Patent Publication Number: US-9410518-B2

Title: Tappet

Description:
BACKGROUND 
     The invention concerns a tappet particularly for a pump or a compressor, said tappet comprising a tubular housing on whose drive-side annular end face two flat sections recessed from an outer shell of the housing lie diametrically opposite each other, a bolt supporting a roller being mounted in said flat sections, a separate bridge member protruding, axially below said roller, through an inner shell of the housing, an output-side end face of the bridge member serving as a contacting surface for a tappet follower part, said bridge member bearing against undersides of said flat sections in direction of the drive-side annular end face and being held in direction of an output-side annular end face of said housing by a ring which is fixed to the inner shell. 
     A tappet of the pre-cited type is disclosed in DE 102012211113.1. This tappet is suitable for loading a pump piston of a fuel injection pump. As can be seen in  FIG. 1 , the retention of the bridge member in axial direction outwards from the housing is realized through a snap ring that is held on lugs protruding radially inwards from the housing. 
     A drawback of the above solution is that a mounting of the bridge member over the drive-side annular end face has to be performed in a very controlled and exact manner so as to avoid any collision with the lugs. Furthermore, due to the inwards protruding components (lugs, snap ring), the radial design space in the lower region of the housing is restricted, so that under certain circumstances not enough design space is available for a resetting spring, or the like, on the output-side end face of the bridge member. In addition, the lugs weaken the housing. Depending on the case, deformation of the outer shell of the housing can occur in the region of the lugs. 
     SUMMARY 
     It is therefore an object of the invention to provide a tappet that is free of the said drawbacks. In particular, the tappet should be easy to mount and possess an enlarged design space beneath its bridge member. 
     The above object is achieved according to the invention in that the ring is a split spring strip and is seated in a complementary groove of the inner shell of the housing so as not to protrude, or to protrude only slightly, radially inwards out of the groove, at least two tabs projecting radially inwards from an upper side of the ring on which the bridge member is fixed in direction of the output-side annular end face. 
     In this way, a tappet free of the aforesaid drawbacks is created. The ring is conceived as a sheet metal or plastic ring. If necessary, a spring means spreading the ring may also be arranged in the separating gap. The design space under the bridge member, i.e. in direction of the output-side annular end face of the housing is configured such that no lugs or the like can extend any longer radially from the inner shell of the housing. However, any bevels required, are not affected by this. Thus, the bridge member can at first be relatively freely introduced into the housing (in the direction “head first mounting) till its rotational orientation relative to the contacting surface on the undersides of the flat sections becomes necessary. Important in this context however is that, due to the unrestricted design space, larger resetting springs can be installed, so that higher forces/torques become possible. 
     A preferred additional feature of the invention concerns a tappet that is connected to a pump piston via a spring plate. For realizing the free design space under the bridge member, the tabs of the ring advantageously extend in a complementary annular recess of an annular region of the spring plate. The latter holds the ring during operation of the tappet. 
     According to a further specification of the invention, the spring plate comprises through-openings that start from an outer edge thereof. These through-openings enable a good flow-through of e.g. diesel oil/lubricant, or they prevent a “pumping-up of the tappet. The through-openings may also be disposed outside of the outer edge. In addition, they help to save tappet mass. 
     The beam-shaped configuration of the, for example, punched bridge member proposed in a further dependent claim, permits a through-flow of e.g. diesel oil/lubricant laterally along the bridge member as well as a good handling and a simple mounting of the bridge member in mass production. 
     According to a further proposition of the invention, a lug protrudes from a transverse end face of the bridge member, which lug may also be made alternatively as a separate component. The lug is inserted e.g. through a punched opening of the housing, so that the tappet is endowed with an anti-rotation device of a simple structure which is secure against loss. The bridge member is thus a multifunctional component. 
     According to the invention, transverse end faces of the bridge member extend in osculation on the inner shell of the housing. Through this feature, mounting is facilitated and, compared to a bowstring-like configuration, edge contact is avoided. 
     According to a further feature of the invention, the bridge member is braced via the lugs of the ring, free of lash, within the tappet at least in axial direction. It is thus fixed against rattling. 
     Finally, it is also proposed to configure the bridge member as a sheet metal punched part having a relatively large thickness. This measure helps to keep the costs of production at a low level. If necessary, the bridge member may also be made by machining or by creative forming. 
     The proposed tappet is intended for use at least for an indirect loading of a pump piston of a fuel injection pump of a quality or quantity controlled internal combustion engine. In the same manner it would also be possible to use the tappet in a valve train of an internal combustion engine, an axial or radial piston compressor or in a similar pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Coming now to the drawing; 
         FIG. 1  shows a longitudinal section through a tappet assembly; 
         FIG. 2  shows a longitudinal section as mentioned above but turned through 90° about the about an axial line; 
         FIG. 3  shows a view corresponding to  FIG. 2 , but from below; 
         FIG. 4  shows an enlarged partial view of the assembly of  FIG. 1  in the section containing the bridge member; 
         FIG. 5  shows a spatial view of the ring comprising tabs; 
         FIG. 6  shows a spatial view of the housing of the tappet seen from underneath and 
         FIG. 7  shows the tappet of  FIG. 6  in the assembled state. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The figures show a tappet  1  for a high pressure fuel pump. The tappet  1  (s.  FIG. 1, 2, 6, 7 ) comprises a thin-walled housing  2  made out of sheet steel. Two flat sections  5  recessed from an outer shell  4  of the housing  2  lie diametrically opposite each other on a drive-side annular end face  3  of the housing  2  and can best be seen in  FIG. 6 . A bolt  7  supporting a roller  6  is mounted in the flat sections  5 . 
     A separate beam-type bridge member  9  protrudes, axially below the roller  6 , through an inner shell  8  of the housing  2  (s.  FIG. 1, 2, 7 ), and a tappet follower part  11 , configured as a pump piston, is in contact with an output-side end face  10  of the bridge member  9 . As can be clearly seen, the bridge member  9  bears against undersides  12  of the flat sections  5  in direction of the drive-side annular end face  3  (s.  FIG. 1, 7 ). In direction of an output-side annular end face  13  of the housing  2 , a lash-free retention of the bridge member  9  is achieved through a ring  14  that is fixed to the inner shell  8 , (see also  FIG. 5 ), said ring  14  being a split spring strip. The ring  14  is seated in a circumferential groove  15  of the inner shell  8  of the housing  2  and does not protrude into the inner space of the tappet. 
     Two tabs  17  situated diametrically opposite each other project radially inwards from an upper side  16  of the ring  14 . The bridge member  9  is fixed on these tabs  17  in direction of the output-side annular end face  3 . 
     The pump piston  11  disclosed in  FIG. 1-3  is retained on the output-side end face  10  of the bridge member  9  through a sheet metal spring plate  18  such that the pump piston  11  can execute a lateral deviation movement relative to the tappet  1 . This spring plate  18  bears through an annular region  20  starting from an outer edge  19  of the spring plate  18  against the output-side end face  10  of the bridge member  9  (see also  FIG. 4 ). The aforesaid bent tabs  17  are seated in an annular recess  20  in an upper side  21  of the annular region  20  of the spring plate  18 . 
       FIG. 3  additionally shows that the spring plate  18  is provided with through-openings  23  that start from an outer edge  22  of the spring plate  18  for enabling a flow-through of a medium (oil, fuel). 
     As can best be seen in  FIG. 7  combined with  FIG. 1 , a lug  25  projects from a transverse end face  24  of the bridge member  9 . This lug  25  extends through a recess  27  of the skirt of the housing  2  and serves as an anti-rotation device for the tappet  1  relative to its guide in the fuel pump. The skirt recess  27  extends from an upper crossbar  28  of a window  29  arranged in the housing  2 , which window  29  is formed by one of the recessed flat sections  5  in the housing  2 . 
     As can be seen in  FIG. 7 , both transverse end faces  24 ,  26  of the bridge member  9  are provided with a radius that is similar to a radius of the inner shell  8  of the housing  2  and said transverse end faces  24 ,  26  extend directly in front of the inner shell  8  of the housing  2 . 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Tappet 
           2  Housing 
           3  Drive-side annular end face 
           4  Outer shell 
           5  Flat section 
           6  Roller 
           7  Bolt 
           8  Inner shell 
           9  Bridge member 
           10  Output-side end face 
           11  Tappet follower part, pump piston 
           12  Underside 
           13  Output-side annular end face 
           14  Ring 
           15  Groove 
           16  Upper side 
           17  Tab 
           18  Spring plate 
           19  Outer edge 
           20  Annular region 
           21  Upper side 
           22  Outer edge 
           23  Through-opening 
           24  Transverse end face 
           25  Lug 
           26  Transverse end face 
           27  Skirt recess 
           28  Crossbar 
           29  Window