Patent Publication Number: US-6908044-B2

Title: Injector having inwardly opening valves connected in series

Description:
BACKGROUND INFORMATION 
   Pump nozzle injection systems or pump-line-nozzle injection systems are used in direct injection internal combustion engines. I valves (inwardly opening valves) characterized by a high operating stability may be used in these fuel injection systems. In addition to a high operating stability, shaping of the injection characteristic is also important in order to optimize the course of combustion in the combustion chamber of an engine with regard to formation of carbon black and HC. 
   European Patent Application No. 823 549 describes an injector. This injector includes an injector body and a nozzle needle displaceably accommodated in the injector body. The nozzle needle is pressed into its seat by a closing spring. A fuel supply line is provided for supplying fuel to the nozzle needle in the area of a conical face so that a force is directed against the action of the closing spring. The connection between the fuel supply line and a drain to the low-pressure area of the fuel injector is controlled by using a drain valve. The fuel pressure in a control space, which is defined in part by an area of the nozzle needle or a component accommodated thereon, is controlled by using a control valve. The nozzle needle or the component accommodated on it is oriented so that a force acting on the nozzle needle is generated at a high pressure level in the control space, supporting the force of the closing spring. The drain valve and the control valve are controlled by an electromagnetic actuator which is designed as a component. The control valve and the end face of the nozzle needle or the component cooperating with it (e.g., a push rod or the like) which form a part of the control space are dimensioned so that the control valve is pressure balanced at all times. 
   According to this implementation, the drain valve and the control valve are arranged in series on both sides of an electromagnetic actuator, the lifts of the control valve and drain valve being produced simultaneously by the electromagnetic actuator, and independent triggering of the two valves connected in series is impossible. 
   SUMMARY 
   With the implementation according to an example embodiment of the present invention, inwardly opening valves (I valves) may be connected in series to an injector in such a way that a shaping of the injection characteristic may be achieved by cross-sectional throttling in an intermediate switch state. This implementation according to the present invention makes it possible to achieve very small lifts with which in turn very small injection quantities may be achieved in certain phases of injection in adaptation to the combustion characteristic taking place in the combustion chamber. 
   Due to the series connection of two I valves, their two valve needles may be operated using an actuator—be it an electromagnet or a piezoactuator. Between the two valve needles of the series-connected I valves there is a spring package which may include, for example, two spiral springs in a parallel connection. The spring package may be accommodated between the two valve needles of the series-connected I valves, while the valve needle of the I valve at a distance from the actuator is supported by a spring element. The lift of this valve needle is designed to be smaller than that of the valve needle upstream from it. Both valve needles thus close on actuation of the actuator because of the difference in achieving the respective closed positions on the valve needle seats using different lift paths. 
   Accordingly, the spring package arranged between the valve needles of the first and second I valve acts as a rigid spring in first approximation, so that the spring pretension of the spring element assigned to the first I valve may be overcome in a first actuating movement of the actuator. With a further increase in actuating force by the actuator, a very small lift path may be implemented, depending on the triggering of the actuator, by way of the reserve lift path provided on the second I valve in the area of its valve needle seat, this valve path permitting shaping of the injection characteristic through cross-sectional throttling at the second I valve which takes into account the advance of combustion in the combustion chamber of the engine through metered addition of very small injection quantities. During throttling due to a constriction of cross section at the first I valve, the second I valve downstream from the first I valve as seen in the direction of flow of the fuel remains in its closed position and has no effect on the metering of the fuel volume after closing its valve needle. Metering of fuel is accomplished only through the reserve lift path and its utilization at the second I valve through appropriate triggering of the actuator. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a schematic diagram of a double-I valve having a gradual connection option. 
       FIG. 1.1  shows another embodiment of a double-I valve having individual I valves arranged overhead. 
