Abstract:
The invention relates to a tool for the electrochemical machining of a fuel injection device, the tool having an electrode holder and an electrode element which forms a cathode during the machining operation in order to be able to electrochemically remove material from the fuel injection device in a machining region. The electrode element is arranged in such a way that it can be displaced in relation to the electrode holder.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 35 USC 371 application of PCT/EP 2006/062128 filed on May 8, 2006. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an improved tool for electrochemical machining of a fuel injection device. 
     2. Description of the Prior Art 
     Fuel injection devices are components of fuel injection systems. With these systems, fuel can be delivered from a tank to the combustion chambers of an internal combustion engine. Pumps, in particular high-pressure pumps, can be used, which subject the fuel to pressure and deliver it to the fuel injection devices. The fuel injection devices typically have a housing in which a plurality of chambers are provided for carrying and/or holding fuel. Between these chambers, sharp-edged transition regions may be embodied, especially whenever the individual chambers are made by metal-cutting machining. In the regions of the sharp-edged transitions, burrs can be formed, which have to be removed before the fuel injection device is put into operation. 
     In addition to mechanical methods, the possibility exists of removing these burrs by way of electrochemical machining. Such a method provides that an electrode, connected as a cathode, is brought to a machining region of a fuel injection device that is to be deburred, the latter being connected as an anode. An electrolyte fluid can be delivered to the machining region, and as a result, electrochemical reactions take place at the electrode connected as a cathode and at the workpiece connected as an anode. At the anode, positively charged cations are removed, which together with hydroxide ions react to form a metal hydroxide and settle out as sludge. At the cathode, various chemical reduction reactions take place. 
     The method described is quite suitable for enabling a defined quantity of material to be removed from the housing of a fuel injection device. However, especially in undercut regions of the housing, it can be difficult to position the electrode in the fuel injection device in such a way that an optimal work gap is formed between the electrode and the work region. 
     With this as the point of departure, the object of the present invention is to further develop a tool for electrochemical machining of a fuel injection device such that deburring, with good material removal rates, is made possible even in undercut regions of the fuel injection device. 
     SUMMARY AND ADVANTAGES OF THE INVENTION 
     Because the electrode element is disposed movably relative to the electrode holder, the electrode element can be moved independently of the electrode holder. Thus the electrode holder can be introduced into the fuel injection device, and the electrode element can be adjusted independently of the electrode holder in its position relative to the machining region, for instance with the aid of an actuating element. Thus via the actuating element, the width in particular of the work gap between the electrode element and the machining region can be adjusted. Thus even machining regions that are very difficult to access can be machined with high material removal rates. Because of the good removal of material, it is also attained that work steps beforehand and afterward that must sometimes be done manually can be omitted. This contributes to making the fuel injection device capable of being produced in great numbers with high quality. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Especially preferred exemplary embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a sectional view of a tool in a first embodiment of the invention, in which an electrode element occupies a first position; 
         FIG. 2  shows a view corresponding to  FIG. 1 , in which the electrode element occupies a second position; 
         FIG. 3  is a sectional view of a tool in a second embodiment of the invention, in which an electrode element occupies a first position; and 
         FIG. 4  is a view corresponding to  FIG. 3 , in which the electrode element occupies a second position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1 , the housing of a fuel injection device is identified by reference numeral  10 , and a tool for machining the injection device is identified by reference numeral  12 . 
     In the injection device  10 , a bore  14  is provided, which is shown in different portions in the sectional planes selected in  FIGS. 1 and 2 . The bore  14  discharges into a substantially rotationally symmetrical chamber  16 , in which the tool  12  is partially received. The and bore  14  and chamber  16  adjoin one another and there form a machining region  18 , from which burr material is to be removed with the aid of the tool  12 . 
     The machining region  18  is provided adjacent to a protrusion  20 , which extends into the chamber  16 , so that from the standpoint of the tool  12 , the machining region  18  is located in an undercut region and is therefore poorly accessible. 
     The tool  12  has an electrode holder  22  of electrically insulating material, which is received entirely in the chamber  16  in the injection device  10 ; an electrode element  24 , which is supported pivotably on the electrode holder  22 ; and an actuating element  26 , which is embodied in elongated form and protrudes out of the chamber  16  in the injection device  10 . 
     The actuating element  26  is embodied substantially cylindrically and is supported displaceably in a receiving element  28 . With the aid of a locking screw  30  that is supported in the receiving element  28  and extends radially to the actuating element  26 , the actuating element can be fixed in a defined position inside the receiving element  28 . 
     The receiving element  28  has a radially outward-pointing protrusion  32 , which adjoins a collar  34  that is embodied on a guide element  36 . The actuating element  26  is guided in the guide element  36 . The protrusion  32  of the receiving element  28  and the collar  34  of the guide element  36  are received in an inner chamber  38  in a clamping element  40 . The clamping element  40  defines the inner chamber  38  with a female threaded surface  42 . Via a head  44  that engages the collar  34  of the guide element  36  from behind, the clamping element  40  and thus the receiving element  28  as well as the guide element  36  can be firmly clamped on a machine, not shown, so that the tool  12  can be supplied with electrical energy and with electrolyte fluid. The inner chamber  38  in the clamping element  40  is sealed off from the machine, not shown, with the aid of a seal  46 . The receiving element  28 , on its end remote from the injection device  10 , has a pin  48  with which the radial position of the tool  12  relative to the machine is defined. 
     The receiving element  28  moreover, on its end remote from the injection device, has a guide pin  50 , which engages a groove  51  in the actuating element  26 , so that the rotary position of the actuating element  26  relative to the receiving element  28  is defined. 
     In its interior, the actuating element  26  has a line  52 , which on the end toward the injection device  10  discharges at a bore  54 . The bore  54  leads to a fluid chamber  56 , which is defined by a sleeve  58  that is embodied in one piece with the guide element  36 . 
     The electrode holder  22  plunges with a wall portion  60  into the sleeve  58 , and with this wall portion  60 , it defines an electrode chamber  62 . 
     The electrode holder  22  has a bolt  64  on which the electrode element  24  is pivotably supported. The electrode element  24  moreover has a slot  66 , in which a sliding-block pin  68  is received that is part of the actuating element  26 . 
     A contact spring  70  is disposed between the actuating element  26  and the electrode element  24 . This spring is anchored firmly by one end in the material comprising the actuating element  26 , and with its other end it presses against the electrode element  24 , so that by way of the contact spring  70 , an electrical connection is made between the actuating element and the electrode element  24 . 
     Adjacent to the electrode holder  22 , a compression spring  72  is provided, which is braced by one end on the end face of the wall portion  60  of the electrode holder  22 . On its other end, the compression spring  72  is braced on a shoulder  74  that is embodied in the guide element  36 . 
     In  FIG. 1 , the electrode element  24  is shown in its retracted position. To put the electrode element  24  in the projected position shown in  FIG. 2 , the receiving element  28  and the clamping element  40  are moved, via a drive mechanism not shown, in the direction of the injection device  10 . As a result of the connection between the receiving element  28  and the actuating element  26 , the actuating element  26  is moved into the electrode chamber  62 , counter to the action of the compression spring  72 . In the process, the sliding-block pin  68  slides inside the slot of the electrode element  24 , so that the electrode element  24  is pivoted, in the pivoting direction marked  76 , in the direction toward the machining region  18 . Thus a work gap  78  between the electrode element  24  and the machining region  18  can be optimally adjusted. 
     In the position of the electrode element  24  shown in  FIG. 2 , the contact spring  70  is compressed compared to the position of the electrode element  24  shown in  FIG. 1 . Thus in any position of the electrode element  24 , it can assure the electrical contacting between the actuating element  26  and the electrode element  24 . 
     The embodiment of the invention shown in  FIGS. 3 and 4  differs from the embodiment shown in  FIGS. 1 and 2  in the embodiment of the electrical contacting of the electrode element. In  FIG. 3 , an injection device  110  is provided into which a tool  112  plunges in some portions. The tool  112  is equivalent in its essential construction to that of the tool  12  of  FIGS. 1 and 2 . The tool  112  likewise has an electrode holder  122 , an electrode element  124 , and an actuating element  126 . The actuating element  126  is received in a receiving element  128 , guided in a guide element  136  and can be fastened with the aid of a clamping element  140  on a machine, not shown. The actuating element  126 , on its end toward the electrode element  124 , has a displaceably supported bolt element  180 , which is in contact with the electrode element  124 . The bolt element  180 , on its end remote from the electrode element  124 , has a bolt head  182 , which is subjected to pressure by a spring  184  in order to press the bolt element  180  against the electrode element  124  for the sake of electrical contacting. 
     In  FIG. 3 , the tool  112  is shown in the retracted state of the electrode element  124 . As the tool  112  is moved into the injection device  110 , a spring  172  is compressed. The actuating element  126  with its sliding-block pin  168  is moved into the injection device, so that the electrode element reaches its projected position (see  FIG. 4 ). In the position of the electrode element  124  shown in  FIG. 4 , the bolt element  180  has been shifted by some distance from the position shown in  FIG. 3 , and as a result the spring  184  is compressed. The spring  184  assures the electrical contacting of the electrode element  124  in every position of the electrode element. 
     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.