Abstract:
A method of laser drilling a component is disclosed. The method includes contacting a sacrificial material with the component. The method also includes aligning a laser drilling tool with the sacrificial material and the component. The method further includes incidenting a laser beam on the sacrificial material. The method includes containing a trumpet effect caused by the laser beam within a thickness of the sacrificial material. Further, the method includes forming a reverse tapered orifice within the component. The method also includes removing the sacrificial material from the component.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a system and method for laser drilling of a component, and more particularly, to the system and method of laser drilling a reverse tapered orifice within the component. 
       BACKGROUND 
       [0002]    A laser drilling process may be used for creating orifices within a component, for example, a fuel injector. However, in some situations, the laser drilling process may increase a surface roughness of the orifices which may lead to a clogging of fuel flowing through the orifice. Additionally, the laser drilling process may lead to an increase in a K factor associated with fluid dispersion characteristics of the orifice. The term “K factor” is defined as the difference between diameters of the orifice at each end divided by ten. 
         [0003]    U.S. Pat. No. 8,268,182 discloses a processing method of forming a through-hole in a work-piece by means of a pulsed laser beam includes the steps of providing a removable sacrifice layer on the work-piece, forming a through-hole in the work-piece by the laser beam in a state where the sacrifice layer is provided, and removing the sacrifice layer from the work-piece after the step of forming the through-hole. 
         [0004]    The present disclosure is directed to mitigating or eliminating one or more of the drawbacks discussed above. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    In one aspect of the present disclosure, a method of laser drilling a component is disclosed. The method includes contacting a sacrificial material with the component. The method also includes aligning a laser drilling tool with the sacrificial material and the component. The method further includes incidenting a laser beam on the sacrificial material. The method includes containing a trumpet effect caused by the laser beam within a thickness of the sacrificial material. Further, the method includes forming a reverse tapered orifice within the component. The method also includes removing the sacrificial material from the component. 
         [0006]    In another aspect of the present disclosure, a system for laser drilling an orifice within a fuel injector is disclosed. The system includes a laser drilling tool. The system also includes a sacrificial material placed in contact with the fuel injector. The sacrificial material is aligned with the laser drilling tool. Further, the sacrificial material is positioned at an end of the component at which a laser beam is incident. Further, a thickness of the sacrificial material is such that a trumpet effect caused by the laser beam is contained within the sacrificial material. 
         [0007]    In yet another aspect of the present disclosure, a fuel injector is disclosed. The fuel injector includes a body and a plunger. The fuel injector includes a smoothened inner wall of the fuel injector defining a reverse tapered orifice therein. The smoothened inner wall is configured to be formed by detachably connecting a sacrificial material at an end of the component at which a laser beam is incident. Further, a thickness of the sacrificial material is such that a trumpet effect caused by the laser beam is contained within the sacrificial material. 
         [0008]    Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a cross-sectional view of an exemplary component for laser drilling, according to one embodiment of the present disclosure; 
           [0010]      FIG. 2  is a schematic diagram of a laser drilling system for creating an orifice within the component; 
           [0011]      FIG. 3  is a cross-sectional view showing a portion of the component, the orifice and a sacrificial material provided in contact with the component; and 
