Abstract:
A camshaft phaser is provided for varying the phase relationship between a crankshaft and a camshaft in an engine. The camshaft phaser includes a stator having lobes. A rotor is disposed within the stator includes vanes interspersed with the stator lobes to define alternating advance and retard chambers. A lock pin is provided for selective engagement with a lock pin seat for preventing relative rotation between the rotor and the stator. Pressurized oil disengages the lock pin from the seat while oil is vented for engaging the lock pin with the seat. A phase relationship control valve is coaxial with the rotor and controls the flow of oil into and out of the chambers. A lock pin control valve is coaxial with the phase relationship control valve and controls the flow of oil to and from the lock pin. The control valves are operational independent of each other.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/049,167 filed on Mar. 16, 2011, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD OF INVENTION 
       [0002]    The present invention relates to a hydraulically actuated camshaft phaser for varying the phase relationship between a crankshaft and a camshaft in an internal combustion engine; more particularly to such a camshaft phaser that is a vane-type camshaft phaser, and more particularly to a vane-type camshaft phaser which includes a first oil control valve located coaxially within the camshaft phaser to control engagement and disengagement of a lock pin and a second oil control valve that is coaxial with the first oil control valve for varying the phase relationship between the crankshaft and the camshaft. 
       BACKGROUND OF INVENTION 
       [0003]    A typical vane-type camshaft phaser 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 one of the advance and retard chambers and vacated 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 an engine camshaft and an engine crankshaft. Camshaft phasers also commonly include an intermediate lock pin which selectively prevents relative rotation between the rotor and the stator at an angular position that is intermediate of a full advance and a full retard position. The intermediate lock pin is engaged and disengaged by vented oil from the intermediate lock pin and supplying pressurized oil to the intermediate lock pin respectively. 
         [0004]    Some camshaft phasers utilize one or more oil control valves located in the internal combustion engine to control the flow of pressurized oil to and from the advance chambers, retard chambers, and lock pin. One example of such a camshaft phaser is shown in United States Patent Application Publication number 2010/0288215. In this arrangement, three separate supply signals need to be included in the camshaft bearing for communication to the camshaft phaser. More specifically, a first passage for the advance chambers, a second passage for the retard chambers, and a third passage for the lock pin is included in the camshaft bearing. Including three separate passages in the camshaft bearing undesirably increases the length of the camshaft bearing. Additionally, space may be limited in the internal combustion engine to package oil control valves therein which are needed to control oil to and from each of the three passages. 
         [0005]    In order to eliminate the packaging concerns and increased camshaft bearing length issues associated with packaging the oil control valve in the internal combustion engine, some manufacturers have included the oil control valve coaxially within the camshaft phaser. While this arrangement is common for oil control valves that need to supply oil to the advance and retard chambers, the arrangement is less common for oil control valves that need to supply oil not only to the advance and retard chambers, but the intermediate lock pin as well. One example of such a camshaft phaser is shown in United States Patent Application Publication number 2004/0055550. However, including a single oil control valve coaxially within the camshaft phaser to control oil to the lock pin in addition to the advance and retard chambers requires an increased camshaft phaser thickness in order to accommodate the passage supplying oil to and from the lock pin. A single oil control valve also prevents independent control of the lock pin function and the phasing function which may make engaging the intermediate lock pin with its lock pin seat difficult. 
         [0006]    What is needed is an axially compact camshaft phaser with valving located coaxially within the camshaft phaser for controlling the phase relationship and for controlling the lock pin. What is also needed is such a camshaft phaser which allows for control of the phase relationship independent of the lock pin. 
       SUMMARY OF THE INVENTION 
       [0007]    Briefly described, a camshaft phaser is provided for controllably varying the phase relationship between a crankshaft and a camshaft in an internal combustion engine. The camshaft phaser includes a stator having a plurality of lobes and connectable to the crankshaft of the internal combustion engine to provide a fixed ratio of rotation between the stator and the crankshaft. The camshaft phaser also includes a rotor coaxially disposed within the stator and having a plurality of vanes interspersed with the stator lobes defining alternating advance chambers and retard chambers. The advance chambers receive pressurized oil in order to change the phase relationship between the crankshaft and the camshaft in the advance direction while the retard chambers receive pressurized oil in order to change the phase relationship between the camshaft and the crankshaft in the retard direction. The rotor is attachable to the camshaft of the internal combustion engine to prevent relative rotation between the rotor and the camshaft. A lock pin is disposed within one of the rotor and the stator for selective engagement with a lock pin seat in the other of the rotor and the stator for substantially preventing relative rotation between the rotor and the stator when the lock pin is engaged with the lock pin seat. Pressurized oil is selectively supplied to the lock pin in order to disengage the lock pin from the lock pin seat while oil is selectively vented from the lock pin in order to engage the lock pin with the lock pin seat. A phase relationship control valve which is coaxial with the rotor is provided for controlling the flow of oil into and out of the advance and retard chambers. A lock pin control valve which is coaxial with the phase relationship control valve is provided for controlling the flow of oil to and from the lock pin. The phase relationship control valve is operational independent of the lock pin control valve. 
