Abstract:
An internal combustion engine includes a crankshaft rotatable about a crankshaft axis; a camshaft rotatable by the crankshaft about a camshaft axis; an engine cover defining an engine cover volume within the internal combustion engine; a drive member disposed within the engine cover volume which transfers rotational motion from the crankshaft to the camshaft; a camshaft phaser disposed within the engine cover volume which controllably varies the phase relationship between the crankshaft and the camshaft; an actuator which operates the camshaft phaser; and an actuator mount within the engine cover volume which mounts the actuator structurally independent of the engine cover, thereby allowing removal of the engine cover independently of the actuator.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This patent application claims the benefit of U.S. provisional patent application Ser. No. 62/031,265, filed on Jul. 31, 2014, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD OF INVENTION 
     The present invention relates to an internal combustion engine with a camshaft phaser for varying the phase relationship between a crankshaft and a camshaft of the internal combustion engine, more particularly to such an internal combustion engine where an actuator is provided for operating the camshaft phaser, and even more particularly to such an internal combustion engine which includes an actuator mount for mounting the actuator structurally independent of an engine cover, thereby allowing the engine cover to be removed independently of the actuator. 
     BACKGROUND OF INVENTION 
     A typical vane-type camshaft phaser for changing the phase relationship between a crankshaft and a camshaft of an internal combustion engine generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is selectively supplied to either the advance chambers or the retard chambers and vented from the other of the advance and retard chambers in order to rotate the rotor within the stator and thereby change the phase relationship between the camshaft and the crankshaft. Some camshaft phasers include a valve spool within the camshaft phaser in order to selectively supply and vent oil to and from the advance and retard chambers as necessary in order to achieve the desired phase relationship between the camshaft and the crankshaft. When the oil is vented from either the advance chambers or the retard chambers, the oil is typically drained out of the camshaft phaser and allowed to reach a drive member, such as a chain, gear, or belt, which transfers rotational motion from the crankshaft to the camshaft phaser. While this may be acceptable to some drive members, particularly chains and gears, other drive members, particularly belts, may not tolerate exposure to oil. 
     United States Patent Application Publication No. US 2014/0150742 A1 to Kinouchi teaches a camshaft phaser having a first tubular portion extending from a housing of the camshaft phaser and a second tubular portion that extends from a solenoid of the camshaft phaser. The first tubular portion cooperates with the second tubular portion to form an oil accumulating chamber which captures oil that is vented from the camshaft phaser, thereby preventing oil from reaching the drive belt. However, the solenoid actuator is attached to an engine cover which encloses the drive belt. Consequently, in order to remove the engine cover to replace or service the drive belt, the solenoid must be separated from the camshaft phaser, and oil that has accumulated in the oil accumulating chamber is allowed to escape and contaminate the area occupied by the drive belt. As a result, the oil that has escaped must be cleaned up before reassembling the engine cover. 
     What is needed is a camshaft phaser which minimizes or eliminates one or more the shortcomings as set forth above. 
     SUMMARY OF THE INVENTION 
     Briefly described, an internal combustion engine includes a crankshaft rotatable about a crankshaft axis; a camshaft rotatable by the crankshaft about a camshaft axis; an engine cover defining an engine cover volume within the internal combustion engine; a drive member disposed within the engine cover volume which transfers rotational motion from the crankshaft to the camshaft; a camshaft phaser disposed within the engine cover volume which controllably varies the phase relationship between the crankshaft and the camshaft; an actuator which operates the camshaft phaser; and an actuator mount within the engine cover volume which mounts the actuator structurally independent of the engine cover, thereby allowing removal of the engine cover independently of the actuator. 
     Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       This invention will be further described with reference to the accompanying drawings in which: 
         FIG. 1  is an exploded isometric view of an internal combustion engine in accordance with the present invention; 
         FIG. 2  is an axial cross-sectional view a portion of the internal combustion engine in accordance with the present invention; 
         FIG. 3  is a radial cross-sectional view of a camshaft phaser of the internal combustion engine in accordance with the present invention; 
         FIG. 4A  is an axial cross-sectional view of a portion of the camshaft phaser, taken through section line  4 - 4  of  FIG. 3 , showing an actuator in an energized state of operation; 
         FIG. 4B  is an axial cross-sectional view of a portion of the camshaft phaser, taken through section line  4 - 4  of  FIG. 3 , showing the actuator in an unenergized state of operation; 
         FIG. 5  is an isometric view of the internal combustion engine in accordance with the present invention with an engine cover installed; 
         FIG. 6  is the isometric view of  FIG. 5  now shown with the engine cover separated; 
         FIG. 7  is an isometric view of the internal combustion engine in accordance with the present invention showing an alternative engine cover installed; 
         FIG. 8  is the isometric view of  FIG. 7  now shown with the engine cover separated; 
         FIG. 9  is an isometric view of the internal combustion engine in accordance with the present invention showing another alternative engine cover installed; 
         FIG. 10  is the isometric view of  FIG. 9  now shown with the engine cover separated; 
         FIG. 11  an axial cross-sectional view of an alternative internal combustion engine in accordance with the present invention; 
         FIG. 12  is an isometric view of the internal combustion engine of  FIG. 11  with an engine cover installed; and 
         FIG. 13  is the isometric view of  FIG. 12  now shown with the engine cover separated. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring to  FIGS. 1 and 2 , an internal combustion engine  10  is shown in accordance with the present invention. Internal combustion engine  10  generally includes one or more pistons (not shown), a crankshaft  12  which rotates about a crankshaft axis  14 , a camshaft  16  which is supported in a camshaft support  18  and rotates about a camshaft axis  20 , and a camshaft phaser  22  which rotates about camshaft axis  20 . Internal combustion engine  10  may be, for example only, spark ignited or compression ignited and may be fueled by any liquid fuel or gaseous fuel customarily used, for example only, liquid fuels such as gasoline, diesel fuel, alcohol, ethanol, and the like and blends thereof or gaseous fuels such as natural gas, propane, and the like. The pistons, which are connected to crankshaft  12 , reciprocate as a result of combustion of the fuel within the respective combustion chambers (not shown). Reciprocation of the pistons causes crankshaft  12  to rotate about crankshaft axis  14 . Crankshaft  12  includes a crankshaft pulley  24  which may be toothed as shown and which rotates a drive member  26 , for example, a drive belt which is toothed to mate with crankshaft pulley  24 . Camshaft phaser  22  is rotated by drive member  26  and is connected to camshaft  16 ; consequently, camshaft  16  rotates about camshaft axis  20  as a result of crankshaft  12 . Rotation of camshaft  16  about camshaft axis  20  causes one or more combustion valves (not shown) to open and close. The combustion valves allow a charge of air and/or fuel into the combustion chambers and/or exhaust constituents out of the combustion chambers. Camshaft phaser  22  allows the phase of rotation of camshaft  16  relative to crankshaft  12  to be varied, thereby varying the timing of opening and/or closing of the combustion valves relative to crankshaft  12  as will be described in greater detail later. An engine cover  28  (not shown in  FIG. 1 ) encloses drive member  26  and camshaft phaser  22  in an engine cover volume  29  defined in internal combustion engine  10  by engine cover  28 . 