       FIG. 2  shows the spring force plotted over the lift path of the I valve(s). 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a schematic diagram of a double-I valve having a gradual connection option. In this figure, a fuel injector  1  includes a first housing part  2  and another housing part  3  which are in contact at a joint  45 . The two-part design selected here for the injector housing facilitates assembly of inwardly opening valves (I valves)  8  and  24  accommodated in the housing in series. An actuator  4 , designed as an electromagnet according to the diagram in  FIG. 1 , is situated in the upper area of first housing part  2 . Actuator  4  includes a plate-shaped element  5  which is accommodated on an upper end face  29  of a second valve needle  25  of second valve  24 . A solenoid  6  is situated opposite plate  5 . A lift path  7  is provided between plate  5  of actuator  4 . On energization of solenoid  6 , this lift path  7  is overcome and an actuating movement into second valve needle  25  of second switching valve  24  is initiated. 
   A first valve needle  9  of first valve  8  (I valve) is inserted into second housing part  3  of fuel injector  1 . Valve needle  9  has an upper end face  10  which protrudes into a hollow space  4  in first housing part  2 . On the end opposite end face  10 , first valve needle  9  is provided with an equalizing piston  16 , a first spring element  19  being in contact with its end face  18 . First spring element  19  may be designed as a spiral spring and is supported on second housing part  3 . First valve needle  9  of I valve  8  is annularly surrounded by a first chamber  13  which may be acted upon by fuel under high pressure through an inlet  20 . Beneath first chamber  13 , a second chamber  14  is formed in second housing part  3 , a pressure relief line  17  branching off from here into the low-pressure area of the fuel injector. A valve needle seat  12  is formed between first chamber  13  and second chamber  14  of first I valve  8 . Valve seat  12  of first I valve  8  is formed by a valve seat face  21  on the housing side and a conical section  22 , the valve sealing face of first valve needle  9 . In the diagram according to  FIG. 1 , the lift path traveled by first valve needle  9  to reach its closed position on valve needle seat  8  is labeled as  11 . An annular gap  15  is provided beneath valve needle seat  12  in second housing part  3  and is in contact with valve needle seat  12  of first I valve  8 , connecting first chamber  3  and second chamber  14  of first I valve  8 . 
   Second valve needle  25  of second I valve  24  is accommodated in first housing part  2  of fuel injector  1 , plate  5  opposite solenoid  6  being attached to upper end face  29  of the valve needle. Second valve needle  25  is provided with an equalizing piston  42  on the end opposite end face  29  of second needle  25 . Second valve needle  25  of second I valve  24  is annularly surrounded by a third chamber  26 . In addition, a fourth chamber  27  surrounds second valve needle  25  of second I valve  24  above equalizing piston  42  formed on second valve needle  25 . A valve needle seat  31  is formed between third chamber  26  and fourth chamber  27 . Valve needle seat  31  ends on the housing side in an annular gap  28 , which is closed when second valve needle  25  is closed. 
   A conical valve sealing face  32  is formed on second valve needle  25 , and in the area of valve needle seat  32 , it is opposite a valve seat face  33  formed on the housing side, i.e., on first housing part  2 . Second valve needle  25  of second I valve  24  travels a lift path labeled as  36  within first housing part  2  of injector  1 . Third chamber  26  of the second I valve communicates via an inlet  23  or  20  with a fuel source (not shown here) while fourth chamber  27  of second I valve  24  includes a pressure relief line  34  through which fourth chamber  27  communicates with the low pressure area (not shown here) of fuel injector  1 . 
   A second spring element  37  is accommodated between end face  30  of second valve needle  25  facing first valve needle  9  and end face  10  of first valve needle  9 . Second spring element  37  is surrounded by a spring plate  35  configured in the form of a disk inserted into hollow space  44  of first housing part  32 . Spring plate  35  is supported with its upper ring face on the border of hollow space  44  in first housing part  2 . A third spring element  38  which surrounds second spring element  37  is supported on its lower ring face  39 . Spring elements  37  and  38  inserted into hollow space  44  in first housing part  2  in the diagram according to  FIG. 1  together form a spring package, which in this case is composed of two parallel spiral springs. Instead of two spring elements  37  and  38  illustrated here, more than two spring elements may also be accommodated in hollow space  44  with appropriate dimensioning of end face  30  and hollow space  44  in first housing part  2 . In addition to the design of second spring element  37  and third spring element  38  as spiral springs, it is also possible to have plate spring packages which could be inserted into hollow space  44 . 