         [0008]    Further features and advantages of the invention will appear more clearly on a reading of the following detail 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 
         [0009]    This invention will be further described with reference to the accompanying drawings in which: 
           [0010]      FIG. 1  is an exploded isometric view of a camshaft phaser in accordance with the present invention; 
           [0011]      FIG. 2A  is an axial cross-section of the camshaft phaser in accordance with the present invention; 
           [0012]      FIG. 2B  is the axial cross-section of  FIG. 2A  showing a phase relationship control valve in a first position for supplying pressurized oil to retard chambers of the camshaft phaser and for venting oil from the advance chambers the camshaft phaser; 
           [0013]    FIG.  2 B′ is an enlarged view of the pertinent elements of  FIG. 2B  without reference numbers to clearly shown the oil flow through the camshaft phaser; 
           [0014]      FIG. 2C  is the axial cross section of  FIG. 2A  showing the phase relationship control valve in a second position for supplying pressurized oil to the advance chambers and for venting oil from the retard chambers; 
           [0015]    FIG.  2 C′ is an enlarged view of the pertinent elements of  FIG. 2C  without reference numbers to clearly shown the oil flow through the camshaft phaser; 
           [0016]      FIG. 3A  is an axial cross section of the camshaft phaser showing a lock pin control valve in a first position for supplying pressurized oil to lock pins of the camshaft phaser for retracting the lock pins from their lock pin seats; 
           [0017]    FIG.  3 A′ is an enlarged view of the pertinent elements of  FIG. 3A  without reference numbers to clearly shown the oil flow through the camshaft phaser; 
           [0018]      FIG. 3B  is an axial cross section of the camshaft phaser showing the lock pin control valve in a second position for vented oil from the lock pins for seating the lock pins in their lock pin seats; 
           [0019]    FIG.  3 B′ is an enlarged view of the pertinent elements of  FIG. 3B  without reference numbers to clearly shown the oil flow through the camshaft phaser; 
           [0020]      FIG. 4  is a radial cross-section of the camshaft phaser taken in the direction of arrows  4  in  FIG. 2A ; 
           [0021]      FIGS. 5A-5D  are enlarged isometric views of a manifold of the camshaft phaser where each Fig. is shown rotated 90° from the previous view; 
           [0022]      FIG. 6A  is an enlarged isometric view of a bushing adaptor of the camshaft phaser; 
           [0023]      FIG. 6B  is an isometric cross-section of the bushing adaptor of  FIG. 6A ; 
           [0024]      FIG. 7A  is an axial cross section of a second embodiment of a camshaft phaser showing a lock pin control valve in a first position for supplying pressurized oil to lock pins of the camshaft phaser for retracting the lock pins from their lock pin seats; 
           [0025]    FIG.  7 A′ is an enlarged view of the pertinent elements of  FIG. 7A  without reference numbers to clearly show the oil flow through the camshaft phaser; 
           [0026]      FIG. 7B  is an axial cross section of the second embodiment camshaft phaser showing the lock pin control valve in a second position for venting oil from the lock pins for seating the lock pins in their lock pin seats; 
           [0027]    FIG.  7 B′ is an enlarged view of the pertinent elements of  FIG. 7B  without reference numbers to clearly show the oil flow through the camshaft phaser; 
           [0028]      FIG. 8A  is an enlarged isometric view of a manifold of the camshaft phaser of the second embodiment; and 
           [0029]      FIG. 8B  is an isometric cross-section of the manifold of  FIG. 8A . 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0030]    In accordance with a preferred embodiment of this invention and referring to  FIGS. 1 ,  2 A, and  4 , internal combustion engine  10  is shown which includes camshaft phaser  12 . Internal combustion engine  10  also includes camshaft  14  which is rotatable based on rotational input from a crankshaft and chain (not shown) driven by a plurality of reciprocating pistons (also not shown). As camshaft  14  is rotated, it imparts valve lifting and closing motion to intake and/or exhaust valves (not shown) as is well known in the internal combustion engine art. Camshaft phaser  12  allows the timing between the crankshaft and camshaft  14  to be varied. In this way, opening and closing of the intake and/or exhaust valves can be advanced or retarded in order to achieve desired engine performance. 
         [0031]    Camshaft phaser  12  includes sprocket  16  which is driven by a chain or gear (not shown) driven by the crankshaft of internal combustion engine  10 . Alternatively, sprocket  16  may be a pulley driven by a belt. Sprocket  16  includes a central bore  18  for receiving camshaft  14  coaxially therethrough which is allowed to rotate relative to sprocket  16 . Sprocket  16  is sealingly secured to stator  20  with sprocket bolts  22  in a way that will be described in more detail later. 
         [0032]    Stator  20  is generally cylindrical and includes a plurality of radial chambers  24  defined by a plurality of lobes  26  extending radially inward. In the embodiment shown, there are four lobes  26  defining four radial chambers  24 , however, it is to be understood that a different number of lobes may be provided to define radial chambers equal in quantity to the number of lobes. 
         [0033]    Rotor  28  includes central hub  30  with a plurality of vanes  32  extending radially outward therefrom and central through bore  34  which is stepped and extends axially therethrough. The number of vanes  32  is equal to the number of radial chambers  24  provided in stator  20 . Rotor  28  is coaxially disposed within stator  20  such that each vane  32  divides each radial chamber  24  into advance chambers  36  and retard chambers  38 . The radial tips of lobes  26  are mateable with central hub  30  in order to separate radial chambers  24  from each other. Preferably, each of the radial tips of vanes  32  includes one of a plurality of wiper seals  40  to substantially seal adjacent advance and retard chambers  36 ,  38  from each other. Although not shown, each of the radial tips of lobes  26  may include a wiper seal similar in configuration to wiper seal  40 . 
         [0034]    Central hub  30  includes a plurality of oil passages  42 A,  42 R formed radially therethrough (best visible as hidden lines in  FIG. 4 ). Each one of the plurality of oil passages  42 A is in fluid communication with one of the advance chambers  36  for supplying oil thereto and therefrom while each one of the plurality of oil passages  42 R is in fluid communication with one of the retard chambers  38  for supplying oil thereto and therefrom. 
         [0035]    Bias spring  44  is disposed within annular pocket  46  formed in rotor  28  and within central bore  48  of camshaft phaser cover  50 . Bias spring  44  is grounded at one end thereof to camshaft phaser cover  50  and is attached at the other end thereof to rotor  28 . When internal combustion engine  10  is shut down, bias spring  44  urges rotor  28  to a predetermined angular position within stator  20  in a way that will be described in more detail in the subsequent paragraph. 
