Apparatus and method of overlapping formation of chamfers and orifices by laser light

#A fuel injector is believed to deliver fuel at specific time intervals and in precise amounts to intake valves and/or the combustion chamber of an internal combustion engine. It is further believed that fuel flowing through a fuel injector typically exits at a nozzle end of the fuel injector, and that the nozzle end typically has a disk with one or more orifices disposed thereon. It is believed that the resulting spray direction, spray particle size, spray mass flow, and spray pattern from the nozzle are a function of, among other variables, the geometry of the orifices.

#An orifice is believed to be formed by drilling through a work piece that can be of any shape, including a flat piece (or disk). There are many known methods of drilling orifices for a fuel injector, including trepanning, mechanical punching and electric discharge machining (EDM). It is believed that these methods are only capable of forming orifices of 150 to 200 microns in diameter or larger. Moreover, it is also believed that these methods are incapable of forming orifices with large targeting angles. It is further believed that future low emission standards will require smaller orifices configured at significantly larger targeting angles for smaller fuel spray droplets and shorter fuel spray duration. It is therefore believed that it will be technically infeasible and/or cost prohibitive to manufacture orifices using known methods once more restrictive emission standards are adopted.

#The present invention provides an apparatus that can form a plurality of orifices that are dimensionally consistent, such as, for example, the diameter, the surface roughness or the entry and exit configurations. In a preferred embodiment, the invention provides a laser machining apparatus. The apparatus includes a laser light source that provides a generally coherent light beam along the beam's axis. The apparatus also includes a light directing device to direct a first portion of light from the light beam to a work piece at a first angle of incidence relative to the beam's axis during a first time interval to form at least one of an orifice and a chamfer. The apparatus further includes an adjustable beam splitter assembly to direct another portion of the light beam to form the other of the at least one of an orifice and a chamfer in the work piece during a second time interval that overlaps a portion of the first time interval.

#The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate an embodiment of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention

#FIG. 1 is an illustration of a preferred embodiment.

#FIG. 2 is an illustration of the orifice and chamfer formed in a workpiece by the preferred embodiment shown in FIG. 1.

#Referring to FIGS. 1 and 2, the laser machining apparatus includes a laser light source 10 that provides a generally coherent light beam 12 along the beam's axis A—A. The apparatus also includes a splitter assembly 50 that includes, preferably, a rotatable beam reflector 14, to direct a first portion of light 16 from the light beam 12 to a work piece 100 via a focusing assembly 30 at a first angle of incidence 20 relative to the beam's axis A—A during a first time interval to form at least one of an orifice 106 and a chamfer 108. The assembly 50 further includes an adjustable beam splitter 22, such as, for example, a prism, to direct another portion of the light beam 24 at a second angle of incidence 26, which can be different from the first angle of incidence 20, to form the other of the at least one of an orifice 106 and a chamfer 108 in the work piece 100 during a second time interval that overlaps a portion of the first time interval. The first and second time intervals can differ in duration, such that the first time interval can be greater than the second time interval or, conversely, the second time interval is greater than the first time interval. That is, the light corresponding to one of the first and second time intervals can be initiated first while the light corresponding to the other time interval is not initiated until a time interval has passed such that both time intervals end at the same instant in time. Preferably, the first and second time intervals are initiated substantially simultaneously and can terminate at the same time or at different intervals.

#The workpiece 100 preferably can include at least a first surface 102 and a second surface 104, wherein the first surface 102 can be generally parallel to the second surface 104. Alternatively, the first surface 102 can be generally non-parallel to the second surface 104. The at least one orifice 106 is disposed along a longitudinal axis extending between the first surface 102 and the second surface 104 of the workpiece 100. The at least one chamfer 108 is disposed proximate at least one of the first surface 102 and the second surface 104. Preferably, two chamfers, one at each end of the orifice, are formed. The at least one orifice 106 formed in the workpiece 100 can be configured to have a surface roughness Ra of less than two microns.

#Using the preferred embodiments, the surface roughness Ra of the orifice 106 is provided between approximately 0.05 and approximately 0.13 microns such that the surface roughness and the cross-sectional shape of the chamfer(s) result in an orifice coefficient between approximately 0.6 and approximately 1.0. As used here, the term “surface roughness Ra” is an arithmetic mean value of the absolute values of a surface profile divided by the quantity of the values sensed by a sensing instrument, such as, for example, a surface profilometer or even by optical scanning, including a laser type atomic force microscope.