Abstract:
An injection nozzle for internal combustion engines is proposed, having a nozzle needle  7  and a second nozzle needle  27;  the first nozzle needle  7  and the second nozzle needle  27  can be triggered independently of one another. The second injection nozzle is opened by lowering the pressure of a hydraulic fluid in a control chamber  37.  By this means, the injection quantity per unit of time and the atomization of the fuel in the combustion chamber can be varied over wide ranges, and moreover a shaping of the injection course can be performed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based on 35 USC 371 application of PCT/DE 01/04338 filed on Nov. 17, 2001; and a continuation of U.S. Ser. No. 10/181,771. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to an injection nozzle for internal combustion engines, having a nozzle body, wherein the nozzle body has at least one first injection port and at least one second injection port, having a first nozzle needle, embodied as a hollow needle and guided in a guide bore of the nozzle body, having a second nozzle needle disposed coaxially to the first nozzle needle, wherein with the first nozzle needle, the injection of fuel through the at least one first injection port is controllable, and with the second nozzle needle the injection of fuel through the at least one second injection port is controllable.  
         [0004]     2. Description of the Prior Art  
         [0005]     In the above injection nozzle, known from German Patent Disclosure DE 42 14 646 A1, the two nozzle needles are each triggered via a respective high-pressure fuel pump.  
       SUMMARY AND OBJECTS OF THE INVENTION  
       [0006]     The object of the invention is to furnish an injection nozzle which is more variable with respect to injection course shaping and fuel atomization and which thus makes internal combustion engines possible that are more economical in fuel consumption, have lower emissions, and are quieter. Moreover, the injection nozzle of the invention should be economical to produce and should be usable without major modifications at the cylinder head of the engine. Finally, the injection systems equipped with the injection nozzles of the invention should also be more economical than known systems of the same variability.  
         [0007]     This object is attained according to the invention by an injection nozzle for internal combustion engines, having a nozzle body, wherein the nozzle body has at least one first injection port and at least one second injection port, having a first nozzle needle, embodied as a hollow needle and guided in a guide bore of the nozzle body, having a second nozzle needle disposed coaxially to the first nozzle needle, wherein with the first nozzle needle, the injection of fuel through the at least one first injection port is controllable, and with the second nozzle needle the injection of fuel through the at least one second injection port is controllable, and wherein a pressure force in the closing direction of the second nozzle needle can be exerted on the second nozzle needle by a hydraulic fluid from a located in a control chamber.  
         [0008]     In the injection nozzle of the invention, the at least one first injection port can be triggered in a simple way independently from the at least one second injection port. This creates the possibility of opening only the at least one first injection port at certain operating points of the engine upon injection, so that the fuel quantity to be injected can be injected into the combustion chamber through a relatively small injection port cross section. As a result,. first, smaller fuel injection quantities can be injected with greater precision, and second, the fuel injected into the combustion chamber through the at least one first injection port at high speed is better distributed, which has a favorable effect on the efficiency, emissions, and noise of the engine.  
         [0009]     In an alternative mode of operation, the at least one second injection port can be opened immediately after the opening of the first injection port, or after a freely selectable time lag, so that a large quantity of fuel can be injected into the combustion chamber in the briefest possible time through the first and second injection ports. Because of the time lag between the opening of the first injection ports and the second injection ports, the injection course can be freely shaped over a wide range. This has advantages in terms of efficiency, the noise produced, and the emissions of the engine.  
         [0010]     Moreover, for triggering the second nozzle needle, a second high-pressure fuel pump is not needed. Instead, a simple, economical pressure supply suffices, for instance from the oil pump of the engine. Furthermore, the second nozzle needle can be triggered more simply and precisely, since for opening the second nozzle needle, the pressure in the control chamber need merely be lowered.  
         [0011]     Because the second nozzle needle is disposed inside the first nozzle needle, the injection nozzle of the invention takes up no more installation space than an injection nozzle of the prior art and accordingly makes do without miniaturized components, which has a favorable effect on both production costs and mass production.  
