JPH0763140A - Forming method for injection hole of fuel injection valve - Google Patents

Abstract

PURPOSE:To form an injection hole of good injection performance high accurately and stably by machining a right cylindrical hole in a flat shaped plate of separate unit from a nozzle main unit of a fuel injection valve, thereafter deformed into a tapered injection hole by drawing working a peripheral part of this right cylindrical hole into a dome shape having prescribed curvature. CONSTITUTION:In order to form an injection hole 18, first relating to a flat- shaped plate 11 of separate unit from a nozzle main unit of a fuel injection valve, a right cylindrical hole 13 is worked to pass through in a plate thickness direction by a right cylindrical working tool 12. Next by using a punch 14, a peripheral part of the hole 13 in the flat-shaped plate 11 is processed by drawing work into a dome shape 15 having prescribed curvature. By a difference between radii of curvature in a small radius of curvature side 16 and a large radius of curvature side 17 of the dome shape 15, the right cylindrical hole 13 is deformed into a tapered injection hole 18. Successively, a peripheral plane part of the dome shape 15, after forming a mounting seat, is separated from a streak material to form a nozzle plate. In this way, the injection hole 18 of cone sectional shape with good injection performance is formed stably and high accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming injection holes in a fuel injection valve for an internal combustion engine.

[0002]

2. Description of the Related Art Generally, an injection hole of a fuel injection valve for an internal combustion engine has a right cylindrical cross section. However, the longer the straight portion of the injection hole, the smaller the flow coefficient and the larger the spray particle size, which adversely affects the injection performance. In order to realize better injection performance (large flow coefficient, small spray particle size), it is conceivable to make the length of the straight portion close to 0, or to use a taper hole having no straight portion, for example, an enlarged diameter. However, if the straight portion is brought close to 0, the plate thickness is small and a problem of withstand voltage occurs, so that it is not feasible. For taper holes, see Shokai 58-1677
Japanese Patent Publication No. 72 discloses a fuel injection valve in which the injection hole is a hole having a tapered surface for expanding the diameter.

[0003]

However, in the conventional processing of the fuel injection valve injection hole consisting of a tapered hole, it is inevitable that the tip of the dome-shaped tip formed by shaving is cut using a conical blade tool. Therefore, as shown in FIG. 5, there is a problem that the hole diameter changes depending on the machining depth of the conical blade tool 1 and the diameter of the hole 2 is difficult to set to a target value. If the hole diameter deviates from a predetermined value, the fuel injection amount measured by the injection hole will deviate from the predetermined value. It is an object of the present invention to stably form a conical cross-section injection hole having a high injection performance (a large flow coefficient and a small spray particle size), and therefore, to form an injection hole of a fuel injection valve that can be formed with high accuracy and little variation. It is to provide a forming method.

[0004]

A method of forming an injection hole of a fuel injection valve according to the present invention for achieving the above object comprises the following method. That is, in the method of forming the injection hole of the fuel injection valve in which the injection hole of the fuel injection valve is processed into a plate separate from the nozzle body, a straight cylindrical hole is processed at a predetermined position of the flat plate, and then the hole of the flat plate is processed. A method of forming an injection hole of a fuel injection valve by drawing a peripheral portion into a dome shape having a predetermined curvature and making the hole into a tapered injection hole.

[0005]

In the above-described method of the present invention, since the straight cylindrical hole is formed in the flat plate, the diameter of the hole is constant irrespective of the processing depth, and the hole diameter can be accurately processed to a constant diameter. Then, since the portion in which this hole is formed is processed into a dome shape by drawing, the hole diameter is increased by the amount of the arc shape of the dome from the straight state of the flat plate, but since the accuracy itself is pulled as it is, The hole diameter has a predetermined value with high accuracy and little variation, and the injection hole can be stably formed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the method for forming the injection hole of the fuel injection valve of the present invention will be described below with reference to FIGS. According to the present invention, the tip plate of the fuel injection valve is formed from a flat plate, which is separate from the nozzle body of the fuel injection valve, such as a flat strip (steel strip), and injection holes are formed in the nozzle plate. Then, fix it to the nozzle body by welding. First, as shown in FIG. 1, a flat plate-shaped plate 11 is processed by a right-cylindrical processing tool 12 (for example, a drill, a punch, etc.) to form a right-cylindrical hole 13 in the plate thickness direction. . In this case, a straight cylindrical hole 1
Therefore, the hole diameter does not change even if the working depth of the working tool 12 changes.

