Patent Publication Number: US-6698674-B2

Title: Fuel injector valve

Description:
FIELD OF THE INVENTION 
     The present invention relates to a fuel injector. 
     BACKGROUND INFORMATION 
     A fuel injector which has a valve needle operated by an actuator is already known. The actuator includes, for example, an electromagnetic coil or a piezoelectric element. An example of a fuel injector of this type is described in German Patent 35 40 660 C2. This fuel injector is capable of being actuated electromagnetically. The fuel injector has a valve housing containing a magnetic coil installed on a field spool. The valve needle combines with a valve-seat surface to form a sealing seat. The end of the valve needle facing the magnetic coil is permanently connected to an armature. Armature and valve needle are moved against the sealing seat by a restoring spring. If a voltage is applied to the magnetic coil, and a current subsequently flows through it, the armature is attracted to the force of the restoring spring by the magnetic field created and it lifts the valve needle off its sealing seat. The fuel can now exit through the injection bore downstream from the valve seat. 
     The disadvantage of this known fuel injector is the fact that the fuel distribution and quantity can only be controlled to a limited extent. The direction in which the fuel exits the fuel injector is determined by the orientation of the injection bore. An adaptation to various operational conditions, such as is necessary in the case of the lean-burn concepts and stratified-charge methods in combination with direct injection into the combustion chamber in particular, is very difficult or not possible at all. 
     From German Patent 40 23 233 A1 a fuel injector is known, which has, at its combustion-chamber end, two hole circles made up of injection bores. In order to be able to separately control the two hole circles, the fuel injector has two coaxial valve needles in one nozzle body. In the region of the combustion-chamber side end sections of the two valve needles, there is also a separating sleeve installed between the two valve needles, whose end face cooperates with one valve seat surface, common to the valve seat surfaces of the two valve needles. The two hole circles are supplied with fuel—along the valve needles—by individual fuel intakes, with each of the two fuel intakes having its own fuel injection pump. This makes it possible to configure the flow rate and orientation of the injection bores of the two hole circles differently from one another and, therefore, control the direction and quantity of fuel injection to a certain degree by triggering the two valve needles separately. The disadvantage, however, is the overall multicomponent design, since three high-precision components—the two valve needles and the separating sleeve—must be manufactured in such a way as to ensure the most precise fit possible, and the fact that it is necessary to provide two fuel injection pumps, or one fuel injection pump doing double duty for each fuel injector. This results in additional costs. Another disadvantage is that there are a total of three sealing seats—one for the first valve needle, second for the second valve needle, and third for the separating sleeve. Furthermore, it is also disadvantageous that triggering occurs purely hydraulically, and no individual regulation based on a characteristic map is possible to the extent possible, in the case of a fuel injector controlled by an actuator. 
     From published German Patent Application 27 11 391 A1 a fuel injector is known that has two valve needles. Both valve needles are acted upon in the closing direction by one spring each and cooperate with one valve seat surface each to form a sealing seat. Different injection orifices are opened by the two valve needles. Control of the valve needles is purely hydraulic, with the opening sequence being determined by the varying spring force of the two valve needle closing springs. An adaptation to performance data of an internal combustion engine—as is typically possible with an actuator-controlled fuel injector—is therefore not feasible. 
     SUMMARY OF THE INVENTION 
     The fuel injector according to the present invention has the advantage over the related art that a fuel distribution in the combustion chamber is possible, which adapts to the requirements of the characteristics map and especially to a lean-burn concept. 
     In particular, the angle under which the fuel is distributed in the spray pattern of the fuel injector, is changeable. This is possible with the fuel injector according to the present invention due to the design using two valve needles, each of which is operated by its own actuator. Moreover, actuation via one actuator at a time, makes the fuel injector easily adaptable to a characteristics map of the internal combustion engine. 
     With this invention it is possible to actuate two different hole circles containing injection bores by the two sealing seats of the two valve needles in an advantageous manner. 
     The injection bores of the different hole circles may have, in particular, different injection angles and be offset against each other. This is also advantageous since, in the case of a small injection quantity and engine load, it is possible to initially actuate only one valve needle, so that a first hole circle is opened. This invention also has, for example, a narrow injection angle of the injection bores, so that a fuel injector jet, made up of the fuel jets of the individual injection bores, is formed having an overall narrow angle range. At a higher load of the internal combustion engine and corresponding demands, during stratified-charge operation, of an internal combustion engine using the lean-burn concept, the second valve needle is lifted off the sealing seat as well. This now also opens up the second hole circle of injection bores. These bores may have a larger injection angle. Thus with this invention the total spray of fuel injected is supplied in a greater angular range. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a section through a generic fuel injector having an actuator-operated valve needle. 