         [0036]    Now referring to  FIGS. 1 ,  3 A, and  3 B; camshaft phaser  12  includes a staged dual lock pin system for selectively preventing relative rotation between rotor  28  and stator  20  at the predetermined angular position which is between the extreme advance and extreme retard positions. Primary lock pin  52  is slidably disposed within primary lock pin bore  54  formed in one of the plurality of vanes  32  of rotor  28 . Primary lock pin seat  56  is formed in camshaft phaser cover  50  for selectively receiving primary lock pin  52  therewithin. Primary lock pin seat  56  is larger than primary lock pin  52  to allow rotor  28  to rotate relative to stator  20  about 5° on each side of the predetermined angular position when primary lock pin  52  is seated within primary lock pin seat  56 . The enlarged nature of primary lock pin seat  56  allows primary lock pin  52  to be easily received therewithin. When primary lock pin  52  is not desired to be seated within primary lock pin seat  56  as shown in  FIG. 3A , pressurized oil is supplied to primary lock pin  52 , thereby urging primary lock pin  52  out of primary lock pin seat  56  and compressing primary lock pin spring  58 . Conversely, when primary lock pin  52  is desired to be seated within primary lock pin seat  56  as shown in  FIG. 3B , the pressurized oil is vented from primary lock pin  52 , thereby allowing primary lock pin spring  58  to urge primary lock pin  52  toward camshaft phaser cover  50 . In this way, primary lock pin  52  is seated within primary lock pin seat  56  by primary lock pin spring  58  when rotor  28  is positioned within stator  20  to allow alignment of primary lock pin  52  with primary lock pin seat  56 . 
         [0037]    Secondary lock pin  60  is slidably disposed within secondary lock pin bore  62  formed in one of the plurality of vanes  32  of rotor  28 . Secondary lock pin seat  64  is formed in camshaft phaser cover  50  for selectively receiving secondary lock pin  60  therewithin. Secondary lock pin  60  fits within secondary lock pin seat  64  in a close sliding relationship, thereby substantially preventing relative rotation between rotor  28  and stator  20  when secondary lock pin  60  is received within secondary lock pin seat  64 . When secondary lock pin  60  is not desired to be seated within secondary lock pin seat  64  as shown in  FIG. 3A , pressurized oil is supplied to secondary lock pin  60 , thereby urging secondary lock pin  60  out of secondary lock pin seat  64  and compressing secondary lock pin spring  66 . Conversely, when secondary lock pin  60  is desired to be seated within secondary lock pin seat  64  as shown in  FIG. 3B , the pressurized oil is vented from the secondary lock pin  60 , thereby allowing secondary lock pin spring  66  to urge secondary lock pin  60  toward camshaft phaser cover  50 . In this way, secondary lock pin  60  is seated within secondary lock pin seat  64  by secondary lock pin spring  66  when rotor  28  is positioned within stator  20  to allow alignment of secondary lock pin  60  with secondary lock pin seat  64 . 
         [0038]    When it is desired to prevent relative rotation between rotor  28  and stator  20  at the predetermined angular position, the pressurized oil is vented from both primary lock pin  52  and secondary lock pin  60 , thereby allowing primary lock pin spring  58  and secondary lock pin spring  66  to urge primary and secondary lock pins  52 ,  60  toward camshaft phaser cover  50  respectively. In order to align primary and secondary lock pins  52 ,  60  with primary and secondary lock pin seats  56 ,  64  respectively, rotor  28  may be rotated with respect to stator  20  by one or more of supplying pressurized oil to advance chambers  36 , supplying pressurized oil to retard chambers  38 , urging from bias spring  44 , and torque from camshaft  14 . Since primary lock pin seat  56  is enlarged, primary lock pin  52  will be seated within primary lock pin seat  56  before secondary lock pin  60  is seated within secondary lock pin seat  64 . With primary lock pin  52  seated within primary lock pin seat  56 , rotor  28  is allowed to rotate with respect to stator  20  by about 10°. Rotor  28  may be further rotated with respect to stator  20  by one or more of supplying pressurized oil to advance chambers  36 , supplying pressurized oil to retard chambers  38 , urging from bias spring  44 , and torque from camshaft  14  in order to align secondary lock pin  60  with secondary lock pin seat  64 , thereby allowing secondary lock pin  60  to be seated within secondary lock pin seat  64 . Supply and venting of oil to and from advance chambers  36 , retard chambers  38 , and primary and secondary lock pins  52 ,  60  will be described in more detail later. 
         [0039]    Now referring to  FIGS. 1 and 2A , camshaft phaser cover  50  is sealingly attached to stator  20  by sprocket bolts  22  that extend through sprocket  16  and stator  20  and threadably engage camshaft phaser cover  50 . In this way, stator  20  is securely clamped between sprocket  16  and camshaft phaser cover  50  in order to axially and radially secure sprocket  16 , stator  20 , and camshaft cover  50  to each other. 
         [0040]    Now referring to  FIGS. 1 ,  2 A,  2 B,  2 C,  6 A, and  6 B; bushing adaptor  68  is coaxially disposed within pocket  70  of camshaft  14  in a close fitting relationship. Bushing adaptor  68  is also coaxially disposed within central through bore  34  of rotor  28  in a press fit relationship to prevent relative rotation therebetween and may be press fit within central through bore  34  until bushing adaptor  68  abuts stop surface  72  formed by the stepped nature of central through bore  34 . When camshaft phaser  12  is attached to camshaft  14 , bushing adaptor  68  coaxially aligns camshaft phaser  12  with camshaft  14 . This allows the rotor  28  to be made more axially compact because axial space is not needed within rotor  28  for receiving camshaft  14  therewithin in order to coaxially align camshaft phaser  12  with camshaft  14 . A network of oil passages is defined in part by bushing adaptor  68  in a way that will be described in detail later. 
         [0041]    Camshaft phaser  12  is attached to camshaft  14  with camshaft phaser attachment bolt  74  which extends axially through bushing adaptor  68  in a close fitting relationship. Rotor  28  is positioned against axial face  76  of camshaft  14  which is provided with threaded hole  78  extending axially into camshaft  14  from pocket  70 . 
         [0042]    Annular oil chamber  80  is formed radially between camshaft phaser attachment bolt  74  and pocket  70  for receiving oil from camshaft oil passages  82  formed radially through camshaft  14 . Oil is supplied to camshaft oil passages  82  from internal combustion engine  10  through an oil gallery (not shown) in camshaft bearing  84 . When camshaft phaser attachment bolt  74  is tightened to a predetermined torque, head  86  of camshaft phaser attachment bolt  74  acts axially on bolt surface  88  of rotor  28 . In this way, camshaft phaser  12  is axially secured to camshaft  14  and relative rotation between rotor  28  and camshaft  14  is thereby prevented. 
         [0043]    Bushing adaptor  68  defines at least in part supply passage  90  for communicating pressurized oil from internal combustion engine  10  to phase relationship control valve  92 . Supply passage  90  may be defined in part by first annular groove  94  formed on the inside diameter of bushing adaptor  68 . First annular groove  94  may be positioned axially within rotor  28 . 
