Patent Publication Number: US-7591436-B2

Title: Fuel injection valve for internal combustion engines

Description:
The present application is a continuation-in-part of application PCT/CH2005/000098, filed on Feb. 21, 2005, and published as WO 2005/080785 A1, that claims priority under 35 U.S.C. §119 to Swiss application 310/04, filed on Feb. 25, 2004, the disclosures of each of which are expressly incorporated by reference herein in their entireties. 

   The present invention relates to a fuel injection valve for the intermittent injection of fuel into the combustion chamber of an internal combustion engine. 
   EP-A-1 273 791 has disclosed a fuel injection valve of this type, in which the control body is seated fixedly in a housing hole by means of a shrink joint and therefore seals the low pressure space with respect to the high pressure space. This is also true of the fuel injection valve which is disclosed in EP-B-0 426 205. Pressing the control body into the housing hole requires a certain amount of expenditure on assembly technology. 
   WO-A-03/095825 discloses an injector for the injection of fuel, in which an annular gap is formed between an injector body and a throttle module which is inserted into the former and is configured as a separate component. In order to seal this annular gap, plastically deformable cutting edges are provided on the throttle module, which are pressed against steps in the injector housing during the assembly of the throttle module. In the fuel injection valve which is described in WO-A-02/084106 and is not of the same generic type, a control space is delimited on one side by a spring collar which is arranged loosely, that is to say not in a sealing manner, in a hole of a nozzle body. Said spring collar is pressed against a corresponding body by the pressure which prevails in the high pressure space of the valve and by the force of a spring. 
   The present invention is based then on the object of providing a fuel injection valve of the type which is mentioned in the introduction, in which the manufacture and installation of the control body into the housing is simpler and therefore less expensive than the known fuel injection valves. 
   According to the invention, this object is achieved with a fuel injection valve having the features of claim  1 . 
   The control body is no longer pressed into the housing, as in the prior art, but is inserted loosely and not in a sealing manner into the opening in the housing. This makes simple installation and dismantling of the control body possible. Furthermore, the control body can be manufactured more inexpensively, as requirements which are not so high have to be placed on the dimensional accuracy and the machining quality. 
   The sealing of the high pressure space with respect to the low pressure space is ensured firstly by the interaction of sealing faces on the control body and on the holding body and secondly by a further sealing face on the holding body bearing against a seat face which is configured on the housing. 
   Preferred refinements of the fuel injection valve according to the invention are described in the dependent claims. 

   
     In the following text, one exemplary embodiment of the subject matter of the invention will be explained in greater detail with reference to the figures, in which, purely diagrammatically: 
       FIG. 1  shows a fuel injection valve in longitudinal section, 
       FIG. 2  shows a part region of the fuel injection valve according to  FIG. 1  in longitudinal section and on an increased scale compared with  FIG. 1 , 
       FIG. 3  shows a part region of the illustration according to  FIG. 2  in longitudinal section and on an increased scale compared with  FIG. 2 , and 
       FIG. 4  shows the holding body of the fuel injection valve which is shown in  FIGS. 1 to 3 , in a perspective illustration. 
   

   The fuel injection valve  1  which is shown diagrammatically in longitudinal section in  FIG. 1  has a housing  2  which is formed by an upper housing part  2   a  and a valve seat element  2   b . The valve seat element  2   b  is connected in a sealing manner to the upper housing part  2   a by means of a holding element  3  which is configured as a clamping nut. 
   The valve seat element  2   b  has a valve seat  4  and injection openings  5 . A central hole  6  which is coaxial with respect to the longitudinal axis A of the housing  2 , has a diameter which changes over its length and defines a high pressure space  7  configured in the interior of the housing  2 . Said high pressure space  7  is connected to a high pressure fuel inlet  8  and extends as far as the valve seat  4 . 
