JP2005140055A - Fuel injection valve for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve for an internal combustion engine, capable of forming homogeneous mixture by uniformizing the atomization level of whole fuel spray. <P>SOLUTION: The fuel injection valve 10 has a preset injection angle to its axis L1 and an injection hole 11 formed into a sectionally rectangular slit. An injection hole inner wall face 11C on the side closer to the axis L1 of the fuel injection valve 10 is formed coarser than an injection hole inner wall face 11B on the side farther from the axis L1. Thus, a separation flow on the inner wall face 11C is accelerated to improve the atomization level of the whole fuel spray. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel injection valve for an internal combustion engine, and more particularly to a fuel injection valve for an internal combustion engine that can uniformize the atomization level of the entire fuel spray and form a homogeneous air-fuel mixture.

  Conventionally, a fuel injection valve of an internal combustion engine in which an injection angle has a predetermined angle with respect to the axis of the fuel injection valve and an injection hole is formed in a slit shape having a rectangular cross section is known (for example, Patent Document 1). reference).

  Such injection holes are fan-shaped slits that expand in the direction of fuel injection, so that the injected fuel is a flat fan spray with a relatively thin thickness, compared to a conical fuel spray. This increases the contact area with air. Therefore, the atomized fuel directly injected into the engine cylinder can be finely atomized.

  In addition, a technique has been proposed in which the atomized fuel is atomized by providing irregularities on the inner wall surface of the injection hole having a circular cross section (see, for example, Patent Document 2).

Japanese Patent No. 3301013 Japanese Patent Laid-Open No. 9-228928

  However, since the fuel injection valve of the conventional internal combustion engine has a predetermined injection angle with respect to the axis of the fuel injection valve, the separation state of the fuel flow generated at the inlet of the injection hole tends to be uneven. . Since atomization is promoted by cavitation due to the separation flow, if the separation state becomes uneven, the atomization level also becomes uneven.

  Therefore, when the atomization distribution of the entire fuel spray becomes non-uniform, there is a region where the atomization level is locally low, and it becomes difficult to form a homogeneous air-fuel mixture in the engine cylinder.

  The present invention has been made in view of the above, and an object of the present invention is to provide a fuel injection valve for an internal combustion engine that can uniformize the atomization level of the entire fuel spray and form a homogeneous air-fuel mixture.

  In order to solve the above-described problems and achieve the object, a fuel injection valve for an internal combustion engine according to the present invention has an injection angle of a predetermined angle with respect to the axis of the fuel injection valve, and the injection hole has a cross section. In the fuel injection valve of the internal combustion engine formed in a rectangular slit shape, the inner wall surface of the injection hole closer to the axis of the fuel injection valve is formed to be rougher than the inner wall surface of the injection hole on the far side. It is what.

  Therefore, according to the present invention, the separation flow is promoted by forming the surface roughness of the portion where the separation flow is weak and the atomization level is poor. This improves the atomization level and makes the atomization level of the entire fuel spray uniform.

  According to the fuel injection valve of the internal combustion engine according to the present invention, since the surface roughness of the inner wall surface of the injection hole is adjusted according to the degree of the separation flow, even if the separation flow is weak and the atomization level is bad, Since the separation flow can be promoted and the atomization level can be improved by forming the surface roughness of the portion roughly, the atomization level of the entire fuel spray can be made uniform, and a homogeneous mixture can be formed. .

  Embodiments of a fuel injection valve for an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a side sectional view showing an injection hole of a fuel injection valve, and FIG. 2 is a front sectional view showing an injection hole of the fuel injection valve.

  As shown in FIGS. 1 and 2, the fuel injection valve 10 has an injection angle of a predetermined angle with respect to the axis L1, and the injection hole 11 is formed in a slit shape having a rectangular cross section. That is, the injection direction axis L2 of the injection hole 11 has a predetermined injection angle α with respect to the axis L1 (see FIG. 4).

  As shown in FIG. 2, the inner wall surface 11 </ b> A of the injection hole 11 is formed with an average roughness produced by electric discharge machining or the like. As shown in FIG. 1, the injection hole inner wall surface 11C on the side close to the axis L1 of the fuel injection valve 10 is formed to be rougher than the injection hole inner wall surface 11B on the side far from the axis L1. In addition, the state in which the roughness is different is indicated by hatching in the drawing. When showing the magnitude relation of the roughness of the inner wall surface, the roughness of the inner wall surface 11B <the roughness of the inner wall surface 11A <the roughness of the inner wall surface 11C.