         [0044]    Supply passage  90  may be further defined by axial grooves  96  which extend axially part way into central through bore  34  of rotor  28 . Axial grooves  96  may be in fluid communication with first annular groove  94  through first connecting passages  98  which extend radially through bushing adaptor  68 . 
         [0045]    Supply passage  90  may be further defined by second annular groove  100  formed on the inside diameter of bushing adaptor  68  and which may be positioned axially within pocket  70  of camshaft  14 . Second annular groove  100  may be in fluid communication with axial grooves  96  through second connecting passages  102  which extend radially through bushing adaptor  68 . 
         [0046]    Supply passage  90  may be further defined by third annular groove  104  formed on the outside diameter of bushing adaptor  68  and axially between first annular groove  94  and second annular groove  100 . Third annular groove  104  may be in fluid communication with second annular groove  100  through second connecting passages  102  and may also be in fluid communication with axial grooves  96  by axially positioning third annular groove  104  on the outside diameter of bushing adaptor  68  such that axial grooves  96  at least partly overlap axially with third annular groove  104 . 
         [0047]    Supply passage  90  may be further defined by blind bore  106  formed axially within camshaft phaser attachment bolt  74 . Blind bore  106  begins at the end of camshaft phaser attachment bolt  74  defined by head  86  and may extend to a point within camshaft phaser attachment bolt  74  that is axially aligned with annular oil chamber  80 . First radial drillings  108  extend radially through camshaft phaser attachment bolt  74  and provide fluid communication from annular oil chamber  80  to blind bore  106  while second radial drillings  110  are spaced axially apart from first radial drillings  108  and extend radially through camshaft phaser attachment bolt  74  to provide fluid communication from blind bore  106  to second annular groove  100 . 
         [0048]    Now referring to  FIGS. 1 ,  2 A,  2 B,  2 C, and  5 A- 5 D; supply passage  90  may be further defined by manifold axial grooves  112  of manifold  114  which is press fit into blind bore  106 . Manifold axial grooves  112  are formed in the outer surface of manifold  114  and begin at an end of manifold  114  proximal to first radial drillings  108  and extend to overlap with second radial drillings  110 . Each manifold axial groove  112  is aligned with and overlaps one second radial drilling  110 . Other features and functions of manifold  114  will be described later in more detail. 
         [0049]    Filter  116  may be captured in blind bore  106  between manifold  114  and shoulder  118  formed in blind bore  106 . Filter  116  substantially prevents foreign matter that may be present in the pressurized oil from being communicated to manifold axial grooves  112  and subsequently to other critical interfaces of camshaft phaser  12 . 
         [0050]    Camshaft phaser attachment bolt  74  includes supply drillings  120  extending radially therethrough for providing fluid communication between first annular groove  94  and blind bore  106 . Supply drillings  120  allow pressurized oil to be supplied to phase relationship control valve  92 . 
         [0051]    Now referring to  FIGS. 1 ,  2 A,  2 B,  6 A, and  6 B; in addition to defining at least in part supply passage  90 , bushing adaptor  68 , also defines at least in part advance passage  122  for selectively communicating pressurized oil from phase relationship control valve  92  to advance chambers  36  and for venting oil therefrom. Advance passage  122  may be defined at least in part by fourth annular groove  124  formed on the inside diameter of bushing adaptor  68  and axially between first annular groove  94  and second annular groove  100 . Through advance oil connecting passages  126 , fourth annular groove  124  is in fluid communication with oil passages  42 A that are in fluid communication advance chambers  36 . Advance oil connecting passages  126  extend radially from fourth annular groove  124  through bushing adaptor  68 . 
         [0052]    Camshaft phaser attachment bolt  74  includes advance drillings  128  extending radially therethrough for providing fluid communication between fourth annular groove  124  and blind bore  106 . Advance drillings  128  allow pressurized oil to be selectively supplied from phase relationship control valve  92  to advance chambers  36 . 
         [0053]    In addition to defining at least in part supply passage  90  and advance passage  122 , bushing adaptor  68  also defines at least in part retard passage  130  for selectively communicating pressurized oil from phase relationship control valve  92  to retard chambers  38 . Retard passage  130  may be defined by axial space  132  formed axially between axial end  134  and head  86 . Axial end  134  may be defined by reduced diameter section  136  which provides radial clearance between central through bore  34  of rotor  28  and reduced diameter section  136 . Axial space  132  is further defined radially between rotor  28  and camshaft phaser attachment bolt  74 . Axial space  132  is in fluid communication with oil passages  42 R that are in fluid communication with retard chambers  38 . 
         [0054]    Camshaft phaser attachment bolt  74  includes retard drillings  138  extending radially through camshaft phaser attachment bolt  74  for providing fluid communication between axial space  132  and blind bore  106 . Retard drillings  138  allow pressurized oil to be selectively supplied from phase relationship control valve  92  to retard chambers  38 . 
         [0055]    Phase relationship control valve  92  is disposed within camshaft phaser attachment bolt  74  and retained therein by retaining ring  140  which fits within groove  142  of camshaft phaser attachment bolt  74 . Phase relationship control valve  92  includes phase relationship valve spool  144  with phase relationship body  146  that is generally cylindrical, hollow and dimensioned to provide annular clearance between phase relationship body  146  and blind bore  106  of camshaft phaser attachment bolt  74 . 
         [0056]    Phase relationship valve spool  144  also includes advance land  148  extending radially outward from phase relationship body  146  for selectively blocking fluid communication between supply drillings  120  and advance drillings  128 . Advance land  148  fits within blind bore  106  of camshaft phaser attachment bolt  74  in a close fitting relationship to substantially prevent oil from passing between advance land  148  and blind bore  106 . 
         [0057]    Phase relationship valve spool  144  also includes retard land  150  extending radially outward from phase relationship body  146  for selectively blocking fluid communication between supply drillings  120  and retard drillings  138 . Retard land  150  is positioned axially away from advance land  148  and fits within blind bore  106  of camshaft phaser attachment bolt  74  in a close fitting relationship to substantially prevent oil from passing between retard land  150  and blind bore  106 . 
