JP3757601B2 - Chamfering method for holes - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for chamfering a hole formed in a nozzle body or the like of a fuel injection nozzle.
[0002]
[Prior art]
As shown in FIG. 5, a plurality of injection holes b for injecting fuel are formed in the nozzle body a of the fuel injection nozzle of the engine. And generally, these nozzle holes b are processed by drilling from the outside. In this way, burrs appear at the nozzle hole c inside the nozzle body a and the flow of fuel is obstructed. Therefore, the nozzle hole c needs to be chamfered as shown in FIG. 6 to completely remove the burrs. . Further, even when no burr is generated by electric discharge machining, the nozzle hole inlet c is a place where the channel cross-sectional area decreases rapidly, so that the change in the channel cross-sectional area is slowed by chamfering, the flow coefficient is improved, and the fluid dynamics It is also necessary to reduce the upper aperture loss.
[0003]
By the way, since the injection hole inlet c is in the space in the narrow hole part d, normal cutting with a cutting tool or the like cannot be performed, and the following two types of chamfering methods are employed.
[0004]
(1) Electrochemical machining method As shown by a solid line in FIG. 6, the edge portion f around the nozzle hole inlet c is electrically decomposed by the electrode e, and sharp corners are rounded.
[0005]
(2) Fluid polishing processing method As shown by the one-dot chain line in FIG. 6, a viscous fluid g having polishing effect mixed with abrasive grains is poured from the inside of the nozzle body into the nozzle hole b at a high pressure (4 to 10 MPa). The edge portion f is polished and rounded.
[0006]
Here, with the electrolytic processing method (1), the variation in processing cannot be controlled. Therefore, in the future, in view of the required accuracy of the nozzle performance, it is expected that the fluid polishing method (2) will become the mainstream.
[0007]
[Problems to be solved by the invention]
However, in the case of the fluid polishing method, if the processing efficiency is improved, it is difficult to uniformly process the entire periphery of the edge portion, and there is a disadvantage that the processing becomes uneven. As a countermeasure, there is a method of lowering the fluid viscosity, but this improves the processing accuracy but decreases the processing efficiency.
[0008]
As described above, a hole chamfering method that can uniformly process the entire periphery of the edge portion in a short time is awaited.
[0009]
[Means for Solving the Problems]
A chamfering method for a hole according to the present invention is a chamfering method for a hole formed in a closed end portion of a cylindrical work whose front end is closed, the hole being chamfered in the cylindrical work. the inlet, after tightening dressed stopping the ball, with applying the die to the ball by inserting a die into the cylindrical body like work, pressing the ball to the inlet of the hole by adding a predetermined pressure to the die, the ball With the centripetal effect, the edge portion of the entrance of the hole is plastically processed while the coaxiality of the ball and the hole is maintained, and the edge portion formed by the plastic processing is polished.
[0010]
According to this, since the edge portion is plastically processed before the polishing process, the time for the polishing process can be reduced, and the entire processing time can be shortened. In addition, since balls are used for plastic working, the entire circumference can be evenly processed by the centripetal effect.
[0011]
Incidentally, the fastening to the inlet of the ball performs suction from the outlet side of the hole is carried out by adsorbing the ball to the inlet of the hole preferred. Moreover, it is preferable that the polishing process is performed by a fluid polishing process. Upper Symbol workpiece may be a nozzle body of a fluid injection nozzle. Further, the hole chamfering method according to the present invention is a hole chamfering method in which a ball is pressed against one end of a hole to plastically process the edge portion of the hole and then the edge portion is polished. Before the ball is pressed, suction is performed from the other end side of the hole so that the ball is adsorbed to one end of the hole.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[0013]
FIG. 4 shows a chamfering apparatus for carrying out the method according to the invention. As shown in the figure, here, a nozzle body 1 of a fuel injection nozzle is used as a work as a workpiece. The nozzle body 1 is formed in a substantially cylindrical shape as a whole, and is formed in a tapered shape in which a lower end portion 2 is tapered and is closed. A small-diameter hole portion 3 that protrudes in a substantially hemispherical shape is formed on the distal end side at the tip and axial center of the distal end portion 2. The hole portion 3 has a plurality of (here, six) small-diameter holes, that is, injection holes 4. The nozzle hole 4 is inclined at a predetermined angle with respect to the nozzle axis direction so as to inject fuel outward in the radial direction and downward. The nozzle holes 4 are arranged at equal intervals in the circumferential direction.
