Abstract:
A fuel injector of a fuel injecting device that is known is provided with an intensifier piston, which intensifies the pressure of the liquid supplied to the fuel injector from a rail pressure to a higher pressure by hydraulic transmission. The disadvantage is that this type of pressure intensification is very expensive and complicated. In the device according to the present invention, the pressure intensification is simpler and more economical. The present invention provides for at least one electromagnetic pressure intensifier to be provided on at least one fuel injector.

Description:
BACKGROUND INFORMATION  
       [0001]    A device for injecting fuel having at least one fuel injector is described in German Patent Application No. DE 100 50 599. This fuel injector is provided with an intensifier piston, which intensifies the pressure of the liquid supplied to the fuel injector from a rail pressure to a higher pressure by hydraulic transmission. The disadvantage is that this type of pressure intensification is very expensive and complicated. 
         [0002]    It is also known to connect two feed pumps one behind the other in series in order to attain a predetermined pressure in a fuel line and in the fuel injector that is flow-connected to the fuel line. Since the pressure increase produced by the second feed pump is not needed in every operating state, this solution is very expensive. 
       SUMMARY OF THE INVENTION  
       [0003]    The device according to the present invention for injecting fuel has the advantage over the related art that the pressure intensification in the fuel injector is simpler and more economical in that an electromagnetic pressure intensifier is situated on at least one fuel injector. 
         [0004]    It is particularly advantageous that the electromagnetic pressure intensifier is connected immediately upstream from the at least one fuel injector. In this way only a very small volume needs to be brought to a higher pressure, so that little energy is expended to increase the pressure and the pressure increase is attainable in a very short time. 
         [0005]    According to a preferred exemplary embodiment, the electromagnetic pressure intensifier is plugged, clipped, welded, or pressed onto an input channel of the fuel injector. These connections are particularly simple and inexpensive. The electromagnetic pressure intensifier is flow-connected to a fuel line. 
         [0006]    It is also advantageous to use an electromagnetic, piezoelectric, or magnetostrictive fuel injector as the fuel injector. 
         [0007]    In addition, it is advantageous if the electromagnetic pressure intensifier has an electromagnet with an exciter coil and an armature, the armature being operatively connected to a piston which is positioned so that it is axially movable in a pressure chamber of the electromagnetic pressure intensifier, since a pressure intensifier of this sort is of particularly simple construction and may be produced very cost-effectively. 
         [0008]    Additionally advantageous is that the electromagnetic pressure intensifier has an inlet channel that opens into the pressure chamber through an intake port, and that the pressure chamber has an outlet that is flow-connected to an inlet channel of the fuel injector. 
         [0009]    It is also advantageous if the flow connection from the inlet channel to the pressure channel is closable and a pressure increase in the pressure chamber and downstream from the outlet of the pressure chamber is achievable via an axial stroke of the piston. 
         [0010]    A preferred embodiment provides for the flow connection from the inlet channel to the pressure chamber to be closed via a separate valve in the inlet channel, via the piston, or via an interaction of the piston with the armature, followed by attainment of a brief pressure intensification via a stroke of the piston. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0011]      FIG. 1  shows a view of a fuel injector having an electromagnetic pressure intensifier. 
           [0012]      FIG. 2  shows a first exemplary embodiment. 
           [0013]      FIG. 3  shows a second exemplary embodiment of the electromagnetic pressure intensifier. 
       
    
    
     DETAILED DESCRIPTION  
       [0014]      FIG. 1  shows a fuel injector having an electromagnetic pressure intensifier. 
         [0015]    The device according to the present invention has at least one fuel injector  1 , which in the case of direct injection, for example, injects fuel into a combustion chamber of a combustion engine, and in the case of manifold injection injects fuel into a so-called intake manifold of a combustion engine. The at least one fuel injector  1  is flow-connected to a fuel line  2 , for example a fuel rail, through which the at least one fuel injector  1  is supplied with fuel. Fuel injector  1  is designed for example as an electromagnetic, piezoelectric, or magnetostrictive valve, but may explicitly be executed in any way desired. 
         [0016]    A feed unit  3  is provided which is designed for example as a dynamic pump and conveys fuel from a reservoir  4  under elevated pressure into fuel line  2 . 
         [0017]    In order to fulfill the increasingly stringent emission standards, the emissions of an internal combustion engine in a so-called cold start must be reduced. This is accomplished in the related art by increasing the pressure in fuel line  2 , so that the spray produced by fuel injector  1  has a smaller mean droplet size. The requisite pressure increase in fuel line  2  is so high, however, that it cannot be attained by provided feed unit  3 . In the related art an additional second feed unit is therefore connected downstream from feed unit  3 ; it is designed, for example, as a dynamic pump, and increases the pressure in the fuel line to the necessary level, or a higher-performance, more expensive feed unit is utilized. 