     With continued reference to  FIGS. 1 and 2  and now with additional reference to  FIG. 3 , camshaft phaser  22  uses pressurized oil to change the phase relationship of camshaft  16  relative to crankshaft  12 . As shown, camshaft phaser  22  is what is commonly referred to in the art as a vane-type camshaft phaser. Camshaft phaser  22  generally includes a stator  30  which acts as an input member, a rotor  32  which acts as an output member and which is disposed coaxially within stator  30 , a back cover  34  closing off one end of stator  30 , a front cover  36  (not shown in  FIG. 1 ) closing off the other end of stator  30 , a camshaft phaser attachment bolt  40  for attaching camshaft phaser  22  to camshaft  16 , and a valve spool  42  for controlling oil as will be described later which is supplied by an oil supply  44  of internal combustion engine  10 . An actuator  46  (not shown in  FIG. 1 ) is provided for positioning valve spool  42  to achieve a desired rotational position of rotor  32  relative to stator  30  as will also be described later. The various elements of camshaft phaser  22  will be described in greater detail in the paragraphs that follow. 
     Stator  30  is generally cylindrical and includes a plurality of radial chambers  48  (only one radial chamber  48  is labeled in  FIG. 1 ) defined by a plurality of lobes  50  extending radially inward. In the embodiment shown, there are four lobes  50  defining four radial chambers  48 , however, it is to be understood that a different number of lobes  50  may be provided to define radial chambers  48  equal in quantity to the number of lobes  50 . Stator  30  may also include a camshaft phaser pulley  52  which is toothed as shown and formed integrally therewith or otherwise fixed thereto. Camshaft phaser pulley  52  is configured to be driven by drive member  26 . While the drive arrangement between crankshaft  12  and camshaft phaser  22  has been illustrated as using pulleys and a belt, it should now be understood that other drive arrangements may be used, for example only, sprockets and a chain or gears. 
     Rotor  32  includes a central hub  54  with a plurality of vanes  56  extending radially outward therefrom and a central through bore  58  extending axially therethrough. The number of vanes  56  is equal to the number of radial chambers  48  provided in stator  30 . Rotor  32  is coaxially disposed within stator  30  such that each vane  56  divides each radial chamber  48  into advance chambers  60  and retard chambers  62 . The radial tips of lobes  50  are mateable with central hub  54  in order to separate radial chambers  48  from each other. Each of the radial tips of lobes  50  and the radial tips of vanes  56  may include one of a plurality of wiper seals  64  to substantially seal adjacent advance chambers  60  and retard chambers  62  from each other. 
     Back cover  34  is sealingly secured, using cover bolts  66 , to the axial end of stator  30  that is proximal to camshaft  16 . A back cover seal  68 , for example only, an O-ring, may be provided between back cover  34  and stator  30  in order to provide an oil-tight seal between the interface of back cover  34  and stator  30 . Tightening of cover bolts  66  prevents relative rotation between back cover  34  and stator  30 . Back cover  34  includes a back cover central bore  70  extending coaxially therethrough. The end of camshaft  16  is received coaxially within back cover central bore  70  such that camshaft  16  is allowed to rotate relative to back cover  34 . In an alternative arrangement, camshaft phaser pulley  52  may be integrally formed or otherwise attached to back cover  34  rather than to stator  30  as described previously. 
     Similarly, front cover  36  is sealingly secured, using cover bolts  66 , to the axial end of stator  30  that is opposite back cover  34 . A front cover seal  72 , for example only, an O-ring, may be provided between front cover  36  and stator  30  in order to provide an oil-tight seal between the interface of front cover  36  and stator  30 . Cover bolts  66  pass through back cover  34  and stator  30  and threadably engage front cover  36 ; thereby clamping stator  30  between back cover  34  and front cover  36  to prevent relative rotation between stator  30 , back cover  34 , and front cover  36 . In this way, advance chambers  60  and retard chambers  62  are defined axially between back cover  34  and front cover  36 . 
     Camshaft phaser  22  is attached to camshaft  16  with camshaft phaser attachment bolt  40  which extends coaxially through central through bore  58  of rotor  32  and threadably engages camshaft  16 , thereby clamping rotor  32  securely to camshaft  16 . In this way, relative rotation between stator  30  and rotor  32  results in a change in phase relationship or timing between crankshaft  12  and camshaft  16 . 
