, and each main nozzle hole 6 has a main nozzle hole center line 13 with the hemispheric side surface It is formed so as to substantially pass through the spherical center 24 of 20a, and is opened at a substantially right angle to the hemispherical side surface 20a. On the other hand, the auxiliary injection hole 25 is formed so that the auxiliary injection hole center line 12 coincides with the nozzle axis 7 and is opened at a substantially right angle to the horizontal lower surface 20b.

  As a result, fuel can be injected from either the main injection nozzle 6 or the auxiliary injection nozzle 25 at a substantially right angle with respect to the outer peripheral surface of the injection unit 20, thereby preventing the occurrence of irregular vortices during fuel injection. In addition, variations in fuel distribution in the combustion chamber 4 can be reduced.

  As shown in FIGS. 1 to 3, 5, and 6, the main injection hole 6 has an injection hole length L <b> 1 and an injection hole diameter d <b> 1 as in the case of the conventional multi-injection fuel injection nozzle 1. The fuel injected from the main nozzle 6 spreads to the spray length S1 at the spray angle θ1 to form a conical main spray 16. The tip of the main spray 16 is the inner wall 10a of the cavity 10. The fuel constituting the main spray 16 does not adhere to the inner wall 10a.

  On the other hand, in the auxiliary injection hole 25, the injection hole diameter is set to d2 smaller than the injection hole diameter d1 of the main injection hole 6 as in the conventional multi-injection fuel injection nozzle 1, and is not increased. Is shortened to L21 which is shorter than the nozzle length L1 of the main nozzle hole 6.

  As a result, while preventing the penetration force from increasing due to the increase in the spray amount as described above, the shape factor is decreased from L2 / d2 to L21 / d2, and the spray angle is expanded from θ2 to θ21. The length can be shortened from S2 to S21.

  Further, as shown in FIGS. 1 and 2, such a structure in which only the nozzle hole length is shortened from L2 to L21 without increasing the nozzle hole diameter of the auxiliary nozzle 25 (hereinafter referred to as “hole nozzle length adjusting structure”). In this embodiment, as described above, the lower half portion of the hemispherical injection portion 3 is horizontally cut and removed, and a horizontal lower surface 20b is formed as a deletion surface on the outer opening 25a of the auxiliary injection port 25. Although provided, it is not particularly limited, and for example, a deletion surface may be provided toward the opening inner side 25b of the auxiliary injection hole 25.

  However, when a deletion surface is provided on the outer opening 25a of the auxiliary nozzle 25 as in the present embodiment, the injection start position of the auxiliary spray 26 rises from the position 27 to the position 28, and as a result, the tip of the auxiliary spray 26 The distance 30 from the protrusion 11 to the flat surface portion 11a becomes longer, and it is possible to further suppress the fuel constituting the auxiliary spray 26 from adhering to the flat surface portion 11a.

  That is, a single auxiliary injection hole 25 is provided at the lower end of the injection part 20 of the nozzle body 22, a plurality of main injection holes 6 are provided around the auxiliary injection hole 25, and the auxiliary injection hole 25 is combusted at the top 9 a of the piston 9. In the multi-injection fuel injection nozzle 21 that is disposed substantially perpendicularly to the flat surface portion 11a of the projection 11 formed substantially at the center of the cavity 10 constituting the chamber 4, the injection hole diameter d2 of the auxiliary injection port 25 is set as the main injection port. 6 has a nozzle hole length adjusting structure that is smaller than the nozzle hole length L1 of the main nozzle hole 6 and is formed smaller than the nozzle hole diameter d1 of the auxiliary nozzle 25. While increasing the spray amount by increasing the diameter d1 and maintaining the penetrating force of the main spray 16 to be injected strongly, the auxiliary nozzle 25 sets the nozzle diameter d2 small to enhance the penetrating force by increasing the spray amount. Prevented Thus, by shortening the nozzle length from L2 to L21 and increasing the spray angle from θ2 to θ21, the penetration force can be sufficiently relaxed, and the spray length of the auxiliary spray 26 is reduced from S2 to S21. The fuel can be atomized before colliding with the flat surface portion 11a, and the fuel can be reliably prevented from adhering to the flat surface portion 11a.

  Thereby, even in the multi-hole fuel injection nozzle 21 of the opposed arrangement type, the air in the cavity 10 immediately below the multi-hole fuel injection nozzle 21 is effectively used, and black smoke at low load or white smoke immediately after start-up The engine performance can be improved by suppressing the occurrence of the engine.

  Further, since the nozzle hole length adjusting structure is formed by forming a horizontal lower surface 20b as a deletion surface on the outer opening 25a of the auxiliary nozzle 25, the outer outer surface 25a of the auxiliary nozzle 25 is formed on the plane portion by forming the horizontal lower surface 20b. It can be separated from 11a, the front part of the auxiliary spray 26 can be made difficult to contact the flat part 11a, and the fuel adhesion to the flat part 11a can be further suppressed, and the engine performance can be further improved.