           [0012]      FIG. 4  is a flowchart for a method of laser drilling the component. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or the like parts.  FIG. 1  is a cross-sectional view of an exemplary component, according to one embodiment of the present disclosure. More specifically, the component includes a fuel injector  100  of an engine (not shown). The fuel injector  100  can be used in an internal combustion engine or any other machine where fuel injection takes place. The fuel injector  100  can be configured to deliver a uniformly atomized fuel mixture into a combustion chamber (not shown) of the engine. 
         [0014]    The fuel injector  100  includes a substantially solid body  102 . The fuel injector  100 , and the body  102  thereof, can include various features which can define the fuel injector  100  as including a hollow cylindrical configuration or design. The fuel injector  100  can include a fuel delivery passage  104 . The fuel delivery passage  104  can be provided within the body  102  of the fuel injector  100 . The fuel delivery passage  104  can be configured to fluidly communicate and deliver fuel through the body  102  of the fuel injector  100  such that the fuel can be filled or otherwise delivered within the body  102  of the fuel injector  100  to effectuate discharge of fuel as provided herein. The body  102  can also include a conical portion or a spray tip  106  provided at a lower or fuel outlet section of the fuel injector  100 . 
         [0015]    In the exemplary embodiment shown in  FIG. 1 , the fuel injector  100  also includes a plunger  108  slidably received within the body  102  of the fuel injector  100 . The plunger  108  can include a solid circular cross-section. As further illustrated in the exemplary embodiment shown in  FIG. 1 , the plunger  108  can include a conical end portion or tip provided at a lower end of the plunger  108 , wherein the conical end portion or tip of the plunger  108  can be formed to include a dimension and shape which substantially correspond to and align with a dimension and shape of an inner part of the spray tip  106 . During operation, the fuel injector  100  can be energized or otherwise actuated such that the pressurized fuel within the body  102  of the fuel injector  100  can be sprayed out through a single or a plurality of orifices  110 , which in one example can be via the energization of an electromagnet which can cause the plunger  108  to move within the body  102  of the fuel injector  100  to effectuate an injection event such that the pressurized fuel can be sprayed out through a single or a plurality of orifices  110 . The shape of the one or more orifices  110  (also referred to as the “reverse tapered orifice(s)  110 ”, as provided herein) is provided in a manner such that the fuel sprayed out is atomized or discharged as fine liquid particles, so that the fuel particles may be burnt easily. The design of the fuel injector  100  included herein is exemplary. The number of the orifices  110  may vary based on the application. 
         [0016]    As shown in the accompanying figures, each of the one or more orifices  110  includes an orifice inner wall  111  which defines each orifice  110  as an open passage formed within and extending through the body  102  of the fuel injector  100  within the spray tip  106  thereof. In particular, each orifice  110  has a reverse tapered configuration. The term “reverse tapered orifice” used herein refers to each orifice  110  which is drilled such that each orifice  110  and orifice inner wall  111  thereof is formed by an inwardly sloping orifice inner wall  111  having a diameter which gradually decreases along the length of each orifice  110  from a diameter D 1  of the orifice  110  at a fuel entry point  112  (See  FIG. 3 ) of the orifice  110  positioned proximate to the inner part or interior of the spray tip  106  to a diameter D 2  at a fuel exit point  114  (See  FIG. 3 ) of the orifice  110  positioned proximate to and opening out into an outer surface of the fuel injector  100 , shown in the Figures and defined herein as an incident end  132  of the fuel injector  100  (wherein D 1 &gt;D 2 ). 
         [0017]    As such, each orifice  110  can be defined as including a generally frustoconical three-dimensional passage shape or geometry. The fuel dispersion characteristics of the fuel injector  100  may depend on factors such as, a cross-section of the orifice  110 . One of the parameters associated with the cross section of the orifice  110  is defined as “K factor” such that: 
         [0000]    
       