   An injection valve element  9  which is configured as a valve needle and is coaxial with respect to the housing longitudinal axis A is arranged in the interior of the housing  2 , that is to say in the hole  6 , which injection valve element  9  interacts by way of its tip with the valve seat  4  in the closed position which is shown in  FIG. 1 , in order to close the injection openings  5 . In order to open the injection openings  5 , the injection valve element  9  is raised from the valve seat  4  by means of a hydraulic control apparatus  10 , the construction of which will be explained in greater detail using  FIGS. 2 and 3 . The injection valve element  9  is guided in the valve seat element  2   b  by way of a part piece which is configured as a guide  9   a , by means of a tight sliding fit. In order to ensure a hydraulic connection, the injection valve element  9  is provided with ground-down faces in the region of this guide  9   a . The injection valve element  9  is pressed downward in the closing direction by means of a closing spring  11 . At its lower end, the closing spring  11  is supported on a supporting ring  12  which rests on a shoulder  13  on the injection valve element  9 . At the other end, the closing spring  11  is supported on a spacer sleeve  14  which surrounds the injection valve element  9 . 
   The relatively long, hollow cylindrical spacer sleeve  14  bridges the region of the opening of the high pressure fuel inlet  8  into the central hole  6  and is guided at its ends on the wall of the hole  6  by means of guide faces  15 ,  16  ( FIG. 2 ). Here, the play between the guide face  15 ,  16  and the wall of the hole  6  is between 1/100 and 1/10 mm. Between its ends which are provided with the guide faces  15 ,  16 , the spacer sleeve  14  has a smaller diameter, with the result that an annular space  17  is formed between the wall of the hole  6  and the outer circumference of the spacer sleeve, which annular space  17  is connected to the high pressure fuel inlet  8 . The spacer sleeve  14  is provided with passage openings  18 , through which fuel can pass from the annular space  17  into the interior of the spacer sleeve  14 . 
   A stop shoulder  19  is configured in the housing  2 , which stop shoulder  19  serves as a stop for the spacer sleeve  14  during a displacement of the latter in the upward direction and is intended to interact with a stop face  20  which is configured on the lower end of the spacer sleeve  14  ( FIG. 2 ). At its upper end, the spacer sleeve  14  presses against a hollow cylindrical guide sleeve  21  which belongs to the hydraulic control apparatus  10  and is guided at the upper end in the central hole  6  by means of a guide face  22 . There is an annular space  23  between the guide sleeve  21  and the wall of the hole  6 , which annular space  23  is connected to the interior of the spacer sleeve  14  via passages  24 , which are provided at the lower end of the guide sleeve  21  or at the upper end of the spacer sleeve  14 , and belongs to the high pressure space  7 . 
   In the following text, further elements of the hydraulic control apparatus  10  will be described with reference to  FIGS. 2 and 3 . 
   At its end which lies opposite the valve seat  4 , the injection valve element  9  has a double action control piston  25  which is guided in the guide sleeve  21  with a tight sliding fit. The control piston  25  is loaded on its underside by the high fuel pressure in the high pressure space  7  and with its upper side delimits a control space  26  which is delimited laterally by the guide sleeve  21 . An intermediate valve body  27  is situated in the guide sleeve  21 , which intermediate valve body  27  can be displaced in the direction of the longitudinal axis A and has a lower end side  27   a . The intermediate valve body  27  is guided in the guide sleeve  21  with a play of typically from 0.03 to 0.2 millimeters. A throttle passage  31  which is coaxial with respect to the longitudinal axis A and extends between the lower and upper end sides  27   a ,  27   b  of the intermediate valve body  27  extends in the intermediate valve body  27 . 