         [0018]    To eliminate the costs of this second, more expensive, feed unit, the present invention provides for an electromagnetic pressure intensifier  5  to be situated on the at least one fuel injector  1  to increase the pressure. For example, at least one pressure intensifier  5  is provided on each fuel injector  1 . 
         [0019]    The at least one electromagnetic pressure intensifier  5  is connected directly upstream from the at least one fuel injector  1 , and for example is plugged, clipped, pressed, or welded or the like onto an input channel  8  of fuel injector  1 . In this way, electromagnetic pressure intensifier  5  is firmly connected to fuel injector  1  and situated directly on the latter. 
         [0020]    According to the present invention, the pressure of the fuel is not increased already in fuel line  2 , as in the related art, but just shortly before and/or in fuel injector  1 , via electromagnetic pressure intensifier  5 . The volume within fuel injector  1  is a great deal smaller than the volume of fuel line  2  from reservoir  4  to fuel injector  1 , so that significantly less energy is required to increase the pressure. In addition, the pressure increase is attained faster in injector  1  through the electromagnetic pressure intensifier  5  than through a feed unit  3  situated in fuel line  2 , at a greater distance from fuel injector  1  in terms of the flow connection. 
         [0021]      FIG. 2  shows a first exemplary embodiment of the electromagnetic pressure intensifier. 
         [0022]    In the case of the electromagnetic pressure intensifier according to  FIG. 2 , the parts that remain the same or work the same as in the device according to  FIG. 1  are identified by the same reference numerals. 
         [0023]    For example, electromagnetic pressure intensifier  5  is a re-engineered electromagnetic fuel injector which is executed, for example, as described below. Electromagnetic pressure intensifier  5  has a housing  9  in which an electromagnet  7  having an exciter coil  10  and an axially movable armature  11  is situated. A pressure chamber  14 , in which a piston  15  actuated by electromagnet  7  is situated so that it is axially movable with respect to an axis  12 , is provided in housing  9 . Armature  11 , piston  15 , and/or exciter coil  10  are situated, for example, centered with respect to axis  12 . Over part of its axial length, armature  11  is surrounded ring-like by exciter coil  10 , which is situated in an induction cup  13 . An inlet channel  16  opens via an intake port  17  into pressure chamber  14  of pressure intensifier  5 , for example on the periphery of pressure chamber  14 . Inlet channel  16  is flow-connected upstream to fuel line  2 . Pressure chamber  14  of electromagnetic pressure intensifier  5  is flow-connected to fuel injector  1  via an outlet  18 . 
         [0024]    Piston  15  of electromagnetic pressure intensifier  5  is mechanically coupled with armature  11  and connected to it. Piston  15  is moved by means of a return spring  21  into a first position, in which piston  15  bears against a stop  22  for example, and in which intake port  17  opens into pressure chamber  14 . When no current is flowing through exciter coil  10 , piston  15  is in this first position, thus enabling a dry-running operation. 
         [0025]    If current is applied to exciter coil  10 , armature  11  executes an axial stroke with piston  15 , for example in the direction of fuel injector  1 . According to the first exemplary embodiment, after a first partial stroke, piston  15  covers intake port  17 , thereby closing the flow connection with inlet channel  16 . Intake port  17  may also be closed in any other way desired, for example, by a separate valve in inlet channel  16 . After intake port  17  is closed, the remaining partial stroke of piston  15  produces a pressure increase in pressure chamber  14  and in the part of fuel injector  1  that is flow-connected to outlet  18  of electromagnetic pressure intensifier  5 , since fuel injector  1  is closed at this time and piston  15  is therefore operating on a closed volume of liquid. In this way, pressure intensifier  5  produces a pressure increase in the fuel shortly before the opening of fuel injector  1 . When fuel injector  1  opens after a predefined pressure increase has been reached, at least part of the fuel whose pressure has been increased by electromagnetic pressure intensifier  5  is injected into the combustion chamber or into the intake manifold of the internal combustion engine. The predefined pressure increase is dependent on the particular operating state of the internal combustion engine, and is calculated in each case from parameters of the engine controller in order to open the fuel injector at an optimal point in time. 
         [0026]    For example, housing  9  has an air flow hole  30  in the area of coil  10  in order to ensure pressure equalization. 
         [0027]    After or shortly before or simultaneous with the closing of fuel injector  1 , exciter coil  10  is de-energized, so that piston  15  of electromagnetic pressure intensifier  5  is moved by the force effect of return spring  21  on piston  15  from a second position back to the first position. Since intake port  17  is again open in the first position, liquid flows from inlet channel  16  into pressure chamber  14  and into fuel injector  1  downstream from outlet  18  of electromagnetic pressure intensifier  5 , replacing the quantity of fuel injected in the last injection. 
