Abstract:
A fuel injection valve for an internal combustion engine includes an armature assembly including an injector needle reciprocable between a closed position and an open position; a needle seat for receiving the injector needle in the closed position, the needle seat including a central opening therethrough; a discharge orifice disk disposed downstream of the needle seat, the discharge orifice disk directing fuel toward a desired location; and a turbulence generator disposed upstream of the discharge orifice disk.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates in general to electromagnetic fuel injectors for internal combustion engines and, in particular, to the generation of fuel turbulence in such fuel injectors. 
     Increasingly stringent exhaust emission standards have driven the automotive industry to discover ways of achieving more complete combustion and thereby lower emissions. One way of achieving more complete combustion is by using fuel injectors with improved fuel atomization. 
     Fuel injectors typically comprise an electromagnetically actuated needle valve disposed in a fuel volume. The needle valve is reciprocated axially within the fuel volume in response to energization and deenergization of an actuator to selectively open and close a flow path through the fuel injector. Particularly, the valve body or housing defining the fuel volume has an aperture or orifice at one end forming a seat for the end of the needle valve whereby its reciprocating motion enables an intermittent flow of fuel through the orifice. Typically, the fuel emitted from a fuel injector is atomized downstream of the orifice to provide the necessary fuel/air mixture in the combustion chamber of the engine. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a fuel injector with improved atomization. 
     This and other objects of the invention are achieved by a fuel injection valve for an internal combustion engine comprising an armature assembly including an injector needle reciprocable between a closed position and an open position; a needle seat for receiving the injector needle in the closed position, the needle seat including a central opening therethrough; a discharge orifice disk disposed downstream of the needle seat, the discharge orifice disk directing fuel toward a desired location; and a turbulence generator disposed upstream of the discharge orifice disk. 
     The discharge orifice disk defines at least one opening therein for directing fuel toward the desired location. 
     In one embodiment, the turbulence generator comprises a first turbulence generator disk having a central opening smaller than the central opening in the needle seat and a second turbulence generator disk having a central opening at least as large as a diameter of a circle containing the at least one opening in the discharge orifice disk, the first turbulence generator disk disposed downstream of the needle seat and the second turbulence generator disk disposed downstream of the first turbulence generator disk. 
     In a second embodiment, the central opening in the needle seat is smaller than a diameter of a circle containing the at least one opening in the discharge orifice disk and the turbulence generator comprises a turbulence generator disk having a central opening at least as large as the diameter of the circle containing the at least one opening in the discharge orifice disk and wherein the turbulence generator disk is disposed downstream of the needle seat. 
     In a third embodiment, the turbulence generator comprises a first turbulence generator disk having a plurality of openings therein, the plurality of openings being aligned such that, when viewed in a longitudinal direction of the fuel injector, the plurality of openings at least partially overlap the at least one opening in the discharge orifice disk, and a second turbulence generator disk having a central opening at least as large as a diameter of a circle containing the at least one opening in the discharge orifice disk, the first turbulence generator disk disposed downstream of the needle seat and the second turbulence generator disk disposed downstream of the first turbulence generator disk. 
     In a fourth embodiment, the central opening in the needle seat is smaller than a diameter of a circle containing the at least one opening in the discharge orifice disk and the turbulence generator comprises a counterbore in the needle seat, the counterbore having a diameter at least as large as the diameter of the circle containing the at least one opening in the discharge orifice disk wherein the counterbore is downstream of the central opening in the needle seat. 
     Further objects, advantages and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is an enlarged sectional view of the bottom portion of one embodiment of a fuel injector according to the present invention. 
     FIG. 2 is an enlarged sectional view of the bottom portion of a second embodiment of a fuel injector according to the present invention. 
     FIG. 3 is an enlarged sectional view of the bottom portion of a third embodiment of a fuel injector according to the present invention. 
     FIG. 4 is an enlarged sectional view of the bottom portion of a fourth embodiment of a fuel injector according to the present invention. 