   A spring element  28  is arranged in the control space  26 , which spring element  28  is supported on one side on the intermediate valve body  27  and on the other side on a supporting element  29  which rests on an annular shoulder  30  on the guide sleeve  21  ( FIG. 3 ). The spring element  28  surrounds a central projection  25   a  of the control piston  25  and generates a force on the intermediate valve body  27 , which force is substantially smaller than the force which is exerted by the closing spring  11 . When the injection valve  1  is closed, the lower end side  27   a  of the intermediate valve body  27  is arranged at a spacing a from the upper side  29   a  of the supporting element  29  (see  FIG. 3 ). The supporting element  29  serves as a stop which limits the movement of the intermediate valve body  27  downward. The supporting element  29  could also be of one piece with the guide sleeve  21  and configured as one workpiece with the latter. 
   The intermediate valve body  27  bears with the upper end side  27   b  against a lower end side  32   a , which serves as a sealing face, of a control body  32  which is arranged loosely, that is to say not in a sealing manner, in the central hole  6 . Together with the upper side  21   a  of the guide sleeve  21 , the lower end side  32   a  of the control body  32  seals the control space  26  with respect to the high pressure space  7 . The control body  32  bears with an upper end side  32   b  against the underside  33   a  of a holding body  33 . The holding body  33  is screwed into a recess  35  in the housing  2  by means of an external thread  34 . The holding body  33  is provided with countersunk holes  36  which serve to introduce a tool for screwing and tightening the holding body  33  (see also  FIG. 4 ). 
   The holding body  33  is screwed fixedly into the housing recess  35  in such a way that it bears with a first annular sealing face  37  which is configured on its underside  33   a  against a seat face  38  which is configured on the base of the recess  35  in the housing  2  and surrounds the central hole  6 . A second, likewise annular sealing face  39  adjoins said first sealing face  37  of the holding body  33 , which second sealing face  39  lies in the same plane as the first sealing face  37 . A sealing face  40  which is configured on the upper end side  32   b  of the control body  32  bears against said second sealing face  39 . The sealing faces  37 ,  38 ,  39  and  40  preferably seal close to the circumference of the hole  6 . Here, the sealing faces  37  and  39  of the holding body  33  are advantageously configured on a single flat end face of the holding body  33 . 
   The control body  32  has a continuous control passage  41  which extends coaxially with respect to the longitudinal direction A and has a throttle restriction  42  at its end which opens into the upper end face  32   b  of the control body  32 . The control passage  41  is hydraulically connected to the throttle passage  31  in the intermediate valve body  27 . 
   The sealing face  40  on the upper end side  32   b  of the control body  32  surrounds the control passage  41 . 
   Further passages  43  are formed in the control body  32 , which passages  43  are offset laterally with respect to the control passage  41  and open into the lower end side  32   a  of the control body  32 . At the other end, the passages  43  are connected to an annular groove  44  on the outer circumference of the control body  32 , which annular groove  44  is connected to the annular space  23  and in which therefore the high fuel pressure prevails. In the injection valve  1  which is situated in the closed position, that is to say therefore between the injection processes, the passages  43  are closed by the intermediate valve body  27  which is pressed with its upper end side  27   b  against the lower end side  32   a  of the control body  32 . 
   In order to control the movement of the injection valve element  9 , an electromagnetically actuated pilot valve  45  is accommodated in the housing  2 , which pilot valve  45  has a displaceable valve stem  46  and a closure body  47  which is separate from the former and rests between injection processes on that upper end side  32   b  of the control body  32  which serves as a valve seat face, and closes the control passage  41 . A pilot valve spring  48  which presses the closure body  47  against the upper end side  32   b  of the control body  32  acts on the valve stem  46  and therefore also on the closure body  47 . 
   In order to actuate the valve stem  46 , there is an electromagnet arrangement  49  which comprises a magnet body  50  having a magnet coil  51  and a magnet armature  52 . The valve stem  46  is connected fixedly to the magnet armature  52  and is guided displaceably in the magnet body  50 . 