         [0028]      FIG. 3  shows a second exemplary embodiment of the electromagnetic pressure intensifier. 
         [0029]    In the case of the electromagnetic pressure intensifier according to  FIG. 3 , the parts that remain the same or work the same as in the device according to  FIG. 1  and in the electromagnetic pressure intensifier according to  FIG. 2  are identified by the same reference numerals. 
         [0030]    The second exemplary embodiment of the electromagnetic pressure intensifier differs from the first exemplary embodiment in that inlet channel  16  is closed not by piston  15 , but by an interaction of armature  11  with piston  15 , and that an antechamber  23  is provided between coil  10  and pressure chamber  14  when viewed in the axial direction. Inlet channel  16  does not open into pressure chamber  14 , as in the first exemplary embodiment, but rather into antechamber  23 . Armature  11  and piston  15  are not connected to each other in a single piece in the second exemplary embodiment, but are executed as separate parts which are situated in such a way that they are at least partially movable relative to each other in the axial direction. 
         [0031]    In antechamber  23  a first return spring  21 . 1  is provided, which has one of its ends braced against piston  15  and acts on armature  11  with its other end to return it to its position. A second return spring  21 . 2 , which has one of its ends braced against housing  9  and acts on piston  15  with its other end to return it to its position, is provided in pressure chamber  14 . First return spring  21 . 1  is softer than second return spring  21 . 2 . 
         [0032]    For example, inlet channel  16  is partially formed in armature  11 , and leads centrally with regard to axis  12  into antechamber  23  via at least one intake port  17  provided on armature  11 . Intake port  17  may also be provided on the periphery of antechamber  23 , however, and inlet channel  16  may not be provided in armature  11 , but separately or on housing  9 . 
         [0033]    Armature  11 , piston  15 , and/or coil  10  are situated, for example, centered with respect to axis  12 . Armature  11  has a closing section  24  on its end facing piston  15 , which is spherically shaped, for example. Antechamber  23  is connected to pressure chamber  14  via a connecting orifice  25 . Piston  15  has a pressure chamber inlet  28 , which is situated centered with regard to axis  12  and has on its end facing antechamber  23   a , for example, spherical valve seat  29 . Valve seat  29  of piston  15  cooperates with closing section  24  of armature  11  after a predefined axial stroke of armature  11 , and opens or closes the flow connection between antechamber  23  and pressure chamber  14 . 
         [0034]    When no current is flowing through exciter coil  10 , piston  15  is in the first position against stop  22 , with armature  11  and piston  15  spaced at a distance from each other axially. As a result, when no current is flowing through exciter coil  10  there is a flow connection from antechamber  23  via connecting orifice  25  and pressure chamber inlet  28  of piston  15  into pressure chamber  14 , which is used to fill pressure chamber  14  and fuel injector  1 . 
         [0035]    If current is applied to exciter coil  10 , only armature  11  first executes an axial stroke, for example in the direction of fuel injector  1 . After a first partial stroke of armature  11 , armature  11  strikes valve seat  29  of piston  15  with its closing section  24 , and in this way closes pressure chamber inlet  28 . After a first partial stroke of armature  11 , armature  11  moves piston  15  along with it, so that armature  11  and piston  15  carry out a mutual stroke in the subsequent partial stroke of armature  11 . After pressure chamber inlet  28  is closed, the mutual partial stroke of armature  11  and piston  15  produces a pressure increase in pressure chamber  14  and in the part of fuel injector  1  that is flow-connected to outlet  18  of electromagnetic pressure intensifier  5 , since fuel injector  1  is closed at this time and piston  15  is therefore operating on a closed volume of liquid. When fuel injector  1  opens after a predefined pressure increase has been reached, at least part of the fuel whose pressure has been increased by electromagnetic pressure intensifier  5  is injected into the combustion chamber or into the intake manifold of the internal combustion engine. 
         [0036]    After or shortly before or simultaneous with the closing of fuel injector  1 , exciter coil  10  is de-energized, so that piston  15  and armature  11  execute a mutual return stroke in the direction of stop  22  due to the force effect from second return spring  21 . 2 . After piston  15  has reached stop  22 , armature  11  alone executes an additional return stroke due to the force effect from first return spring  21 . 1 . Due to this motion of armature  11  relative to piston  15 , pressure chamber  28  is again opened, so that liquid flows from inlet channel  16  and/or antechamber  23  into pressure chamber  14  and into fuel injector  1  downstream from outlet  18  of electromagnetic pressure intensifier  5 , and in so doing replaces the quantity of fuel injected in the last injection.