Patent Publication Number: US-7588016-B2

Title: Fuel injection apparatus for a multicylinder internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a 35 USC 371 application of PCT/EP 2006/050448 filed on Jan. 25, 2006. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a fuel injection apparatus for a multicylinder internal combustion engine. 
   2. Description of the Prior Art 
   A fuel injection apparatus known from EP 0 299 337 A has a high-pressure pump that delivers fuel to a high-pressure accumulator that is also referred to as a rail. For each cylinder of an internal combustion engine, an injector is provided for fuel injection; each injector is connected to the high-pressure accumulator by means of a hydraulic line. This fuel injection apparatus has the disadvantage of high costs for production and assembly due to the presence of the high-pressure accumulator between the high-pressure pump and the injectors. Because of the high pressure that prevails in it, the high-pressure accumulator must have a high strength. In addition, the presence of the high-pressure accumulator increases the amount of space required by the fuel injection apparatus in the region surrounding the internal combustion engine. 
   SUMMARY AND ADVANTAGES OF THE INVENTION 
   The fuel injection apparatus according to the invention has the advantage over the prior art that it does not require a high-pressure accumulator, thus simplifying production and assembly as well as reducing the amount of space it requires. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Several exemplary embodiments of the invention are explained in detail herein below, with reference to the drawings, in which: 
       FIG. 1  is a simplified depiction of a fuel injection apparatus for an internal combustion engine according to a first exemplary embodiment, 
       FIG. 2  is an enlarged depiction of an injector of the fuel injection apparatus, and 
       FIGS. 3 through 10  show the fuel injection apparatus according to other exemplary embodiments. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 through 10  show a fuel injection apparatus for a multicylinder internal combustion engine that is preferably an autoignition engine of a motor vehicle. The fuel injection apparatus has a high-pressure pump  10  that delivers highly pressurized fuel. Each cylinder of the engine is provided with an injector  12  that can inject fuel into the combustion chamber of the cylinder. In  FIGS. 1 through 10 , only some of the injectors  12  are shown; additional injectors before the last injector  12   d  are indicated by dots. As shown in  FIG. 2 , the injector  12  has a fuel injection valve  14 , which injects fuel into the combustion chamber of the cylinder, and has an electrically triggered actuator  16 . The actuator  16  controls the opening and closing motion of an injection valve member  15  of the fuel injection valve  14 . Preferably, the actuator  16  is a piezoelectric actuator that changes in size depending on an electrical voltage that is applied to it. This change in size permits the execution of a switching function that can be used to open or close the injection valve member  15 . An electric or electronic control unit  18  triggers the actuator  16 . The actuator  16  is situated in a fuel-filled chamber  20  in a housing  22  of the injector  12 . For example, the actuator  16  can act on a piston  17  that delimits a control chamber  19 ; the pressure prevailing in the control chamber  19  acts on the injection valve member  15  in the closing direction. A prestressed spring  21  holds the piston  17  in contact with the actuator  16 . A prestressed spring  23  also acts on the injection valve member  15  in the closing direction. When the control unit  18  applies an electrical voltage to the actuator  16 , the actuator expands and pushes the piston  17  toward the control chamber  19 , resulting in a high pressure therein, which holds the injection valve member  15  in its closed position so that no injection of fuel occurs. If the control unit  18  does not apply any electrical voltage to the actuator  16 , then the actuator contracts so that the spring  21  moves the piston  17  away from the control chamber  19 , thus reducing the pressure in the control chamber  19 . The high pressure acting on the injection valve member  15  in the opening direction then moves it into its open position counter to the force of the low pressure prevailing in the control chamber  19  and counter to the force of the spring  23  so that an injection of fuel occurs. 
   The housing  22  of the injector  12  is provided with two high-pressure connections  24  that convey highly pressurized fuel to and from the injector  12 . The high-pressure connections  24  are connected to the chamber  20  that contains the actuator  16 . In addition, the high-pressure connections  24  are connected via the chamber  20  to the fuel injection valve  14  in order to supply it with the fuel required for the fuel injection. The chamber  20  thus constitutes a high-pressure accumulator from which the fuel is drawn for the injection. The chamber  20  has a sufficiently large volume in order to permit it to store the volume of fuel required for the fuel injection. The chamber  20  can have a volume of between 1 and 5 cm 3 , in particular approximately 2 cm 3 . 