     FIG. 2 shows a detail cutaway view of a first embodiment of a fuel injector according to the present invention. 
     FIG. 3 shows a detail cutaway view of a second embodiment of a fuel injector according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     Before describing two embodiments of a generic fuel injector in more detail, based on FIGS. 2 and 3, an already-known fuel injector, serving as an example of a fuel injector having an actuator, is briefly explained regarding its essential components, using FIG.  1 . 
     Fuel injector  1  is configured as a fuel injector for fuel injection systems of mixture-compressing, externally-ignited internal combustion engines. Fuel injector  1  is suited in particular for direct injection of fuel into a combustion chamber (not shown) of an internal combustion engine. 
     Fuel injector  1  has a nozzle body  2 , which guides a valve needle  3 . Valve needle  3  is mechanically linked to a valve closing body  4 , which cooperates with a valve seat surface  6  situated on a valve seat body  5 , to form a sealing seat. Fuel injector  1  in the example of this embodiment is a fuel injector  1  opening toward the inside and having an injection bore  7 . Nozzle body  2  is sealed against stationary pole  9  of a magnetic coil  10  (which acts as an actuator here) by seal  8 . Magnetic coil  10  is encapsulated in a coil housing  11  and wound onto a field spool  12  adjacent to an internal pole  13  of magnetic coil  10 . Internal pole  13  and stationary pole  9  are separated by a clearance  26  and are supported by a connecting component  29 . Magnetic coil  10  is energized via line  19  by an electric current feedable via an electric plug-in contact  17 . Plug-in contact  17  is enclosed by a plastic sheathing  18 , which may be sprayed onto internal pole  13 . 
     Valve needle  3  is situated in a valve needle guide  14  configured as a disk. Lift adjustment is carried out by paired adjusting disk  15 . On the other side of adjusting disk  15  is armature  20 . This is connected in a friction-locked manner via flange  21  to valve needle  3 , which is connected to flange  21  via weld  22 . Flange  21  supports a restoring spring  23  which, in the present design of fuel injector  1 , is preloaded by a sleeve  24 . Valve needle guide  14 , armature  20 , and valve seat body  5  contain fuel channels  30   a  through  30   c , which direct the fuel, which is supplied via a central fuel feed  16  and filtered by filter element  25 , to injection bore  7 . Fuel injector  1  is sealed by seal  28  against a cylinder head (not shown in detail) or a fuel distributor. 
     In the rest state of fuel injector  1 , armature  20  is acted upon by restoring spring  23  against its lift direction in such a way that valve closing body  4  is held tightly on valve seat  6 . When magnetic coil  10  is energized, it builds up a magnetic field that moves armature  20  against the force of restoring spring  23  in the direction of lift, with the lift being defined by working clearance  27  at rest between internal pole  12  and armature  20 . Armature  20  takes along flange  21 , welded to valve needle  3 , also in lift direction. Valve closing body  4 , which is mechanically linked to valve needle  3 , lifts off the valve seat surface, and fuel is supplied via injection bore  7 . 
     When the coil current is turned off, armature  20 , after sufficient reduction of the magnetic field, drops off the internal pole  13  due to the pressure of restoring spring  23 , thus causing flange  21 , which is mechanically linked to valve needle  3 , to move against the direction of the lift. This also moves the valve needle  3  in the same direction, thus causing the valve closing body  4  to rest on valve seat surface  6  and fuel injector  1  to close. 
     FIG. 2 shows the combustion chamber side segment of a fuel injector  31  according to the present invention, along with the lower segment of a valve body  32 . A valve seat body  33  is connected to valve body  32  via a circumferential weld  34 . A first valve needle  35  which, in the embodiment presented here, is connected to a valve closing body  36  in one piece and configured as a hollow cylinder, acts together with a valve seat surface  37  to form an outer sealing seat  38 . A second solid valve needle  39  which, in its segment facing the combustion chamber, is also configured as a one-piece valve closing body  40 , cooperates with a second valve seat surface  41 , which in turn is formed in valve seat body  33 , to form a second inner sealing seat  42 . Second valve needle  39  is situated in an inner longitudinal opening  64  of the first valve needle  35 . 