         
           
             
               
                 
                   K 
                   = 
                   
                     
                       
                         D 
                          
                         
                             
                         
                          
                         1 
                       
                       - 
                       
                         D 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     10 
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
         [0000]    wherein, 
         [0018]    D 1 =entry diameter of orifice 
         [0019]    D 2 =exit diameter of orifice 
         [0000]    The entry and exit diameters D 1 , D 2  of the orifice  110  can be specified such that an appropriate and desired, specific K factor is obtained. In one embodiment, the value of the K factor can be approximately between −5 and 10 for application in the fuel injector  100 . It should be noted that other parameters may be considered in different applications of the disclosure and is not limited to that disclosed herein. 
         [0020]    The present disclosure contemplates drilling the reverse tapered orifice  110  within the fuel injector  100 , herein disclosed as the fuel injector  100 , using a laser drilling tool  116 . However, the disclosure may be utilized for other applications as well without any limitation. The method of providing the reverse tapered orifices  110  within the fuel injector  100  will now be described in detail in connection with  FIGS. 2 and 3 . 
         [0021]    Referring to  FIG. 2 , schematic view of an exemplary laser drilling system  118  is provided, according to one embodiment of the present disclosure. The laser drilling system  118  includes the laser drilling tool  116 . The laser drilling tool  116  can include a laser source  120  which emits a laser beam  122 . The laser source  120  can be any type of known light source that is capable of producing the laser beam  122  of required power, coherency, pulse width, pulse repetition time, and wavelength based on the application. The laser source  120  can be selected such that the laser beam  122  is compatible with the fuel injector  100  to be laser drilled. Further, a frequency of the laser beam  122  used for drilling of the orifice  110  may also vary based on the application. As further disclosed herein, according, at least in part, to the method and laser drilling system  118  of the present disclosure, the laser beam  122  of an athermal high pulse frequency can produce reverse tapered orifices  110  having a smoothened orifice inner wall  111 . 
         [0022]    The laser drilling tool  116  also includes a laser drilling head  124 . In the illustrated embodiment, the laser drilling head  124  can include a trepanning head configured to produce the reverse tapered orifice  110  within the fuel injector  100 . Alternatively, the laser drilling head  124  may embody any other type of drilling head known in the art. The laser drilling head  124  can also include a beam conditioner (not shown) which can be configured to modify a path of the laser beam  122  so that a focus point of the laser beam  122  can execute a circular, elliptical or any other closed loop path. The incident path of the laser beam  122  can form the orifice inner wall  111  which can define an outer periphery of the orifice  110  to be formed using the laser drilling process. 
         [0023]    The beam conditioner of the laser drilling head  124  can be configured to receive the laser beam  122  from the laser source  120 . The beam conditioner also includes an optical element (not shown). The optical element of the beam conditioner can be configured to modify the path of the laser beam  122 . The optical element can be rotatably provided within the beam conditioner. The laser drilling tool  116  can also include a focusing element  126  wherein the laser beam  122  is focused by the focusing element  126  onto the focus point. The laser drilling tool  116  further includes a power supply (not shown) to power the laser drilling tool  116 . 
         [0024]    Further, the laser drilling system  118  can include a platform  128 . The platform  128  can be configured to hold the component, which in the embodiment shown, is fuel injector  100 , during a laser drilling operation. The platform  128 , in one embodiment, can be movable, such that, after the drilling of an orifice  110 , the platform  128  can be moved in order to drill a subsequent orifice  110  on the fuel injector  100 . The platform  128  can be embodied as a multi-axis motion platform, wherein in the illustrated embodiment, the platform  128  is a five-axis motion platform. It should be noted that the laser drilling head  124  and the fuel injector  100  may be configured to be movable in relation to each other. 
         [0025]      FIG. 3  is a detailed schematic view of a portion of the fuel injector  100  being drilled. A sacrificial material  130  is removably positioned in abutting contact with the fuel injector  100 , and more specifically, in abutting contact with the outer surface of the fuel injector  100  defined and shown as the incident end  132  of the fuel injector  100  with respect to the laser beam  122 . In one embodiment, the sacrificial material  130  may be maintained in contact with the fuel injector  100  using a pressure tool  134 , as illustrated in  FIG. 2 . Alternatively, or additionally, a spring elasticity of the sacrificial material  130  may help in maintaining the contact with the fuel injector  100 . Further, the sacrificial material  130  is positioned in alignment with the laser drilling tool  116 . The sacrificial material  130  can be made of a material similar to or, alternatively, different from that of the fuel injector  100 . In one embodiment, the sacrificial material  130  can be made of a metal. In another embodiment, the sacrificial material  130  can be made of a ceramic non-metal. In yet another embodiment, the sacrificial material  130  can be made of a polymer. The sacrificial material  130  can embody a strip, a piece of foil, shim stock, a cap or a pre-shaped geometry. 