   In addition to the countersunk holes  36 , the holding body  33  also has a central hole  53  (see also  FIG. 4 ), in which the valve stem  46  extends and in which the closure body  47  is guided displaceably. A stop shoulder  54  which engages into an annular groove  55  on the valve stem  46  protrudes into said central hole  53 . The stop shoulder  54  serves to limit the stroke of the valve stem  46  during an excitation of the electromagnet arrangement  49 . Here, the maximum possible stroke b of the valve stem  46  is smaller than the spacing c between the magnet armature  52  and the magnet body  50 , with the result that the magnet armature  52  does not bear against the magnet body  50 , even when the pilot valve  45  is open. The stop shoulder  54  for the valve stem  46  lies outside the effective magnetic field of the electromagnet arrangement  49 . 
   In order for it to be possible to insert the valve stem  46  into the holding body  33 , the latter is provided with an eccentrically arranged recess  56  which is open toward the central hole  53 . The valve stem  46  is introduced into the recess  56  in a manner which is offset laterally with respect to the axis of the central hole  53 . If the annular groove  55  of the valve stem  46  is situated at the level of the stop shoulder  54 , the valve stem  46  is displaced in the transverse direction into the central hole  53 . 
   In addition to closing the control passage  41 , the closure body  47  which is guided loosely in the hole  53  serves to set the stroke b of the valve stem  46  accurately. The magnitude of the stroke b can be fixed accurately by the use of a closure body  47  having a defined height. If accurate setting of this type should not be necessary, which can be the case, for example, in another refinement of the stroke limitation of the valve stem  46 , the closure body  47  can be omitted. In this case, the control passage  41  is closed directly by the valve stem  46 , as is known, for example, from EP-A-1 273 791. In the solution which is shown in the figures, the lower, spherical end  46   a  of the valve stem  46  acts on the flat upper end face  47   b  of the closure body  47  ( FIG. 3 ). In the opposite case, the upper end face  47   b  of the closure body  47  could be of spherical configuration and interact with a flat end face  46   a  of the valve stem  46 . In both cases, the sealing action of the pilot valve  45  is improved. 
   The central hole  53  and the recess  56  in the holding body  33  belong to a low pressure space  57  which is flow-connected to a low pressure outlet  58  ( FIGS. 1 and 2 ). A line (not shown) leads back to a fuel reservoir from this low pressure outlet  58 . The closure body  47  is provided with longitudinal grooves  47   a  which permit a throughflow of fuel from the control passage  41  into the low pressure space  57  when the closure body  47  is raised by the control body  32 . 
   As has already been mentioned, the high fuel pressure which can be 2000 bar and more prevails in the annular groove  44  in the control body  32 . In order to prevent it being possible for relatively great amounts of fuel to pass from this annular groove  44  which belongs to the high pressure space  7  to the low pressure space  57  past the control body  32  which is inserted into the housing  2  not in a sealing manner, the first sealing face  37  of the holding body  33  which is screwed into the housing  2  is pressed in a sealing manner against the seat face  38  in the housing  2 . Furthermore, the control body  32  is pressed by the fuel pressure in the high pressure space  7  with its sealing face  40  against the other sealing face  39  on the holding body  33 . Here, requirements which are not excessively high are made on the surface quality of the sealing faces  37 ,  39  and  40  and the seat face  38 . It can be sufficient to grind these faces, in order to achieve a satisfactory sealing action, because the sealing action does not have to be 100%. Expensive post-machining steps are therefore not necessarily required. If a 100% sealing action should be necessary or desired, it can be achieved with finely lapped faces. However, if the leakage is substantially smaller than the amount of fuel which is relieved via the control passage  41  (for example, 10% of the latter or less), the leakage does not play a role in practice as a rule. 
   The method of operation of the fuel injection valve  1  which is shown in  FIGS. 1 to 3  is as follows: the starting point is the state which is shown in these figures, in which the injection valve element  9  is situated in the closed position and the intermediate valve body  27  bears sealingly against the control body  32 . The electromagnet arrangement  49  is not excited and the closure body  47  closes the control passage  41 . The same pressure prevails in the control space  26  as in the high pressure space  7 . 