         [0012]     In a variant of the invention, it is provided that a control chamber that can be subjected to a control pressure is present in the nozzle body, and that a second nozzle spring acting on the second nozzle needle and disposed in the control chamber is present, so that the second nozzle needle is pressed into its closing direction by the second nozzle spring, and the closing force, which is composed of the spring force of the second nozzle spring and the pressure force resulting from the control pressure in the control chamber, can be controlled within wide limits and with high chronological resolution by controlling the control pressure.  
         [0013]     To make production and installation upon assembly of the injection nozzle of the invention simpler, the nozzle body is in multiple parts and has both an intermediate ring and a nozzle holder body, and/or a guide bush is provided in the guide bore; the guide bush can also serve as a stroke stop for the second nozzle needle. Using a guide bush is advantageous, for among other reasons, especially because the guide bush can be made of more wear-resistant material, and if the guide bush wears, only the guide bush has to be replaced, rather than the entire injector.  
         [0014]     In a further embodiment of the invention, the intermediate ring acts as a stroke stop for the first nozzle needle, so that the stroke of the first nozzle needle can be set with great precision.  
         [0015]     In another embodiment of the invention, a control piston is guided in the guide bush; the control piston defines the control chamber and transmits the pressure force, resulting from the control pressure in the control chamber, to the second nozzle needle, so that the area of the end face of the control piston can be selected independently of the diameter of the guide bore.  
         [0016]     To simplify installation and calibration, it can be provided that the first nozzle spring is braced at least indirectly, for instance via an adjusting shim, via the guide bush or directly on the nozzle body ( 1 ). The guide bush can also serve as a stroke stop for the second nozzle needle, so that the stroke of the second nozzle needle is limited.  
         [0017]     In a further feature of the invention, a pressure bolt is provided between the first nozzle spring and the first nozzle needle; the pressure bolt transmits the closing force of the first nozzle spring to the first nozzle needle, which makes for a compact, simple design.  
         [0018]     If, as provided in a further advantageous feature of the invention, the pressure bolt serves as a stroke stop for the second nozzle needle, then the stroke stop for the second nozzle needle can be adjusted more precisely, since the axial spacing between the second sealing cone and the stroke stop is very short. Moreover, the second nozzle needle is closed simultaneously with the first nozzle needle, thus avoiding undesired after injections of fuel into the combustion chamber through the second injection ports.  
         [0019]     It can additionally be provided that the pressure bolt is guided by the nozzle body, and in particular the intermediate ring of the nozzle body, and/or that the pressure bolt at least partly takes on the guidance of the second nozzle needle, thus further improving production, installation and function.  
         [0020]     In another exemplary embodiment of the invention, the second nozzle needle is embodied in two parts, thus simplifying production and installation.  
         [0021]     In another feature of the invention, the cross section of the at least one first injection port and the cross section of the at least one second injection port are equal in size, so that at all operating points, good atomization of the fuel in the combustion chamber is obtained. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     Further advantages and advantageous features of the invention can be learned from the description contained herein below, taken in conjunction with the drawings, in which:  
         [0023]      FIG. 1 , a first exemplary embodiment of an injection nozzle of the invention;  
         [0024]      FIG. 2 , an enlarged detail of  FIG. 1 ; and  
         [0025]      FIG. 3 , a second exemplary embodiment of an injection nozzle of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]      FIG. 1  shows an exemplary embodiment of an injection nozzle of the invention in longitudinal section. The nozzle body  1  is adjoined by a shim  3  and a nozzle holder body  5 . The nozzle body  1 , shim  3  and nozzle holder body  5  can also be embodied in one piece. The multi-part embodiment shown in  FIG. 1 , however, has advantages in terms of the production, installation and adjustment of the injection nozzle. The nozzle body  1 , shim  3  and nozzle holder body  5  are braced against one another by means of a union nut  6 . At the same time, the shim  3  is a stroke stop for the first nozzle needle  7 .  
         [0027]     In the nozzle body  1 , a first nozzle needle  7  is guided in a guide bore  9 . The guide bore  9  continues in the shim  3  and nozzle holder body  5  as well and has changing diameters.  
         [0028]     In the nozzle body  1 , a pressure chamber  11  is embodied, which is defined by a pressure shoulder  13  of the first nozzle needle  7 . Via a high-pressure inlet  15 , fuel from a high-pressure fuel pump, not shown, can be pumped into the pressure chamber  11 .  
         [0029]     A first nozzle spring  17 , via a pressure bolt  18 , presses the first nozzle needle  17  into a first sealing seat  19 , shown only in suggested form in  FIG. 1 , at the end of the nozzle body  1 .  
         [0030]     In the closed state of the first nozzle needle  7 , a sealing cone  21  of the first nozzle needle  7 , in conjunction with the first sealing seat  19 , prevents fuel from the pressure chamber  11  from passing through a first injection port  23  into the combustion chamber, not shown in  FIG. 1 , of an internal combustion engine, also not shown. The tip of the nozzle needle of the invention is shown in more detail in  FIG. 2  and will be described in greater detail below in conjunction with that figure.  
         [0031]     The mode of operation of the first nozzle needle is equivalent to that of a conventional injection nozzle. If the pressure force exerted on the pressure shoulder  13  by the fuel located in the pressure chamber  11  is greater than the closing force of the first nozzle spring  17 , the first nozzle needle  7  lifts from the first sealing seat  19  and thus uncovers the at least one first injection port  23 , and the injection begins. Fuel flows out of the pressure chamber  11  through an annular gap (not shown), formed by the guide bore  9  and the first nozzle needle  7 , in the direction of the first injection port  23 .  
         [0032]     The first nozzle needle  7  has a central bore  25 , in which a second nozzle needle  27  is guided. The second nozzle needle  27 , in the exemplary embodiment shown in  FIG. 1 , is embodied in two parts and comprises the portions  27   a  and  27   b . The two-part embodiment of the second nozzle needle  27  is done for reasons of production and installation. In the region of the nozzle holder body  5 , a guide bush  29  is provided on the upper end of the guide bore  9 , and a control piston  31  is guided in the guide bush.  
         [0033]     Between the control piston  31  and the end  33  of the guide bore  9 , a second nozzle spring  35  is disposed, which causes the control piston  31  to contact the second nozzle needle  27 . The end  33  of the guide bore  9  and the control piston  31  define a control chamber  37 , into which a control pressure inlet  39  discharges. The control chamber  37  is filled with a hydraulic fluid, whose pressure can be controlled via the control pressure inlet  39 . Fuel, motor oil, and other fluids can be used as the hydraulic fluid.  
         [0034]     The pressure of the control chamber  37  filled with hydraulic fluid is exerted via the control piston  31 , in the same direction as the second nozzle spring  35 , on the second nozzle needle  27  and presses this nozzle needle into a second valve seat, not shown in  FIG. 1 . By lowering the pressure in the control chamber  37 ; the closing force of the second nozzle needle  27  can be decreased to such an extent that the second nozzle needle  27  opens.  
         [0035]     An underside  41  of the guide bush  29 , together with a shoulder  43  of the second nozzle needle, forms a stroke stop for the second nozzle needle  27 .  
         [0036]     In the exemplary embodiment shown in  FIG. 1 , the first nozzle spring  17  is braced against the nozzle holder body  5  via an adjusting shim  45  and the guide bush  29 . By changing the adjusting shim  45 , the prestressing of the first nozzle spring  17  can be adjusted in the simplest possible way and with high precision.  
         [0037]     In  FIG. 2 , the tip of an injection nozzle of the invention is shown enlarged. The first sealing cone  21  of the first nozzle needle  7  and its counterpart in the nozzle body  1  are designed such that linear contact results. This line of contact will be called the first sealing seat  19  and is shown as a dashed line in  FIG. 2 . As  FIG. 2  clearly shows, the first sealing seat  19  separates the fuel, which is at high pressure, in an annular gap  47  between the guide bore  9  and the first nozzle needle  7  from the first injection ports  23 , when the injection nozzle is closed. In the exemplary embodiment of  FIG. 2 , two first injection ports  23  are shown, which face one another. However, it is also possible for injection nozzles of the invention to be equipped with a different number of first injection ports  23  or second injection ports  49 .  
         [0038]     Somewhat farther toward the tip of the nozzle body  1 , two second injection ports  49  are shown. The second injection ports  49  are sealed off from a second sealing cone  51  and its counterpart in the nozzle body  1 . Once again, a linear area of contact results between the second sealing cone  51  and the nozzle body  1 , and this will hereinafter be called the second sealing seat  53 .  
         [0039]     The mode of operation of the injection nozzle of the invention will now be described, referring back and forth to  FIG. 1  and  FIG. 2 .  
         [0040]     When the high-pressure fuel system, not shown, which among other elements has a high-pressure fuel pump, pumps fuel at high pressure via the high-pressure inlet into the pressure chamber  11 , the first nozzle needle  7  lifts from the first sealing seat  19 , as soon as the pressure force, exerted on the pressure shoulder  13  by the fuel in the pressure chamber  11 , is greater than the closing force of the first nozzle spring  17 . Once the first nozzle needle  7  has lifted from the first sealing seat  19 , the fuel can flow out of the pressure chamber  11  via the annular gap  47  through the first injection ports  23  into the combustion chamber, not shown. At some operating points of the engine, not shown, the injection is optimal if the fuel is injected solely through the first injection ports  23 .  
         [0041]     If the opening cross sections of the first injection ports  23  are inadequate to inject enough fuel into the combustion chambers within the available time, then the second nozzle needle  27  can be opened in addition. This is accomplished by lowering the pressure in the control chamber  37 . Since the second sealing seat  53  has a smaller diameter than the second nozzle needle  27 , the fuel that is at high pressure and is flowing out of the annular gap  47  toward the first injection ports  23  exerts a force counter to the closing force on an annular face  55  of the second nozzle needle  27 . The annular face  55  is defined by the second sealing seat  53  and the outer diameter of the second nozzle needle  27 . As soon as this force is greater than the closing force, the latter comprising the spring force of the second nozzle spring  35  and the pressure force of the hydraulic fluid located in the control chamber  37 , the second nozzle needle  27  lifts from the nozzle body  1  as well and thus uncovers the second injection ports  49 . In this state, large quantities of fuel can flow within a short time through the first injection ports  23  and second injection ports  49  into the combustion chamber, not shown.  
         [0042]     If the pressure in the control chamber  37  is lowered with a time lag after the opening of the first nozzle needle  7 , an injection course can be shaped. In a first phase, when only the first nozzle needle  7  is opened, only little fuel flows through the first injection ports  23 . Upon the opening of the second nozzle needle, the quantity of fuel injected per unit of time increases sharply.  
         [0043]     In  FIG. 3 , a second exemplary embodiment of an injection nozzle of the invention is shown. Because of the agreement with the first exemplary embodiment in terms of components and function, the description of  FIGS. 1 and 2  applies, and only the differences will be explained below.  
         [0044]     In the exemplary embodiment of  FIG. 3 , the second nozzle needle  27  is divided at the level of the pressure bolt  18 . The upper part  27   b  of the second nozzle needle  27 , where it passes through the pressure bolt  18 , has a smaller diameter than the lower part  27   a  of the second nozzle needle  27 . A central bore  57  in the pressure bolt, which bore guides the upper part  27   b  of the second nozzle needle  27 , also has a smaller diameter than the lower part  27   a  of the second nozzle needle  27 . The lower end  59 , in terms of  FIG. 3 , of the pressure bolt  18  therefore forms a stroke stop for the nozzle needle  27 . Because of the shorter spacing, compared to the first exemplary embodiment, between the second sealing seat (see  FIG. 2 ) and the stroke stop formed by the lower end  59  of the pressure bolt  18 , first, the stroke of the nozzle needle can be adjusted more precisely, and second, it is assured that the stroke of the second nozzle needle  27  is dependent on the stroke of the first nozzle needle  7 . The stroke of the second nozzle needle  27  can be greater, at maximum by the stroke play designated as  61  in  FIG. 3 , than the stroke of the first nozzle needle  7 .  
         [0045]     When the first nozzle needle  7  closes, the pressure bolt  18 , offset by the stroke play  61 , also closes the second nozzle needle  27 . This prevents after injections into the combustion chamber (not shown) from the second injection ports  49  (see  FIG. 2 ).  
         [0046]     It has proved advantageous if the total of the opening cross sections of the first injection ports  23  is approximately equal to the total of the opening cross sections of the second injection ports  49 .  
         [0047]     The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments are possible within the spirit and scope of the invention, the latter being defined by the appended claims.