Patent Publication Number: US-6663024-B2

Title: Compact high-pressure resistant injector for fuel injection

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 U.S.C. 371 application of PCT/DE 01/02026, filed on May 25, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     In injectors for injecting fuel into combustion chambers of internal combustion engines, the high-pressure resistance of the injectors that can be used is primary. In existing injector designs whose housings include a separate nozzle inlet and a nozzle chamber surrounding the nozzle needle, and given the constantly increasing pressure level in the high-pressure collection chamber (common rail), their high-pressure resistance is becoming increasingly important in terms of their usability, and such injectors are reaching the limits to their high-pressure resistance. 
     2. Prior Art 
     German Patent DE 37 28 817 C2 relates to a fuel injection pump for internal combustion engines. The control valve member used in this fuel injection pump comprises a valve shaft, forming a guide sleeve and sliding in a conduit, and a valve head connected to the valve shaft and oriented toward the actuating device. The sealing face of the valve head cooperates with a face of the control bore that forms the valve seat. The valve shaft has a recess on its circumference, and the axial length of this recess extends from the orifice of the fuel supply line as far as the beginning of the valve head sealing face that cooperates with the valve seat, and in the recess, a face exposed to the pressure of the fuel supply line is formed. This face is equal in area to a face of the valve head that is exposed to the pressure of the fuel supply line, in the closed state of the control valve. As a result, in the closed state the valve is in pressure equilibrium; in addition, a spring element spring that loads the control valve toward its open position is disposed in the guide sleeve of the control valve member. 
     SUMMARY OF THE INVENTION 
     With the compact design proposed according to the invention of an injector for injecting fuel into combustion chambers of internal combustion engine, its high-pressure resistance can be increased considerably, since the nozzle supply line and the nozzle chamber, which surrounds the nozzle needle in the region of its discharge into the combustion chamber, can now be omitted. A much more compact design of an injector can thus be attained, which furthermore is considerably easier to manufacture from the standpoint of production technology. The nozzle needle in the injector configuration proposed according to the invention no longer takes on any sealing function. Guidance of the nozzle needle in the housing of the injector can therefore be provided without canting in guide regions, which can be smaller than in nozzle needle guides that also perform a sealing function. A smaller area can therefore be machined with higher surface quality, which has a positive effect on the production costs for the injector proposed according to the invention. 
     An integral embodiment of control parts and nozzle needle that are embodied as merging with one another makes it possible to dispose a spring element that generates high closing forces in the housing of the injector. As a result, the closing time of the nozzle needle on its seat can be favorably affected, so that the incident leakage losses in the injector proposed according to the invention, of compact design, can be kept within narrow limits. 
     Because fuel that is at extremely high pressure is delivered substantially vertically, and its inflow is into an annular gap surrounding the control part, incident pulsations or pressure fluctuations in the delivered fuel can be better damped, and in particular are not propagated during the injection phase, so that the shaping of the precisely defined injection course is unimpaired by pulsations in the fuel. 
     Another advantage intrinsic to the embodiment according to the invention is considered to be that the nozzle needle can be provided with inlet faces, by way of which fuel entering via the annular gap between the nozzle needle and the injector housing flows to the seat of the injection nozzle. The delivery of fuel through annular gaps is the primary way of achieving substantially greater high-pressure resistance of the injector proposed according to the invention, since the nozzle inlet and the nozzle chamber can be omitted. Besides the advantages of easier production and greater attainable durability, the elimination of the line system to the nozzle needle makes a substantially faster pressure buildup at the injection nozzle tip possible. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in detail below in conjunction with the drawings, in which: 
     FIG. 1, the longitudinal section through an injector of the invention, with an integrally embodied control part and nozzle needle; and 
     FIG. 2, an enlarged view of the guide region of the nozzle needle in the injector housing, with inlet faces for the fuel to the injection nozzle tip. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The view in FIG. 1 is of a longitudinal section through an injector configured according to the invention, with an integrally embodied control part and a nozzle needle immediately adjoining the control part. 
     The injector  1  embodied according to the invention includes an injector housing  2 , in which a control part  3  with a cup-shaped recess is received. The control part  3  is embodied with an outer diameter d 2  in its upper region, which outer diameter d 2  is also identified by reference numeral  6 , and is received movably on the outer face of a guide 
     The guide  7  is embodied on the injector housing  2  of the injector  1  as a tubularly extending structural component extending parallel to the axis of symmetry  4  of the injector, and this component is surrounded on its outer face by a spring element  8 , which by way of example can be embodied as a spiral spring. The spring element  8  is braced with its windings on one end on the annularly extending outer diameter region  6  of the control part  3 , and on the other end it is braced in an annular recess in the injector housing  2 . In the interior of the guide  7 , which extends essentially coaxially to the axis of symmetry  4  of the injector  1 , a through bore  9  is provided. An outlet throttle element  19  is let into the guide  7  on the face end of the guide  7 ; the through bore extending coaxially to the axis of symmetry  4  discharges, below a ball-shaped sealing element  11 , into a hollow chamber  14  of an actuator-actuated control element  10 . 
     In the configuration of FIG. 1, the actuator-actuated control element  10  is integrated with the injector housing  2 . The aforementioned through bore  9  in the guide  7  discharges on one end into the hollow chamber  14  of the actuator-actuated control element  10 , and on the other, a leak fuel outlet  15  branches off from the hollow chamber  14  of the actuator-actuated control element  10 . In the view shown in FIG. 1, the upper end of the through bore  9  of the guide  7  is closed by a ball-shaped sealing element  11 , which is pressed into its sealing seat  13  by a thrust bolt  12 . The closing force at the sealing element  11  is generated by the subjection of the thrust bolt  12  to a piezoelectric actuator, an electromagnet, or a hydraulic-mechanical converter, whose configuration is not shown in further detail in the view of FIG.  1 . 
