Patent Publication Number: US-2018051666-A1

Title: Rotary needle fuel injector

Description:
FIELD 
     The invention generally relates to fuel injectors, and more particularly to a rotary needle fuel injector. 
     BACKGROUND 
     In some internal combustion engines, a specific fuel injection rate is desired to help achieve the operating targets. For example, modern diesel engines often use injection strategies in order to meet combustion emissions and noise constraints. In a conventional fuel injector, a desired fuel injection rate shape over time is approximated by executing multiple injection pulses at specified times and durations. It can be difficult to achieve a desired injection profile with this approach due to limitations in timing the activation of an injector needle relative to the timing of a combustion process. 
     Conventional fuel injectors for diesel engines include an internal needle which moves linearly within an injector housing. When the needle is positioned against a seat, which acts as a sealing surface on the housing, the fuel that is supplied to the housing is blocked. As the needle moves away from the seat, a pathway past the needle and through one or more nozzle holes is created to a downstream combustion chamber. A pressure difference between the high pressure fuel supply and the combustion chamber drives the fuel through the nozzle holes into the combustion chamber. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     Embodiments of the disclosure are related to systems and methods for a rotary needle fuel injector that achieves a desired injection profile. 
     One embodiment includes a rotary needle fuel injector having a housing including a wall having a non-circular aperture extending through the wall, and a rotatable rod inside the housing and having a bore through which fuel is supplied. The rotatable rod has an aperture communicating with the bore and in selective communication with the non-circular aperture in the housing wall. 
     Another embodiment includes a rotary needle fuel injector having a housing including a wall having a plurality of non-circular apertures extending through the wall, and a rotatable rod inside the housing and having a bore through which fuel is supplied. The rotatable rod has a plurality of apertures communicating with the bore and in selective communication with the non-circular apertures in the housing wall. The non-circular apertures each include an axis of symmetry extending along a direction of rotation of the rotatable rod, an axis of asymmetry perpendicular to the axis of symmetry, and a ratio of a cross-sectional area of a first region of the non-circular aperture to a cross-sectional area of a second region of the non-circular aperture ranges from about 1:10 to about 1:1.5. 
     The details of one or more features, aspects, implementations, and advantages of this disclosure are set forth in the accompanying drawings, the detailed description, and the claims below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a rotary needle fuel injector in accordance with an embodiment of the invention. 
         FIG. 2  is an exploded view of the rotary needle fuel injector of  FIG. 1 . 
         FIG. 3  is an enlarged schematic view of the non-circular aperture of  FIG. 1 . 
         FIG. 4A  is a schematic view of non-overlapping positions of the apertures. 
         FIG. 4B  is a schematic view of partially overlapping apertures. 
         FIG. 4C  is a schematic view of fully overlapping apertures. 
         FIG. 5  is an illustration of fuel flow versus time for a rotary needle fuel injector embodying the present invention and a conventional fuel injector. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments will be described below. Various modifications to the described embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the described embodiments. Thus, the described embodiments are not limited to the embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. 
     An embodiment of a rotary needle fuel injector  100  is shown in  FIGS. 1 and 2 . The rotary needle fuel injector  100  includes a housing  110  having a housing wall  120  including at least one non-circular aperture  130  extending through the housing wall  120 . The housing wall  120  further defines a cavity  170 . The rotary needle fuel injector  100  additionally includes a rotatable rod  140  positioned for rotation inside the cavity  170 . The rod  140  has a bore  150  through which fuel is supplied. The rotatable rod  140  further includes at least one aperture  160  extending through a wall  145  of the rotatable rod  140  and in communication with the bore  150  such that fuel can flow from the bore  150  to the at least one aperture  160 . The at least one aperture  160  in the rod  140  is in selective communication with the at least one non-circular aperture  130  in the housing wall  120  such that when aligned, fuel can flow from the at least one aperture  160  in the rod  140  into and through the at least one non-circular aperture  130  in the housing  110  for injection into a combustion chamber. The rotatable rod  140  may be rotated by an actuator  180  (e.g., a hydraulic, electrical (e.g., piezoelectric), or electromagnetic (e.g., stepper motor) actuator). The actuator  180  may control the rotation of the rotatable rod  140  to within 7 of seconds of arc. 