         [0058]    Now referring to  FIGS. 1 ,  2 A,  2 B, and  2 C; phase relationship valve spool  144  is axially moveable within blind bore  106  with input from phase relationship control valve actuator  152  and phase relationship spool spring  154 . Phase relationship control valve actuator  152  is preferably an electrically actuated solenoid, but may be any type of actuator for axially moving phase relationship valve spool  144 . Phase relationship spool spring  154  is grounded to camshaft phaser attachment bolt  74  by seat  156  which is formed on the end of manifold  114  distal from first radial drillings  108 . A first end of phase relationship spool spring  154  is seated on seat  156  while a second end of phase relationship spool spring  154  is seated within phase relationship spool spring pocket  158  formed in an end of phase relationship valve spool  144 . In this way as shown in  FIG. 2B , phase relationship spool spring  154  biases phase relationship valve spool  144  away from seat  156  when phase relationship control valve actuator  152  is not energized, thereby positioning phase relationship valve spool  144  within blind bore  106  such that pressurized oil is supplied to retard drillings  138  from supply drillings  120  while oil is vented from advance drillings  128  through central passage  160  of phase relationship valve spool  144  and through the end of blind bore  106  that is adjacent to head  86 . In contrast as shown in  FIG. 2C , when phase relationship control valve actuator  152  is energized, the biasing force of phase relationship spool spring  154  is overcome to position phase relationship valve spool  144  within blind bore  106  such that pressurized oil is supplied to advance drillings  128  while oil is vented from retard drillings  138  to the end of blind bore  106  that is adjacent to head  86 . 
         [0059]    Now referring to  FIGS. 1 ,  2 A,  2 B,  3 A,  3 B, and  5 A- 5 D; the function and additional features of manifold  114  will now be described. Manifold  114  is cylindrical and hollow and is included to provide passages for selectively supplying pressurized oil to primary and secondary lock pins  52 ,  60  for removing primary and secondary lock pins  52 ,  60  from primary and secondary lock pin seats  56 ,  64  respectively. Manifold  114  is also included to provide passages for selectively venting oil from primary and secondary lock pins  52 ,  60  for seating primary and secondary lock pins  52 ,  60  from primary and secondary lock pin seats  56 ,  64  respectively. 
         [0060]    Manifold supply connecting passages  162  extend radially through manifold  114  in order to provide fluid communication from manifold axial grooves  112  to manifold central bore  164  which contains lock pin control valve  166  in a close fit sliding relationship. 
         [0061]    Manifold  114  also includes blind axial grooves  168  for selectively supplying pressurized oil to primary and secondary lock pins  52 ,  60  and for selectively venting oil from primary and secondary lock pins  52 ,  60 . Blind axial groves  168  extend axially on the outer circumference of manifold  114  and are not open to either the end of manifold  114  proximal to first radial drillings  108  or the end of manifold  114  distal from first radial drillings  108 . Lock pin connecting passages  170  (shown as hidden lines in  FIGS. 5A-5D ) extend radially through manifold  114  to provide fluid communication between manifold central bore  164  and blind axial grooves  168 . 
         [0062]    Manifold  114  also includes vent grooves  172  for communicating oil from manifold central bore  164  that has been vented from primary and secondary lock pins  52 ,  60 . Vent grooves  172  are located in the outer circumference of manifold  114  and extend axially into manifold  114  from the end of manifold  114  that is distal from first radial drillings  108 . Vent connecting passages  174  extend radially through manifold  114  to provide fluid communication between manifold central bore  164  and vent grooves  172 . Vent connecting passages  174  are spaced axially away from lock pin connecting passages  170  in the direction toward the end of manifold  114  that is distal from first radial drillings  108 . One of the vent grooves  172  extends axially further than the other vent grooves  172  and includes auxiliary vent connecting passage  176  to provide fluid communication between manifold central bore and vent groove  172  as shown best in  FIGS. 5C and 5D . Auxiliary vent connecting passage  176  is spaced axially away from lock pin connecting passages  170  and manifold supply connecting passages  162  in the direction toward the end of manifold  114  that is proximal to first radial drillings  108 . The function of auxiliary vent connecting passage  176  will be discussed in more detail later. 
         [0063]    Now referring to  FIGS. 1 ,  2 A,  2 B,  3 A,  3 B,  6 A, and  6 B; bushing adaptor  68  includes fifth annular groove  178  formed on the inside diameter thereof. Fifth annular groove  178  is axially aligned with lock pin drillings  180  that extend radially through camshaft phaser attachment bolt  74  as best shown in  FIGS. 3A and 3B . Each lock pin drilling  180  is aligned with and is in fluid communication with one blind axial groove  168 . In this way, each blind axial groove  168  is in fluid communication with fifth annular groove  178 . 
         [0064]    Primary lock pin drilling  182  and secondary lock pin drilling  184  extend from fifth annular groove  178  radially through bushing adaptor  68 . Primary lock pin drilling  182  is in fluid communication with primary lock pin passage  186  that extends through camshaft  14  and rotor  28  for supplying pressurized oil to primary lock pin  52  and for venting oil from primary lock pin  52 . Similarly, secondary lock pin drilling  184  is in fluid communication with secondary lock pin passage  188  that extends through camshaft  14  and rotor  28  for supplying pressurized oil to primary lock pin  52  and for venting oil from primary lock pin  52 . 
         [0065]    Lock pin control valve  166  includes lock pin valve spool  190  with lock pin valve spool body  192  that is generally cylindrical and dimensioned to provide annular clearance between lock pin valve spool body  192  and manifold central bore  164 . 
         [0066]    Lock pin control valve  166  also includes vent land  194  extending radially outward from lock pin valve spool body  192  for selectively blocking fluid communication between manifold central bore  164  and vent grooves  172  through vent connecting passages  174  as shown in  FIG. 3A . Vent land  194  fits within manifold central bore  164  in a close fitting relationship to substantially prevent oil from passing between vent land  194  and manifold central bore  164 . 
         [0067]    Lock pin control valve  166  also includes supply land  196  extending radially outward from lock pin valve spool body  192  for selectively blocking fluid communication between manifold central bore  164  and blind axial grooves  168  through manifold supply connecting passages  162 . Supply land  196  fits within manifold central bore  164  in a close fitting relationship to substantially prevent oil from passing between supply land  196  and manifold central bore  164 . 