     FIGS. 5-11 schematically show the relationship between various size openings in the turbulence generator and the openings in the discharge orifice disk of a fuel injector according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is directed toward fuel injectors with improved fuel atomization as a means of achieving more complete combustion and thereby lower emissions. In general, the invention uses a turbulence generator upstream of the fuel injector discharge orifice disk to increase turbulence and thereby achieve finer atomization. 
     FIGS. 1-4 are enlarged sectional views of the bottom portion of fuel injectors according to the present invention. In FIGS. 1-4, like reference numerals refer to like features. 
     FIG. 1 shows a first embodiment of a fuel injector  30  according to the present invention. The fuel injector  30  includes a housing  34 , an injector needle  32 , a needle seat  36 , a needle seat central opening  40 , a discharge orifice disk  42 , at least one opening  44  in the discharge orifice disk  42 , a backup washer  38  and a turbulence generator in the form of a turbulence generator disk  46 . The discharge orifice disk  42  may have one, two, three, four or more openings  44 . 
     When the needle  32  is lifted, fuel flows through the central opening  40  of the seat  36  and through the at least one opening  44  of the discharge orifice disk  42 . The discharge orifice disk directs the fuel toward a desired location. The turbulence generator disk  46  is sandwiched between the discharge orifice disk  42  and the needle seat  36 . The backup washer  38  maintains the discharge orifice disk  42  and turbulence generator disk  46  in place. The housing  34  has a crimp  35  which holds the backup washer  38  in place. 
     In one preferred embodiment, the discharge orifice disk  42  includes four openings  44  of equal size in the shape of circles. The openings  44  are preferably equally spaced around the center of the discharge orifice disk  42 . 
     In the embodiment shown in FIG. 1, the step  45  created between the central opening  40  of the seat  36  and the opening in the turbulence generator disk  46  generates turbulence in the fuel flowing towards the discharge orifice disk  42 . The increased turbulence of the fuel increases atomization of the fuel and thereby increases combustion efficiency. The step  45  is created by making the diameter of the central opening  40  in the seat  36  smaller than the diameter of a circle containing the four openings  44  of the discharge orifice disk. 
     In the embodiment shown in FIG. 1, the turbulence generator disk  46  does not obstruct the flow of fuel through the openings  44  in the discharge orifice disk  42 . That is, the central opening of the turbulence generator disk  46  is at least as large as the diameter of a circle containing the four openings  44  in the discharge orifice disk  42 . Therefore, the disk  46  provides a fuel flow path to the openings  44 . 
     FIG. 2 shows a second embodiment of a fuel injector  31  according to the present invention. In FIG. 2, the turbulence generator comprises a first turbulence generator disk  47  disposed downstream of the needle seat  37  and a second turbulence generator disk  48  disposed downstream of the first turbulence generator disk  47 . To provide a fuel path through the openings  44  of the discharge orifice disk  42 , the second turbulence generator disk  48  has a central opening at least as large as a diameter of a circle containing the four openings  44  of the discharge orifice disk  42 . In addition, the central opening  40  in the seat  37  is at least as large as the diameter of a circle containing the four openings  44  in the discharge orifice disk  42 . The first turbulence generator disk  47  has a central opening smaller than the central opening  40  in the needle seat  36 . Therefore, the first turbulence generator disk  47  provides a step or obstruction in the way of the fuel flow. The step  49  created by the disk  47  increases turbulence in the fuel flow and, thereby, increases fuel atomization and improves combustion efficiency. 
     FIG. 3 shows a third embodiment of a fuel injector  53  according to the present invention. The embodiment of FIG. 3 is similar to the embodiment of FIG. 2 except that the first turbulence generator disk  50  is different. In FIG. 3, the perimeter of the central opening of the first turbulence generator disk  50  is bent or angled upstream. The angled portion  51  juts out into the fuel stream and generates turbulence. 
     FIG. 4 shows a fourth embodiment of a fuel injector  55  according to the present invention. In FIG. 4, there are no separable turbulence generator disks. The central opening  40  of the needle seat  52  is smaller than a diameter of a circle containing the four openings  44  of the discharge orifice disk  42 . Directly below the central opening  40  in the seat  52 , the seat  52  includes a counterbore  54 . A diameter of the central opening in the counterbore  54  is at least as large as the diameter of a circle containing the four openings  44  of the discharge orifice disk  42 . Therefore, the counterbore  54  provides a flow passage for the fuel to the discharge orifice disk. The step  56  created by the counterbore  54  generates turbulence in the fuel. 
     The turbulence disks may be made of, for example, 302 stainless steel. 
     FIGS. 5-8 schematically represent different sizes of the central opening  40  in the needle seat  36  or, alternatively, the central opening in the first turbulence generator disk  47 , in relation to the openings  44  in the discharge orifice disk  42 . The solid line  60  in FIGS. 5-8 represents either the central opening  40  in the seat  36  or the central opening in the first turbulence generator disk. The dotted lines in FIGS. 5-11 represent the four openings  44  in the discharge orifice disk  42 . 
     In embodiments where the circle  60  represents the opening in the first turbulence generator disk  47 , it should be understood that a second turbulence generator disk  48  must be inserted between the first turbulence generator disk and the discharge orifice disk. The second turbulence generator disk would have an opening at least as large as a circle containing the four openings  44  of the discharge orifice disk  42  to provide a fuel flow path to the openings  44 . In embodiments where the circle  60  represents the needle seat central opening  40 , it will be understood that downstream of the central opening  40 , either the seat is counterbored to a diameter to provide free flow through the openings  44  or a turbulence generator disk is inserted below the seat wherein the turbulence generator disk has a central opening to provide a free flow of fuel through the openings  44 . 
     As shown in FIG. 5, only a small portion of the openings  44  in the discharge orifice disk  42  are masked. In FIGS. 6 and 7, increasingly larger amounts of the openings  44  are masked. In FIG. 8, the openings  44  are completely masked. In general, the greater the amount of masking, the greater the amount of turbulence that is generated. 
     The present invention also contemplates a turbulence generator disk having a plurality of openings rather than a single central opening. FIGS. 9-11 schematically show embodiments of the invention wherein the first turbulence generator disk includes a plurality of openings. In FIG. 9, the plurality of openings  66  formed in the first turbulence generator disk are aligned such that, when viewed in a longitudinal direction of the fuel injector, the plurality of openings  66  at least partially overlap the four openings  44  in the discharge orifice disk  42 . It will be understood that in each of the embodiments shown in FIGS. 9-11, a second turbulence generator disk disposed downstream of the first turbulence generator disk has a central opening at least as large as a diameter of a circle containing the four openings  44  in the discharge orifice disk  42  so that a free fuel flow path is established. 
     The embodiment of FIG. 10 is similar to the embodiment of FIG. 9 in that the openings  68  in the first turbulence generator disk have a reniform shape but are somewhat “slimmer” than in FIG.  9 . 
     In the embodiment shown in FIG. 11, the openings  70  in the first turbulence generator disk are aligned such that, when viewed in a longitudinal direction of the fuel injector, the openings  70  do not overlap at all the four openings  44  in the discharge orifice disk  42 . 
     In the embodiments shown in FIGS. 9-11, center lines of the four openings  66 ,  68 ,  70 , respectively, of the first turbulence generator disk define a circle such that, when viewed in a longitudinal direction of the fuel injector, the circumference of the circle overlaps the center points of the four openings  44  in the discharge orifice disk  42 . FIGS. 9-11 show four openings  66 ,  68 ,  70  having a generally reniform shape, however, it will be understood that less than four or more than four openings may be used and the openings may assume a variety of shapes. The test for a successful turbulence generator is that it generates turbulence in the fuel prior to fuel discharge through the discharge orifice disk  42 . 
     While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the invention, as defined in the appended claims and equivalents thereof.