   When actuator  4  is triggered by energizing solenoid  6 , plate  5 , which is accommodated on end face  29  of second valve needle  25 , is pulled in the direction of solenoid  6 , i.e., the plate lift labeled as  7  is reduced. Due to the insertion movement of second valve needle  25  into first housing part  2 , first valve needle  9  of first I valve  8  is also actuated against first spring element  19  which supports it. During the insertion movement of second valve needle  25  into first housing part  2 , second spring element  37  of the spring package in hollow space  44 , which acts on end face  10  of first valve needle  9  of first I valve  8 , functions as a rigid spring in first approximation, so that first valve needle  9  of the first I valve is inserted into its valve needle seat  12  according to its lift path  11  and closes it by its contact with seat faces  21  and/or  22 . The rigidity of second spring element  37  is much greater than the spring rigidity of first spring element  19  supporting equalizing piston  16  of first valve needle  9 , this spring element in turn being supported in second housing part  3 . 
   During the insertion movement of second valve needle  25  and the closing of first valve needle  9  on its valve needle seat  12  which results from this insertion movement, second valve needle  25  of second I valve  24  is inserted into first housing part  2  over only a portion of its lift path  36 . Thus, until reaching a closed position, there is still a reserve lift  41  available at second valve needle  25 . When the force on actuator  4  is increased, e.g., through further energization of solenoid  6 , its plate  5  travels further toward solenoid  6 , thereby applying an increased actuating force on second valve needle  25  of second I valve  24 . End face  30  of equalizing piston  42  of second valve needle  25  thus travels toward the inner bore through which second spring element  37  passes, i.e., the edge of the bore until end face  30  of equalizing piston  42  rests on spring plate  35 . With a further insertion movement corresponding to the actuating force generated at actuator  4 , both the spring force of second spring element  37  as well as the spring force of third spring element  38  supporting spring plate  35  in hollow space  44  then act on second valve needle  25 . Depending on the actuating force applied to actuator  4 , the throttling applied to second valve needle seat  31  may be varied so that only the smallest quantities of fuel flow out of third chamber  26  of second I valve  24  into inlet  20  toward the nozzle. 
   The seat cross section which creates the connection of third chamber  26  and chamber  27  depends on the actuating force generatable by actuator  4  and the force of spring package  37  and/or  38  counteracting it in the hollow space of first housing part  2  and the force of spring  19  in the hollow space of bottom housing part  3 . With this example embodiment, it is possible to achieve extremely small lift paths with which in turn favorable injection quantity characteristics may be achieved; these may be optimally utilized in the combustion chamber of an engine, depending on the combustion phase prevailing there. 
     FIG. 1.1  illustrates another example embodiment of an arrangement of a double-I valve inside a housing. An actuator  4 , which is designed as an electromagnet, similar to the design in  FIG. 1 , is arranged in the upper area of a second housing part  3 . Actuator  4  includes a plate-shaped element  5  which acts on a thrust bolt. A solenoid  6  is situated opposite plate-shaped element  5 . When solenoid  6  is energized, plate-shaped element  5  bridges plate lift  7  toward solenoid  6 , so that a vertical upward movement is imposed upon that thrust bolt, which is connected to plate-shaped element  5 . This results in an actuating movement of second valve needle  25  of second I valve  24  within first housing part  2 . In contrast with the diagram according to  FIG. 1 , in the example embodiment of  FIG. 1.1 , first I valve  8 , whose first valve needle  9  includes an equalizing piston  16 , is supported by a spring package composed of spring elements  37  and/or  38  on its lower end face  18 . End face  18  of first valve needle  9  is supported directly by second spring element  37 , a spring plate  35  which has been inserted into hollow space  44  being itself supported on its lower side by third spring element  38 . Two spring elements  37  and  38  are supported on end face  40  of hollow space  44  in the housing. Valve needle seat  12  of first I valve  8  is designed by analogy with the valve needle seat of first I valve  8  according to the illustration in FIG.  1 . 
   In contrast with the diagram of a double-I valve  8 ,  24  according to the illustration in  FIG. 1 , second I valve  24  is oriented in the opposite direction from the first I valve in first housing part  2 , i.e., standing on its head. Valve needle seat  31  of the second I valve is designed so it is twisted relative to valve needle seat  31  of second I valve  24  according to the diagram in  FIG. 1  in first housing part  2  there. In contrast with the diagram of  FIG. 1.1 , where the spring package, including second spring element  37  and third spring element  38 , is situated between end faces  30  of second I valve  24  and end face  10  of first valve needle  9  of first I valve  8 , an element  46  configured in the form of a disk is situated between above-mentioned end faces  30  and  10  of valve needles  25  and  9 . This element is designed with a diameter greater than the outside diameter of first and second valve needles  9  and  25 . Disk-shaped element  46  which functions as a dividing element is surrounded by space which is bordered by the wall of an inside bore of a ring  47 . 
   Chambers  13  and  26 , each being assigned to first I valve  8  and second I valve  24 , respectively, may be joined downstream by a bore within the housing accommodating a volume directed out of the two chambers. 
     FIG. 2  shows the spring force plotted over the lift paths of the first and second I valves in the housing of the injector which is configured in two parts. 
   According to the variant embodiment illustrated in  FIG. 1 , two I valves  8  and  24  are connected in series, their valve needles  9  and  25  being connected by a rigid spring implemented in the form of a spring package, so that both valve needles  9  and  25  are operable with one actuator  4 . 
   Both valve needles  9  and  25  are equipped with different lifts  36  and  11 , respectively, the spring elements assigned to these valve springs  9  and  25 , i.e., first spring element  19  and second and third spring elements  37  and  38 , respectively, in the hollow space  44  of first housing part  2  having different spring characteristics. The first spring element has a spring characteristic c 1  which is smaller than spring characteristic c 2  of second spring element  37  in hollow space  44 . In the valve-open position, first spring element  19  and second spring element  37  of the spring package are under the same prestressing force. This point is labeled as “ 1 ” in the diagram according to FIG.  2 . On actuation by actuator  4 , whether it is a piezoactuator or a solenoid valve, this force acts only on first spring element  19 , in simplified terms; second spring element  37  of the spring package in hollow space  44  represents in first approximation a rigid spring. Both valve needles  9  and  25  are moved in the direction of their valve needle seats  12  and  31 , respectively. First valve needle  9  of first I valve  8  is the first to reach its valve needle seat  12  and closes it. This point is labeled as  2  in the diagram according to FIG.  2 . With a further increase in actuating force by actuator  4  on end face  29  of second valve needle  25 , another lift path  41  may be traveled by second valve needle  25  until end face  30  of equalizing piston  42  reaches spring plate  35 . Until reaching spring plate  35  in hollow space  44 , second spring element  37  acts in accordance with its spring rigidity c 2 . Lift path  41  thus follows a continuous line  37  running between  3  and  4  in the diagram. 
   On reaching spring plate  35  which is under prestress by third spring element  38  in hollow space  44 , another force level is to be overcome by actuator  4 , represented in the diagram as illustrated in  FIG. 2  by the continuous line between  4  and  5 . After 5 in the diagram, as illustrated in  FIG. 2 , second spring element  37  and third spring element  38  of the spring package in hollow space  44  act as springs connected in parallel having rigidities c 2  and c 3 , respectively. Finally at point  6 , second valve needle  25  of second I valve  24  has moved into its valve needle seat  31  so that second I valve  24  is also in its closed position in first housing part  2 . 
   According to the design of first spring element  19  which acts upon end face  18  of equalizing piston  16  of first valve needle  9  and according to the designs of second spring element  37  between end faces  30  and  10  of first valve needle  9  and second valve needle  25 , respectively, and the design of third spring element  38  which acts upon spring plate  35  in the interior of hollow space  44 , a very small residual lift path may be established between positions  5  and  6  according to the diagram in FIG.  2  through suitable triggering of the actuator, so that the desired throttling and thus the shaping of the injection characteristic may be achieved in accordance with the progress of combustion in the combustion chamber of an engine. The injection quantity when first I valve  8  is closed depends only on the throttling at valve seat  31  of second valve needle  25  of second I valve  24  in first housing part  2  of fuel injector  1 .