Patent Publication Number: US-8113159-B2

Title: Camshaft phaser and drive adapter for a concentric camshaft

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/105,181, filed Oct. 14, 2008, which is incorporated herein by reference as if fully set forth. 
    
    
     FIELD OF INVENTION 
     The present invention relates to a camshaft adjuster or phaser for adjusting and fixing the phase position of a camshaft relative to the crankshaft of an internal combustion engine. 
     BACKGROUND 
     Camshafts are used in internal combustion engines in order to actuate the gas exchange valves. The camshaft in an internal combustion engine includes a plurality of cams that engage cam followers (i.e. bucket tappets, finger levers or rocker arms). When the camshaft rotates, the cams lift the cam followers which in turn actuate gas exchange valves (intake, exhaust). The position and the shape of the cams define the opening period and amplitude as well as the opening and closing time of the gas exchange valves. 
     Concentric camshaft assemblies are also known in which separate intake and exhaust camshafts are concentrically arranged by providing a hollow outer camshaft in which an inner camshaft is located, with the inner camshaft cam lobes being rotatable on the outer camshaft, and connected through slots in the hollow outer camshaft to the inner camshaft. This allows the use of separate camshafts for intake and exhaust valve actuation within generally the same space required for a single camshaft. 
     A camshaft adjuster generally comprises a timing gear, which can be a chain wheel, a belt wheel or a gear wheel, and it is connected in fixed rotation to the crankshaft by a chain, a belt or a gear drive, and acts as an input to the adjuster. The adjuster also includes an output connection to the camshaft. An adjusting input is also provided which can be a hydraulic, pneumatic or even electric drive to adjust the output rotation relative to the input. Commonly used arrangements include adjusters that operate on the vane-cell principle. 
     A single cam phaser (SCP) is shown in U.S. Pat. No. 7,284,517. This SCP allows the timing of an inner camshaft and/or an outer camshaft to be adjusted relative to an engine crankshaft. This phaser uses a separate nose support piece that is separately supported in the first camshaft bearing in order to carry the axial load from the timing chain into the outer camshaft. This requires the nose support piece to have tight tolerances, so that the radial load imparted by the timing chain or belt into the timing gear or pulley on the phaser is transmitted from the phaser into the more structurally rigid outer shaft. If such a load is supported mainly by the inner camshaft, such as shown in the arrangements of DE 10 2005 014 680 A1 or DE 10 2006 024 794 A1, bending of the inner shaft may occur, thereby causing the inner and outer camshafts to bind, preventing intake versus exhaust valve timing adjustment. Additionally, the rear plate of U.S. Pat. No. 7,284,517 has to be assembled separately to the outer camshaft prior to the front plate then being assembled and connected to the inner camshaft. This further complicates engine assembly. 
     In one known hydraulically activated camshaft phaser which operates on the vane-cell principle, the front and rear covers of the phaser are separately attached to the inner and outer camshafts. The drawback of this arrangement is that durability is somewhat limited, and attaching the vanes to the covers is cumbersome. Due to having the vanes of the phaser connected to front and rear covers of the phaser, seals are required to retain the pressurized hydraulic fluid required to move the vanes of the phaser. Such seals are subject to wear and eventual failure. Further, such a multipart arrangement greatly increases labor and time in assembling this known SCP phaser as the engine is assembled. In assembling such a phaser to a concentric camshaft, the risk of internal phaser contamination is high. Furthermore the installation time and complexity are increased since multiple portions must be separately attached to multiple parts of the camshaft. This also requires more complex disassembly and assembly in the field for service. 
     SUMMARY 
     The present invention relates to a camshaft adjuster for a concentric camshaft of an internal combustion engine. The adjuster includes a stator that is connected to a timing gear, and a rotor located within the stator and connected to the outer camshaft. The rotor includes a plurality of vanes that extend into spaces created between inwardly directed projections of the stator to define first and second sets of chambers on each side of the vanes. Front and rear side walls are provided for the phaser that close the sides of the chambers. An outer cover is attached to the stator and is connected to the inner camshaft by a drive adapter that extends through a center opening in the rotor. Radial loads acting on the timing gear are transmitted radially from the stator to the rotor and into the outer camshaft. 
