METHOD FOR MANUFACTURING INJECTION OPENINGS AND FUEL INJECTOR HAVING SUCH INJECTION OPENINGS

Abstract

A method for manufacturing injection openings of a fuel injector, including: manufacturing a prechamber with the aid of a mechanical, cutting method, in particular with the aid of milling or drilling or with the aid of laser ablation, producing a radius at the transition of the prechamber between a prechamber wall and a prechamber base with the aid of a laser, and/or introducing grooves into the prechamber wall and/or the prechamber base, and manufacturing a spray hole in the prechamber base.

Claims

1-10. (canceled)

11. A method for manufacturing injection openings of a fuel injector, the method comprising: producing a prechamber with the aid of a mechanical, cutting process or laser ablation; producing a radius at a transition of the prechamber between a prechamber wall and a prechamber base with the aid of a laser, and/or introducing grooves into the prechamber wall, and/or the prechamber base; and producing a spray hole in the prechamber base.

12. The method of claim 11, wherein the spray hole is manufactured with the aid of the laser.

13. The method of claim 11, wherein material removal is also carried out on the prechamber base during production of the radius at the prechamber.

14. The method of claim 11, wherein grooves are introduced into the prechamber wall and/or in the prechamber base with the aid of the laser.

15. The method of claim 14, wherein the grooves are introduced as circumferential grooves.

16. The method of claim 11, wherein a second prechamber is introduced at a transition area between the prechamber and the spray hole, a second radius being provided at the second prechamber at the transition area between the wall and the base.

17. A fuel injector for metering fuel, comprising: at least one injection opening having a prechamber and a spray hole; and at least one of: a radius formed at the prechamber at a transition area between a prechamber wall and a prechamber base; and/ groove introduced into the prechamber wall and/or the prechamber base.

18. The fuel injector of claim 17, further comprising: at least one groove, which is formed completely circumferential in the prechamber wall and/or in the prechamber base.

19. The fuel injector of claim 17, wherein a second prechamber at a transition between the first prechamber and the spray hole, a second radius being formed at a transition between a wall and a base of the second prechamber.

20. The fuel injector of claim 17, further comprising: one of: (i) a valve housing, in which the injection opening is provided, and (ii) a spray hole disk, in which the injection opening is provided.

21. The method of claim 11, wherein the mechanical, cutting process includes milling or drilling.

22. The method of claim 11, wherein a second prechamber is introduced, in particular with the aid of a laser, at a transition area between the prechamber and the spray hole, a second radius being provided at the second prechamber at the transition area between the wall and the base.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 shows a schematic sectional view of a fuel injector according to a first exemplary embodiment of the present invention.

[0016] FIG. 2 shows a schematic sectional view of an injection opening from FIG. 1 during the manufacturing method.

[0017] FIG. 3 shows a schematic sectional view of the injection opening from FIG. 2 in the finished state.

[0018] FIG. 4 shows a schematic sectional view of an injection opening according to a second exemplary embodiment of the present invention.

[0019] FIG. 5 shows a schematic sectional view of an injection opening according to a third exemplary embodiment of the present invention.

[0020] FIG. 6 shows a schematic sectional view of an injection opening according to a fourth exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0021] A fuel injector 1 according to a first exemplary embodiment of the present invention and a first method according to the present invention are described in detail in the following with reference to FIGS. 1 through 3.

[0022] FIG. 1 schematically shows a fuel injector 1, which includes multiple injection openings 2 in a valve housing 6. Fuel injector 1 includes a valve needle 11 including a ball 12, which unblocks and blocks injection openings 2 on a valve seat. Valve needle 11 is connected via an entraining element 13 to an armature 21 of a magnetic actuator 20. Magnetic actuator 20 further includes a coil 22, a pole core 23, and a magnetic pot 24. A working gap 25 is provided, in this case, between armature 21 and pole core 23 in the axial direction. Armature 21 is reset to the starting position shown in FIG. 1, which is the closed position of the fuel injector, in a known way with the aid of a restoring element 15. The restoring force of the restoring element may be defined with the aid of an adjusting sleeve 16.

[0023] Fuel is fed, as indicated by arrow A in FIG. 1, in the axial direction through adjusting sleeve 16 and hollow entraining element 13 into a space 17 in the area of valve needle 11. Passages 14 are provided in entraining element 13 for this purpose.