         [0068]    Lock pin control valve  166  is axially moveable within manifold central bore  164  with input from lock pin control valve actuator  198  and lock pin valve spool spring  200 . Lock pin control valve actuator  198  is preferably an electrically actuated solenoid, but may be any type of actuator for axially moving lock pin control valve  166 . Lock pin valve spool spring  200  is grounded to closed end  202  of manifold  114  which gives manifold  114  a cup-shaped cross-sectional shape. A first end of lock pin valve spool spring  200  is seated against closed end  202  while a second end of lock pin valve spool spring  200  is seated within spring recess  204  formed in the end of lock pin valve spool  190  proximal to closed end  202  as best shown in  FIG. 3B . In this way, lock pin valve spool spring  200  biases lock pin valve spool  190  away from closed end  202  when lock pin control valve actuator  198  is not energized, thereby positioning lock pin valve spool  190  within manifold central bore  164  such that supply land  196  blocks pressurized oil from entering manifold central bore through manifold supply connecting passages  162  while oil is allowed to vent to vent grooves  172  from primary and secondary lock pins  52 ,  60  through vent connecting passages  174  which are in fluid communication with manifold central bore  164 , lock pin connecting passages  170 , blind axial grooves  168 , lock pin drillings  180 , fifth annular groove  178 , and primary and secondary lock pin passages  186 ,  188 . When lock pin control valve actuator  198  is not energized as shown in  FIG. 3B , auxiliary vent connecting passage  176  is in fluid communication with manifold central bore  164 . In this way, the volume defined between closed end  202  and spring recess  204  is vented to prevent a sealed chamber from being formed that would require added force from lock pin control valve actuator  198  to compress a volume of air when actuated. In contrast, when lock pin control valve actuator  198  is energized as shown in  FIG. 3A , the biasing force of lock pin valve spool spring  200  is overcome to position lock pin valve spool  190  within manifold central bore  164  such that pressurized oil is allowed to be communicated to primary and secondary lock pins  52 ,  60  through manifold supply connecting passages  162  (not visible in  FIG. 3A ), manifold central bore  164 , lock pin connecting passages  170 , blind axial grooves  168 , lock pin drillings  180 , fifth annular groove  178 , and primary and secondary lock pin drillings  182 ,  184  while vent land  194  blocks vent connecting passages  174 . When lock pin control valve actuator  198  is energized, auxiliary vent connecting passage  176  is blocked by supply land  196  to prevent fluid communication between manifold central bore  164  and vent groove  172  through auxiliary vent connecting passage  176 . 
         [0069]    In operation and referring to  FIGS. 2A ,  2 B,  3 A,  3 A′,  3 B, and  3 B′; when a change in phase relationship between camshaft  14  and the crankshaft of internal combustion engine  10  is desired, pressurized oil from internal combustion engine  10  is supplied to primary and secondary lock pins  52 ,  60  where the path taken by the pressurized oil is represented by arrows P. This is accomplished by energizing lock pin control valve actuator  198  to prevent fluid communication from blind axial grooves  168  to vent connecting passages  174 , to block auxiliary vent connecting passage  176 , and to allow fluid communication from manifold axial grooves  112  to manifold supply connecting passages  162 . In this way, pressurized oil from internal combustion engine  10  is supplied to annular oil chamber  80  through camshaft oil passages  82 . From annular oil chamber  80 , the pressurized oil is supplied to blind bore  106  through first radial drillings  108 . The pressurized oil is then passed through filter  116  before reaching manifold axial grooves  112 . Oil flow through this area is shown as hidden lines in FIGS.  3 A and  3 A′ because manifold axial grooves  112  are not visible in  FIGS. 3A ,  3 A′,  3 B, and  3 B′. The pressurized oil then passes through manifold supply connecting passages  162  (also not visible in  FIGS. 3A ,  3 A′,  3 B, and  3 B′) to reach manifold central bore  164 . After reaching manifold central bore  164 , the pressurized oil passes through lock pin connecting passages  170  to reach blind axial grooves  168 . The pressurized oil then passes through lock pin drillings  180  which supply the pressurized oil to fifth annular groove  178 . Fifth annular groove  178  subsequently supplies pressurized oil to primary and secondary lock pin drillings  182  and  184  which cause primary and secondary lock pins  52 ,  60  to retract from primary and secondary lock pin seats  56 ,  64  respectively. For clarity, FIG.  3 A′ is provided without reference numbers and without elements that do not define the oil passages to clearly show the path taken by the pressurized oil as represented by arrows P. 
         [0070]    Now referring to  FIGS. 2A ,  2 B,  2 B′,  2 C, and  2 C′; with primary and secondary lock pins  52 ,  60  now retracted from primary and secondary lock pin seats  56 ,  64  respectively, the phase relationship between camshaft  14  and the crankshaft of internal combustion engine  10  can now be altered. This is accomplished by supplying pressurized oil to either the advance chambers  36  or to the retard chambers  38  while oil is vented from the chambers that are not receiving pressurized oil. A portion of the pressurized oil that is supplied to manifold axial grooves  112  passes through second radial drillings  110  to supply the pressurized oil to second annular groove  100 . The pressurized oil is then communicated to third annular groove  104  through second connecting passages  102  which then communicate the pressurized oil to axial grooves  96 . The pressurize is then supplied to first annular groove  94  through first connecting passages  98  before being supplied to phase relationship control valve  92  through supply drillings  120 . 
         [0071]    If the pressurized oil is desired to be supplied to retard chambers  38 , phase relationship control valve actuator  152  is placed in an unenergized state of operation. In this state of operation and as shown in  FIG. 2C , phase relationship valve spool  144  is positioned within blind bore  106  to allow the pressurized oil to be communicated to retard drillings  138  from first connecting passages  98  where the path taken by the pressurized oil is represented by arrows P. Retard drillings  138  then communicate the pressurized oil to axial space  132  where the pressurized oil is then communicated to retard chambers  38  through oil passages  42 R. 