[0014]
A shaft center hole 5 for accommodating a needle valve or the like is provided in the shaft center portion inside the nozzle body 1. Here, a die 6 is slidably inserted into the shaft hole 5 so as to be movable up and down. It has become. An annular fuel reservoir 7 that protrudes radially outward is formed in the middle of the axial hole 5, and a fuel supply hole 8 that opens to the upper portion is communicated with the fuel reservoir 7. The nozzle body 1 is reduced in diameter at a position closer to the distal end than the fuel reservoir 7, that is, the cylindrical portion of the nozzle body 1 is formed of a large diameter portion 9 on the proximal end side and a small diameter portion 10 on the distal end side.
[0015]
In this apparatus, a table 11 for fitting and fixing such a nozzle body 1 is provided. That is, the table 11 is provided with a fitting hole 12 that opens upward, and the small-diameter portion 10 of the nozzle body 1 is inserted into the fitting hole 12 from above. The tip 2 of the nozzle body 1 abuts the bottom surface of the fitting hole 12 and the large-diameter portion 9 of the nozzle body 1 abuts the top surface of the table 11, thereby restricting the movement of the nozzle body 1 in the axial direction or the vertical direction. Is done. An O-ring 13 is accommodated and disposed at an intermediate position of the fitting hole 12 so as to ensure a lower airtightness.
[0016]
A small fitting hole 14 for fitting the hole portion 3 is provided at the axial center position of the bottom wall portion of the fitting hole 12. A suction hole 15 is provided continuously below the small fitting hole 14 so that at least the outlet at the lower end of the injection hole 4 is exposed in the suction hole 15. The lower end of the suction hole 15 is opened and connected to a vacuum pump via a hose or the like (not shown).
[0017]
On the other hand, in this apparatus, a ball supply device 17 for dropping and supplying the ball 16 into the nozzle body 1 from the fuel supply hole 8 is provided. As shown in FIG. 1, the nozzle hole 4 has an inlet 18 at one end thereof opened into the hole 3, but the ball 16 has a size that can close the inlet 18, preferably 1.4 to 1.6 times the diameter of the nozzle hole. The same number of outer diameters (about φ 0.3-1 mm) is supplied as the number of nozzle holes.
[0018]
Further, as shown in FIG. 1, the die 6 presses the supplied ball 16 against the inlet 18 of the nozzle hole 4 and plastically processes an edge portion (corner portion) 19 around the inlet 18. . That is, a small-diameter processed portion 20 that can be inserted into the hole portion 3 is integrally formed at the tip end and the axial center position of the die 6. And the process part 20 is formed in the base end part 21 in the column shape, and the front-end | tip part 22 in the shape of a point. The outer peripheral surface of the tip portion 22 is formed in a rounded shape having a radius of curvature larger than the ball radius, and all the balls 16 can be adapted to the outer peripheral side.
[0019]
Next, a method for chamfering a nozzle hole using this apparatus will be described.
[0020]
First, as shown in FIG. 4, the nozzle body 1 after processing the nozzle holes 4 is set on the table 11 in a state where the die 6 is kept in the raised position. Then, the same number of balls 16 as the nozzle holes 4 are dropped and supplied into the nozzle body 1. Next, a vacuum pump (not shown) is started. Then, since airtightness is secured at the position of the O-ring 13, the balls 16 in the nozzle body 1 are sucked through the suction holes 15 and the nozzle holes 4, and are not fixed to the inlets 18 of the respective nozzle holes 4 one by one. It becomes adsorbed. As a result, the nozzle hole 4 is closed, and the balls 16 come into contact with the edge 19 of the nozzle hole 4 evenly over the entire circumference. At this time, if some of the balls 16 are not fixed to the injection hole inlet 18, the table 11 may be vibrated as appropriate, and the balls 16 may be rolled and fixed.
[0021]
Thereafter, the die 6 is lowered and, as shown in FIG. 1, the tip 22 of the processed portion 20 is applied to each ball 16 and a predetermined pressure is applied to the die 6 to force the ball 16 to the edge portion 19 of the nozzle hole 4. Press on. At this time, due to the centripetal effect of the ball 16, the coaxiality between the ball 16 and the nozzle hole 4 is maintained, so that the ball 16 hits the edge portion 19 evenly and presses the edge portion 19 evenly. In this case, the edge portion 19 is plastically processed, and as shown in FIG. 2, the edge portion 19 is recessed uniformly over the entire circumference, and the ball shape is transferred.