     The operation of the rotary needle fuel injector  100  results in selective communication of apertures  130 ,  160  to provide the desired injection to the combustion chamber.  FIGS. 1 and 2  illustrate a single row of apertures  160  in the rotatable rod  140  and a single row of apertures  130  in the housing  110 , each row is shown as having five apertures. In other embodiments, the number of rows, the number of holes in each row and the shape of the apertures  160  may change (e.g., single row, plurality of rows, and/or grid). The at least one aperture  160  in the rotatable rod  140  is illustrated as being circular in shape and extends through the wall  145  of the rotatable rod  140 . In other embodiments the at least one aperture  160  in the rotatable rod  140  may be non-circular in shape. During the rotation of the rotatable rod  140 , the aperture  160  enters into selective communication with the non-circular aperture  130 . The selective communication repeats as the rod  140  rotates within the cavity  170 , such that each aperture  160  in the row of apertures  160  in the rotatable rod  140  will selectively communicate with each non-circular aperture  130  in the row of apertures  130  in the housing  110 , as the rod  140  rotates through three hundred sixty degrees of rotation. 
     As illustrated, the size of the non-circular aperture  130  in the housing  110  generally increases in the direction of rotation  190  of the rotatable rod  140 . To state it yet another way, the non-circular aperture  130  in the housing generally increases from a smaller size to a larger size in the direction of rotation  190  of the rotatable rod  140 . As illustrated, the non-circular aperture is tear-drop shaped. Additionally, the cross-sectional shape of the non-circular aperture  130  extending through the housing wall  120  remains substantially constant through the thickness of the housing wall  120 . In other embodiments, the cross-sectional shape of the non-circular aperture  130  may increase in size, and/or decrease in size through the thickness of the housing wall  120 . Furthermore, the shape of each of the non-circular apertures  130  may be the same or different. Additionally, in other embodiments the shape of the at least one aperture  160  in the rotatable rod  140  may be non-circular in shape. 
       FIG. 3  schematically illustrates the non-circular aperture  130  through the housing wall  120 . The non-circular aperture  130  has a length L in the direction of rotation  190 , between a leading distal end  231  and a trailing distal end  232 . The leading distal end  231  overlaps first with the aperture  160  of the rotatable rod  140 , and the trailing distal end  232  is the last point of overlap with the aperture  160  of the rotatable rod  140 . The distal ends  231 ,  232  are spaced apart in the direction of rotation by length L. In the illustrated embodiment, L can be 40 to 300 microns depending on the particular injector application. In other embodiments, the length of the aperture  160  in the direction of rotation  180  may be shorter than 40 microns or longer than 300 microns. Furthermore, the leading and trailing distal ends  231 ,  232  lie on an axis  210  that is parallel to the direction of rotation  190 . The non-circular aperture  130  is symmetrical about the axis  210 , and therefore, the axis  210  is an axis of symmetry. Furthermore, the axis of symmetry  210  is substantially perpendicular to a direction of fuel flow from the bore  150  through the apertures  160  and  130 . 