   An injection cycle is triggered by the excitation of the electromagnet arrangement  49 . Here, the magnet armature  52  is pulled against the magnet body  50 , which has the consequence that the valve stem  46  is raised from the closure body  47 . The closure body  47  can then be displaced upward under the action of the fuel pressure in the control passage  41  and opens the control passage  41 . The control passage  41  and therefore also the control space  26  are now connected to the low pressure space  57 . The pressure in the control space  26  begins to drop. As a result, the injection valve element  9  moves away from the valve seat  4  and opens the injection openings  5 . The injection process begins. Here, fuel is displaced out of the control space  26  through the throttle passage  31  and the control passage  41  into the low pressure space  57 . During the entire opening process of the injection valve element  9 , the intermediate valve body  27  remains in contact with the control body  32 . The opening stroke of the injection valve element  9  is limited, for example, by the fact that the projection  25   a  of the control piston  25  comes into contact with the intermediate valve body  27 . 
   In order to end the injection process, the electromagnet arrangement  49  is de-energized. This has the consequence that, under the force of the pilot valve spring  48 , the valve stem  46  and, together with it, the closure body  47  are moved downward, until the closure body  47  comes into contact with the control body  32 . The low-pressure-side opening of the control passage  41  is closed again by the closure body  47 . The pressure in the control passage  41  begins to rise. Together with the circumstance that the high fuel pressure prevails in the passages  43  in the control body  32 , this leads to the intermediate valve body  27  moving away from the sealing contact with the control body  32 . The downward movement of the intermediate valve body  27  is ended by stops on the upper side  29   a  of the supporting element  29 . As a result of the fact that the passages  43  in the control body  32  are opened by the movement of the intermediate valve body  27  away from the control body  32 , fuel can flow under high pressure through these passages  43  and the throttle passage  31  and along the entire circumference of the intermediate valve body  27 , which accelerates the closing process of the injection valve element  9  to a pronounced extent. As soon as the injection valve element  9  bears against the valve seat  4  again and closes the injection openings  5 , the injection process is ended. 
   Immediately after this, the intermediate valve body  27  is moved back into its sealing position under the force of the spring element  28 . The fuel injection element  1  is then ready for the next injection process. 
   The spacer sleeve  14  which bridges the region of the high pressure fuel inlet  8  makes it possible to arrange the closing spring  11  below the high pressure fuel inlet  8 , with the result that the wall thickness of the housing  2  can be kept great in the region of the high pressure fuel inlet  8 , without it being necessary to increase the external diameter of the housing  2 . The spacer sleeve  14  transmits the force of the closing spring  11  to the control body  32  via the guide sleeve  21 . 
   During assembly, the injection valve element  9 , together with the closing spring  11  and the spacer sleeve  14  which is pushed over it, is inserted into the valve seat element  2   b , this subassembly is introduced into the upper housing part  2   a  and is fastened by means of the holding element  3  to the upper housing part  2   a . The stop shoulder  19  in the upper housing part  2   a  limits the insertion path of the spacer sleeve  14  in the central hole  6 , which makes the assembly of the control body  32  considerably simpler. 
   As mentioned, the supporting element  29  serves as a stop for the intermediate valve body  27 , as a result of which the opening path of the intermediate valve body  27  is limited. This affords advantages during preinjections at short time intervals. 
   As a result of the fact that the control body  32  is inserted loosely into the central hole  6 , no particular requirements have to be made of the control body  32  with regard to manufacture and machining. In addition, the installation of the control body  32  into the housing  2  is comparatively simple. This all has a favorable effect on the costs. 
   In the exemplary embodiment shown, the fuel is fed to the valve seat  4  via the central housing hole  6 . However, the special structural solutions which are described can also be used in fuel injection valves, in which the fuel is fed to the valve seat via a feed channel which is offset laterally with respect to the housing longitudinal axis A, as is known, for example, from U.S. Pat. No. 5,775,301.