[0022]
Thereafter, the die 6 is raised and the vacuum pump is stopped. And the edge part 19 after plastic working is lightly grind | polished by the above-mentioned fluid grinding | polishing processing method. Then, each corner 23 made by plastic working is chamfered and rounded. Thus, the chamfering process of the nozzle hole 4 is completed, and the nozzle hole 4 has a trumpet shape in which the vicinity of the inlet portion is enlarged.
[0023]
As described above, according to the present method, since the plastic processing by the ball 16 is performed before the edge portion 19 is polished, the time required for the polishing process is reduced, and thus the time required for the entire chamfering process is significantly reduced. Can do. In addition, according to this method, it is expected that the machining time which has conventionally required about 2 to 30 minutes can be stopped within one minute.
[0024]
Further, since the balls 16 are used for plastic working, the plastic working can be performed uniformly over the entire circumference, and therefore, the chamfering can be performed evenly over the entire circumference, and the processing accuracy can be greatly improved.
[0025]
Here, for example, when the nozzle body 1 is made of SCM, the ball 16 is preferably made of a harder material such as cemented carbide, ceramic or SUJ. The material is selected in consideration of the life and cost of the ball 16, the processing shape, etc., but it is possible or appropriate to use SUJ at the trial production stage and cemented carbide or ceramic at the mass production stage.
[0026]
In addition, for the final polishing process, for example, a normal method using a grindstone or the like may be employed. However, according to this method, chips are generated and the processing thereof is complicated. Therefore, the present method which does not generate chips is extremely advantageous.
[0027]
Furthermore, in this method, even if the position of the nozzle hole inlet 18 varies somewhat due to a hole processing error, the ball 16 can be securely fixed and plastic processing can be performed. Therefore, all the nozzle holes 4 can be chamfered reliably and uniformly.
[0028]
The embodiment of the present invention is not limited to the above. In addition, although the fuel injection nozzle of the engine has been exemplified here, other fluid injection nozzles such as a mechanical lubricating oil nozzle, a spinning nozzle, and a cleaning nozzle can be applied. Further, the present invention is not limited to such nozzle parts, and can be applied to chamfering of all holes.
[0029]
【The invention's effect】
In short, according to the present invention, an excellent effect is exhibited that the edge portion of the hole can be chamfered uniformly over the entire circumference in a short time.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view for explaining a chamfering method according to the present invention.
FIG. 2 is an enlarged view showing an edge portion of a hole after plastic working.
FIG. 3 is an enlarged view showing an edge portion of a hole after polishing.
FIG. 4 is a longitudinal sectional view showing a chamfering apparatus.
FIG. 5 is a longitudinal sectional view showing a nozzle body.
FIG. 6 is an enlarged view for explaining a conventional chamfering method.
[Explanation of symbols]
1 Nozzle body 4 Injection hole 16 Ball 19 Edge part

Claims (5)

A chamfering method for a hole formed in a closed end portion of a cylindrical workpiece whose front end portion is closed,
After fixing the ball to the entrance of the hole opened in the cylindrical workpiece, insert a die into the cylindrical workpiece and apply the die to the ball, and apply a predetermined pressure to the die. pressing the ball to the inlet of the hole, while maintaining the coaxiality between the ball and the hole by centripetal effect of the ball, an edge portion of the inlet of the hole to plastic working, the edge portion made by the plastic working A method for chamfering a hole, characterized in that the surface is polished. Fastening to said inlet of said ball, chamfering method of claim 1, wherein the hole by performing suction from the outlet side of the hole carried out by adsorbing the ball to the inlet of the hole.   The hole chamfering method according to claim 1 or 2, wherein the polishing is performed by a fluid polishing method. The hole chamfering method according to claim 1, wherein the workpiece is a nozzle body of a fluid ejection nozzle . A method of chamfering a hole in which a ball is pressed against one end of a hole and the edge portion of the hole is plastically processed, and then the edge portion is polished.
A method of chamfering a hole, wherein suction is performed from the other end side of the hole before the ball is pressed so that the ball is adsorbed to one end of the hole.

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