     In the upper part of the injector housing  2  of the injector  1  in terms of the view in FIG. 1, a substantially vertically extending inlet  16  from the high-pressure collection chamber (common rail) is shown. The inlet  16  discharges into the hollow chamber that receives the spring element  8 , and from there, the fuel that is at extremely high pressure flows around the control part  3  and flows along an annular gap  18  in the direction of the nozzle needle  22 . The annular gap  18 , which is formed between the jacket face of the control part, embodied with the outer diameter  6  (d 2 ) and the inside face of the injector housing  2 , serves to damp vibration or pulsation in the fuel, which is at high pressure, upon its delivery into the interior of the injector housing  2 . Via an inlet throttle  21 , embodied in the side wall of the control part  3  in the outer diameter region  6 , the fuel at high pressure enters the control chamber  20 , which is defined on the one hand by the face end of the guide  7 , in which an outlet throttle  19  is provided, and on the other by the bottom of the cup-shaped interior of the control part  3 . 
     Below the control chamber  20  the outer diameter d 2  of the control part  3  narrows to a guide diameter  29 , in which (see the illustration in FIG. 2) guides  23  and  25  are embodied, which are intended for the nozzle needle  22 . The guide regions  23  and  25  can be embodied as rings extending annularly along the jacket of the nozzle needle  22 , which are guided in a correspondingly configured bore of the injector housing  2 . The upper guide region  23  and the lower guide region  25  no longer assume any sealing function; instead, between the two guide regions  23  and  25 , an annular hollow chamber  24  that forms an annular gap is formed, where the fuel at high pressure flows in upon a pressure relief of the control chamber  20  and a vertical motion of the control part  3  together with the nozzle needle  22 . 
     From the lower guide  25 , the fuel flows into an annular gap  31  (see the view in FIG. 2) surrounding the lower part of the nozzle needle  22 , as far as the nozzle tip  32 . Embodied on the nozzle tip  32  is a seat  27 , by way of which the bore  30  protruding into the combustion chamber of an internal combustion engine can be closed and opened. The seat bottom  28  is embodied with a reduced diameter d 3 . 
     The injector housing  2  of the injector  1 , in the view of FIG. 1, is screwed into a socket  33  and can be unscrewed from the socket by simple rotation, once the lead line connections have been removed. 
     Below the transitional region between the control part  3  and the nozzle needle  22 , inlet faces  26  for the fuel delivery to the nozzle tip  32  are embodied on the nozzle needle  22 . The inlet faces  26  extend in the upper guide region  23  and the lower guide region  25  of the nozzle needle  22 , and as a result the upper inlet face  26 , as shown in FIG. 2, is in communication with the lower inlet face  26  above the inlet ring or annular gap  31 , via the annular gap  24  created between the nozzle needle jacket face  22  and the housing bore. This assures that via the inlet faces  26 , in the case of opening of the nozzle needle  22  as a result of a pressure relief of the control chamber  20 , fuel is pumped as far as the nozzle tip  32  of the injector housing  2 , where it can be injected into the combustion chamber of an engine. 
     The function of the injector shown in the views in FIG.  1  and FIG. 2 is as follows: By triggering of the control element  10 , the thrust bolt  12  acting on the sealing element  11  is relieved, as a result of which the through bore  9  disposed essentially parallel to the axis of symmetry  4  is subjected to fuel emerging from the control chamber  20 . Via the outlet throttle  19  let into the face end of the guide  7 , the control volume flows into the through bore and from there through the uncovered sealing seat  13  into the hollow chamber  14  and from there out via the leak fuel line  15 . 
     By opening of the control element  10 , the pressure and the fuel volume in the control chamber  20  decrease, as a result of which the cup-shaped control part  3  is moved vertically upward along its guide face on the guide  7 . During the upward motion, the annular edge of the control part  3 , acted upon by the spring element  8 , rests on and compresses the spring element  8 . During the upward motion of the control part  3 , the nozzle needle  22  moves out of its seat in the injector housing  2 , so that the fuel supply available on the high-pressure side can flow laterally via the inlet faces  26  into the annular hollow chamber  24  and from there, via the lower inlet face  26 , enters the gap between the jacket of the nozzle needle  22  and the inner wall of the injector housing  2 . As a result, the requisite injection pressure and the fuel volume required for injection into the combustion chamber of an internal combustion engine, which can be injected into the combustion chamber via the obliquely disposed bore  30 , is available at the nozzle needle tip  32 . Part of the diameter (d 1 -d 3 ) is already force-balanced by means of the diameter d 2  of the outer region of the control part  3 . If the spring element aid is dimensioned appropriately for a complete force equilibrium of the nozzle needle  22 , optimal opening and closing of the nozzle needle  22  at the nozzle needle tip  32  can be established. 
     Conversely, if the control element  10  is positioned by actuation of an actuator, then the thrust bolt  12  acts on the sealing element  11  and closes the through bore  9  at the sealing seat  13 . As a result, by the continuous replenishing flow of fuel at high pressure via the inlet throttle  21 , a high pressure builds up in the control chamber  20 . As the result of the buildup of pressure in the control chamber  20 , the control part  3  moves vertically downward out along the guide  7 , so that the nozzle needle  22  and its needle tip  32  move into their seat  27 . The closing motion of the nozzle needle  22  in its seat  27  in the region of the nozzle tip  32  is reinforced by suitable dimensioning of the spiral spring  8  embodied as a compression spring, so that fast closure of the nozzle needle  22  ensues, and thus the leakage losses can be kept within narrow limits. 
     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.