   In a first exemplary embodiment of the fuel injection apparatus shown in  FIG. 1 , only a first injector  12   a  of the injectors  12  is connected to the high-pressure pump  10 ; a hydraulic line  26  leading from the high-pressure outlet of the high-pressure pump  10  is connected to a high-pressure connection  24  of the injector  12   a . Preferably, the first injector  12   a  connected to the high-pressure pump  10  is the injector situated the closest to the high-pressure pump  10  in the engine. The cylinders of the engine and therefore the injectors  12  associated with them are situated in an in-line arrangement. The other high-pressure connection  24  of the first injector  12   a  is connected to a hydraulic line  27  that leads to another injector  12   b  and is connected to a high-pressure connection  24  of said injector  12   b . Preferably, the injector  12   b  is situated adjacent to the first injector  12   a . The other high-pressure connection  24  of the injector  12   b  is connected to a hydraulic line  27 , which in turn leads to another, preferably adjacent injector  12  and is connected to a high-pressure connection  24  of said injector  12 . The last injector  12   d  is connected to the preceding adjacent injector only via a hydraulic line  27  connected to one of its two high-pressure connections  24  while a pressure sensor  28  is provided at its other high-pressure connection  24 . Alternatively, the pressure sensor  28  can also be provided at another injector  12 , in one of the hydraulic lines  27  between the injectors  12 , in the hydraulic line  26  between the high-pressure pump  10  and the first injector  12   a , or at the high-pressure pump  10 . The injectors  12  of the cylinders of the internal combustion engine are hydraulically connected to one another in series; only the first injector  12   a  is directly connected to the high-pressure pump  10 . 
   The pressure sensor  28  is connected to the electric control unit  18  and supplies it with a signal for the pressure that is actually prevailing in the injectors  12 . On the suction side of the high-pressure pump  10 , a fuel metering device  30  is provided, which can change the quantity of fuel that the high-pressure pump  10  aspirates and delivers at high pressure. The fuel metering device  30  can, for example, be used to set an adjustable flow cross section on the suction side of the high-pressure pump  10 . For example, the suction side of the high-pressure pump  10  is supplied with fuel from a tank  31  by a fuel-supply pump  34 ; the fuel metering device  30  is situated between the fuel-supply pump  34  and the high-pressure pump  10 . The control unit  18  triggers the fuel metering device  30  so that the high-pressure pump  10  supplies the injectors  12  with a highly pressurized fuel quantity that is required in order to maintain a predetermined pressure in the injectors  12  for the fuel injection. 
   It is possible for the high-pressure pump  10  to have only a single pump element; the hydraulic line  26  leading to the first injector  12   a  is connected to the outlet of this pump element. Alternatively, it is also possible for the high-pressure  10  to have several pump elements, for example two or three pump elements; the outlets of the pump elements are brought together at a shared connection to the high-pressure pump  10  to which is connected the hydraulic line  26  leading to the first injector  12   a.    
     FIG. 3  shows the fuel injection apparatus according to a second exemplary embodiment whose basic design is the same as that of the first exemplary embodiment. By contrast with the first exemplary embodiment, however, in this case, the last injector  12   d  is also directly connected to the high-pressure pump  10  by means of a hydraulic line  26 . As in the first exemplary embodiment, the last injector  12   d  is likewise connected to the adjacent injector via a hydraulic line  27 . The high-pressure pump  10  in this case is provided with two high-pressure connections, one of which is connected to the first injector  12   a  and the other of which is connected to the last injector  12   d . The pressure sensor  28  can be provided at one of the injectors  12 , in a hydraulic line  27  between the injectors  12 , in a hydraulic line  26  between the high-pressure pump  10  and one of the injectors  12 , or at the high-pressure pump  10 . If the high-pressure pump  10  has only one pump element, then this pump element must be provided with two high-pressure connections for attachment of the two hydraulic lines  26  leading to the respective injectors  12   a  and  12   d . If the high-pressure pump  10  has two pump elements, then the hydraulic line  26  to the first injector  12   a  is connected to the outlet of the one pump element and the hydraulic line  26  to the last injector  12   d  is connected to the outlet of the other pump element. If the high-pressure pump  10  has more than two pump elements, then their outlets are combined to form two high-pressure connections on the high-pressure pump  10 , with each high-pressure connection connected to a hydraulic line  26  that leads to an injector  12   a  or  12   d.    