     Preferably, the drive adapter has a hollow cylindrical body with first and second ends. The first end includes a slot or recess, and the second end has a portion configured to matingly engage a corresponding portion of the inner camshaft. A fastener can extend through the hollow body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing Summary and the following detailed description will be better understood when read in conjunction with the appended drawings, which illustrate a preferred embodiment of the invention. In the drawings: 
         FIG. 1  is a side view of the camshaft adjuster of the present invention; 
         FIG. 2  is a section view through the camshaft adjuster of  FIG. 1 ; 
         FIG. 3  shows the adjuster in  FIG. 2  attached to a camshaft, shown schematically; 
         FIG. 4  is a section view taken along line  4 - 4  in  FIG. 1 ; 
         FIG. 5  is a front view of the drive adapter; and 
         FIG. 6  is a rear view of the draft adapter. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Certain terminology is used in the following description for convenience only and is not limiting. The words “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward 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, derivatives thereof and words of similar import. 
     Referring now to  FIG. 1 , the outside of a camshaft adjuster  1  is shown in which a cover  15  attached by bolts  10  to a stator  50  are visible. The bolts  10  extend and attach radially into the stator  50 . The cover  15  includes cut-away portions  17  that are defined between fastening portions  18  of the cover  15 . In addition to reduced weight and materials used, the cut-away portions  17  allow for visual inspection of the adjuster. 
       FIG. 2  shows the adjuster  1 , having front and rear sidewalls  20 ,  25  and a stator  50  located between them. The stator  50  includes inwardly directed projections  52  that define recesses  100  therebetween. A rotor  55  is disposed between the sidewalls and inside the stator  50 . The rotor  55  includes preferably five radially outwardly extending vanes  95  that extend into the recesses  100  in the stator to define first and second sets of pressure chambers  105 ,  110 . The first and second sets of pressure chambers  105 ,  110  are pressurized with a hydraulic fluid provided by first and second pressure medium passages  115 ,  116 . By pressurizing the first pressure chambers  105  or the second pressure chambers  110 , the rotor  55  is rotated by the pressurized fluid acting on the vanes  95  to either advance or retard a position of the rotor  55 , and hence the outer camshaft  86  connected thereto, relative to the stator  50  and the inner camshaft  85  and crankshaft. By pressurizing both sets of chambers  105 ,  110 , the rotor  55  is hydraulically locked in a generally fixed position relative to the stator  50 . 
     Pressurized hydraulic fluid is provided to the passages  115 ,  116  in a known manner via oil passages in or between the inner and outer camshafts  85 ,  86 , which are fed by oil passages in a camshaft bearing journal support. An ECU (engine control unit) controlled flow valve (not shown) is used to control the flow of pressurized hydraulic fluid to one or both of the first and second sets of chambers  105 ,  110  via the passages  115 ,  116 . 
     The inwardly directed projections of the stator  50  slidingly engage the radial outer surface of the rotor  55 , allowing loads to be radially transferred from the stator  50  to the rotor  55 . As shown in  FIG. 3 , preferably the front end of the outer camshaft  86  extends to a position that is generally axially aligned with the timing gear  5 . 
     As shown in  FIG. 4 , a locking pin  125  is preferably located in the rotor  55  and is used to fix the position of the rotor  55  relative to the stator  50  when the pressure chambers  105 ,  110  are not pressurized, such as at engine startup. The first and second sidewalls  20 ,  25  are joined by fasteners or screws  40  to the stator  50 . 
     The adjuster  1  also includes a tension equalization spring  35  which is preferably a helical spring. The spring  35  is connected to the rotor  55  by helical spring cover  45  which extends through a clearance opening in the front sidewall  20  and is pressed against the rotor  55  by the hollow bolt  70 , and is also connected to the stator  50  via two of the five fasteners  40  that extend through the front sidewall  20  to engage the spring  35 . The spring  35  equalizes the force required to advance the rotor  55  relative to the stator  50  in comparison to the force required to retard the position of the rotor  55  relative to the stator  50 . 