     Valve seat body  33  has an inner guide opening  65 , in which first valve needle  35  and its valve closing body  36  are guided. Adjacent to a fuel chamber  43 , outside of the first valve needle  35  and its valve closing body  36 —in relation to center axis  45 —is a fuel inlet  44  (indicated here by an arrow) to first or outer sealing seat  38 . This fuel inlet  44  is created, for example, by bevels at the outer circumference of valve closing body  36 , so that the fuel in the inner guide opening  65  is able to flow downstream. A first outer hole circle  46  of injection bores is situated in valve seat body  33 . A second inner hole circle  47  of injection bores is also situated in valve seat body  33 . In the embodiment selected here, the injection bores of first hole circle  46  have a smaller angle relative to center axis  45  than the injection bores of second hole circle  47 . The injection bores of both hole circles  46 ,  47  may be offset by a circumferential angle (not visible in the representation selected here), so that the fuel jet of one injection bore sprays into the space between two injection bores of the other hole circle. 
     First hole circle  46  is situated within first or outer sealing seat  38  in relation to center axis  45 . Accordingly, second hole circle  47  is situated within second sealing seat  42  in relation to center axis  45 . When both valve needles  35 ,  39  along with their valve-closing bodies  36 ,  40  rest on their respective sealing seats  38 ,  42 , hole circles  46 ,  47  are sealed off from fuel inlet  44 . When first valve needle  35  and its valve-closing body  36  are lifted off their first sealing seat  38 , a connection between fuel inlet  44  and first hole circle  46  is established. 
     The injection bores of first hole circle  46  have a smaller angle in relation to center axis  45 . This creates, in the combustion chamber, a narrow fuel injection jet, which widens under a narrow angle. Second hole circle  47  is separated from fuel inlet  44  by a second valve needle  39  having second valve closing body  40 , which still rests on second sealing seat  42 , separated from fuel inlet  44 . Should a further widening fuel injection jet be desired, second valve needle  39  with its valve closing body  40  may be lifted from its second sealing seat  42  by a second actuator, which is not shown here. This opens up a connection from fuel inlet  44  and finally from fuel chamber  43  to second hole circle  47  as well. The fuel injection jet is now supplemented by the fuel that is injected through the injection bores of second hole circle  47  under a wider angle in relation to center axis  45 , which results in a widening of the fuel injection jet. 
     FIG. 3 shows an alternative embodiment according to the present invention in a cutaway view of the segment of fuel injector  48  facing the combustion chamber. A valve seat body  50  is situated in a valve body  49  and connected to it by a weld  51 . Weld  51 , for example extends in a circle around center axis  61 . 
     A first hollow cylindrical valve needle  52 , whose segment facing the combustion chamber is configured as one-piece valve closing body  53 , cooperates with a first valve seat surface  54 , situated in valve seat body  50 , to form a first inner sealing seat  55 . A second hollow cylindrical valve needle  56 , whose segment facing the combustion chamber is configured as one-piece valve closing body  57 , cooperates with a second valve seat surface  58  of valve seat body  50  to form a second outer sealing seat  59 . In contrast to the embodiment shown in FIG. 2, the designations of first and second valve needle are reversed in the case of the embodiment shown here. Second valve needle  56  has an inner longitudinal opening  66  which houses first valve needle  52 . 
     In this embodiment, the fuel reaches the first inner sealing seat  55  through fuel feed or inlet  60 , configured as inner bore of first valve needle  52 , instead of through outer fuel inlet  44 . The inflow of the fuel is indicated by arrow in fuel feed  60 . A first inner hole circle  62  of injection bores is situated outside of first sealing seat  55  in valve seat body  50 , in relation to center axis  61 . A second outer hole circle  63  of injection bores is situated outside of second sealing seat  59 , in relation to center axis  61 . First sealing seat  55  seals off first hole circle  62  from fuel feed  60 , and first sealing seat  55  as well as second sealing seat  59  seal off second hole circle  63  and its injection bores from fuel feed  60 . The designations of the two hole circles as first hole circle  62  and second hole circle  63  are also reversed compared to the respective hole circles in FIG.  2 . 
     As already described in FIG. 2, first hole circle  62  is connected, accordingly, to fuel feed  60 , when first valve needle  52  along with its valve closing body  53  is lifted off first sealing seat  55 . A fuel injection jet is injected into the combustion chamber (not shown here). The fuel injection jet is configured depending on the angle and placement of the injection bores of first hole circle  62 . Should a different configuration of the fuel injection jet be required to correspond to a certain operating point in the characteristics map of the internal combustion engine, second valve needle  56 , which is completely independently triggerable by an actuator (not shown here), can additionally be lifted, together with its valve closing body  57 , off second sealing seat  59  and open up fuel feed  60  to second hole circle  63 . 
     The angular orientation and placement of the injection bores of first hole circle  62  and second hole circle  63  are only used as examples in the embodiment shown here in FIG. 3 and, correspondingly, in the embodiment in FIG.  2 .