Patent Publication Number: US-2015083062-A1

Title: Outer housing for a hydraulic lash adjuster with tapered oil feed annulus

Description:
INCORPORATION BY REFERENCE 
     The following documents are incorporated herein by reference as if fully set forth: U.S. Provisional Application No. 61/880,296, filed Sep. 20, 2013. 
    
    
     FIELD OF INVENTION 
     This application is generally related to a hydraulic lash adjuster and is more particularly related to an outer housing for a hydraulic lash adjuster. 
     BACKGROUND 
     Hydraulic lash adjusters are used in valve trains of internal combustion engines to accommodate lash and to control valve lift modes. Internal combustion engines include cylinder heads in which the lash adjusters are arranged to have a plurality of hydraulic fluid galleries that feed pressurized hydraulic fluid to ports defined in an outer housing of the hydraulic lash adjuster. A plunger is arranged within a bore of the outer housing and is axially displaceable to perform the hydraulic lash adjustment as well as optionally a switching function to provide a partial or zero lift opening of the associated valve. When the switching function is provided, one of the ports feeds hydraulic fluid into a chamber of the plunger that directs the hydraulic fluid to an open-ended nose portion and actuates a switching function of the rocker arm or finger lever assembly between first and second valve lift modes. A significant amount of pressure loss occurs when the hydraulic fluid flows from the hydraulic fluid gallery of the cylinder head to a space defined between the cylinder head and an outer surface of the outer housing. The pressure loss increases the amount of time required to execute the switching function of the rocker arm assembly and reduces engine performance. It is desirable to minimize the amount of time required to perform the switching function and to minimize the pressure loss when hydraulic fluid travels from the cylinder head gallery to the ports on the outer housing of the adjuster. 
     SUMMARY 
     An outer housing for a hydraulic lash adjuster with a tapered oil feed annulus is provided. The outer housing is positionable within a cylinder head of an engine which includes a plurality of hydraulic fluid galleries. The outer housing includes an annular body with an open first axial end, a closed second axial end, a radially inner wall defining an axial bore, and a radially outer wall. The radially outer wall includes a first annular groove located adjacent to the first axial end, and a first port is located in the first annular groove. A radially outer surface of the first annular groove tapers radially inwardly between a first axial end and a second axial end. The first port is located adjacent to the second axial end of the first annular groove. The tapered outer surface of the first annular groove reduces resistance of hydraulic fluid flowing from a hydraulic fluid gallery in the cylinder head into the first port. The tapered outer surface directs hydraulic fluid towards the second axial end of the first annular groove and the first port. 
     In another embodiment, the radially outer surface of the first annular groove tapers radially inwardly between the first axial end and a center-point of the first port. 
     In one preferred embodiment the outer housing includes a second annular groove located adjacent to the second axial end, and a second port is located in the second annular groove. 
     Preferred arrangements with one or more features of the invention are described below and in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The foregoing Summary as well as the following Detailed Description will be best understood when read in conjunction with the appended drawings. In the Drawings: 
         FIG. 1  is a perspective view of a hydraulic lash adjuster with a plunger according to the invention. 
         FIG. 2  is a perspective view of the hydraulic lash adjuster of  FIG. 1  in an engine valve train assembly. 
         FIG. 3  is a cross-sectional view of the outer housing positioned in a bore of a cylinder head. 
         FIG. 4  is a cross-sectional view of an outer housing of a hydraulic lash adjuster according to one embodiment of the invention. 
         FIG. 5  is a perspective view of the outer housing of  FIG. 4 . 
         FIG. 6  is an enlarged view of a first annular groove of the outer housing of  FIGS. 4 and 5 . 
         FIG. 7  is an enlarged cross-sectional view of the first annular groove of the outer housing of  FIGS. 4-6 . 
         FIG. 8  is a cross-sectional view of an outer housing of a hydraulic lash adjuster according to another embodiment of the invention. 
         FIG. 9  is a perspective view of the outer housing of  FIG. 8 . 
         FIG. 10  is an enlarged view of a first annular groove of the outer housing of  FIGS. 8 and 9 . 
         FIG. 11  is an enlarged cross-sectional view of the first annular groove of the outer housing of  FIGS. 8-10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     Certain terminology is used in the following description for convenience only and is not limiting. The words “inner,” “outer,” “inwardly,” and “outwardly” refer to directions towards and away from the parts referenced in the drawings. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof. The terminology includes the words specifically noted above, derivates thereof, and words of similar import. 
       FIG. 1  shows a preferred embodiment of a hydraulic lash adjuster  1  including an outer housing  2 . As shown in  FIGS. 4 and 8 , the outer housing  2  includes a radially inner wall  10  that defines an axial bore  11  in which a plunger  4  is axially displaceable.  FIG. 2  shows the hydraulic lash adjuster  1  and the outer housing  2  arranged in an engine valve train assembly. When fully assembled, the outer housing  2  is arranged within a bore  7  of a cylinder head  5  of the engine as shown in  FIG. 3 . The engine includes a plurality of hydraulic fluid galleries  9  that feed into the cylinder head  5  for supplying hydraulic fluid to the outer housing  2 . Hydraulic fluid flows through the outer housing  2  and into the plunger  4 . An axial end of the plunger  4  includes an opening that feeds hydraulic fluid to a rocker arm or finger lever assembly  3  for performing a switching function between valve modes. 
       FIGS. 4 and 5  show more detailed views of a preferred embodiment of the outer housing  2  for the hydraulic lash adjuster  1 . The outer housing  2  includes an annular body with an open first axial end  6  and a closed second axial end  8 . The outer housing  2  has a radially outer wall  12  that includes a first annular groove  14  located adjacent to the first axial end  6 , and a preferably second annular groove  16  located adjacent to the second axial end  8 . In a preferred embodiment, the first and second annular grooves  14 ,  16  have an axial length of approximately 6.0 mm. The first and second annular grooves  14 ,  16  preferably have a radial depth approximately between 0.4 mm and 0.5 mm. In a more preferred embodiment, the radial depth of the first and second annular grooves  14 ,  16  is approximately 0.45 mm. One of ordinary skill in the art recognizes the radial depth and axial lengths of the annular grooves can vary depending on the application. 
     A first port  18  is located in the first annular groove  14 , and a second port  20  is located in the second annular groove  16 . Each port  18 ,  20  extends through the radially inner and outer walls  10 ,  12  to the axial bore  11  of the outer housing  2 . The ports  18 ,  20  are preferably circular and the diameter of the ports can vary depending on the application. The ports  18 ,  20  are each aligned with at least one hydraulic fluid gallery  9  defined in the cylinder head  5  of the engine. During operation, hydraulic fluid flows from the galleries  9  defined in the cylinder head  5  to the ports  18 ,  20  and eventually to respective axial ends of the plunger  4 . In a preferred embodiment, the first port  18  is used for the switching function of the rocker arm assembly  3  and the second port  20  is used for lash adjustment. The radially inner wall  10  can include annular grooves at the location of the first and second ports  18 ,  20 .  FIGS. 6 and 7  show a radially outer surface  22  of the first annular groove  14  tapers radially inwardly between a first axial end  24  and a second axial end  26 . The first port  18  is preferably located adjacent to the second axial end  26  of the first annular groove  14 . The tapered surface of the radially outer wall  22  directs hydraulic fluid from the gallery  9  of the cylinder head  5  towards the first port  18  and away from the first axial end  24  of the first annular groove  14 . Because the hydraulic fluid is directed via the tapered surface  22 , the hydraulic fluid enters the first port  18  faster and the switching function of the rocker arm assembly  3  is performed more quickly than the prior art. The tapered surface  22  reduces the pressure loss that typically occurs when hydraulic fluid travels from the gallery  9  to the first port  18 . The tapered surface  22  increases the volume between the cylinder head  5  and the first annular groove  14 , and facilitates a faster pressure rise of the hydraulic fluid for actuating a locking pin of the switching rocker arm, resulting in faster locking pin switching times. 
     In a preferred embodiment shown in  FIGS. 4-7 , the radially outer surface  22  of the first annular groove  14  tapers radially inwardly by approximately  3  degrees between the first axial end  24  and the second axial end  26 . In this embodiment, the entire radially outer surface  22  of the first annular groove  14  is tapered. One of ordinary skill in the art will recognize from the present disclosure that the radially outer surface  22  can taper at varying degrees depending on the requirements of a specific application. Due to the tapered radially outer surface  22 , a thickness of the outer housing  2  in the first annular groove  14  preferably decreases from approximately 1.25 mm at the first axial end  24  to approximately 0.6 mm at the second axial end  26 . 
     In another embodiment shown in  FIGS. 8-11 , the radially outer surface of the first annular groove  14  tapers radially inwardly between the first axial end  24  and a center-point  28  of the first port  18 . In this embodiment, only a portion of the radially outer surface  22  of the first annular groove  14  is tapered. According to this embodiment, the thickness of the outer housing  2  in the first annular groove  14  preferably decreases from approximately 1.25 mm at the first axial end  24  to approximately 0.66 mm at the center-point of the first port  18 . 
     Having thus described various embodiments of the present hydraulic lash adjuster in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description above, could be made in the apparatus without altering the inventive concepts and principles embodied therein. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore to be embraced therein. 
     LOG TO REFERENCE NUMBERS  
       1 . Hydraulic Lash Adjuster 
       2 . Outer Housing 
       3 . Rocker Arm Assembly 
       4 . Plunger 
       5 . Cylinder Head 
       6 . First Axial End of Outer Housing 
       7 . Bore of Cylinder Head 
       8 . Second Axial End of Outer Housing 
       9 . Hydraulic Fluid Galleries 
       10 . Radially Inner Wall 
       11 . Axial Bore 
       12 . Radially Outer Wall 
       14 . First Annular Groove 
       16 . Second Annular Groove 
       18 . First Port 
       20 . Second Port 
       22 . Radially Outer Surface of the First Annular Groove 
       24 . First Axial End of the First Annular Groove 
       26 . Second Axial End of First Annular Groove 
       28 . Center-point of First Port