Patent Publication Number: US-6669117-B2

Title: Fuel injection valve for internal combustion engines

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 USC 371 application of PCT/DE 01/00003 filed on Jan. 5, 2001. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is directed to a fuel injection valve for internal combustion engines. 
     2. Description of the Prior Art 
     One fuel injection valve of the type with which this invention is concerned is known from German Published, Nonexamined Patent Application DE 196 08 575. On the end toward the combustion chamber of the valve member, a substantially conical tip is formed. This tip is divided into two portions; the tip cone angle of the outer portion, toward the combustion chamber, is greater than that of the inner portion, toward the valve member. As a result, an encompassing annular edge is embodied as a sealing face on the jacket face of the valve member tip. 
     The valve member is disposed in a bore, embodied as a blind bore, and the closed end, toward the combustion chamber, is embodied as a valve seat, which substantially has a conical shape. At least one injection opening is embodied in the valve seat and connects the interior of the valve with the combustion chamber, when the valve member is lifted from the valve seat. 
     In the closing position of the fuel injection valve, the valve member with its valve sealing face comes to rest on the valve seat. The cone angle of the valve seat is dimensioned such that the valve member is seated on the valve seat essentially only with its annular edge. On the one hand, this produces good sealing of the pressure chamber from the injection openings, but on the other it raises the problem that because of the high pressure per unit of surface area, deformations of the valve member and valve seat occur over time. The annular edge and/or the valve seat deform, causing the effective seat diameter of the valve member to change. As a result, the effective flow cross section of the fuel injection valve also changes, as does the size of the faces on the valve member that are subjected to pressure, which adversely affects the course of fuel injection and the injection precision. 
     SUMMARY OF THE INVENTION 
     The fuel injection valve of the invention has the advantage over the prior art that the part of the valve member tip bearing the valve sealing face is embodied as a yielding annular collar, and as a result in the closing position of the valve member, the part bearing the valve sealing face, after an initial line contact, rests two-dimensionally on the valve seat. The outer edge of the annular collar defines a fixed seat diameter. Because of the increasing bearing area of the valve member on the valve seat, a relatively small pressure per unit of surface area exists in the region of the valve seat, leading to less wear in this region. Thus the seat diameter remains constant over the service life of the fuel injection valve. 
     In an advantageous feature, the valve sealing face is partly undercut by the annular groove, so that the annular collar is embodied in liplike fashion to an increased extent, and the deformation work of the annular collar is reduced. By varying the shape of the annular groove, the yielding of the annular collar can be adapted to the applicable material comprising the valve member and the valve body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages and features of the invention can be learned from the detailed description contained below, taken with the drawings, in which: 
     FIG. 1 shows a longitudinal section through a valve body with a valve member; 
     FIG. 2 is an enlarged detail of FIG. 1 in the region of the valve seat; and 
     FIG. 3 is an enlarged detail of FIG. 2 in the region of the valve sealing face. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1, a longitudinal section is shown through an exemplary embodiment of the fuel injection valve of the invention. A valve body  1 , whose end face remote from the combustion chamber, in the installed position, comes at least indirectly to rest on a valve retaining body, not shown in the drawing, has a bore  5  embodied as a blind bore. The bottom face is embodied as a valve seat  11  and is approximately conical, with a cone angle a (see FIG.  3 ), and the inside diameter of the valve seat  11  decreases toward the combustion chamber. At least one injection opening  13 , which connects the bore  5  to the combustion chamber, is embodied at the valve seat  11 . 
     Disposed in the bore  5  is a pistonlike valve member  7 , which is guided in the bore  5  with a larger-diameter portion, remote from the combustion chamber, and which toward the combustion chamber changes into a smaller-diameter valve member shaft  7 ′, thereby forming a pressure shoulder  15 . Between the wall of the bore  5  and the valve member shaft  7 ′, a pressure chamber  17  is formed, which surrounds the valve member  7  and the pressure shoulder  15  and extends as far as the valve seat  11 . An inlet conduit  21 , embodied in the valve body  1 , by way of which the pressure chamber  17  can be filled with fuel at high pressure discharges into the pressure chamber  17 . 
     On the end toward the combustion chamber, the valve member shaft  7 ′ changes into a valve member tip  30 , whose outer jacket face is approximately conical and forms a valve sealing face  9  (FIGS.  2  and  3 ), which cooperates with the valve seat  11 . By the force of a closing spring, not shown in the drawing, the valve member  7  is pressed with the valve sealing face  9  against the valve seat  11 , so that in this closing position, the injection opening  13  is sealed off from the pressure chamber  17  by the valve sealing face  9 . In the open position of the valve member  7 , that is, when the valve sealing face  9 , as the result of an axial motion of the valve member  7  away from the combustion chamber, lifts from the valve seat  11 , counter to a closing force and under the influence of the fuel, delivered to the pressure chamber  17  at high pressure, the pressure chamber  17  communicates with the combustion chamber via the injection opening  13 , and fuel is injected into the combustion chamber. 
     In FIG. 2, an enlargement of the fuel injection valve shown in FIG. 1 is shown in the closed position, in the region of the valve seat  11 . The jacket face of the valve member tip  30  is divided into two portions, separated from one another by an annular furrow  25 . The first valve member portion  30   a , forming the end of the valve member  7 , has a conical jacket face with a cone angle γ, while the second valve member portion  30   b , which adjoins the annular furrow  25  to the side of the valve member shaft  7 ′, has a frustoconical jacket face with a cone angle β. The cone angle γ is greater than the cone angle β, and the two portions of the valve member tip  30  are embodied such that only the jacket face of the second, frustoconical valve member portion  30   b  bears the valve sealing face  9 . 
     At the transition from the valve member shaft  7 ′ to the valve member tip  30 , or to the second conical portion  30   b , an annular groove  23  is formed, which isolates the second valve member portion  30   b  that bears the valve sealing face  9  and is preferably embodied in such a way that it partly undercuts the portion  30   b . As a result, an annular collar  28  is formed, which is resiliently yielding and thus, upon contact with the valve seat  11 , can adapt by deformation, under the influence of the closing force, to the valve seat  11 . The annular furrow  25  disposed at the transition between the two valve member portions  30   a ,  30   b  of the valve member tip  30  assures a better distribution of fuel in the volume between the valve member tip  30  and the valve seat  11 , in the event that more than one injection opening  13  is provided on the valve seat  11 . The annular furrow  25  is located upstream of the outgoing injection openings  13 . 
     In FIG. 3, an enlargement of the valve member  7  in the region of the valve sealing face  9  is shown. The jacket face of the annular collar  28  has an opening angle β, which is not equal to but rather is somewhat larger than the cone angle α of the valve seat  11 . The differential angle φ is dimensioned such that the annular collar  28 , which in the closing position of the valve member  7  is pressed against the valve seat  11  by the force of the closing spring, can yield purely elastically inward perpendicular to the face of the valve seat  11  and thus rests two-dimensionally on the valve seat  11 . The resilience is reinforced by the fact that part of the valve sealing face  9  is undercut by the annular groove  23 , so that a reduced cross section is formed at the base of the annular collar. 
     The sealing edge  34 , which forms the edge remote from the combustion chamber of the valve sealing face  9 , is as a result of this design not pressed into the valve seat  11 , since the full force of the closing spring acts on the valve seat  11  only after the deformation. The diameter of the initial contact of the valve member  7  with the valve seat  11  remains unchanged with use. To lessen the deformation work of the annular collar  28 , with the goal of having a large valve sealing face  9  rest two-dimensionally on the valve seat  11 , the differential angle φ between the cone angles of the valve sealing face  9  and valve seat  11  must be less than 1°, and preferably must be from 0.25 to 0.750. 
     In the closing position of the valve member  7  toward the valve seat  11 , the sealing edge  34  first comes to rest on the valve seat  11 . By the force of the closing spring, the valve member  7  is pressed farther onto the valve seat  11 , causing the annular collar  28  to be pressed inward, until the entire frustoconical valve sealing face  9  comes to rest on the valve seat  11 . 
     Instead of dividing the valve member tip  30  into two valve member portions  30   a ,  30   b  by means of an annular furrow, it can also provided that the annular furrow  25  is omitted, and as a result an annular edge is formed by the different cone angles of the two valve member portions  30   a ,  30   b  at the transition between them. 
     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.