         [0026]    As further shown in the detailed schematic view illustrated in  FIG. 3 , the sacrificial material  130  is configured or formed to include a thickness T 1  which corresponds to and/or is proportionate with respect to a radius R 1  of a trumpet effect caused by the laser beam  122 , and more particularly, formed by the path and/or orientation of the laser beam  122  during a laser drilling operation and the formation of the reverse tapered orifice  110  such that the arcuate portion of the path of the laser beam  122  defined and shown in  FIG. 3  as radius R 1  of the trumpet effect is contained within the sacrificial material  130  and the orifice inner wall  111  of the reverse tapered orifice  110  includes a non-curved, or substantially rectilinear reverse tapered profile. The term “trumpet effect” used herein refers to formation of the rounded radius R 1  on and/or through a surface on which the laser beam  122  is incident. Accordingly, the thickness T 1  of the sacrificial material  130  is substantially equivalent to the chord length of the arc defined by radius R 1  of the trumpet effect caused by the laser beam  122 . 
         [0027]    As indicated above, the reverse tapered orifice  110  is formed within the fuel injector  100  via the laser beam  122 , and in a manner consistent with the foregoing, the sacrificial material  130  includes a thickness T 1  sized in corresponding proportion and substantially equivalent with the axial path length of the radius R 1  of the trumpet effect such that the arcuate contour of the trumpet effect is completely contained within the sacrificial material  130  and does not reach the orifice inner wall  111  of the reverse tapered orifice  110  of the fuel injector  100 . 
         [0028]    Moreover, the orifice inner walls  111  of the orifices  110  can be formed via the presently disclosed method and system  118  such that the orifice inner walls  111  include a low surface roughness and increased smoothness. Also, as a result of the transition point in the laser beam  122  path and/or angle at the interface between the sacrificial material  130  and the outer surface or incident end  132  of the fuel injector  100  which can be defined by the thickness T 1  of the sacrificial material  130 , the orifice  110  and the reverse tapered orifice inner walls  111  thereof can be defined by a sharp, un-rounded angle at the fuel exit point  114  (See  FIG. 3 ) of the orifice  110 . The sacrificial material  130  is removed at the end of the laser drilling operation. 
       INDUSTRIAL APPLICABILITY 
       [0029]    The present disclosure relates to the laser drilling system  118  for the drilling of the reverse tapered orifices  110  within the fuel injector  100 . A combination of the trepanning head and the multi-axis platform  128  may allow for the drilling of orifices  110  having inclined inner walls. Also, the laser drilling system  118  may be utilized in achieving an appropriate and desired, specific value of the K factor for the reverse tapered orifices  110 . In one example, the drilling system  118  may be utilized in achieving a K factor for the reverse tapered orifices  110  greater than 4. Additionally, the athermal high pulse frequency of the laser beam  122  allows a very small amount of material removal from the fuel injector  100 , thereby creating the reverse tapered orifices  110  with an improved surface finish wherein the orifice inner walls  111  of the orifice  110  are smooth. 
         [0030]    The laser drilling system  118  of the present disclosure therefore provides surface roughness equal or better than that provided by traditional techniques of extrusion honing and eliminates surface waviness on the surface of the components being drilled. The laser drilling system  118  also eliminates a risk for recast and fatigue crack propagation within the drilled components. Also, the periphery of the orifice  110  defined on a surface of the fuel injector  100  is sharply formed. 
         [0031]    The thickness T 1  of the sacrificial material  130  provided in contact with the fuel injector  100  is proportionate to the radius R 1  of the trumpet effect, as provided above. Hence, the trumpet effect is eliminated from the fuel injector  100 . It should be noted that the laser drilling system  118  disclosed herein is not limited to the application disclosed herein. The disclosure may also be utilized for drilling of the orifices  110  within other components such as, injection meters, fuel filters and so on. 
         [0032]      FIG. 4  is a flowchart for a method  400  of laser drilling the fuel injector  100 . In the illustrated embodiment, the component includes the fuel injector  100 . At step  502 , the sacrificial material  130  is contacted with the fuel injector  100 . The sacrificial material  130  is maintained in contact with the fuel injector  100 , such as, for example, by using the pressure tool  134  or the spring elasticity of the sacrificial material  130 . At step  504 , the laser drilling tool  116  is aligned with the sacrificial material  130  and the fuel injector  100 . At step  506 , the laser beam  122  is incident on the sacrificial material  130 . At step  508 , the trumpet effect caused by the laser beam  122  is contained within the thickness T 1  of the sacrificial material  130 . At step  510 , the reverse tapered orifice  110  is formed within the fuel injector. The reverse tapered orifice  110  includes the smoothened orifice inner wall  111  defining the reverse tapered orifice  110 . At step  512 , the sacrificial material  130  is removed from the fuel injector  100 . 
         [0033]    It will be apparent to those skilled in the art that various modifications and variations can be made to the system of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalent.