Abstract:
A fuel injection device for internal combustion engines having a magnet valve that has a damping chamber and a relief chamber which communicate hydraulically through a damping throttle that damps in both laminar and turbulent fashion. As a result, the waviness of the characteristic curves of the fuel injection system is reduced and its function is improved.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a 35 USC 371 application of PCT/DE 00/04587 filed on Dec. 22, 2000. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention is based on a fuel injection device, having a magnet valve for controlling fuel flows, which valve, in at least one of its positions, closes a damping chamber in the magnet valve that communicates constantly with a relief chamber via a damping throttle. 
   2. Description of the Prior Art 
   A fuel injection device of the type with this invention is concerned is known from Published, Nonexamined German Patent Application DE-OS 196 16 084 A1, employs an insert piece with a through bore acting as a damping throttle between the damping chamber and the relief chamber. The damping performance of this through bore is not always satisfactory. Moreover, the installation space required for the insert piece is comparatively great. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   The primary object of the invention is to furnish a fuel injection device with further improved performance. 
   According to the invention, this object is attained with a fuel injection device, having a magnet valve for controlling fuel flows, which valve, in at least one of its positions, closes a damping chamber in the magnet valve that communicates constantly with a relief chamber via a damping throttle, and in which the damping throttle throttles in both laminar fashion and turbulent fashion. 
   SUMMARY OF THE INVENTION 
   By this provision, the damping performance of the damping throttle can be adapted to the requirements of the fuel injection system within wider limits compared to the prior art. As a consequence, because of the use of the damping throttle of the invention, the waviness of the characteristic curves of a fuel injection device of the invention is decreased markedly. Furthermore, the characteristic curves of the fuel injection device of the invention become smooth. Both effects contribute to improving the performance of the fuel injection system. Furthermore, by the use of the damping throttle of the invention, the variations between different examples of a structurally identical fuel injection device are reduced, so that the variation in operating performance of internal combustion engines equipped with the fuel injection devices of the invention is reduced as well. 
   In a variant of the invention, it is provided that the damping throttle is embodied in a support plate, which is disposed between the damping chamber and the relief chamber and which closes off the damping chamber toward the relief chamber, so that a very compact design, because it is shallow in structure, is possible. 
   Further features of the invention provided that the turbulent throttle of the damping throttle is embodied in the form of a through bore that connects the damping chamber and the relief chamber, and in a further features, the through bore has a recess on at least one end, so that the throttling performance of the turbulent throttle can be adjusted within wide ranges to the particular demands of the fuel injection system. The adjustment is done by means of the diameter and length of the through bore, among other factors. 
   In a further feature of the invention the laminar throttle of the damping throttle is embodied in the form of a gap, so that under all possible operating conditions, the laminar damping performance is reliably achieved. 
   Features of the invention provide that the support plate, on its side toward the damping chamber, has at least one indentation, which with the magnet valve, in particular the electromagnet of the magnet valve, forms a gap, so that the gap can be produced in a simple way. 
   Further features of the invention provide that the indentation is round, that the indentation is disposed substantially concentrically with the through bore, that the indentation or indentations are grooves extending substantially radially to the longitudinal axis of the th rough bore, and that the thickness of the gap or the depth of the indentation or indentations is from 0.1 to 0.2 mm. As a result of these designs, especially good damping performance of the laminar throttle and the damping throttle overall can be attained. The use of a round indentation, with a depth of 0.1 to 0.2 mm and disposed substantially concentrically to the through bore has proved to be especially advantageous. 
   In a further feature of the invention, the indentation is disposed in such a way that it intersects at least one recess in the support plate, so that a communication always exists from the damping chamber to the relief chamber, via the gap formed by the indentation and the electromagnet and via the recess. 
   In a further feature of the invention, the support plate is mounted detachably in the fuel injection device, so that by simply replacing the support plate, the damping performance of the fuel injection device can be changed and improved. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages and advantageous features of the invention can be learned from the ensuing description, taken with the drawings, in which: 
       FIG. 1  is a cross section through a fuel injection device of the invention; 
       FIG. 2  is an enlarged view of the detail X of  FIG. 1 ; 
       FIGS. 3   a ,  3   b  and  3   c  are a cross section and two views from below of a support plate; and 
       FIGS. 4   a  and  4   b  are two further views from below of a support plate. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows part of a distributor injection pump, as a fuel injection device of the invention, in section. In a housing  1  of the fuel injection pump, a bush  2  is inserted, which in turn in its interior has a guide bore  5 , in which a distributor  7  is guided. The distributor is driven to rotate by means not otherwise shown and revolves in synchronism with the rpm of an associated internal combustion engine. It is axially secured against displacement in the housing  1  and has a longitudinal conduit  8 , which communicates on one side with a pump work chamber, not shown further here, and on the other side discharges into a pressure chamber  9 , which is part of a conduit  12  that originates on one face end  10  of the distributor  7  and ends blind and is coaxial to the distributor. The pressure chamber  9  is defined on one side by a valve seat  14 , which changes over into a partial bore  15  extending onward on the relief side of the conduit  12 . The other side of the pressure chamber  9  is adjoined by a coaxial guide bore  16 , which emerges at the face end  10  of the distributor  7 . 
   A magnet disk  18  and a shim  19  are screwed onto this face  10 . The shim  19  has a keyhole-shaped recess  20 . A neck  22  of a valve member  23  of a magnet valve  24  protrudes through a narrow portion of the recess  20  that is coaxial to the distributor. The magnet valve is inserted with its housing  25  into the housing  1  of the fuel injection pump and is fixed there in stationary fashion. In its housing  25 , the magnet valve  24  has an electromagnet  29  with a magnet coil  26 , which is disposed inside a magnet core  27 , which takes the form of a ring-shaped cup, with a middle, sleevelike magnet core  27  and an outer magnet jacket  28 , between which and the middle magnet core  27  the magnet coil  26  is supported. On the face end toward the distributor  7 , the magnet core  27  is supplemented with the magnet disk  18 , which is adapted in diameter to the inside diameter of the outer magnet jacket  28  and with the latter forms only a narrow air gap. As a result, while the electromagnet  29  is stationary, the magnet disk  18 , which is part of the magnetic circuit, can rotate together with the rotating distributor  7 . 
   The middle magnet core  27  has a continuous recess  30 , which serves as a guide  31  for a plunging armature  33 . This armature is secured to a headlike end  34 , adjacent to the neck  22  of the valve member  23 , and upon excitation of the magnet coil  26 , it actuates the valve member  23  to move in the closing direction onto its seat  14 . Acting on the valve member  23  in the opening direction is a compression spring  35 , which is supported in the partial bore  15 . At the same time, the plunging armature  33  can also integrally form the headlike end  34  of the valve member  23 . 
   The stroke of the valve member  23  is limited by the contact of a shoulder  36  of the valve member with the shim  19 . The shoulder  36  is formed by the transition from the part of the valve member  23  that slides in the guide bore  16  to the neck  22 . 
   A support plate  38  is located above the magnet coil  26 . The support plate  38  contains a damping throttle, which connects a damping chamber  40 , defined by the support plate  38  and the plunging armature  33 , to relief chamber  41 . The relief chamber  41  adjoins the support plate  38  on the far side thereof and communicates with fuel-carrying chambers of the fuel injection pump. 
   The support plate  38  can optionally be replaced to enable optimal adaptation of the damping throttle to the fuel injection system. 
   In operation of the fuel injection device, the valve member  23  is urged in the opening direction by the compression spring  35 , so that the valve member  23  is lifted from its valve seat  14 , and the pressure chamber  9  can be relieved toward the relief side. In this position of the magnet valve  24 , high pressure cannot build up in the pump work chamber, not shown, and correspondingly high pressure cannot be carried to a fuel injection valve over one of a plurality of supply lines  43 , which communicate in alternation with the pressure chamber  9  or the longitudinal conduit  8  upon rotation of the distributor. 
   When current is supplied to the magnet coil  26 , a magnetic flux is created, which moves the plunging armature  33  toward the magnet disk  18  until the valve member  23  comes into contact with its valve seat  14 . As already indicated, the stroke in the opening direction is limited by the contact of the shoulder  36  with the shim  19 . The passage of the head  34  through the shim  18  makes the keyhole-shaped design of the recess  20  possible. In this respect, in a known manner, the head  34  of the valve member  23  is passed through an eccentrically located larger diameter, and then the neck  22  is positioned in the coaxial position to the distributor axis. 
     FIG. 2  shows an enlarged detail of the fuel injection device. In this view, the disposition of the support plate  38  between the damping chamber  40  and the relief chamber  41  is clearly shown. The support plate  38  has a through bore  45  acting as a turbulent throttle. By means of a countersunk recess  47 , the through bore  45  is shortened, which can have an advantageous effect on the damping properties. The laminar throttle, which together with the aforementioned turbulent throttle forms the damping throttle of the fuel injection system, is not shown in FIG.  2 . 
   In  FIG. 3   c , a further detail of  FIG. 2  is shown. The support plate  38  rests on the middle magnet core  27 . Unlike  FIG. 2 , the countersunk recess  47  of the through bore  45  is disposed on the underside of the support plate  38 . Between the support plate  38  and the middle magnet core  27 , there is a gap  49  that is formed by an indentation  51  in the support plate  38 .  FIGS. 3   a  and  3   b  each show a view from below of a support plate  38  with variously shaped indentations  51 . 
   In  FIG. 3   b , two parallel indentations  51  are provided. In  FIG. 3   a , a wide indentation  51  is provided. The indentations in  FIGS. 3   a  and  3   b  extend between two recesses  53 . Protruding through these recesses  53 , in the built-in state of the support plate, are the plug contacts that supply current to the magnet valve. Also in the built-in state, the recesses  53  are in hydraulic communication with the relief chamber  41 , so that via the gap  49  and the recesses  53 , fuel can flow out of the damping chamber  40  into the relief chamber  41 . In  FIGS. 3   a  and  3   b , the countersunk recess  47  is not shown. 
   Further views of support plates  38  from below are shown in  FIGS. 4   a  and  4   b . In these versions, the indentations  51  are circular, which has proved to be especially advantageous. The countersunk recess  47  is shown in  FIG. 4   b.    
   With the fuel injection device described above and the associated magnet valve, an exact fuel quantity control is obtained, in particular in the case contemplated here in which, with the aid of the magnet valve, the high-pressure pumping phase along with the injection onset and injection duration of the fuel injection pump is determined. Via the rotating distributor, and via a respective supply line  43 , the associated fuel injection valve is triggered and supplied with the high-pressure injection quantity controlled by the magnet valve  24 . With only slight mass, the magnet valve is very fast and vibration-free, with the optimally adaptable damping contemplated here. 
   The foregoing relates to 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.