         [0072]    At the same time, the pressurized oil is prevented from being communicated from first connecting passages  98  to advance drillings  128  by advance land  148 . Also at the same time, advance land  148  allows the oil to be vented from advance chambers  36  by placing advance drillings  128  in fluid communication with central passage  160  where the path taken by the vented oil is represented by arrows V. In this way, oil is allowed to be vented from advance chambers  36  through oil passages  42 A. The vented oil then passes from oil passages  42 A to fourth annular groove  124  through advance oil connecting passages  126 . The oil is then communicated to central passage  160  through advance drillings where the oil is then vented through the end of camshaft phaser attachment bolt  74 . Oil communicated through the end of camshaft phaser attachment bolt  74  is shown as hidden lines because the passages therethrough are not visible in this view. For clarity, FIG.  2 B′ is provided without reference numbers and without elements that do not define the oil passages to clearly show the path taken by the pressurized oil represented by arrows P and the path taken by the vented oil represented by arrows V. 
         [0073]    However, if the pressurized oil is desired to be supplied to advance chambers  36 , phase relationship control valve actuator  152  is placed in an energized state of operation. In this state of operation as shown in  FIG. 2C , phase relationship valve spool  144  is positioned within blind bore  106  to allow the pressurized oil to be communicated to advance drillings  128  from first connecting passages  98  where the path taken by the pressurized oil is represented by arrows P. Advance drillings  128  then communicate the pressurized oil to fourth annular groove  124  where the pressurized oil is then communicated to advance chambers  36  through advance oil connecting passages  126  and oil passages  42 A. 
         [0074]    At the same time, the pressurized oil is prevented from being communicated from first connecting passages  98  to retard drillings  138  by retard land  150 . Also at the same time, retard land  150  allows the oil to be vented from retard chambers  38  by placing retard drillings  138  in fluid communication with central passage  160  where the path taken by the vented oil is represented by arrows V. In this way, oil is allowed to be vented from retard chambers  38  through oil passages  42 R. The vented oil then passes from oil passages  42 R to axial space  132  and then through retard drillings  138  and out the end of camshaft phaser attachment bolt  74 . For clarity, FIG.  2 C′ is provided without reference numbers and without elements that do not define the oil passages to clearly show the path taken by the pressurized oil represented by arrows P and the path taken by the vented oil represented by arrows V. 
         [0075]    In operation and referring to  FIGS. 2A and 3B , when it is desired to lock rotor  28  at the predetermined angular position with respect to stator  20 , oil is vented from primary and secondary lock pins  52 ,  60  in order to seat primary and secondary lock pins  52 ,  60  within primary and secondary lock pin seats  56 ,  64  respectively. This is accomplished by placing lock pin control valve actuator in an unenergized state of operation. In the unenergized state of operation, lock pin valve spool  190  is positioned within manifold central bore  164  to prevent fluid communication between manifold supply connecting passages  162  and lock pin connecting passages  170  with supply land  196 . In this way, pressurized oil is prevented from being supplied to primary and secondary lock pins  52 ,  60 . 
         [0076]    At the same time, vent land  194  no longer blocks vent connecting passages  174  and auxiliary vent connecting passage  176 , and as a result, lock pin connecting passage  170  is now in fluid communication with vent connecting passage  174 . In this way, the oil is vented from primary and secondary lock pins  52 ,  60  through primary and secondary lock pin passages  186 ,  188  where the path taken by the vented oil is represented by arrows V. The oil from primary and secondary lock pin passages  186 ,  188  is then passed to fifth annular groove  178  through primary and secondary lock pin drillings  182 ,  184  respectively before being communicated to blind axial grooves  168  through lock pin drillings  180 . The oil is then communicated from blind axial grooves  168  to manifold central bore  164  through lock pin connecting passages  170  before being communicated to vent grooves  172  through vent connecting passages  174 . The oil is then vented through the end of camshaft phaser attachment bolt  74  by passing through central passage  160 . Oil communicated through the end of camshaft phaser attachment bolt  74  is shown as hidden lines because the passages therethrough are not visible in this view. For clarity, FIG.  3 B′ is provided without reference numbers and without elements that do not define the oil passages to clearly show the path taken by the vented oil represented by arrows V. 
         [0077]    With the oil vented from primary and secondary lock pins  52 ,  60 , primary and secondary lock pin springs  58 ,  66  urge primary and secondary lock pins  52 ,  60  respectively toward camshaft phaser cover  50 . However, unless primary and secondary lock pins  52 ,  60  are already aligned with primary and secondary lock pin seats  56 ,  64  respectively, one or both of the primary and secondary lock pins  52 ,  60  will not be seated within primary and secondary lock pin seats  56 ,  64  respectively. In order to seat primary and secondary lock pins  52 ,  60  within primary and secondary lock pin seats  56 ,  64  respectively, the phase relationship between rotor  28  and stator  20  will need to be altered. This may be accomplished by supplying the pressurized oil to either advance chambers  36  or retard chambers  38  as needed to achieve the predetermined angular relationship of rotor  28  within stator  20 . This may also be accomplished by allowing bias spring  44  to urge rotor  28  to the predetermined angular position. Furthermore, this may be accomplished by allowing torque from camshaft  14  to urge rotor  28  to the predetermined angular position. As described earlier, primary lock pin  52  will be seated within primary lock pin seat  56  first thereby holding rotor  28  near the predetermined angular position. Secondary lock pin  60  will then be seated within secondary lock pin seat  64  when secondary lock pin  60  is aligned with secondary lock pin seat  64 . 
         [0078]    Now referring to  FIGS. 7A ,  7 B,  8 A, and  8 B; a second embodiment camshaft phaser  12 ′ in accordance with the present invention is shown. Reference numbers of elements used in the description of camshaft phaser  12  will also be used in the description of element of camshaft phaser  12 ′ that are identical to the elements of camshaft phaser  12 . The differences of camshaft phaser  12 ′ relative to camshaft phaser  12  will now be described. Rather than using a spool-type valve to control oil being supplied to and from primary and secondary lock pins  52 ,  60  as camshaft phaser  12  uses, camshaft phaser  12 ′ uses a poppet-type valve to control oil being supplied to and from primary and secondary lock pins  52 ,  60 . In order to implement a poppet-type valve to control oil being supplied to and from primary and secondary lock pins  52 ,  60 , manifold  114 ′ is provided which is press fit within blind bore  106 . Manifold  114 ′ includes manifold axial grooves  112  which are formed in the outer surface of manifold  114 ′ and begin an end of manifold  114 ′ proximal to first radial drillings  108  and extend to overlap with second radial drillings  110  (not visible in  FIGS. 7A ,  7 B,  8 A, and  8 B) of camshaft phaser attachment bolt  74 . Each manifold axial groove  112  is aligned with and overlaps one second radial drilling  110  to supply pressurized oil to phase relationship control valve  92  in the same way manifold axial grooves  112  of manifold  114  supply pressurized oil to phase relationship control valve  92  the embodiment of camshaft phaser  12 . 