     The timing gear  5  is preferably attached to or formed on the stator  50 . Alternatively, it can be formed on or attached to the front or rear sidewalls  20 ,  25 . 
     The main body  2  of the phaser  1 , including the stator  50 , rotor  55  with vanes  95  and locking pin  125  (if present), front and rear sidewalls  20 ,  25  along with the timing gear  5 , and the spring  35  and cover  45 , is preassembled as a unit to allow for higher quality and ease of installation. 
     At installation, prior to the cover  15  being installed, the main body  2  is placed on the end of the inner and outer camshafts  85 ,  86 , with the timing pin  90  of the outer camshaft  86  engaging in a timing pin bore  75  of the rotor  55 . A hollow bolt  70  is then installed and clamps the rotor  55  to the outer camshaft  86 . 
     A drive adapter  80  is preferably used to connect the stator  50  to the inner camshaft  85 . The drive adapter  80  includes an open cylindrical body  82 , having first and second ends  83 ,  84 , and a length sufficient to extend axially through the main body  2 . The first end  83  includes a slot or recess in which the locating tabs  16  of the cover engage  82 . The second end  84  has a keyed portion  88  for positive engagement in the front end of the inner camshaft  85 . The slot  81  at the front end of the drive adapter  80  receive the locating tabs  16  of the cover  15 , which in conjunction with the keyed portion  88  at the second end  84 , to define and maintain the proper timing location of the inner camshaft  85  relative to the crankshaft via the stator  50  and cover  15 . 
     The cover  15 , which includes an opening for a central fastener  60  and locating tabs  16  on each side of the opening, is then installed. The locating tabs  16  of the cover  15  are received in the slot  81  at the front of the drive adaptor  80  to define and maintain the proper timing location of the inner camshaft  85  relative to the crankshaft via the stator  50  and cover  15 . The central fastener  60  is inserted through a central bore of a drive adapter  80  and engages in a threaded opening in the front of the inner camshaft  85 , clamping the cover  15  to the drive adapter  80  and the inner camshaft  85 . The bolts  10  are then installed to attach the cover  15  to the stator  50 . 
     Preferably, the cover  15  is a deep drawn sheet metal part but can also be cast, milled, laser cut, etc. The cover  15  transfers the rotary movement of the stator  50  to the inner camshaft  86 . 
     Owing to its unique design, the main body  2  of the camshaft phaser  1  of the present invention can be installed as a pre-assembled unit, thus no seals are required to be handled at installation for sealing the inner and outer chambers as in the known conventional design. Furthermore, no contamination of the internal phaser can occur when the phaser is installed. The main body  2  of phaser  1 , including the stator  50 , rotor  55  and the front and rear covers  25 ,  20  is also removable and replaceable as a single unit with greatly reduced labor. 
     Since timing chains or belts generally have limited slack to maximize efficiency, a camshaft adjuster cannot normally pass onto or off of an inner nose of a camshaft while the chain or belt is attached to the phaser sprocket and the crankshaft sprocket. By using, the drive adapter  80  of the present invention, the phaser  1  can be attached to or detached from the inner crankshaft  85  while the drive chain is attached to the timing gear  5  and the crankshaft sprocket (not shown). This is because the drive adapter  80  and bolt  60  can be slid into or out from the hollow bolt  70  to engage or disengage from the inner camshaft  85 , which, as shown in  FIG. 3 , does not axially overlap with the camshaft adjuster  1  in the installed position. 
     Removal is also facilitated by use of the drive adapter  80 , which eliminates the need for a large clearance at the front of the phaser  1  in the engine compartment to slide the phaser off the front of an extended inner camshaft. 
     Having thus described the present invention 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 of the invention, could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein. The present embodiment and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein.