The present invention relates to a method for manufacturing injection openings of a fuel injector and to a fuel injector having such injection openings.
Different embodiments of fuel injectors having injection openings are believed to be understood from the related art. In the case of direct-injecting systems in particular, such injection openings frequently have a spray hole and a prechamber. Due to the provision of the prechambers, however, a cross section of a component is reduced, which results, in particular, in a deflection of the lines of force occurring when internal pressure (fuel pressure) is applied to the component. Furthermore, the provision of prechambers reduces a wall thickness between adjacent injection openings or to an outer wall of the fuel injector. This may then result in problems with regard to the mechanical strength. The prechambers of the injection openings for fuel injectors have been previously manufactured, for example, using a cutting method, in particular drilling. Alternatively, a manufacture of the injection openings with the aid of a laser would also be possible, the laser having the disadvantage, however, that only low material-removal rates are achievable as compared to mechanical material-removing methods. The spray hole is manufactured in a second step, non-cutting methods such as spark erosion and laser drilling also being used, in part. An edge results between the prechamber wall and the prechamber base, which results in a strong deflection of lines of identical stress in the component.
The method according to the present invention for manufacturing injection openings of a fuel injector having the features described herein has the advantage over the related art in that injection openings may be manufactured to include prechambers which withstand greater loads, in particular higher fuel pressures, without an enlargement of wall thicknesses or the like being necessary therefor. In this case, the injection opening according to the present invention has a prechamber and the actual spray hole which, starting from the prechamber, injects the fuel into a combustion chamber or the like. The method according to the present invention includes the steps of manufacturing the prechamber with the aid of a mechanical, cutting method, in particular by milling or drilling, or with the aid of laser ablation. In addition, a radius is manufactured at a transition of the prechamber between a prechamber wall and a prechamber base with the aid of a laser. In addition, the spray hole is introduced into the prechamber base of the prechamber. According to the present invention, a, e.g., mechanically material-removing, method, which may remove a large amount of material in a short time, may therefore be combined with a laser method which, in particular, manufactures roundings at the transition between the prechamber wall and the prechamber base. The roundings have a radius R in such a way that the lines of identical stress are deflected less extremely, so that the injection opening according to the present invention withstands greater loads, in particular higher fuel pressures, without becoming damaged. Further, the method according to the present invention additionally or alternatively may include the introduction of grooves into the prechamber wall and/or the prechamber base for producing a radius at a transition of the prechamber. The groove or the grooves may therefore be provided independently of the provision of a radius at the transition of the prechamber and are also used for relieving material stress, so that greater loads on the prechamber due to pressures or the like are possible.
The further descriptions herein show refinements of the present invention.
The spray hole may also be manufactured with the aid of a laser. As a result, which may be both the radius in the transition area between the prechamber wall and the prechamber base, as well as the spray hole itself may be manufactured in one machining step. Further, the prechamber base may also be machined using the laser, in order to obtain a good surface. In this case, only a small material thickness is removed from the prechamber base.
According to one further embodiment of the present invention, grooves are introduced into the prechamber wall and/or the prechamber base with the aid of the laser. The grooves also have a positive effect on the distributions of stress in the component, so that a less extreme deflection of the distributions of stress occurs. The forces which may be absorbed by the component having the injection opening may also be increased as a result. The grooves in this case may be configured as completely circumferential grooves, which may be having an essentially U-shaped cross section.
Further, a second, smaller prechamber, which has a second radius at a transition area between the wall and the base of the second prechamber, may be introduced at the transition between the prechamber and the actual spray hole. Further, the second, smaller prechamber may also be provided with the aid of a laser.
The second radius at the transition between a wall area and a base area of the second prechamber may also be manufactured with the aid of a laser.
Furthermore, it may be provided to manufacture the prechamber in a first step with the aid of the mechanical, cutting method and then all further work to be performed using the laser is carried out in one setting.
The present invention further relates to a fuel injector including at least one injection opening, which has a prechamber and a spray hole. The prechamber has a radius at a transition between a prechamber wall and a prechamber base in order to deflect stress lines less extremely in the component including the injection opening.
Instead of the radius, a groove may be introduced into the prechamber wall and/or the prechamber base. Furthermore, a combination of the radius and the groove at the prechamber of the injection opening is also possible.
Further, one or multiple groove(s) may be provided in the prechamber wall and/or in the prechamber base, which may be completely circumferential. The grooves may be produced with the aid of a laser.
Further, a second prechamber, which has a second radius at a transition area between the wall and the base of the second prechamber, may be provided between the prechamber and the spray hole. The fuel injector further may include a valve housing, in which the injection opening is provided. Alternatively, the fuel injector includes a spray hole disk, in which at least one, which may be multiple injection openings is/are formed.
Exemplary embodiments of the present invention are described in detail in the following with reference to the accompanying drawing. In the drawing, identical or functionally identical parts are labeled using the same reference numerals.
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
Fuel is fed, as indicated by arrow A in
Injection opening 2 and its manufacture are schematically shown in
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.
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.
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.
In
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.
Number | Date | Country | Kind |
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10 2014 206 782.0 | Apr 2014 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2015/053374 | 2/18/2015 | WO | 00 |