     FIG. 4  shows the fuel injection apparatus according to a third exemplary embodiment in which the cylinders of the internal combustion engine are situated in a V-shaped arrangement, with several cylinders arranged in series in each cylinder row. Only the first injector  12   a  of a first cylinder row is directly connected to the high-pressure pump  10  and the remaining injectors  12  are connected to one another in series via hydraulic lines  27 . The injectors  12  that are situated the farthest from the high-pressure pump  10  in the two cylinder rows are also connected to each other via a hydraulic line  27 . The pressure sensor  28  is provided at the injector  12   d  that is the closest to the high-pressure pump  10  in the second cylinder row. The pressure sensor  28  can also be provided in another location, as indicated in the first exemplary embodiment. The high-pressure pump  10  is embodied as described in conjunction with the first exemplary embodiment. 
     FIG. 5  shows the fuel injection apparatus according to a fourth exemplary embodiment that differs from the third exemplary embodiment only in that each of the injectors  12 , which is situated the closest to the high-pressure pump  10  in each of the cylinder rows, is connected to the high-pressure pump  10  by means of a respective hydraulic line  26 . The remaining injectors  12  are connected to one another in series by means of the respective hydraulic lines  27 . The high-pressure pump  10  is embodied as described in conjunction with the second exemplary embodiment. 
     FIG. 6  shows the fuel injection apparatus according to a fifth exemplary embodiment whose basic design is the same as that of the first exemplary embodiment. The fuel injection apparatus according to the fifth exemplary embodiment is additionally provided with a pressure control valve  32  that can change the pressure prevailing in the injectors  12 . The pressure control valve  32  can, for example, be provided at the high-pressure pump  10 . The pressure sensor  28  can be provided at the last injector  12   d . Alternatively, the pressure control valve  32  can also be provided at the last injector  12   d , as in the variant depicted in  FIG. 7 , and the pressure sensor  28  can be provided in one of the hydraulic lines  27  between the injectors  12 . The pressure control valve  32  and the pressure sensor  28  can also be mounted in any other location. The pressure control valve  32  is connected to the control unit  18 , which triggers it to adjust the pressure prevailing in the injectors  12  to a predetermined value. When the control unit  18  triggers the pressure control valve  32 , it is possible to change the pressure prevailing in the injectors  12  very quickly. The control unit  18  can trigger the fuel metering device  30  in such away that the high-pressure pump  10  supplies the injectors  12 , at least essentially, with only the highly pressurized fuel quantity required for the fuel injection, thus making it possible to keep the output capacity of the high-pressure pump  10  to a minimum. 
     FIG. 8  shows the fuel injection apparatus according to a sixth exemplary embodiment that is embodied essentially the same as the third exemplary embodiment with the cylinders of the engine situated in a V-shaped arrangement, with the addition of the pressure control valve  32 . The connection of the injectors  12  to the high-pressure pump  10  via the hydraulic line  26  and to one another via the hydraulic lines  27  is the same as in the third exemplary embodiment so that only the first injector  12   a  is directly connected to high-pressure pump  10 . The pressure control valve  32  is provided, for example, at the high-pressure pump  10  and the pressure sensor  28  is provided at the last injector  12   d . Alternatively, the pressure control valve  32  can also be provided, as in the variant depicted in  FIG. 9 , at the last injector  12   d  and the pressure sensor  28  can be provided in one of the hydraulic lines  27  between the injectors  12 . The pressure control valve  32  and the pressure sensor  28  can also be provided in any other location. 
     FIG. 10  shows the fuel injection apparatus according to a seventh exemplary embodiment in which, by contrast with the sixth exemplary embodiment, each of the injectors  12  that is the closest to the high-pressure pump  10  in each of the two cylinder rows is connected to the high-pressure pump  10  by means of a respective hydraulic line  26 . The injectors  12   d  that are situated the farthest from the high-pressure pump  10  in the two cylinder rows are not connected to each other, but are instead each provided with a respective pressure control valve  32 . A respective pressure sensor  28  is situated in one of the hydraulic lines  27  between the injectors  12  in each of the two cylinder rows. The respective pressure control valve  32  and pressure sensor  28  of the two cylinder rows can also be provided in any other location. In the seventh exemplary embodiment, there are thus separate high-pressure branches for the injectors  12  of the two cylinder rows of the engine, each row with its own pressure control valve  32  and pressure sensor  28 . 
   The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.