     With continued reference to  FIGS. 1-3  and now with additional reference to  FIGS. 4A and 4B , pressurized oil is selectively supplied to advance chambers  60  and vented from retard chambers  62  in order to cause relative rotation between stator  30  and rotor  32  which results in advancing the timing of camshaft  16  relative to crankshaft  12 . Conversely, oil is selectively supplied to retard chambers  62  and vented from advance chambers  60  in order to cause relative rotation between stator  30  and rotor  32  which results in retarding the timing of camshaft  16  relative to crankshaft  12 . Advance oil passages  74  may be provided in rotor  32  for supplying and venting oil to and from advance chambers  60  while retard oil passages  76  may be provided in rotor  32  for supplying and venting oil to and from retard chambers  62 . Supplying and venting of oil to and from advance chambers  60  and retard chambers  62  is controlled by valve spool  42 , as will be discussed in the paragraphs that follow, which is coaxially disposed slidably within a valve bore  78  of camshaft phaser attachment bolt  40  such that valve bore  78  is centered about camshaft axis  20 . 
     Oil supply  44  provides a supply of pressurized oil to valve spool  42  through radial camshaft passages  80  which communicate with a camshaft counterbore  82  which forms a camshaft annular oil passage  84  with a portion of camshaft phaser attachment bolt  40 . The oil then passes from camshaft annular oil passage  84  to an axial rotor oil passage  86  which extends axially into rotor  32 . The oil is subsequently communicated to an annular rotor oil supply groove  88  which extends radially outward from central through bore  58  and intersects axial rotor oil passage  86 . Annular rotor oil supply groove  88  is axially aligned with bolt oil supply passages  90  which extend radially through camshaft phaser attachment bolt  40  from valve bore  78 . In this way, oil from oil supply  44  is supplied to valve spool  42 . 
     Valve spool  42  includes a body  92  that is generally cylindrical, hollow, and dimensioned to provide annular clearance between body  92  and valve bore  78  of camshaft phaser attachment bolt  40 . Valve spool  42  also includes an advance land  94  extending radially outward from body  92  for selectively blocking fluid communication between bolt oil supply passages  90  and advance bolt passages  96  which extend radially outward through camshaft phaser attachment bolt  40  from valve bore  78  and communicate with advance oil passages  74  of rotor  32  through an annular rotor advance oil groove  98  which extends radially outward from central through bore  58 . Advance land  94  fits within valve bore  78  of camshaft phaser attachment bolt  40  in a close fitting relationship to substantially prevent oil from passing between advance land  94  and valve bore  78 . Valve spool  42  also includes a retard land  100  extending radially outward from body  92  for selectively blocking fluid communication between bolt oil supply passages  90  and retard bolt passages  102  which extend radially outward through camshaft phaser attachment bolt  40  from valve bore  78  and communicate with retard oil passages  76  of rotor  32  through an annular rotor retard oil groove  104  which extends radially outward from central through bore  58 . Retard land  100  is spaced axially from advance land  94  and fits within valve bore  78  of camshaft phaser attachment bolt  40  in a close fitting relationship to substantially prevent oil from passing between retard land  100  and valve bore  78 . 
     Valve spool  42  is axially moveable within valve bore  78  with input from actuator  46  and a spool spring  106  which is positioned axially between valve spool  42  and the bottom of valve bore  78 . When actuator  46  is in an unenergized state of operation as shown in  FIG. 4B , valve spool  42  is positioned in a retard position, by force of spool spring  106 , to allow pressurized oil to be supplied to retard chambers  62  as shown by arrows P. At the same time, oil within advance chambers  60  is allowed to be vented through a central passage  108  formed coaxially through valve spool  42  and then out through the end of valve bore  78  as shown by arrows V. 
     Conversely, when actuator  46  is in an energized state of operation as shown in  FIG. 4A , valve spool  42  is positioned in an advance position, by force from actuator  46  overcoming force of spool spring  106 , to allow pressurized oil to be supplied to advance chambers  60  as shown by arrows P. At the same time, oil within retard chambers  62  is allowed to be vented through the end of valve bore  78  as shown by arrows V. 
     Drive member  26  may not be compatible with the oil supplied to camshaft phaser  22 ; consequently, a dry zone  110  may be formed within engine cover volume  29 . Drive member  26  is located within dry zone  110  which is substantially free of the oil supplied to camshaft phaser  22 . Actuator  46 , which may be a solenoid actuator, is mounted to internal combustion engine  10  via an actuator mount  111  which is at least partially within engine cover volume  29  and dry zone  110  as actuator mount  111  will be described in greater detail later. Dry zone  110  is formed by a sealing arrangement which may comprise an actuator to camshaft phaser seal  112  and an engine to camshaft phaser seal  114 . The sealing arrangement will be described in greater detail in the paragraphs that follow. 