     The non-circular aperture  130  further defines a mid-point  240  which is defined as halfway between the leading distal end  231  and the trailing distal end  232 . A perpendicular axis  220  runs through the mid-point  240  perpendicular to the axis  210 . The perpendicular axis  220  defines an axis of asymmetry of the aperture  130 . The axis of asymmetry  220  is substantially perpendicular to the direction of fuel flow from the bore  150  through the apertures  160  and  130 . The non-circular aperture  130  further defines a width W in a direction perpendicular to the direction of rotation  190 . The width W corresponds to the widest portion of the non-circular aperture  130  in a direction perpendicular to the direction of rotation  190 . The width W may lie along the axis of asymmetry  220  of the non-circular aperture or may be located elsewhere within the non-circular aperture  130 . In the illustrated embodiment, the width W can be 70 microns to 200 microns. In other embodiments, the widest section or width W of the non-circular aperture  130  in the direction perpendicular to the direction of rotation  190  may be outside of the previous range. The region of the aperture  130  between the leading distal end  231  and the perpendicular axis  220  is defined as a first region  250 . The region between the trailing distal end  232  and the perpendicular axis  220  is defined as a second region  260 . A ratio of the area of the first region  250  to the area of the second region  260  may be 1:50 to 1:1.3. In other embodiments, the ratio of the area of the first region  250  to the area of the second region  260  may be 1:10 to 1:1.5. 
     The specific shape of the non-circular aperture  130  may be chosen to determine the rate at which a cross-section of the non-circular aperture  130  in selective communication with the aperture  160  changes for each unit of arc of rotation of the rotatable rod  140 . This allows for the fine tuning of the fuel injection rate profile. As an alternative to the illustrated tear-drop shape, the non-circular aperture  130  may include one or more other non-circular shapes (e.g., oval, ovoid, ellipse, triangle, parallelogram, rhombus, rectangle, square, diamond, and combinations thereof). The specific shape can be customized to achieve the desired injection rate profile. 
     During the operation of the rotary needle fuel injector  100 , the apertures  130 ,  160  are in varying degrees of overlap.  FIGS. 4A, 4B and 4C  illustrate the overlap of the apertures  130  and  160  during the rotation of the rotatable rod  140 .  FIG. 4A  illustrates no overlap between the non-circular aperture  130  and the aperture  160  resulting in no fuel flow through the rotatory needle fuel injector  100  (or at least through the illustrated apertures  130 ,  160 ). As the rotatable rod  140  rotates such that the apertures  130  and  160  partially overlap, as shown in  FIG. 4B , fuel flows through the rotary needle fuel injector  100 . To allow the maximum fuel flow through the rotary needle fuel injector  100 , the rotatable rod  140  is positioned to allow the complete overlap of the non-circular aperture  130  and the aperture  160  as shown in  FIG. 4C . Furthermore, in order to allow the maximum fuel flow through the rotary needle fuel injector  100  the diameter of the circular aperture  160  in the rod  140  is greater than or equal to the larger of the length dimension L of the non-circular aperture  130  in the direction of rotation  190  or the width dimension W of the non-circular aperture  130  in a direction perpendicular to the direction of rotation  190 . 
       FIG. 5  illustrates a fuel injection rate profile  400  of an embodiment of a rotary needle fuel injector  100  versus a conventional pulsed injection profile. A conventional needle type fuel injector relies on a series of pulsed injections of fuel in order to provide the actual fuel injection rate  410  to the engine. The series of pulses is limited by the rate in which the needle of the needle type fuel injector can be actuated. The combination of the shape of the non-circular aperture  130 , the size and shape of the aperture  160  in the rod  140 , and the rotation of the rotatable rod  140  can be coordinated to provide the desired, uninterrupted fuel injection profile to the engine  420 . Uninterrupted fuel injection may result in more precisely controlled engine output and/or an increase in the rate of engine responsiveness to a driver&#39;s input, as compared to conventional fuel injectors. 
     The apertures  130 ,  160  of the rotary needle fuel injector  100  may be formed using various computer-controlled manufacturing techniques (e.g., laser drilling). Techniques such as computer-controlled laser drilling allow for the aperture shapes/profiles to be customized based on the performance requirements of the engine. Control of the aperture shapes/profiles through the thickness of the housing wall  110  and the rod wall  145  allows the volume and/or turbulence of the fuel flow through the injector  100  to be customized. 
     It is believed that embodiments described herein and many of their attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely explanatory, and it is the intention of the following claims to encompass and include such changes.