JP4710785B2 - Fuel injection nozzle for internal combustion engine - Google Patents

Description

  The present invention relates to a structure of a fuel injection nozzle for an internal combustion engine.

  Recently, a technique for forming a large number of injection holes at the tip of a fuel injection nozzle is known in order to uniformly inject fuel into a combustion chamber of an internal combustion engine. As an example of a technology related to this, in a fuel injection nozzle in which a group injection hole having first and second minute injection holes is opened on the inner peripheral surface of a sack chamber of a nozzle body, a seat surface of the nozzle body and a needle A technique for suppressing the occurrence of cavitation by setting a large angle difference from the first conical surface (see, for example, Patent Document 1).

  In addition, the nozzle body has a plurality of nozzle holes each opened to a plurality of frustoconical surfaces, the valve needle has a plurality of tapered surfaces provided with abutting portions that abut against the valve seat of the frustoconical surface, A technique has been proposed in which the angle of the plurality of frustoconical surfaces and the tapered surface is changed to control the injection amount from the injection hole in accordance with the lift amount of the valve needle (see, for example, Patent Document 2).

  Furthermore, a technique for controlling the shape of the spray by defining distances and angles between a plurality of nozzle holes provided in the nozzle body has also been proposed (see, for example, Patent Document 3).

  In any of the above techniques, a plurality of injection holes are provided at the tip of the guide hole for the needle inside the nozzle body so as to be distributed and opened in the radial direction or the axial direction. In this case, when the needle is retracted and the fuel injection nozzle is opened, the fuel is introduced toward the center of the tip of the guide hole inside the nozzle body. There may be a difference in the fuel pressure between the opening of the hole and the opening of the injection hole provided in a portion away from the center of the tip.

Then, the reach distance and particle size of the fuel injected from the plurality of nozzle holes are different, and it may be difficult to spray the fuel uniformly in the combustion chamber.
JP 2004-27955 A JP 2000-320429 A JP 2001-165017 A

  The present invention has been made in view of the above prior art, and an object thereof is to provide a plurality of nozzle holes in a fuel injection nozzle that injects fuel into a combustion chamber from a plurality of nozzle holes formed in a nozzle body. Therefore, it is to provide a technology that can inject fuel more evenly.

  To achieve the above object, the present invention relates to a fuel injection nozzle that opens and closes as a needle moves forward and backward in a guide hole of a nozzle body. Among them, a fuel injection nozzle in which a conical seat portion is provided at the tip of the guide hole of the nozzle body, and a plurality of nozzle holes are distributed in the radial direction or the axial direction near the top of the seat portion. It is. Then, by removing a part of the fuel introduced near the top of the seating portion from the vicinity of the top when the needle is retracted and opened, the fuel pressure at the openings of the plurality of nozzle holes is equalized. The biggest feature is to make it.

More specifically, a seat portion having a substantially conical shape with a small hole diameter is provided at the tip of the guide hole provided in the axial direction, and a concave sac chamber is provided near the top of the seat portion and the sac chamber and the outside a nozzle body having a plurality of injection holes are open distributed away from the central tip portion of at least the guide hole through the door,
The guide hole is inserted into the guide hole so as to be reciprocally movable, and by moving forward in the guide hole, a substantially conical tip is brought into contact with the seating portion to block the fuel path leading to the injection hole and in the guide hole. A needle that releases the fuel path leading to the nozzle hole by releasing the contact of the tip with the seat by retreating the fuel, and opens and closes the fuel by moving the needle forward or backward A nozzle,
The fuel pressure at the openings of the plurality of nozzle holes is equalized by removing a part of the fuel introduced near the top of the seating portion from the vicinity of the top when the needle is retracted and opened. A fuel pressure equalizing means is further provided.

  Here, the operation when the needle is retreated and the fuel injection nozzle is opened in the above configuration will be described. At this time, the fuel flows between the tip portion of the needle and the seat portion along the seat portion, and flows into the vicinity of the top portion of the seat portion. Then, it flows into a plurality of nozzle holes opened near the top of the seating portion and is injected.

  At this time, the fuel introduced to the vicinity of the top of the seating portion flows at a high pressure toward the center of the tip of the top, so that the pressure at the center of the tip of the top temporarily becomes particularly high. In that case, it will be in the state in which a pressure falls as it leaves | separates from the front-end | tip center of a top part to radial direction or an axial direction.

  Therefore, when fuel is injected through the plurality of nozzle holes in this state, the fuel injected from the nozzle hole near the center of the tip of the top portion has a long reach distance and a small particle size, and is in a portion away from it. The fuel injected from the opening nozzle hole has a short reach distance and a large particle size. As a result, it may be difficult to spray the fuel uniformly on the combustion chamber.

  Therefore, in the fuel injection nozzle of the internal combustion engine according to the present invention, when the needle is retracted and opened, a part of the fuel introduced near the top of the seating portion is removed from the vicinity of the top, so that the plurality of injection holes The fuel pressure equalizing means for equalizing the fuel pressure at the opening of the fuel cell is provided. Then, a part of the fuel flowing toward the center of the top of the seating part is removed from the top, so that the fuel pressure at the center of the top of the seating part can be reduced, and the vicinity of the top of the seating part The fuel pressure distribution in can be equalized.

  As a result, the fuel pressure in the openings of the plurality of nozzle holes can be equalized, and the injection from each nozzle hole can be equalized.

  Here, the fuel pressure equalizing means may be a nozzle body fuel passage that opens at the center of the top of the seating portion of the nozzle body and leaks fuel from the vicinity of the top to the outside of the nozzle body.

  That is, fuel is leaked from the center of the tip of the top of the seat where the fuel pressure is highest to the outside of the nozzle body. Thereby, the fuel pressure near the top part of the seating part can be equalized more effectively, and the fuel injection from the plurality of nozzle holes can be equalized.

  Here, the nozzle body fuel passage only needs to be able to leak the fuel from the center of the top end of the seating portion and does not need a function of injecting the fuel, so the hole diameter is small compared to the plurality of injection holes for fuel injection. It's okay. The diameter of the nozzle body fuel passage is predetermined in relation to the value of the fuel pressure to be reduced.

Further, the fuel pressure equalization means may be an in-needle fuel passage that opens to substantially the center of the tip portion of the needle and collects or evacuates fuel by allowing the fuel to pass through the needle from the vicinity of the top.

  Also by this, the fuel pressure in the vicinity of the top of the seating portion can be equalized by reducing the fuel pressure at the center of the tip of the top of the seating portion, and the fuel injection from the plurality of nozzle holes can be equalized. Can do.

  Here, the in-needle fuel passage only needs to be able to collect or retract fuel from the center of the tip of the seating portion, and does not need a function of injecting fuel. Compared to a plurality of injection holes for fuel injection, The pore diameter may be small. The hole diameter of the fuel passage in the needle is determined in advance in relation to the value of the fuel pressure to be reduced.

  In addition, about the means to solve the subject of the above-mentioned this invention, it can use combining as much as possible.

  In the present invention, in the fuel injection nozzle that injects fuel into the combustion chamber from the plurality of nozzle holes formed in the nozzle body, the fuel can be injected more uniformly from the plurality of nozzle holes.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a view for explaining the entire fuel injection nozzle 1 to which the present invention is applied. FIG. 1A is a cross-sectional view of the entire fuel injection nozzle 1. FIG.1 (b) is an enlarged view at the time of seeing the fuel injection nozzle 1 from the front end side. As shown in FIG. 1 (a), a fuel injection nozzle 1 (hereinafter also referred to as nozzle 1) of this embodiment is composed of a nozzle body 2 and a needle 3 incorporated in the nozzle body 2, and is an internal combustion engine. It is incorporated in an injector (not shown) attached to each cylinder of the engine.

  The nozzle body 2 is provided with a guide hole 4 into which the needle 3 is inserted, a fuel passage 5 and an injection hole 6. A seat portion 7 is formed at the lower end portion of the guide hole 4 so that the diameter of the guide hole 4 becomes conical, and a sac chamber 8 is formed at a portion corresponding to the top portion of the seat portion 7. The fuel passage 5 is provided in communication with a fuel reservoir chamber 9 having an enlarged inner diameter in the middle of the guide hole 4, and introduces high-pressure fuel into the fuel reservoir chamber 9. The needle 3 is inserted into the guide hole 4 of the nozzle body 2 and is provided so as to be capable of moving forward and backward in the axial direction. At the tip of the needle 3, a contact portion 10 is provided as a tip that is seated on the seat 7 when the needle 3 is closed.

  As can be seen from FIGS. 1 (a) and 1 (b), in the fuel injection nozzle 1, an injection hole 6 is formed so as to penetrate the inner wall and the outer wall of the sack chamber 8. As shown in FIG. 1B, the nozzle holes 6 are arranged so as to form three nozzle hole arrays 6 a, 6 b, 6 c concentrically around the center of the nozzle body 2. The fuel injection nozzle 1 has such a large number of injection holes 6 so that fuel is evenly supplied to the combustion chamber during fuel injection.

  Next, the detail of the front-end | tip part of the conventional fuel injection nozzle is demonstrated. FIG. 2 is an enlarged cross-sectional view of the tip portion of the conventional fuel injection nozzle 1. 2A shows a state where the needle 3 is lowered and closed, and FIG. 2B shows a state where the needle 3 is lifted and opened.

  In the state of FIG. 2A, the needle 3 is lowered, and the contact portion 10 of the needle 3 is in contact with the seating portion 7 of the nozzle body 2. Accordingly, the fuel supplied to the nozzle 1 passes from the fuel passage 5 of the nozzle body 2 through the fuel reservoir chamber 9, passes through the guide hole 4 (annular space formed around the needle 3), and comes into contact with the seat portion 7. The contact portion 10 is filled. From this state, when the force for urging the needle 3 in the valve opening direction (upward in FIG. 2B) rises to the valve opening pressure of the needle 3, the needle 3 lifts the guide hole 4 and moves to FIG. ), The fuel path leading to the injection hole 6 is opened. As a result, the fuel flows into the sac chamber 8 through the space between the seating portion 7 and the contact portion 10, and the fuel is injected into the combustion chamber through the nozzle hole 6.

  By the way, at the moment when the needle 3 is lifted as described above, the fuel flows between the seating portion 7 and the abutting portion 10 toward the tip center portion 8a of the sack chamber 8. As a result, the fuel pressure at the front end center portion 8a of the sac chamber 8 becomes maximum, and a state in which the fuel pressure decreases as the distance from the front end center portion 8a of the sac chamber 8 decreases temporarily occurs.

  Then, the fuel injected from the nozzle holes 6 in the first row 6a near the center of the sack chamber 8 is injected far and the particle size is fine, and the fuel injected from the nozzle holes 6 in the second row 6b and the third row 6c is There is a tendency that the particle size is large without being sprayed so far. As a result, it may be difficult to spray fuel evenly in the combustion chamber of the internal combustion engine.

  Therefore, in the present embodiment, when high pressure fuel flows into the tip center portion 8 a of the sac chamber 8 by lifting the needle 3, a part of the fuel in the sac chamber 8 is transferred to the outside of the nozzle body 2. A leak passage that leaks into the nozzle hole 6 is provided separately from the nozzle hole 6.

  FIG. 3 shows a detailed view of the nozzle tip portion in the present embodiment. In FIG. 3, the leak passage 15 in the present embodiment is provided so as to communicate the tip center portion 8 a of the sack chamber 8 and the outside of the nozzle body 2 in the axial direction of the nozzle body 2. As a result, even when high pressure fuel flows into the tip center portion 8 a of the sack chamber 8 by lifting the needle 3, the fuel at the tip center portion 8 a having the highest fuel pressure is transferred to the outside of the nozzle body 2. I can escape.

  By doing so, the distribution of the fuel pressure in the sac chamber 8 can be made more uniform, and the reach distance and particle size of the fuel injected from the nozzle holes 6 in the nozzle hole arrays 6a to 6c can be made more uniform. Can do. As a result, fuel can be sprayed more evenly in the combustion chamber.

  Since the leak passage 15 is provided to lower the fuel pressure at the front end center portion 8a of the sac chamber 8, the amount of fuel leaked from the leak passage 11 to the outside is equal to the fuel injection amount from the nozzle hole 6. There may be few compared. Therefore, it can be said that there is almost no influence on the state of combustion in the combustion chamber.

  Depending on the shape and capacity of the sac chamber 8, it may be necessary to increase the hole diameter of the leak passage 11 to some extent to leak more fuel. In such a case, the amount of fuel leaked from the leak passage 15 increases, which may interfere with the top surface of the piston. If it does so, the fuel adhering to the top face of a piston may remain unburned, and there is a possibility of deteriorating emission by being discharged after that. In such a case, a recess for avoiding interference with the fuel leaked from the leak passage may be provided on the top surface of the piston.

FIG. 4 shows a schematic view of the combustion chamber 30 when the amount of fuel leaked from the leak passage 15 is large. In this case, a cavity 32 for receiving fuel injected from the injection hole 6 is formed on the top surface 31 a of the piston 31. The leak passage 11 is formed at the center of the cavity 32.
A recess 33 is formed to avoid the fuel injected from the fuel from interfering.

  By forming such a recess 33, it is possible to suppress the fuel injected from the leak passage 11 from directly adhering to the cavity 32 of the piston top surface 31a. And it can suppress that the fuel adhering to the cavity 32 remains unburned and is discharged | emitted later and an emission deteriorates.

  In the above description, the example in which the leak passage 15 is formed in the axial direction from the front end central portion 8a of the sack chamber 8 has been described, but the arrangement and number of the leak passages 15 are not limited to this. FIG. 5 shows another example of forming the leak passage.

  FIG. 5A shows an example in which a plurality of leak passages 16 are provided in the vicinity of the front end central portion 8 a of the sack chamber 8. FIG. 5B shows an example in which a plurality of leak passages 17 having a diameter smaller than that of the nozzle holes 6 are formed on the distal end side of the nozzle hole row 6a, and the leak passage rows 17a are configured concentrically. is there.

  In this embodiment, the leak passage corresponds to the fuel pressure equalizing means and the nozzle body fuel passage.

  Next, a second embodiment of the present invention will be described. In this embodiment, when the needle 3 is lifted and the fuel flows into the front end central portion 8a of the sack chamber 8, the fuel is not leaked from the nozzle body 2 to the outside, but is released to the needle 3 side. explain.

  In FIG. 6, sectional drawing of the fuel-injection nozzle 1 in a present Example is shown. As shown in FIG. 6A, in this embodiment, a fuel recovery passage 18 is formed on the central axis of the needle 3. The tip of the fuel recovery passage 18 may be opened, for example, in the fuel reservoir 9 or may be connected to a fuel tank (not shown).

  According to this configuration, even when high-pressure fuel flows toward the tip center portion 8a of the sac chamber 8 when the needle 3 is lifted, the fuel in the tip center portion 8a of the sack chamber 8 is recovered into the needle 3. Thus, the fuel pressure in the vicinity of the tip center portion 8a can be reduced. As a result, the injection from the plurality of nozzle holes 6 can be performed more evenly.

  FIG. 6B shows an example in which the fuel withdrawal passage 19 is formed on the center line of the needle 3. In this example, an air chamber 19a is provided inside the needle 3, and the fuel withdrawal passage 19 communicates the tip portion of the needle 3 and the air chamber 19a.

  Then, when the fuel pressure in the vicinity of the front end center portion 8a of the sac chamber 8 rises when the needle 3 is lifted, the high pressure fuel is evacuated to the fuel retracting passage 19, and the fuel pressure in the front end center portion 8a of the sack chamber 8 Can be reduced. Here, the fuel introduced into the fuel withdrawal passage 19 remains in the fuel withdrawal passage 19 and is held in a compressed state of the air in the air chamber 19a. And when the fuel pressure in the front-end | tip center part 8a of the sac chamber 8 becomes a steady state and falls, it will return from the opening part by the side of the sac chamber 8. FIG.

