JP2008309079A - Fuel injection nozzle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection nozzle inhibiting variation of fuel sprays among injection holes. <P>SOLUTION: The fuel injection nozzle 1 is provided with a needle 10 capable of reciprocating in an axial direction, a nozzle body 20 including a plurality of injection hole 26 jetting fuel at a lower part thereof and a seat surface 24 on which a needle 10 is seated at an upper part than the injection hole, and a projection part 25 projecting toward an axial line of the needle 10 between the injection hole 26 and the seat surface 24. Since the fuel injection nozzle 1 is provided with a projection part 25, variation of fuel sprays among the injection holes 26 can be inhibited. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection nozzle, and more particularly to a fuel injection nozzle for an internal combustion engine.

2. Description of the Related Art Conventionally, a fuel injection nozzle used for an internal combustion engine is known to include a needle, a nozzle body having a plurality of injection holes for ejecting fuel, and a seat surface on which the needle is seated (Patent Document 1). To 4).
By the way, in such a fuel injection nozzle, when the needle is eccentric, there is a possibility that uniform fuel spray cannot be obtained from a plurality of injection holes. In response to such a problem, Patent Document 4 discloses a fuel injection nozzle in which a guide that is described on the inner peripheral surface of a needle mounting hole provided in the nozzle body is provided on the outer peripheral surface of the needle tip. Thereby, eccentricity of the needle is prevented.

JP 2006-009622 A Japanese Patent Laid-Open No. 08-144895 JP 2005-180375 A Japanese Patent Laid-Open No. 07-119582

  However, a clearance is set between the nozzle body and the needle so that the fuel passes and the needle can reciprocate with respect to the nozzle body. For this reason, the eccentricity of the needle caused by the pressure from the fuel or the like cannot be completely prevented. Therefore, it is necessary to suppress variations in fuel spray from a viewpoint different from the fuel injection nozzle disclosed in Patent Document 4.

  Accordingly, an object of the present invention is to provide a fuel injection nozzle in which variations in fuel spray between nozzle holes are suppressed.

The object is to provide a needle that can reciprocate in the axial direction, a nozzle body having a plurality of nozzle holes for ejecting fuel at the lower part, and a seat surface on which the needle sits above the nozzle holes, the nozzle holes, This can be achieved by a fuel injection nozzle comprising a protruding portion protruding toward the axis of the needle between the seat surfaces.
The said structure WHEREIN: By providing the protrusion part which protruded toward the axis line of the needle between a nozzle hole and a seat surface, the dispersion | variation in the fuel spray between nozzle holes can be suppressed.

Moreover, the said structure WHEREIN: The said protrusion part can employ | adopt the structure currently formed separately from the said nozzle body.
Since the protruding portion is formed separately from the nozzle body, it is possible to avoid complication of the structure of the nozzle body.

Moreover, the said structure can employ | adopt the structure by which the said protrusion part is hold | maintained in the said nozzle body by shrink fitting.
Thereby, a protrusion part is stably hold | maintained in a nozzle body.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel injection nozzle by which the dispersion | variation in the fuel spray between nozzle holes was suppressed can be provided.

  Hereinafter, a fuel injection nozzle according to the present invention will be described with reference to the drawings.

  FIG. 1 is a partial cross-sectional view of the fuel injection nozzle 1. FIG. 2 is an enlarged view around the distal end portion 14 of the needle 10. The fuel injection nozzle 1 is a nozzle that supplies fuel pressurized by a fuel pump (not shown) into a cylinder of an internal combustion engine. As shown in FIG. 1, the fuel injection nozzle 1 includes a needle 10 that can reciprocate in its axial direction and a nozzle body 20 that houses the needle 10.

  The needle 10 is formed in a substantially round bar shape from a metal material such as carbon steel. The needle 10 has a tip portion 14 having a three-stage conical surface, a small diameter portion 15 having a substantially cylindrical shape coaxial with the tip portion 14, a substantially cylindrical shape coaxial with the small diameter portion 15, and having a diameter larger than that of the small diameter portion 15. Has a large diameter portion 16.

  The nozzle body 20 is formed in a substantially cylindrical shape with a metal material such as carbon steel. As shown in FIGS. 1 and 2, the nozzle body 20 includes an injection hole 26 for injecting fuel into a cylinder (not shown) of the internal combustion engine, a seat surface 24 on which the tip end portion 14 is seated, and a seat surface 24. Also, it has a sac chamber 44 provided downstream (lower) in the fuel flow direction and communicating with the inside of the cylinder of the internal combustion engine through the nozzle hole 26. Further, the shaft hole 21 that accommodates the small-diameter portion 15 upstream of the sac chamber 44 with a predetermined radial clearance is accommodated, and the large-diameter portion 16 is accommodated slidably in the axial direction upstream of the shaft hole 21. There are a sliding hole 22, an oil reservoir chamber 41 that is formed between the shaft hole 21 and the sliding hole 22 and temporarily stores fuel, and a fuel hole 23 that guides the fuel to the oil reservoir 41. As shown in FIG. 1, the gap between the small diameter portion 15 and the shaft hole 21 forms a first fuel passage 42 from the oil reservoir chamber 41 to the sac chamber 44.

  The needle 10 is always urged by the urging force of the spring 30 in the direction of closing the sack chamber 44. The needle 10 closes the sac chamber 44 when the distal end portion 14 is seated on the seat surface 24, and opens the sac chamber 44 when the distal end portion 14 is detached from the seat surface 24. The tip end portion 14 is detached from the seat surface 24 when the fuel pressure in the oil sump chamber 41 and the first fuel passage 42 becomes larger than the urging force by the spring 30. In addition, a gap formed between the front end portion 4 and the seat surface 24 by this separation forms a second fuel passage 43 from the first fuel passage 42 toward the sac chamber 44.

  As shown in FIG. 2, the nozzle body 20 has a protruding portion 25 that protrudes toward the needle axis A between the nozzle hole 26 and the seat surface 24. The protrusion 25 is formed in an annular shape so as to surround the needle axis A. The protruding portion 25 is formed so as to separate the tip portion 14 of the needle 10 from the sack chamber 44. Further, the upper surface of the protruding portion 25 is formed so as to be substantially orthogonal to the needle axis so as to face the tip portion 14 of the needle 10. Further, the lower surface of the projecting portion 25 is formed so as to increase in diameter toward the sack chamber 44. Thus, the protrusion 25 is formed so as to restrict the flow path from the second fuel passage 43 toward the sac chamber 44. The function of the protrusion 25 will be described later.

  Further, the distal end portion 14 has a seat portion 18 that comes into liquid-tight contact with the seat portion of the seat surface 24 and blocks the second fuel passage 43. In the first embodiment, as shown in FIG. 2, the substantially circular ridge line (edge) forming the most downstream portion of the second-stage conical surface forms the sheet portion 18. Thereby, the front-end | tip part 14 sits on the seat surface 24, and the sac chamber 44 is closed.

  When a predetermined amount of fuel is discharged from the fuel pump, the fuel injection nozzle 1 is supplied to the oil reservoir 41 and the first fuel passage 42 via the fuel hole 23. When the pressure of the fuel in the oil sump chamber 41 and the first fuel passage 42 becomes larger than the depressing force of the spring 30, the tip end portion 14 is detached from the seat surface 24.

  By this separation, the second fuel passage 43 is opened by moving away from the seat surface 18 of the tip portion 14 from the seat surface 24. As a result, the fuel flows into the sac chamber 44 and the fuel is injected from the nozzle hole 26.

Next, problems that may occur in the conventional fuel injection nozzle will be described in detail. FIG. 3 is an explanatory diagram of problems that may occur in a conventional fuel injection nozzle.
In addition, the conventional fuel injection nozzle shown in FIG. 3 uses the same code | symbol regarding the location substantially the same as the fuel injection nozzle which concerns on a present Example.

  FIG. 3A is an enlarged view of the vicinity of the tip of the conventional fuel injection nozzle. FIG. 3A shows the periphery of the tip portion 14x in a state where the needle 10x is detached from the seat surface 24x. As shown in FIG. 3A, when the tip portion 14x is detached from the seat surface 24x, the needle 10x may be eccentric and the needle axis A and the nozzle body axis B may be displaced. In FIG. 3 (a), the needle 10x is slightly decentered to the left, and the second fuel passage 43x on the right side is wider than the second fuel passage 43x on the left side. In such a case, more high-pressure fuel flows into the sac chamber 44x from one side with respect to the needle 10x. Therefore, in FIG. 3A, the difference in pressure received by the high pressure fuel is large between the left side and the right side of the needle 10x.