     Referring again to  FIGS. 1 and 2 , actuator to camshaft phaser seal  112  provides a seal between actuator mount  111  and front cover  36 . Actuator mount  111  includes an actuator mount seal support  116  which is ring-shaped and substantially centered about camshaft axis  20 . Actuator mount seal support  116  extends axially away from actuator mount  111  toward camshaft phaser  22 . Actuator to camshaft phaser seal  112  includes an actuator to camshaft phaser seal supporting body  118  which is ring shaped and secured coaxially within actuator mount seal support  116 , for example, by a press fit. Alternatively, actuator to camshaft phaser seal supporting body  118  may be secured to actuator mount seal support  116  by surrounding actuator mount seal support  116 , i.e. the radial relationship between actuator to camshaft phaser seal supporting body  118  and actuator mount seal support  116  may be reversed from the relationship shown in the figures. Actuator to camshaft phaser seal supporting body  118  may be made of a rigid material, for example, metal or plastic. Actuator to camshaft phaser seal  112  also includes an actuator to camshaft phaser seal lip seal  120  which extends radially inward from actuator to camshaft phaser seal supporting body  118 . Actuator to camshaft phaser seal lip seal  120  may be molded and bonded to actuator to camshaft phaser seal supporting body  118  and may be made of an elastomeric or rubber-like material, for example only, Nitrile Butadiene Rubber (NBR), Viton®, or silicone. Front cover  36  includes a front cover sealing body  122  for radially mating with actuator to camshaft phaser seal lip seal  120 . Front cover sealing body  122  may include a sleeve (not show) in a radially surrounding relationship which provides the necessary harness and surface finish to withstand rubbing with respect to actuator to camshaft phaser seal lip seal  120 , however, the sleeve may be omitted as shown if front cover sealing body  122  is made from a material of adequate hardness and surface finish. Front cover sealing body  122  is ring-shaped and extends axially away from front cover  36  toward engine cover  28  in a coaxial relationship with actuator mount seal support  116 . Front cover sealing body  122  is sized to elastically deform actuator to camshaft phaser seal lip seal  120  when assembled in order to provide an oil-tight seal between front cover sealing body  122  and actuator to camshaft phaser seal lip seal  120 . Actuator to camshaft phaser seal lip seal  120  is sized to provide sufficient compliance to accommodate mismatch in concentricity between actuator to camshaft phaser seal  112  and front cover sealing body  122  due to manufacturing tolerances. In this way, oil that is vented from advance chambers  60  and retard chambers  62  through the end of valve bore  78  is prevented from entering dry zone  110  as camshaft phaser  22  rotates with respect to actuator to camshaft phaser seal  112  in operation. In addition to actuator to camshaft phaser seal lip seal  120 , actuator to camshaft phaser seal  112  may include a dust seal lip which protects actuator to camshaft phaser seal lip seal  120  from external contamination that may have undesirable effects on actuator to camshaft phaser seal lip seal  120 . 
     Engine to camshaft phaser seal  114  provides a seal between camshaft support  18  and back cover  34 . A camshaft support bore  124 , which is cylindrical, extends into camshaft support  18  in a coaxial relationship with camshaft  16 . Engine to camshaft phaser seal  114  includes an engine to camshaft phaser seal supporting body  126  which is ring shaped and secured coaxially within camshaft support bore  124 , for example, by a press fit. Engine to camshaft phaser seal supporting body  126  may be made of a rigid material, for example, metal or plastic. Engine to camshaft phaser seal  114  also includes an engine to camshaft phaser seal lip seal  128  which extends radially inward from engine to camshaft phaser seal supporting body  126 . Engine to camshaft phaser seal lip seal  128  may be molded and bonded to engine to camshaft phaser seal supporting body  126  and may be made of an elastomeric or rubber-like material, for example only, Nitrile Butadiene Rubber (NBR), Viton®, or silicone. Engine to camshaft phaser seal  114  may also include an engine to camshaft phaser seal dust lip seal  130  which extends radially inward from engine to camshaft phaser seal supporting body  126  and may be made from the same material as engine to camshaft phaser seal lip seal  128 . Engine to camshaft phaser seal dust lip seal  130  protects engine to camshaft phaser seal lip seal  128  from external contamination that may have undesirable effects on engine to camshaft phaser seal lip seal  128 . Back cover  34  includes a back cover sealing body  132  for radially mating with engine to camshaft phaser seal lip seal  128 . Back cover sealing body  132  is ring-shaped and extends axially away from back cover  34  into camshaft support bore  124  in a coaxial relationship with camshaft support bore  124 . Back cover sealing body  132  is sized to elastically deform engine to camshaft phaser seal lip seal  128  when assembled in order to provide an oil-tight seal between back cover sealing body  132  and engine to camshaft phaser seal lip seal  128 . 
     With continued reference to  FIGS. 1 and 2  and now with additional reference to  FIGS. 5 and 6 , actuator mount  111  includes an actuator mount body  134  with an actuator mount aperture  136  extending axially therethrough such that actuator mount aperture  136  allows a portion of actuator  46  to extend therethrough. Actuator mount seal support  116 , which was described above, is defined by actuator mount body  134 . Actuator  46  is fixed to actuator mount  111 , for example, with actuator bolts  138  which threadably engage actuator mount  111 . Actuator  46  is sealed to actuator mount  111 , for example by an O-ring, gasket, or sealant (not show), thereby preventing oil from reaching dry zone  110  through actuator mount aperture  136 . Actuator mount  111  includes actuator mount mounting bosses  140  to receive actuator mount bolts  142  which threadably engage internal combustion engine  10 , thereby clamping actuator mount  111  to internal combustion engine  10 . 
     Engine cover  28  includes an engine cover aperture  144  extending therethrough which allows an electrical connector  146  of actuator  46  to be accessible outside of engine cover volume  29  and dry zone  110 , thereby allowing a mating connector (not shown) to be attached to electrical connector  146  in order to control actuator  46 . As shown, engine cover aperture  144  may extend through engine cover  28  in a direction substantially parallel to camshaft axis  20 . An engine cover to actuator seal  148  may be provided between engine cover  28  and actuator  46  in order to prevent foreign material from the environment from entering dry zone  110  through engine cover aperture  144 . Alternatively, actuator seal  148  may be provided between engine cover  28  and actuator mount  111  in order to prevent foreign material from the environment from entering dry zone  110  through engine cover aperture  144 . Also alternatively, actuator seal  148  may be a radial seal rather than an axial seal as shown. 
     A rotor drain passage  150  is provided axially through central hub  54  of rotor  32  in order to return oil to oil supply  44  that is vented from advance chambers  60  and retard chambers  62  through the end of valve bore  78 . The oil exits the rotor drain passage  150  that is proximal to camshaft  16  and is prevented from entering dry zone  110  by engine to camshaft phaser seal  114  and is subsequently returned to oil supply  44 . 
     Since actuator  46  is mounted to internal combustion engine  10  structurally independent of engine cover  28 , engine cover  28  can be removed from internal combustion engine  10  in order to service drive member  26  without the need to remove actuator  46  from internal combustion engine  10 . In order to remove engine cover  28 , engine cover  28  is moved in a direction parallel to camshaft axis  20  until electrical connector  146  no longer passes through engine cover aperture  144 . Since actuator  46  does not need to be removed, there is no risk of contaminating dry zone  110  with oil from camshaft phaser  22  when servicing drive member  26 . It should be noted that actuator mount  111  is within the path of drive member  26 , i.e. each actuator mount mounting boss  140  is located within the inner periphery of drive member  26 , and consequently, drive member  26  can be removed while actuator  46  and actuator mount  111  are attached to internal combustion engine  10 . 
     In an alternative arrangement as shown in  FIGS. 7 and 8 , an engine cover  28 ′ is provided. Engine cover  28 ′ differs from engine cover  28  in that engine cover  28 ′ includes an engine cover aperture  144 ′ which extends through engine cover  28 ′ in a direction that is substantially perpendicular to camshaft axis  20 . In this way, engine cover  28 ′ can be removed from internal combustion engine  10  in direction that is substantially perpendicular to camshaft axis  20 . This may be particularly useful when internal combustion engine  10  is in an environment which does not allow engine cover  28 ′ to be displaced parallel to camshaft axis  20  a sufficient amount to facilitate remove of engine cover  28 ′. 
     In another alternative arrangement as shown in  FIGS. 9 and 10 , an engine cover  28 ″ is provided. Engine cover  28 ″ differs from engine cover  28  and engine cover  28 ′ in that engine cover  28 ″ interfaces with an actuator mount  111 ″ rather than with actuator  46 . Engine cover  28 ″ includes an engine cover aperture  144 ″ which is discontinuous and substantially “U” shaped, i.e. engine cover aperture  144 ″ is not defined by engine cover  28 ″ in a 360° relationship. Actuator mount  111 ″ is shaped to be complementary to engine cover aperture  144 ″ such that the interface between actuator mount  111 ″ and engine cover aperture  144 ″ is sealed, for example with an O-ring, gasket, or sealant, thereby preventing foreign material from entering dry zone  110  from the environment. Since engine cover aperture  144 ″ is discontinuous, removal of engine cover  28 ″ may be accomplished by displacing engine cover  28 ″ in a direction either parallel or perpendicular to camshaft axis  20  or at any angle therebetween. The arrangement of engine cover  28 ″ and actuator mount  111 ″ also allows for service of actuator  46  without removal of engine cover  28 ″. 
     While actuator to camshaft phaser seal  112  has been illustrated as being fixed to actuator mount  111 , it should now be understood that actuator to camshaft phaser seal  112  may alternatively be attached to actuator  46 . It should also now be understood that actuator mount  111  may be integrally formed with actuator  46 . These alternatives similarly apply to and actuator mount  111 ″. 
     As described above, actuator  46  is used to position valve spool  42  in order to change the rotational position of rotor  32  within stator  30 . However, in an alternative arrangement, actuator  46  may be used to position valve spool  42  in order to affect a lock pin which selectively prevents and allows rotor  32  to rotate relative to stator  30 . In a further alternative arrangement, actuator  46  may be used to position valve spool  42  to change the rotational position of rotor  32  within stator  30  and to affect the lock pin. In this way actuator  46  is generally said to operate camshaft phaser  22 . 
     While the invention as described above has been describe in relation to camshaft phaser  22  which uses hydraulics to change the phase relationship of camshaft  16  relative to crankshaft  12 , the invention is also envisioned to apply to camshaft phasers which use an electric motor to change the phase relationship of camshaft  16  relative to crankshaft  12 . In the paragraphs that follow, such an arrangement will be described. 
     Referring now to  FIGS. 11-13 , an internal combustion engine  310  is shown in accordance with the present invention. Internal combustion engine  310  generally includes one or more pistons (not shown), a crankshaft  312  which rotates about a crankshaft axis  314 , a camshaft  316  which is supported in a camshaft support  318  and rotates about a camshaft axis  320 , and a camshaft phaser  322  which rotates about camshaft axis  320 . Internal combustion engine  310  may be, for example only, spark ignited or compression ignited and may be fueled by any liquid fuel or gaseous fuel customarily used, for example only, liquid fuels such as gasoline, diesel fuel, alcohol, ethanol, and the like, and blends thereof or gaseous fuel such as natural gas, propane, and the like. The pistons, which are connected to crankshaft  312 , reciprocate as a result of combustion of the fuel within respective combustion chambers (not shown). Reciprocation of the pistons causes crankshaft  312  to rotate about crankshaft axis  314 . Crankshaft  312  includes a crankshaft pulley  324  which rotates a drive member  326 , for example, a drive belt. Camshaft phaser  322  is rotated by drive member  326  and connected to camshaft  316 ; consequently, camshaft  316  rotates about camshaft axis  320  as a result of crankshaft  312 . Rotation of camshaft  316  about camshaft axis  320  causes one or more combustion valves (not shown) to open and close. The combustion valves may allow a charge of air and/or fuel into the combustion chambers and/or exhaust constituents out of the combustion chambers. Camshaft phaser  322  allows the phase of rotation of camshaft  316  relative to crankshaft  312  to be varied, thereby varying the timing of opening and/or closing of the combustion valves relative to crankshaft  312  as will be described in greater detail later. An engine cover  328  encloses drive member  326  and camshaft phaser  322  in an engine cover volume  329  defined in internal combustion engine  310  by engine cover  328 . 
     Camshaft phaser  322  comprises a gear drive unit illustrated as a harmonic gear drive unit  334 ; a rotational actuator  336  operationally connected to harmonic gear drive unit  334 ; an input pulley  338  operationally connected to harmonic gear drive unit  334  and driven by drive member  326  via crankshaft  312 ; an output hub  340  attached to harmonic gear drive unit  334  and mounted to an end of camshaft  316 ; and a bias spring  342  operationally disposed between output hub  340  and input pulley  338 . Rotational actuator  336 , hereinafter referred to as actuator  336 , may be, for example only, a DC electric motor. 
     Harmonic gear drive unit  334  comprises an outer first spline  344  which may be either a circular spline or a dynamic spline as described below; an outer second spline  346  which is the opposite (dynamic or circular) of outer first spline  344  and is coaxially positioned adjacent outer first spline  344 ; a flexspline  348  disposed radially inwards of both outer first spline  344  and outer second spline  346  and having outwardly-extending gear teeth disposed for engaging inwardly-extending gear teeth on both outer first spline  344  and outer second spline  346 ; and a wave generator  350  disposed radially inwards of and engaging flexspline  348 . 
     Flexspline  348  is a non-rigid ring with external teeth on a slightly smaller pitch diameter than the circular spline. Flexspline  348  is fitted over and elastically deflected by wave generator  350 . 
     The circular spline is a rigid ring with internal teeth engaging the teeth of flexspline  348  across the major axis of wave generator  350 . 
     The dynamic spline is a rigid ring having internal teeth of the same number as flexspline  348 . The dynamic spline rotates together with flexspline  348  and serves as the output member. Either the dynamic spline or the circular spline may be identified by a chamfered corner at its outside diameter to distinguish one spline from the other. As shown, the chamfered corner has been used to identify outer second spline  346 . 
     As is disclosed in the prior art, wave generator  350  is an assembly of an elliptical steel disc supporting an elliptical bearing, the combination defining a wave generator plug. A flexible bearing retainer surrounds the elliptical bearing and engages flexspline  348 . Rotation of the wave generator plug causes a rotational wave to be generated in flexspline  348  (actually two waves 180° apart, corresponding to opposite ends of the major ellipse axis of the disc). 
     During assembly of harmonic gear drive unit  334 , flexspline teeth engage both circular spline teeth and dynamic spline teeth along and near the major elliptical axis of the wave generator. The dynamic spline has the same number of teeth as the flexspline, so rotation of the wave generator causes no net rotation per revolution therebetween. However, the circular spline has slightly fewer gear teeth than does the dynamic spline, and therefore the circular spline rotates past the dynamic spline during rotation of the wave generator plug, defining a gear ratio therebetween (for example, a gear ratio of 50:1 would mean that 1 rotation of the circular spline past the dynamic spline corresponds to 50 rotations of the wave generator). Harmonic gear drive unit  334  is thus a high-ratio gear transmission; that is, the angular phase relationship between outer first spline  344  and outer second spline  346  changes by 2% for every revolution of wave generator  350 . 
     Of course, as will be obvious to those skilled in the art, the circular spline may instead have slightly more teeth than the dynamic spline has, in which case the rotational relationships described below are reversed. 
     Input pulley  338  is rotationally fixed to a housing  352  which acts as an input member and which includes a housing bore  354  which extends coaxially therethrough within which output hub  340  and harmonic gear drive unit  334  are coaxially located. A back cover  356  is attached to an axial end of housing  352  that is proximal to camshaft  316  while a front cover  358  is fixed to the axial end of housing  352  that is opposite back cover  356 . Back cover  356  and front cover  358  will be described in greater detail later. 
     Output hub  340 , which acts as an output member for camshaft phaser  322 , includes a central through bore  360  extending coaxially therethrough. Output hub  340  is disposed coaxially within housing  352  and mates with housing bore  354 , thereby defining a journal bearing interface  362  between output hub  340  and housing  352  which substantially prevents tipping and radial movement of output hub  340  within housing  352  while allowing output hub  340  to rotate within housing  352 . Output hub  340  is attached to camshaft  316  by a camshaft phaser attachment bolt  364  which extends through central through bore  360  and threadably engages camshaft  316 . In this way, output hub  340  is clamped securely to camshaft  316  and relative rotation between output hub  340  and camshaft  316  is prevented. 
     A coupling adaptor  366  is mounted to wave generator  350  and extends through front cover  358  being supported by a bearing  368  mounted in front cover  358 . A coupling  370  is mounted to a motor shaft  372  of actuator  336  and fixed thereto in order to prevent relative rotation between coupling  370  and motor shaft  372 . Coupling  370  engages coupling adaptor  366 , permitting wave generator  350  to be rotationally driven by actuator  336 , as may be desired to alter the phase relationship between outer first spline  344  and outer second spline  346 . In this way, actuator  336  is generally said to operate camshaft phaser  322 . Further features of coupling adaptor  366  and coupling  370  are disclosed in United States Patent Application Publication No. US 2012/0291729 A1 to David et al., the disclosure of which is incorporated herein by reference in its entirety. 
     In order to ensure smooth operation and provide resistance to wear, journal bearing interface  362  may be supplied with oil, for example, from internal combustion engine  310 . Oil under pressure may be supplied via an oil gallery (not shown) of internal combustion engine  310  through camshaft radial oil passages  374  of camshaft  316  to a camshaft counter bore  376  which extends axially into camshaft  316 . From camshaft counter bore  376 , the oil is communicated to an annular space formed radially between camshaft phaser attachment bolt  364  and central through bore  360  of output hub  340  where the oil is passed through a filter  378  located within central through bore  360  of output hub  340  and is communicated to journal bearing interface  362  through one or more output hub oil passages  380  that extend radially outward through output hub  340  to journal bearing interface  362  from central through bore  360  of output hub  340 . Oil that passes by journal bearing interface  362  in the axial direction away from back cover  356  is allowed to lubricate harmonic gear drive unit  334 , bearing  368 , and coupling  370  through gravity and dynamics of camshaft phaser  322  in use. It should now be understood that additional oil passages may be provided, for example as disclosed in United States Patent Application Publication No. US 2012/0312258 A1 to Kimus et al., the disclosure of which is incorporated herein by reference in its entirety. 