  Further, as described above, while maintaining the nozzle diameter d2 of the auxiliary nozzle 25 smaller than the nozzle diameter d1 of the main nozzle 6, the nozzle length L21 of the auxiliary nozzle 25 is set shorter than the nozzle length L1 of the main nozzle 6. Even in this case, as shown in FIG. 4, when the shape factor L21 / d2 of the auxiliary nozzle 25 is too larger than the shape factor L1 / d1 of the main nozzle 6, the nozzle length L21 becomes extremely long and spraying occurs. The angle θ21 becomes narrower and the spray length S21 becomes longer. For example, when the shape factor L21 / d2 increases from L1 / d1 to F1, the black smoke density increases from C1 to C2.

  On the other hand, if the shape factor L21 / d2 of the auxiliary nozzle 25 is too smaller than the shape factor L1 / d1 of the main nozzle 6, the nozzle length L21 becomes extremely short and the thickness of the member near the auxiliary nozzle 25 becomes extremely thin. For example, when the shape factor L21 / d2 decreases from L1 / d1 to F2, the black smoke density hardly changes from C1, but a minute crack or the like is generated in the member near the auxiliary nozzle 25, and the pressure resistance and heat resistance are reduced. The strength is significantly reduced. Therefore, it is preferable that the shape factor L21 / d2 of the auxiliary nozzle 25 is substantially the same as the shape factor L1 / d1 of the main nozzle 6.

  That is, the ratio of the nozzle length L21 to the nozzle diameter d2 in the auxiliary nozzle 25 and the ratio of the nozzle length L1 to the nozzle diameter d1 in the main nozzle 6 are set to be substantially the same by the nozzle length adjustment structure. The nozzle length L21 of the auxiliary nozzle 25 is too long and the spray angle θ21 is narrowed, the penetration force is increased and the spray length S21 of the auxiliary nozzle 26 is increased, or the nozzle length L21 of the auxiliary nozzle 25 is too short. Good engine performance and nozzle durability can be reliably prevented by reducing the thickness of the member near the auxiliary nozzle 25 and reducing the durability of the multi-nozzle fuel injection nozzle 21 by reducing the strength such as pressure resistance and heat resistance. Can be secured.

  The present invention provides a single auxiliary injection port at the lower end of the injection part of the nozzle body, and a plurality of main injection ports are provided around the auxiliary injection port. The auxiliary injection port is an abbreviation of a cavity that constitutes a combustion chamber at the top of the piston. The present invention can be applied to all the multi-injection fuel injection nozzles arranged to face each other at a substantially right angle with respect to the flat portion of the projection formed at the center.

It is side surface partial sectional drawing of the front part of the multi-injection fuel injection nozzle concerning this invention. It is also an enlarged view. It is side surface partial sectional drawing of the combustion chamber vicinity which shows the spray condition by the multi-injection fuel injection nozzle concerning this invention. It is explanatory drawing which shows the influence of the shape factor of an auxiliary nozzle hole on the black smoke density | concentration at the time of low load. It is side surface partial sectional drawing of the front part of the conventional multi-injection fuel-injection nozzle. It is side surface partial sectional drawing of the combustion chamber vicinity which shows the spray condition by the conventional multi-injection fuel-injection nozzle.

Explanation of symbols

4 Combustion chamber 6 Main injection port 9 Piston 9a Top 10 Cavity 11 Projection 11a Flat surface 20 Injection unit 20b Deletion surface 21 Multi-injection fuel injection nozzle 22 Nozzle body 25 Auxiliary injection port 25a Outer opening d1 Main injection port diameter d2 Injection of auxiliary injection port Diameter L1 Main nozzle hole length L21 Auxiliary nozzle hole length

Claims (3)

  A single auxiliary injection port is provided in the injection part of the nozzle body, and a plurality of main injection ports are provided around the auxiliary injection port, and the auxiliary injection port is formed at a substantially central portion of the cavity constituting the combustion chamber at the piston top. In the multi-injection fuel injection nozzle arranged opposite to the plane portion of the body at a substantially right angle, the auxiliary injection hole has a nozzle diameter smaller than the main injection hole diameter, and the auxiliary injection nozzle length is set to the main injection hole. A multi-nozzle fuel injection nozzle comprising a nozzle length adjusting structure that is set to be shorter than the nozzle hole length.   2. The multi-nozzle fuel injection nozzle according to claim 1, wherein the nozzle length adjusting structure is formed by forming a deletion surface outside the opening of the auxiliary nozzle.   The ratio of the nozzle hole length to the nozzle hole diameter in the auxiliary nozzle hole and the ratio of the nozzle hole length to the nozzle hole diameter in the main nozzle hole are set substantially the same by the nozzle hole length adjusting structure. Item 3. The multi-hole fuel injection nozzle according to Item 2.

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