Patent Publication Number: US-10774692-B2

Title: Tappet

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase of PCT Application No. PCT/DE2018/100211 filed on Mar. 8, 2018 which claims priority to DE 10 2017 109 761.9 filed on May 8, 2017, the entire disclosures of which are incorporated by reference herein. 
     TECHNICAL FIELD 
     This disclosure concerns a tappet for a fuel pump or for a valve timing gear, in each case of an internal combustion engine. The tappet includes a hollow cylindrical housing comprising two separate portions which lie successively in alignment. The two separate portions are joined together in the region of their facing inner faces and are permanently connected together via a joint. The tappet has a roller on its drive side and an abutment for a follower part on its output side, which abutment is formed on a separate insert that is radially supported on the housing in the joined region of the two portions. 
     BACKGROUND 
     Such a tappet is shown in  FIG. 2  of US 2016/0091074. The insert with abutment is configured as a thick-walled disc which bears on a floor of the pot-like housing portion on the output side. The drive-side housing portion is a solid part and on one side extends with an annular region over a bottom-side diameter reduction of the output-side portion. On the other side, two tabs protrude from the drive-side housing portion (see also  FIG. 7 ) in the drive direction to receive a roller bolt which is fixed axially by an additional ring cap surrounding the tabs. 
     The above-mentioned tappet is constructed comparatively solidly and is overly complex in structure. Adaptation to different or greater installation lengths (e.g. for cam drives on the crankshaft side) is extremely difficult. It has also been found that the disc can detach in some cases, at least during transport of the tappet. Also, because of the stepping in the central region, the assembled housing of the tappet only has an inadequate guide length for its support. 
     A further tappet consisting of two successively aligned portions is disclosed in DE 10 2014 218 961 A1. The abutment for the follower part is formed directly on a bottom of the output-side portion. 
     DE 35 19 015 A1 discloses a tappet with a separately joined base plate for a cam run-up. An annular flange protrudes from an inner casing of a shroud of the tappet and receives a hydraulic play-adjustment element for a follower member contact. 
     A one-piece tappet is described in DE 10 2013 204 178 A1. A plate is applied to the housing axially below the roller for a cam run-up, and a pump piston bears against the lower face of said plate when installed. 
     SUMMARY 
     It is an object of this disclosure to create a simply structured tappet which is easy to install and has good guide properties, and which can also very easily be adapted to different installation lengths. 
     According to the disclosure, this object is achieved in that the insert has a central annular collar, from which on one side a sleeve portion protrudes in the direction of the drive side, and from which on the other side a dome-like attachment protrudes towards the output side. The radial support is provided at the joined region of the two portions by an outer ring of the annular collar. For the axial support of the insert, an outer face of the sleeve portion rests on at least one radial indentation of the drive-side portion, and an end face of the dome-like attachment has the abutment for the follower part. 
     Thus, a simply constructed tappet is provided with a good guide length. With unchanged basic type of one of the housing portions, such as the part carrying the roller, different fuel pump types can be served by pairing second portions with inserts of different “height”. 
     The insert described herein consists firstly of the central annular collar from which a sleeve portion protrudes axially in one direction and bears axially on indentations of the housing, such as on undersides of the indented housing flat carrying the roller bolt. On the other side, the insert has a dome-like attachment with end-side abutment for the pump piston. By varying a height of this attachment, the tappet can very easily be adapted to different installation lengths. Said attachment may also protrude beyond the housing or lie “deeper” than its output-side annular edge. 
     According to one embodiment, the tappet has an installation height which corresponds to at least 1.8 times its outer diameter. This installation height is measured between an upper edge of the roller and an output-side outer face of the housing. The outer diameter is placed on the outer casing of the pump-side portion of the housing. 
     By joining the two portions together according to the disclosure by means of joints produced e.g. by welding, and by simultaneous radially inner support of the insert via its annular collar in this portion, a good stability of the connection is guaranteed. 
     To allow good guidance of the tappet unaffected by the joint, it is proposed to create a groove (constriction) in the connecting region of the housing portions, which groove then contains the weld for example. In some cases, the insert may also be welded here. 
     Suitably, the radially inner part of the joined portions has a radially inwardly bent collar. This serves for additional reinforcement of the structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is shown in the drawings. The drawings show: 
         FIG. 1 : a spatial, partly broken away view of the tappet, and 
         FIG. 2 : the above-mentioned tappet in longitudinal section. 
     
    
    
     DETAILED DESCRIPTION 
     A tappet  1  for a high-pressure fuel pump of an internal combustion engine is shown. It comprises a two-piece, substantially hollow cylindrical housing  2 . 
     On its drive side  3 , the tappet  1  has a roller  4  mounted on a bolt  27  for contact with a cam or a cam package on a crankshaft of the internal combustion engine. On its output side  5 , the tappet  1  has an abutment  6  formed as part of a separate insert  29  which is supported radially and axially on the housing  2 , for a follower part (pump piston). 
     As the two figures clearly show, the housing  2  is constructed from two separate portions  7 ,  8  lying successively in alignment. These are joined together in the region of their facing end faces  9 ,  10 , and connected together via a weld  11 . The weld  11  lies in a groove-shaped indentation  28  axially between the portions  7 ,  8 , and thus does not influence an outer casing of the housing  2 . 
     Two portions  7 ,  8  of the housing  2  consist of a thin-walled sheet steel. In contrast to metal tappets previously produced, because of the “alignment” of the two portions  7 ,  8 , the tappet  1  has a length which is around twice as large as its diameter. It is therefore ideally suited but not exclusively designed for crankshaft-driven injection pumps with relatively large distances, imposed by the design, between the respective cams or eccentrics on the crankshaft and the pump piston of the injection pump to be driven. 
       FIG. 2  shows that a shroud  12  of the output-side portion  8  consists substantially of two annular stages  13 ,  14 . The “lower” annular stage  13  of smaller outer diameter runs in the axial portion of the joint  11 , and on the end side has a radially inwardly oriented stiffening collar  17 . Said stage lies with its outer casing  15  on an inner casing portion  16  at the inner face  9  of the other drive-side portion  7 . 
     The insert  29  mentioned above in the description of the figures has a central plate-like annular collar  18  which is radially supported in the joint region via its outer ring  19 . 
     On one side, a central sleeve portion  20  protrudes from the annular collar  18  in the direction towards the drive side  3 . Its free outer face  21  is axially supported on two radial indentations  22  of the portion  7 . More precisely, two flats  26  indented from the outer casing start from a drive-side face  25  of the housing  2  diametrically opposite each other. The bolt  27  carrying the roller  4  is mounted therein. The undersides of the flats  26  function as the radial indentations  22 . 
     Also, a dome-like attachment  23  protrudes from the annular collar  18  of the insert  29  through the output-side portion  8  of the housing  2 . An end face  24  of the attachment  23  forms the abutment  6  for the pump piston. 
     LIST OF REFERENCE CHARACTERS 
     
         
         
           
               1 ) Tappet 
               2 ) Housing 
               3 ) Drive side 
               4 ) Roller 
               5 ) Output side 
               6 ) Abutment 
               7 ) Portion 
               8 ) Portion 
               9 ) Inner face 
               10 ) Inner face 
               11 ) Joint, weld 
               12 ) Shroud 
               13 ) Annular stage 
               14 ) Annular stage 
               15 ) Outer casing 
               16 ) Inner casing portion 
               17 ) Stiffening collar 
               18 ) Annular collar 
               19 ) Outer ring 
               20 ) Sleeve portion 
               21 ) Outer face 
               22 ) Radial indentation 
               23 ) Attachment 
               24 ) End face 
               25 ) Face 
               26 ) Flat 
               27 ) Bolt 
               28 ) Indentation 
               29 ) Insert