     Outer second spline  346  is secured coaxially to output hub  340 , for example with bolts, thereby securely clamping outer second spline  346  to output hub  340  and thereby preventing relative rotation between outer second spline  346  and output hub  340 . In this way, output hub  340  rotates with outer second spline  346  in a one-to-one relationship. 
     Front cover  358  includes a front cover bore  382  extending axially therethrough. Outer first spline  344  is secured to front cover  358 , for example by bolts, thereby preventing relative rotation between outer first spline  344  and front cover  358 . Front cover bore  382  receives bearing  368  coaxially therewithin such that bearing  368  is fixed within front cover bore  382 , for example, by press fit. Front cover  358  is secured to housing  352 , for example by bolts, thereby preventing relative rotation between front cover  358  and housing  352 . In this way relative rotation between input pulley  338 , housing  352 , front cover  358 , and outer first spline  344  is prevented. 
     Bias spring  342  is captured axially between output hub  340  and back cover  356 . An inner spring tang (not shown) of bias spring  342  is engaged with output hub  340  while an outer spring tang (not shown) of bias spring  342  is engaged with back cover  356 . In the event of a malfunction of actuator  336 , bias spring  342  is biased to back-drive harmonic gear drive unit  334  without help from actuator  336  to a predetermined rotational position of outer second spline  346 . The predetermined position may be a position which allows internal combustion engine  310  to start or run, and the predetermined position may be at one of the extreme ends of the range of authority or intermediate of the phaser&#39;s extreme ends of its rotational range of authority. For example, the rotational range of travel in which bias spring  342  biases harmonic gear drive unit  334  may be limited to something short of the end stop position of the phaser&#39;s range of authority. Such an arrangement would be useful for internal combustion engines requiring an intermediate park position for idle or restart. 
     Drive member  326  may not be compatible with the oil used to lubricate camshaft phaser  322 ; consequently, a dry zone  410  may be formed within engine cover  328 . Drive member  326  is located within dry zone  410  which is substantially free of the oil used to lubricate camshaft phaser  322 . Actuator  336  is mounted to internal combustion engine  310  via an actuator mount  411  which is at least partially within dry zone  410  as actuator mount  411  will be described in greater detail later. Dry zone  410  is formed by a sealing arrangement which may comprise an actuator to camshaft phaser seal  412  and an engine to camshaft phaser seal  414 . The sealing arrangement will be described in greater detail in the paragraphs that follow. 
     Actuator to camshaft phaser seal  412  provides a seal between actuator mount  411  and a front housing sealing body  416  which is sealingly fixed to housing  352 . Actuator mount  411  may define an actuator to camshaft phaser seal bore  418  which is substantially cylindrical in shape, centered about camshaft axis  320 , and extends axially into actuator mount  411 . Actuator to camshaft phaser seal  412  includes an actuator to camshaft phaser seal supporting body  420  which is ring shaped and secured coaxially within actuator to camshaft phaser seal bore  418 , for example, by a press fit. Actuator to camshaft phaser seal supporting body  420  may be made of a rigid material, for example, metal or plastic. Actuator to camshaft phaser seal  412  also includes an actuator to camshaft phaser seal lip seal  421  which extends radially inward from actuator to camshaft phaser seal supporting body  420 . Actuator to camshaft phaser seal lip seal  421  may be molded and bonded to actuator to camshaft phaser seal supporting body  420  and may be made of an elastomeric or rubber-like material, for example only, Nitrile Butadiene Rubber (NBR), Viton®, or silicone. Front housing sealing body  416  radially mates with actuator to camshaft phaser seal lip seal  421 . A portion of front housing sealing body  416  is ring-shaped and extends axially toward actuator  336  and into actuator to camshaft phaser seal bore  418  in a coaxial relationship therewith. Front housing sealing body  416  is sized to elastically deform actuator to camshaft phaser seal lip seal  421  when assembled in order to provide an oil-tight seal between front housing sealing body  416  and actuator to camshaft phaser seal lip seal  421 . Actuator to camshaft phaser seal lip seal  421  is sized to provide sufficient compliance to accommodate mismatch in concentricity between actuator to camshaft phaser seal  412  and front housing sealing body  416  due to manufacturing tolerances. In this way, oil that exits the end of housing  352  which is proximal to actuator  336  is prevented from entering dry zone  410  as camshaft phaser  322  rotates with respect to actuator to camshaft phaser seal  412  in operation. In addition to actuator to camshaft phaser seal lip seal  421 , actuator to camshaft phaser seal  412  may include a dust seal lip which protects actuator to camshaft phaser seal lip seal  421  from external contamination that may have undesirable effects on actuator to camshaft phaser seal lip seal  421 . 
