Abstract:
An injection nozzle has a nozzle body, a nozzle needle that is supported displaceably in the nozzle body, a control chamber that communicates with a fluid inlet and a fluid outlet, and a valve element that can open and close the fluid outlet. The control chamber is laterally defined by a displaceable ring which rests on the nozzle needle, and a closing spring presses the ring against the nozzle needle in fluid-tight fashion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a 35 USC 371 application of PCT/DE 02/00847 filed on Mar. 9, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an injection nozzle, having a nozzle body, a nozzle needle that is supported displaceably in the nozzle body, a control chamber that is in communication with a fluid inlet line and a fluid outlet line, and a control element that can open and close the fluid outlet line. 
   2. Description of the Prior Art 
   From the prior art, injection nozzles of the above type are known that are used in common rail injection systems. For closing the needle, they have a closing spring, which is located in the control chamber. The size of the spring thus determines the control chamber volume. Since for good closure of the needle, the spring should have the greatest possible stiffness and is thus relatively large, the control chamber volume also becomes comparatively great. This makes the injector sluggish, and the quantity and instant of injection cannot be defined exactly. 
   One object of the invention is therefore to refine an injection nozzle of the type defined at the outset in such a way that the dimensions of the closing spring can be selected freely, independently of the control chamber volume and independently of the control piston diameter that is important for the needle speed. Another object of the invention is for the nozzle needle guide no longer to have to assume any sealing function. 
   SUMMARY OF THE INVENTION 
   The injection nozzle has the advantage that the control chamber volume can be made quite small, and as a result a rapid response behavior of the nozzle is achieved. High needle speeds can be attained, since the diameter of the control piston can be defined freely. The closing spring makes good closing performance of the nozzle possible. Moreover, the communication between the ring and the nozzle needle is fluid-tight. Thus the nozzle needle guide no longer has any sealing function, which makes the demand for the quality of the guidance less stringent. 
   In a preferred embodiment of the invention, the fluid inlet line has a first throttle element, and the fluid outlet line has a second throttle element. By dimensioning the two throttle elements with reference to the control piston diameter of the valve body, the needle speed can thus be defined in a simple way. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described below in conjunction in the accompanying drawings, in which: 
       FIG. 1  is a sectional view of an injection nozzle of the invention in a first embodiment; 
       FIG. 2  is a sectional view of an injection nozzle of the invention in a second embodiment; 
       FIG. 3  is a sectional view of an injection nozzle of the invention in a third embodiment; 
       FIG. 4  is a sectional view of an injection nozzle of the invention in a fourth embodiment; 
       FIG. 5  is a sectional view of an injection nozzle of the invention in a fifth embodiment, and  FIG. 5   a  shows a detail of one portion thereof; 
       FIG. 6  is a sectional view of an injection nozzle of the invention in a sixth embodiment, and  FIG. 6   a  shows a detail of one portion thereof; 
       FIG. 7 , in a sectional view, an injection nozzle of the invention in a seventh embodiment,  FIG. 7   a  shows a detail of one portion thereof and  FIG. 7   b  shows an alternative design for the portion shown in  FIG. 7   a ; 
       FIG. 8  is a sectional view of an injection nozzle of the invention in an eighth embodiment, and  FIG. 8   a  shows a detail of one portion thereof; and 
       FIG. 9  is a sectional view of an injection nozzle of the invention in a ninth embodiment. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In  FIG. 1 , an injection nozzle is shown in accordance with a first embodiment of the invention. The injection nozzle  10  has a nozzle body  12 , which here is constructed of a plurality of portions  12   a ,  12   b , which are held firmly together by a bracing element  13 . The nozzle body  12  is provided with nozzle openings  14 , through which fuel can be injected into the cylinder of an internal combustion engine. A fuel conduit  16  leads to the nozzle openings. 
   In the nozzle body  12 , a nozzle needle  18  is mounted displaceably in such a way that from an outset position, in which the nozzle openings  14  are closed, it can be put into an injection position, in which the nozzle openings are opened. 
   On the side of the nozzle needle  18  remote from the nozzle openings  14 , a control chamber  20  is formed, one face end of which is formed by the back side of the nozzle needle  18 , and the other face end of which is formed by a valve block  22 . The circumferential wall of the control chamber  20  is formed by a ring  24 , which is disposed in a sealed way displaceably on the outer wall of the valve block  22  and which rests on the flat back side of the nozzle needle  18 . This makes a tolerance compensation possible between the ring  24  and the nozzle needle  18 . 
   A closing spring  28  for the nozzle needle  18  is disposed in a reservoir  26  between the nozzle body  12  and the valve block  22 . The closing spring  28  is braced on the ring  24 , so that the ring is pressed against the nozzle needle  18  with a predetermined force. In this way, on the one hand a fluid-tight contact of the ring  24  with the nozzle needle  18  is obtained, and on the other, the nozzle needle is urged into its outset position. 
   The control chamber has a fluid inlet  30 , which branches off from the fuel conduit and is provided with an inlet throttle  32 . The control chamber  20  also has a fluid outlet  34 , which is provided with an outlet throttle  36 . The cross section of the outlet throttle  36  is greater than the cross section of the inlet throttle  32 . 
   The fluid outlet  34  discharges into a valve chamber  38 , in which a valve element  40  is disposed. The valve element  40  can be moved between a position in which the fluid outlet  34  is closed and a position in which the fluid outlet is opened. Arbitrary means known to one skilled in the art, such as a piezoelectric actuators, can be used to move the valve element  40 . 
   In the outset state, that is, when no fuel is to be injected, the valve element  40  is in the closed position. The fuel is thus dammed up in the control chamber  20 , so that the fuel pressure prevails there. Since the cross section of the back side of the nozzle needle  18  is larger than the cross section of the nozzle needle in the region of the nozzle openings  14 , the force generated in the control chamber  20 , which urges the nozzle needle into the closed position, is greater than the force that is generated at the opposite end of the nozzle needle and that urges the nozzle needle into the opened position. The force of the closing spring  28  is added to this difference. The nozzle needle accordingly remains in the closed position. 
   When fuel is to be injected, the fluid outlet  34  is uncovered by the valve element  40 . Since because of the cross-sectional ratios between the outlet throttle and the inlet throttle the pressure in the control chamber  20  now drops, it is attained that as a result of the fuel pressure acting on the tip of the nozzle needle  18 , the nozzle needle lifts from the nozzle openings  40  and is displaced into the opened position. The displacement is limited by the contact of the back side of the nozzle needle  18  with a protrusion  42 , acting as a stop, of the valve block  22 . 
   Upon the transition of the nozzle needle  18  to the opened position, the ring  24  is pushed back by the nozzle needle; the sealed contact between the ring and the nozzle needle is maintained. The fluid volume positively displaced in the region of the closing spring  28  upon displacement of the ring  24  can bypass the ring and flow into the lower part of the reservoir  26 . Since the pressure in the control chamber  20  is never greater than the pressure in the surrounding parts of the nozzle, the ring  24  is not lifted from the nozzle needle  18 . This embodiment offers the advantage that with respect to the fluid, a tight seal between the nozzle needle  18  and the ring  24  is achieved. This in turn lessens the demands made of fluid tightness of the guidance of the nozzle needle  18  in the nozzle body  12 , thus simplifying the structure of the injection nozzle. Moreover, the size of the closing spring can be selected independently of the control piston diameter and the control chamber volume, which makes it easier to dimension the injector. 
   In  FIG. 2 , an injection nozzle is shown in accordance with a second embodiment of the invention. To the extent that components known from the first embodiment are used in this embodiment, the same reference numerals are employed. In terms of their function, reference is made to the description above. 
   In a distinction from the first embodiment, in which the stop for the nozzle needle is seated on the valve block  22 , the nozzle body  12  here has the protrusion  42 , which limits the displacement of the ring  24  and thus of the nozzle needle  18 . This has the advantage that the stop position of the nozzle needle relative to the nozzle body is defined precisely and does not also depend on the location of the valve block relative to the nozzle body. 
   In  FIG. 3 , an injection nozzle is shown in a third embodiment of the invention. For components known from the above embodiments, the same reference numerals are used, and reference is made to the above descriptions. 
   In a distinction from the first embodiment, the fluid inlet  30  with the inlet throttle  32  is located here in the ring  24 . The inlet throttle  32  and outlet throttle  36  are located in different components, which offers the capability of also combining different versions of the two components, that is, the ring and the valve block. 