Next, as shown in FIG. 2, the peripheral portion of the hole 13 of the flat plate 11 is drawn with a punch 14 into a dome shape 15 having a predetermined curvature. The dome shape 15 can be adjusted by selecting the radius of the punch 14 and the thickness of the strip 11. At this time, due to the difference in curvature between the small radius side 16 of the dome shape and the large radius side 17 of the dome shape, the straight cylindrical hole 13 changes into a tapered injection hole 18 and moves toward the outer periphery of the dome shape 15. Cone-shaped injection hole 18 with an enlarged diameter
Is formed. FIG. 2 shows an example in which the machined hole and the punch have the same axial center. However, when the direction of the injection hole is desired to be changed, the punch and the machined hole are eccentric within the range of the dome diameter. May be.

After forming the dome shape 15, as shown in FIG. 3, the mounting seat 19 is formed on the flat plate portion around the dome shape 15 by pressing or the like, or is formed by machining or the like. Nozzle plate 20 separated from material 11
And The nozzle plate 20 is fixed to the nozzle body 21 by welding or the like. 22 indicates a welded portion.

In the example of FIG. 3, the valve body 23 is attached to the nozzle body 21.
Is formed, and the needle valve 24 is configured to move forward and backward to be seated. However, the structure is not limited to this, and as shown in FIG. 4, a valve seat 25 may be formed on the nozzle plate 20 side, and the needle valve 24 may be advanced and retracted with respect to this valve seat 25 to be seated. . With the configuration shown in FIG. 4, the dead space 26 between the needle valve 24 and the dome shape 15 becomes small, and it is possible to suppress fuel dripping after injection that may occur when the dead space 26 is large. Becomes

Next, the operation of the above injection hole forming method will be described. First, a straight cylindrical hole 1 is formed in the flat plate 11.
Since 3 is machined, the hole diameter is stable and constant regardless of the machining depth of the machining tool 12. Therefore, the accuracy of the hole diameter is high.

Further, when the plate 11 having the holes 13 formed therein is drawn into a dome shape 15, the hole diameter becomes large as the flat plate extends in an arc shape, but since the accuracy is succeeded as it is, the tapered injection hole 18 is used. When it becomes, the hole diameter has reached the specified value with high accuracy. Therefore, the fuel metering is stable,
You can inject the target amount of fuel.

Further, since the holes 13 are formed in the dome shape 15, the straight cylindrical holes at the stage of the flat plate 11 are automatically changed to the tapered injection holes 18 at the stage of forming the dome 15. Therefore, the tapered hole can be formed easily and inexpensively. With this tapered injection hole 18,
Larger flow coefficient and smaller atomized particle size, resulting in
A fuel injection valve with good injection performance can be provided.

Further, in the case of the tapered hole 18, since there is no straight portion in the hole, the plate thickness can be increased as compared with the conventional case without lowering the injection performance. As a result, as shown in FIG. 4, the valve seat 25 can be machined into the nozzle plate 20 itself. As a result, the valve seat formation, which is conventionally performed in a separate process, can be performed in the same process (same drawing process) as the nozzle formation, and the cost can be significantly reduced. Further, even when the valve seat 25 is machined by grinding or the like, the machining position is shallow, so that the machining is easy.

[0014]

According to the present invention, a straight cylindrical hole is formed in a flat plate, and then the peripheral portion of the hole is drawn into a dome shape, so that the processing depth is not affected. A straight cylindrical hole with a high precision diameter can be drilled in a flat plate, and the precision of this straight cylindrical hole can be inherited in forming a dome shape to achieve a highly precise, tapered injection hole with good injection performance. It can be stably formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a step of forming a straight cylindrical hole in a flat plate in a method of forming an injection hole of a fuel injection valve according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a step of drawing a dome-shaped peripheral portion of a plate having a right cylindrical hole formed in the step of FIG.

FIG. 3 is a cross-sectional view of the tip of the fuel injection valve in a state in which a seat is formed on the dome-shaped plate manufactured in the process of FIG. 2 and is welded to the nozzle body.

FIG. 4 shows a case where a valve seat is formed on the nozzle plate itself,
It is sectional drawing of a fuel injection valve front-end | tip part.

FIG. 5 is a cross-sectional view of a conventional method of forming a tapered injection hole in a dome-shaped portion using a conical processing tool.

[Explanation of symbols]

 11 Flat Plate 12 Processing Tool 13 Right Cylindrical Hole 14 Punch 15 Dome Shape 18 Conical (Tapered) Injection Hole 19 Mounting Seat 20 Nozzle Plate 21 Nozzle Main Body 22 Weld 23 Valve Seat 24 Needle Valve 25 Valve Seat

Claims (1)

[Claims] 1. A method for forming an injection hole of a fuel injection valve, wherein the injection hole of the fuel injection valve is formed as a plate separate from the nozzle body, wherein a straight cylindrical hole is formed at a predetermined position of the flat plate, and then the flat plate is formed. A method for forming an injection hole of a fuel injection valve, wherein the hole peripheral portion is drawn into a dome shape having a predetermined curvature to form the hole into a tapered injection hole.