     Engine to camshaft phaser seal  414  provides a seal between camshaft support  318  and a back housing sealing body  422  that is sealingly fixed to the side of housing  352  that is opposite of front housing sealing body  416 . A camshaft support bore  424 , which is cylindrical, extends into camshaft support  318  in a coaxial relationship with camshaft  316 . Engine to camshaft phaser seal  414  includes an engine to camshaft phaser seal supporting body  426  which is ring shaped and secured coaxially within camshaft support bore  424 , for example, by a press fit. Engine to camshaft phaser seal supporting body  426  may be made of a rigid material, for example, metal or plastic. Engine to camshaft phaser seal  414  also includes an engine to camshaft phaser seal lip seal  428  which extends radially inward from engine to camshaft phaser seal supporting body  426 . Engine to camshaft phaser seal lip seal  428  may be molded and bonded to engine to camshaft phaser seal supporting body  426  and may be made of an elastomeric or rubber-like material, for example only, Nitrile Butadiene Rubber (NBR), Viton®, or silicone. Engine to camshaft phaser seal  414  may also include an engine to camshaft phaser seal dust lip seal  430  which extends radially inward from engine to camshaft phaser seal supporting body  426  and may be made from the same material as engine to camshaft phaser seal lip seal  428 . Engine to camshaft phaser seal dust lip seal  430  protects engine to camshaft phaser seal lip seal  428  from external contamination that may have undesirable effects on engine to camshaft phaser seal lip seal  428 . A portion of back housing sealing body  422  is ring-shaped and extends axially into camshaft support bore  424  in a coaxial relationship. Back housing sealing body  422  is sized to elastically deform engine to camshaft phaser seal lip seal  428  when assembled in order to provide an oil-tight seal between back housing sealing body  422  and engine to camshaft phaser seal lip seal  428 . 
     Actuator mount  411  includes an actuator mount body  434  with an actuator mount aperture  436  extending axially therethrough such that actuator mount aperture  436  allows a portion of actuator  336  to extend therethrough. Camshaft phaser seal bore  418 , which was described above, is defined by actuator mount body  434 . Actuator  336  is fixed to actuator mount  411 , for example, with actuator bolts  438  which threadably engage actuator mount  411 . Actuator  336  is sealed to actuator mount  411 , for example by an O-ring, gasket, or sealant (not show), thereby preventing oil from reaching dry zone  410  and/or the external environment through actuator mount aperture  436 . Actuator mount  411  includes actuator mount mounting bosses  440  to receive actuator mount bolts  442  which threadably engage internal combustion engine  310 , thereby clamping actuator mount  411  to internal combustion engine  10 . 
     Engine cover  328  includes an engine cover aperture  444  extending therethrough which allows an electrical connector  446  of actuator  336  to be accessible outside of engine cover volume  329  and dry zone  410 , thereby allowing a mating connector (not shown) to be attached to electrical connector  446  in order to control actuator  336 . As shown, engine cover aperture  444  may be discontinuous and substantially “U” shaped, i.e. engine cover aperture  444  is not defined by engine cover  328  in a 360° relationship. Actuator mount  411  is shaped to be complementary to engine cover aperture  444  such that the interface between actuator mount  411  and engine cover aperture  444  is sealed, for example with an O-ring, gasket, or sealant, thereby preventing foreign material from entering dry zone  410  from the environment. Since engine cover aperture  444  is discontinuous, removal of engine cover  328  may be accomplished by displacing engine cover  328  in a direction either parallel or perpendicular to camshaft axis  20  or any angle therebetween. Alternatively, engine cover aperture  444  may be similar to engine cover aperture  144  described above which is continuous, i.e. engine cover aperture  444  may be defined by engine cover  328  in a 360° relationship. When this alternative approach is taken, actuator  336  or actuator mount  411  may be sealed to engine cover aperture  444 . 
     A drain passage  450  is provided axially through output hub  340  in order to return oil to internal combustion engine  310 . The oil exits drain passage  450  that is proximal to camshaft  316  and is prevented from entering dry zone  410  by engine to camshaft phaser seal  414  and is subsequently returned to internal combustion engine  310 . 
     Since actuator  336  is mounted to internal combustion engine  310  structurally independent of engine cover  328 , engine cover  328  can be removed from internal combustion engine  310  in order to service drive member  326  without the need to remove actuator  336  from internal combustion engine  310 . Since actuator  336  does not need to be removed, there is no risk of contaminating dry zone  410  with oil from camshaft phaser  322  when servicing drive member  326 . The arrangement of engine cover  328  and actuator mount  311  also allows for service of actuator  336  without removal of engine cover  328 . It should be noted that actuator mount  411  is within the path of drive member  326 ; consequently, drive member  326  can be removed while actuator  336  and actuator mount  411  are attached to internal combustion engine  310 . 
     While actuator to camshaft phaser seal  412  has been illustrated as being fixed to actuator mount  411 , it should now be understood that actuator to camshaft phaser seal  412  may alternatively be attached to actuator  336 . It should also now be understood that actuator mount  411 , may be integrally formed with actuator  336 . 
     The embodiment described herein describes harmonic gear drive unit  334  as comprising outer first spline  344  which may be either a circular spline or a dynamic spline which serves as the input member; an outer second spline  346  which is the opposite (dynamic or circular) of outer first spline  344  and which serves as the output member and is coaxially positioned adjacent outer first spline  344 ; a flexspline  348  disposed radially inwards of both outer first spline  344  and outer second spline  346  and having outwardly-extending gear teeth disposed for engaging inwardly-extending gear teeth on both outer first spline  344  and outer second spline  346 ; and a wave generator  350  disposed radially inwards of and engaging flexspline  348 . As described, harmonic gear drive unit  334  is a flat plate or pancake type harmonic gear drive unit as referred to in the art. However, it should now be understood that other types of harmonic gear drive units may be used in accordance with the present invention. For example, a cup type harmonic gear drive unit may be used. The cup type harmonic gear drive unit comprises a circular spline which serves as the input member; a flexspline which serves as the output member and which is disposed radially inwards of the circular spline and having outwardly-extending gear teeth disposed for engaging inwardly-extending gear teeth on the circular spline; and a wave generator disposed radially inwards of and engaging the flexspline. 
     While the gear drive unit of camshaft phaser  22  has been described herein as harmonic gear drive unit  334 , it should now be understood that the invention encompasses camshaft phasers using any known gear drive units. Other gear drive units that may be used within the scope of this invention include, by non-limiting example, spur gear units, helical gear units, worm gear units, hypoid gear units, planetary gear units, and bevel gear units. 
     While this invention has been described in terms of preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.