  As described above, in the present embodiment, in the state where the fuel pressure at the front end center portion 8a of the sac chamber 8 is increased, the fuel is recovered from the fuel recovery passage 18 or the fuel withdrawal passage provided on the central axis of the needle 3. The fuel pressure at the tip center portion 8a of the sac chamber 8 is reduced by introducing the fuel into the sack chamber 8. Thereby, the distribution of the fuel pressure in the sac chamber 8 can be equalized, and the fuel injection from the plurality of nozzle holes 6 can be performed more evenly.

  In this embodiment, the fuel recovery passage and the fuel withdrawal passage correspond to the fuel pressure equalization means and the fuel passage in the needle.

  In the present embodiment, the tip of the fuel recovery passage only needs to be connected to a location where the fuel can be recirculated, and is not limited to the fuel reservoir. For example, a recovered fuel tank may be provided, and a user of the internal combustion engine may recover the fuel stored in the fuel tank.

  Furthermore, the fuel that has passed through the in-needle fuel passage in the above may be leaked into the combustion chamber.

It is a figure which shows the whole structure of the fuel-injection nozzle of the internal combustion engine in the Example of this invention. It is a figure which shows schematic structure of the fuel injection nozzle front-end | tip part of the conventional internal combustion engine. It is a figure which shows schematic structure of the fuel injection nozzle front-end | tip part in Example 1 of this invention. It is a figure which shows schematic structure of the fuel-injection nozzle and combustion chamber vicinity in Example 1 of this invention. It is a figure which shows another example of schematic structure of the fuel injection nozzle front-end | tip part in Example 1 of this invention. It is a figure which shows schematic structure of the fuel injection nozzle front-end | tip part in Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel injection nozzle 2 ... Nozzle body 3 ... Needle 4 ... Guide hole 5 ... Fuel passage 6 ... Injection hole 6a, 6b, 6c ... Injection hole row 7 ... · Seating portion 8 · · · Sack chamber 8a · · · Center portion 9 · · · Fuel reservoir 10 · · · Contact portion 15, 16, 17 · · · Leak passage 18 · · · Fuel recovery passage 19 · · · Fuel saving passage 30 ... Combustion chamber 31 ... Piston 31a ... Piston top surface 32 ... Cavity 33 ... Recess

Claims (4)

At the tip of the guide hole provided in the axial direction, there is a seating portion whose hole diameter is narrowed in a substantially conical shape. A concave sack chamber is provided near the top of the seating portion and penetrates the sack chamber and the outside. A plurality of nozzle holes that are distributed and opened in a direction away from at least the center of the tip of the guide hole ;
The guide hole is inserted into the guide hole so as to be reciprocally movable, and by moving forward in the guide hole, a substantially conical tip is brought into contact with the seating portion to block the fuel path leading to the injection hole and in the guide hole. A needle that releases the fuel path leading to the nozzle hole by releasing the contact of the tip with the seat by retreating the fuel, and opens and closes the fuel by moving the needle forward or backward A nozzle,
By removing a part of the fuel introduced in the vicinity of the top of the seating portion from the vicinity of the top when the needle is retracted and opened, the fuel pressure in the openings of the plurality of nozzle holes is equalized. A fuel injection nozzle for an internal combustion engine, further comprising fuel pressure equalizing means.   The fuel pressure equalizing means is a nozzle body fuel passage that opens at the center of the tip of the top of the seating portion in the nozzle body and leaks fuel from the vicinity of the top to the outside of the nozzle body. A fuel injection nozzle for an internal combustion engine according to claim 1.   2. The fuel pressure equalizing means is an in-needle fuel passage that opens to substantially the center of the tip end portion of the needle and allows fuel to pass through the needle from the vicinity of the top portion to be collected or evacuated. 2. A fuel injection nozzle for an internal combustion engine according to 1. An internal combustion engine having the fuel injection nozzle according to claim 2 in a combustion chamber,
  An internal combustion engine characterized in that a recess for avoiding interference of fuel leaked from the nozzle body fuel passage is provided on a top surface of a piston forming the combustion chamber.

Images