  Next, the reason why the roughness of the inner wall surfaces 11A, 11B, and 11C is set as described above will be described with reference to FIGS. Here, FIG. 3 is a front sectional view showing a flow separation portion generated on the inner wall surface of the injection hole, FIG. 4 is a side sectional view showing a separation portion of the flow generated on the inner wall surface of the injection hole, and FIG. FIG. 6 is a graph showing the relationship between the spray angle α and the atomization level.

  That is, as shown in FIGS. 3 and 4, the injection holes 11 are shown in which the roughness of the inner wall surfaces 11A, 11B, and 11C is substantially the same. Black portions in the figure indicate the fuel flow separation portions 12, 13, and 14 generated in the injection holes 11 formed in this way.

  As shown in FIG. 5, when the sizes (peeling regions) of the peeling portions 12, 13, and 14 generated in the regions of the inner wall surfaces 11A, 11B, and 11C are compared, the region of the inner wall surface 11A is used as a reference. Sometimes, it can be seen that the peeling area of the inner wall surface 11C is small and the peeling area of the inner wall surface 11B is large. This tendency becomes more prominent as the injection angle α increases.

  Further, atomization of the fuel spray is promoted by cavitation due to the separation flow, corresponding to the size relationship of the separation region. Therefore, as shown in FIG. 6, when comparing the size relationship of the atomization level, the atomization level of the inner wall surface 11C is poor and the atomization level of the inner wall surface 11B is good when the region of the inner wall surface 11A is used as a reference. I understand that. That is, it can be seen that when the peeled state becomes non-uniform, the atomization level also becomes non-uniform.

  Therefore, as shown in FIG. 7, according to the present invention, the surface roughness of the inner wall surface 11C where the separation flow is weak is made rougher than the surface roughness of the inner wall surface 11B where the separation flow is strong. In order to promote atomization. This sets the surface roughness of the inner wall surface 11C to be rougher as the injection angle α increases. Here, FIG. 7 is a graph showing the relationship between the injection angle α and the surface roughness.

  Therefore, as shown in FIGS. 8 and 9, by setting the surface roughness of the inner wall surfaces 11A, 11B, and 11C of the injection hole 11 as described above, the generation of the flow separation portion 14 is promoted more than before. Therefore, the atomization level can be made uniform in the fuel spray 15 by the injection hole 11 according to the present invention shown in FIG. 8 than in the fuel spray 20 by the conventional injection hole 11 shown in FIG. it can. Here, FIG. 8 is a schematic diagram showing the atomization state of the fuel spray according to the present embodiment, and FIG. 9 is a schematic diagram showing the atomization state of the fuel spray according to the prior art.

  As described above, according to the fuel injection valve of the internal combustion engine according to this embodiment, the atomization level of the entire fuel spray can be made uniform, and a homogeneous air-fuel mixture can be formed.

  In addition, in the said Example, as shown in FIG.1 and FIG.2, what showed each surface roughness of the inner wall surfaces 11A, 11B, and 11C of the injection hole 11 uniformly formed toward the injection direction was shown. However, the present invention is not limited to this. For example, the distribution of surface roughness may be changed in accordance with the degree of separation flow toward the injection direction.

  As described above, the fuel injection valve of the internal combustion engine according to the present invention is useful for an in-cylinder direct injection engine aiming at uniformizing the atomization level of the entire fuel spray and forming a homogeneous air-fuel mixture.

It is side surface sectional drawing which shows the injection hole of a fuel injection valve. It is front sectional drawing which shows the injection hole of a fuel injection valve. It is front sectional drawing which shows the peeling part of the flow which generate | occur | produces in an injection hole inner wall face. It is side surface sectional drawing which shows the peeling part of the flow which generate | occur | produces in an injection hole inner wall face. It is a graph which shows the relationship between the injection angle (alpha) and a peeling area | region. It is a graph which shows the relationship between the injection angle (alpha) and atomization level. It is a graph which shows the relationship between the injection angle (alpha) and surface roughness. It is a schematic diagram which shows the atomization state of the fuel spray which concerns on a present Example. It is a schematic diagram which shows the atomization state of the fuel spray which concerns on a prior art.

Explanation of symbols

L1 axis line L2 injection direction axis line 10 fuel injection valve 11 injection hole 11A injection hole inner wall surface 11B injection hole inner wall surface 11C farther from the axis line 11C injection hole inner wall surface 12, 13, 14 flow separation portion 15 fuel spray

Claims (1)

In a fuel injection valve of an internal combustion engine in which the injection angle has a predetermined angle with respect to the axis of the fuel injection valve and the injection hole is formed in a slit shape having a rectangular cross section,
A fuel injection valve for an internal combustion engine, characterized in that an injection hole inner wall surface closer to an axis of the fuel injection valve is formed to be rougher than a far injection wall inner wall surface.

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