  FIG. 3 (b) is an explanatory view of the variation in fuel spray when the needle 10x is eccentric, and is a view seen from the front end side of a conventional fuel injection nozzle. When the needle 10x is eccentric, as shown in FIG. 3B, the fuel spray varies between the nozzle holes 26x. As described above, the eccentricity of the needle 10x causes a pressure distribution in the sac chamber 44x in FIG. 3 (a). As a result, the nozzle 10x deviates from the nozzle hole 26x around the high-pressure portion in the sac chamber 44x. This is because a large amount of fuel is injected, and relatively little fuel is injected from the nozzle hole 26x around the low pressure portion in the sac chamber 44x. A similar phenomenon occurs when the needle 10x is tilted.

  The cause of the occurrence of such eccentricity or inclination is, for example, a deviation between the axis of the tip of the needle and the axis of the sliding hole of the nozzle body that slidably accommodates the needle, or a spring that biases the needle There are deviations. Further, as shown in FIG. 3C, for example, a deviation between the inclination angle α ° of the seat surface 24x and the inclination angle β ° of the seat portion 18x with respect to the needle axis is caused.

  However, as shown in FIG. 2, the fuel injection nozzle 1 according to the present embodiment is formed with a protruding portion 25. Even if a pressure distribution is generated upstream of the protrusion 25 due to the eccentricity of the needle 10, the pressure distribution in the protrusion 25 is suppressed in the sack chamber 44 downstream of the protrusion 25. And acts to achieve a uniform pressure. This is because the fuel flowing into the sack chamber 44 from one side of the seat portion 18 due to eccentricity is collected around the needle axis A by the one-end protruding portion 25. Thus, by providing the protrusion 25, the pressure of the fuel in the sac chamber 44 is kept uniform, so that the occurrence of variations in fuel spray between the nozzle holes 26 is suppressed.

  Further, the cross-sectional area of the flow passage narrowed by the protrusion 25 is formed to be larger than the total cross-sectional area of each nozzle hole 26. This is because the high-pressure fuel may not smoothly flow into the sac chamber 44 when the cross-sectional area of the flow path narrowed by the protrusion 25 is smaller than the total cross-sectional area of each nozzle hole 26. .

Next, a modified example of the fuel injection nozzle will be described.
FIG. 4 is an enlarged view around the tip of the needle of a fuel injection nozzle according to a modification. In addition, the fuel injection nozzle which concerns on a modified example attaches | subjects the same code | symbol to the part of the structure similar to the said fuel injection nozzle 1, and abbreviate | omits the description.

  As shown in FIG. 4, the protrusion part 25a is formed. Unlike the fuel injection nozzle 1 described in the first embodiment, the protruding portion 25 a is formed by a member different from the nozzle body 20. Also. The protruding portion 25a is formed of the same material as the nozzle body 20. By forming the projecting portion 25a as a separate member from the nozzle body 20, it is possible to avoid complication of the structure of the nozzle body 20 and to prevent the molding of the nozzle body 20 from being difficult.

  The protruding portion 25a is fitted to the nozzle body 20 at a predetermined position by shrink fitting. Thereby, the protrusion 25a can be held at a predetermined position in the nozzle body 20.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

It is a fragmentary sectional view of a fuel injection nozzle. It is an enlarged view around the front-end | tip part of a needle. It is explanatory drawing of the problem which may occur in the conventional fuel injection nozzle. It is an enlarged view of the front-end | tip part periphery of the needle of the fuel injection nozzle which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection nozzle 10 Needle 14 Tip part 15 Small diameter part 16 Large diameter part 18 Seat part 20 Nozzle body 21 Axial hole 22 Sliding hole 23 Fuel hole 24 Seat surface 25, 25a Protrusion part 26 Injection hole 30 Spring 42 1st fuel passage 43 Second fuel passage 44 Sack chamber

Claims (3)

A needle capable of reciprocating in the axial direction;
A nozzle body having a plurality of nozzle holes for ejecting fuel at a lower part and a seat surface on which the needle is seated above the nozzle holes;
A fuel injection nozzle comprising: a protruding portion protruding toward the axis of the needle between the nozzle hole and the seat surface.   The fuel injection nozzle according to claim 1, wherein the protrusion is formed separately from the nozzle body.   The fuel injection nozzle according to claim 2, wherein the protrusion is held in the nozzle body by shrink fitting.

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