[0024] Injection opening 2 and its manufacture are schematically shown in FIGS. 2 and 3. FIG. 3 shows the finished state of injection opening 2, which includes a prechamber 3 and a spray hole 4. Prechamber 3 includes a prechamber wall 30 and a prechamber base 31. Prechamber wall 30 is configured essentially cylindrical and prechamber base 31 is perpendicular to axial direction X-X of injection opening 2. A transition area between the prechamber wall and prechamber base 31 is formed with the aid of a radius R. Radius R at the transition area between prechamber wall 30 and prechamber base 31 ensures that lines 5 of identical stress, which are plotted in FIG. 3, do not deviate too extremely, in particular in the area of the transition. Areas of sharp deflections of the lines of identical stress usually result in zones having locally high mechanical stress in different levels. A spacious deflection may infer a favorable state of stress. As is apparent from FIG. 3, lines 5 of identical stress each form curves having relatively large radii, also in the transition area having radius R, so that stress peaks in valve housing 6, which would occur in the case of an angular transition between the prechamber wall and the prechamber base, may be avoided according to the present invention.

[0025] FIG. 2 schematically shows the manufacture of injection opening 2. In a first step, prechamber 3 is manufactured to a depth Ti with the aid of a cutting tool, e.g., a drill or a milling cutter. The use of the cutting tool may be carried out in this case at a high rate of material removal. Alternatively, the entire prechamber may also be produced using a laser. In a next step, residual material which still remains and which is labeled with reference numeral 3 in FIG. 2, is removed with the aid of a laser. In this case, material removal takes place on prechamber base 31. Simultaneously, radius R is produced at a transition area between prechamber wall 30 and prechamber base 31 with the aid of the laser. Therefore, a curved transition between prechamber wall 30 and prechamber base 31 is provided, which would not be present in this way if machining were carried out exclusively with the aid of a cutting tool. In a final step, spray hole 4 is then produced with the aid of the laser.

[0026] In the method according to the present invention, both a surface machining of prechamber base 31 and a manufacture of radius R at the transition area between the wall and the base, and spray hole 4 may therefore be manufactured with the aid of the laser.

[0027] Since a quantity of the material to be removed with the aid of the laser is relatively small, short total manufacturing times may be nevertheless achieved according to the present invention. Therefore, due to the idea according to the present invention, a functional value of the component may be improved in terms of increasing the load capacity under higher pressures, without causing notable cost increases in the manufacture of injection opening 2 due to the method according to the present invention. The skillful combination, according to the present invention, of material removal by cutting and laser ablation therefore provides for significant cost advantages in the manufacture, which provide great economic advantages, since the components are mass-produced parts.

[0028] Since arbitrary radii R at the transition area between prechamber wall 30 and prechamber base 31 are manufacturable with the aid of the laser, the method according to the present invention may also be carried out for highly diverse diameters of prechamber 3, each of which is adapted, for example, to different internal combustion engines of varying power or are adapted by different manufacturers.

[0029] FIGS. 4 and 5 show further exemplary embodiments of the present invention. In FIG. 4, an additional, second prechamber 7 is formed, which was also manufactured with the aid of the laser, due to its low depth. In this case, a second radius R2 is formed at the transition between the wall and the base of second prechamber 7. This second radius is therefore adapted to the diameter of second prechamber 7 and is slightly smaller than radius R1 at first prechamber 3. In the exemplary embodiment shown in FIG. 4, a circumferential first groove 8 is furthermore provided in prechamber base 31 and a second circumferential groove 9 is formed in prechamber wall 30. These grooves 8, 9 ensure that a flux of force in valve housing 6 and, therefore, lines 5 of identical stress are forced to undergo a more spacious deflection around the transition area between the wall and the base. Additional grooves 8, 9 may also be manufactured with the aid of the laser and may be set up during the manufacture of spray hole 4.

[0030] In FIG. 5, a further alternative exemplary embodiment of the present invention is represented, no groove being provided in prechamber wall 30, although a first groove 8 and a second groove 10 are formed in prechamber base 31. The two grooves 8, 10, in turn, are provided to be circumferential, a depth of the grooves being different. In this exemplary embodiment, first groove 8 is deeper than second groove 10. Also as a result thereof, a more gentle deflection of lines 5 of identical stress in valve housing 6 is achieved (see FIG. 5). The two grooves 8, 10 in this case effectuate such a deflection of lines 5 of identical stress that material which is located between the two grooves 8, 10 does not need to be removed.

[0031] FIG. 6 shows a further alternative exemplary embodiment of the present invention, which does not include a radius at the transition between the wall and the base of the prechamber, but rather a corner. Instead of the radius, a circumferential first groove 8 is provided in prechamber base 31 and a second circumferential groove 9 is provided in prechamber wall 30.

[0032] Grooves 8, 9 are provided relatively close to the corners without a radius in this case, so that lines of identical stress are forced to undergo a spacious deflection around the corners or around the transition area between the wall and the base. Grooves 8, 9 may likewise be manufactured with the aid of a laser.