   In  FIG. 4 , an injection nozzle is shown in a fourth embodiment of the invention. For components known from the above embodiments, the same reference numerals are used, and reference is made to the above descriptions. 
   In a distinction from the first and second embodiments, the fuel delivery to the nozzle needle  18  takes place here via inflow chambers  44 , which are ground into the nozzle needle. To assure the sealing function between the nozzle needle  18  and the sealing ring  24 , the inflow chambers  44  can be embodied such that they do not extend over the entire guidance height of the needle. In this embodiment, the inlet throttle  34  is accommodated in the nozzle needle. A first chamfer  45  facilitates the inflow of fuel to the fluid inlet  30 . Because of the location of the fluid inlet and fluid outlet in the components, that is, the nozzle needle and the valve block, the possibility exists here of combining various embodiments of these two components. 
   In  FIG. 5 , an injection nozzle is shown in a fifth embodiment of the invention. For components known from the above embodiments, the same reference numerals are used, and reference is made to the above descriptions. 
   The ring  24  is provided here with a second chamfer  46 , so as to attain better sealing by means of a reduced bearing surface area at the flat seat between the ring  24  and the nozzle needle  18 . 
   In  FIG. 6 , an injection nozzle is shown in a sixth embodiment of the invention. For components known from the above embodiments, the same reference numerals are used, and reference is made to the above descriptions. 
   In this embodiment, in the area contact between the ring and the nozzle needle, a sealing element  48  is inserted. This achieves improved sealing off of the control chamber  20  in the region of the connection between the ring and the nozzle needle. The nozzle needle is provided here with an annular groove  50 , since by means of this annular groove, the sealing element  48  can be supported securely. The transmission of force between the nozzle needle  18  and the ring  24  is effected via an annular protrusion  52 . 
   In a further preferred embodiment, as shown in  FIGS. 7 ,  7   a , and  7   b , the sealing element  48  is a sealing spring. A cup spring ( FIG. 7   a ) is especially preferred here. This is particularly advantageous since even if a ring  24  is not seated uniformly on the nozzle needle  18 , the cup spring  48  enables complete sealing between the ring and the nozzle needle. The initial tension of the cup spring  48  should always be less than the tension of the closing spring  28 , so that the ring  24  will always rest on the nozzle needle  18 . 
   If the part  12   a  of the nozzle body and the valve block  22  are embodied in one piece (FIG.  7 ), the assembly of the injection nozzle is simplified and the precision of production of the entire nozzle is improved. 
   In  FIG. 8 , an injection nozzle is shown in an eighth embodiment of the invention. For components known from the above embodiments, the same reference numerals are used, and reference is made to the above descriptions. 
   In this embodiment, the ring  24  comprises a first annular portion  54  and a second annular portion  56 . The boundary face between the first and second annular portions is a spherical-segment face. As a consequence of the assembly of the injection nozzle, the central axis of the valve block  22  may not precisely match the central axis of the nozzle needle  18 ; that is, the two axes may be inclined somewhat relative to one another. Since the ring  24  rests on the outer wall of the valve block, in that case the central axis of the ring also deviates from the central axis of the nozzle needle, making a complete seal between the ring and the nozzle needle impossible. If the ring is constructed of two annular portions, the central axis of the first annular portion  54  then matches the central axis of the nozzle needle, and the central axis of the second annular portion  56  matches the central axis of the valve block. The first and second annular portions with the spherical-segment face have complementary sliding faces so that they can move relative to one another. The common boundary face furthermore makes the sealing between the two annular portions possible. Since the central axes of the nozzle needle and the first annular portion match, a complete seal between the ring  24  and the nozzle needle  18  is achieved. 
   In  FIG. 9 , a further preferred embodiment of the injection nozzle is shown. Here, the nozzle needle  18  comprises a first nozzle needle part  58  and a second nozzle needle part  60 . In a particularly simple way, this makes it possible to compensate for a deviation of axis between the valve block  22  and the nozzle needle  18 . To that end, the first nozzle needle part is advantageously embodied such that it forms a spherical segment and rests with positive engagement in the second nozzle needle part. An especially easily achieved compensation for the deviation in axis is thus realized. 
   The foregoing relates to preferred exemplary embodiments 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.