         [0079]    Manifold  114 ′ includes manifold central bore  164 ′ that extends axially through manifold  114 ′. Manifold central bore  164 ′ includes inner annular rib  206  which defines a portion of manifold central bore  164 ′ that is smaller in diameter than the remainder of manifold central bore  164 ′. Inner annular rib  206  is offset axially from each end of manifold central bore  164 ′ and defines supply seat  208  on the side of manifold  114 ′proximal to first radial drillings  108 . Inner annular rib  206  also defines vent seat  210  on the side of manifold  114 ′ distal to first radial drillings  108 . 
         [0080]    Lock pin connecting passages  170 ′ extend radially through inner annular rib  206  to provide fluid communication between manifold central bore  164 ′ and blind axial grooves  168 . Each blind axial groove  168  is aligned with and is in fluid communication with one lock pin drilling  180  in the same way as in camshaft phaser  12 . 
         [0081]    Manifold  114 ′ together with ball  212  and plunger  214  define lock pin control valve  166 ′. Ball  212  is disposed within the side of manifold central bore  164 ′ that is adjacent to supply seat  208 . Ball  212  is selectively seated against supply seat  208  by pressurized oil and is selectively unseated from supply seat  208  by plunger  214 . 
         [0082]    Plunger  214  includes plunger shaft  216  that extends through central passage  160  of phase relationship valve spool  144  and is sized to provide radial clearance therebetween. Plunger shaft  216  also extends coaxially through phase relationship control valve actuator  152 . Plunger  214  extends part way through inner annular rib  206  and is sized provide radial clearance therebetween. 
         [0083]    Plunger  214  also includes outer annular rib  218  which extends radially outward therefrom. Outer annular rib  218  is sized to provide radial clearance between manifold central bore  164 ′ and to seat against vent seat  210 . 
         [0084]    Plunger  214  also includes spring stop  220  which extends radially outward from plunger shaft  216 . A first end of lock pin valve spring  222  is seated against spring stop  220  while a second end of lock pin valve spring is grounded to plunger guide  224  which is disposed in blind bore  106  adjacent to manifold  114 ′. Lock pin valve spring  222  biases plunger  214  to unseat outer annular rib  218  from vent seat  210  when lock pin control valve actuator  198  is unenergized. Plunger guide  224  includes axial through holes  226  to provide fluid communication through plunger guide  224  as will be discussed later in more detail. 
         [0085]    In operation as shown in  FIG. 7A , when a change in phase relationship between camshaft  14  and the crankshaft of internal combustion engine  10  is desired, pressurized oil from internal combustion engine  10  is supplied to primary and secondary lock pins  52 ,  60 . This is accomplished by energizing lock pin control valve actuator  198  to seat outer annular rib  218  against vent seat  210  and to unseat ball  212  from supply seat  208 . In this way, pressurized oil from internal combustion engine  10  is supplied to annular oil chamber  80  through camshaft oil passages  82  where the path taken by the pressurized oil is represented by arrows. From annular oil chamber  80 , the pressurized oil is supplied to blind bore  106  through first radial drillings  108 . The pressurized oil is then passed through filter  116  and supplied to manifold central bore  164 ′. Because outer annular rib  218  is seated against vent seat  210 , the pressurized oil is forced to exit manifold central bore  164 ′ through lock pin connecting passages  170 ′ to blind axial grooves  168 . The pressurized oil then passes through lock pin drillings  180  which supply the pressurized oil to fifth annular groove  178 . Fifth annular groove  178  subsequently supplies the pressurized oil to primary and secondary lock pin drillings  182  and  184  which cause primary and secondary lock pins  52 ,  60  to retract from primary and secondary lock pin seats  56 ,  64  respectively. For clarity, FIG.  7 A′ is provided without reference numbers and without elements that do not define the oil passages to clearly shown the path taken by the pressurized oil as represented by arrows P. 
         [0086]    With primary and secondary lock pins  52 ,  60  now retracted from primary and secondary lock pin seats  56 ,  64  respectively, the phase relationship phase relationship between camshaft  14  and the crankshaft of internal combustion engine  10  can now be altered. This is accomplished in the same way as in camshaft phaser  12  and will not be further described. 
         [0087]    In operation as shown in  FIG. 7B , when it is desired to lock rotor  28  at the predetermined angular position with respect to stator  20 , oil is vented from primary and secondary lock pins  52 ,  60  in order to seat primary and secondary lock pins  52 ,  60  within primary and secondary lock pin seats  56 ,  64  respectively. This is accomplished by placing lock pin control valve actuator  198  in an unenergized state of operation. In the unenergized state of operation, lock pin valve spring  222  urges plunger  214  away from ball  212  such that plunger  214  no longer prevents ball  212  from seating against supply seat  208 . As a result, pressurized oil from internal combustion engine  10  now seats ball  212  against supply seat  208 . In this way, pressurized oil is prevented from being supplied to primary and secondary lock pins  52 ,  60 . 
         [0088]    At the same time, outer annular rib  218  is unseated from vent seat  210  which places lock pin connecting passage  170 ′ in fluid communication with central passage  160  of phase relationship valve spool  144 . In this way, the oil is vented from primary and secondary lock pins  52 ,  60  through primary and secondary lock pin passages  186 ,  188  where the path taken by the vented oil is represented by arrows. The oil from primary and secondary lock pin passages  186 ,  188  is then passed to fifth annular groove  178  through primary and secondary lock pin drillings  182 ,  184  respectively before being communicated to blind axial grooves  168  through lock pin drillings  180 . The oil is then communicated from blind axial grooves  168  to manifold central bore  164 ′ through lock pin connecting passages  170 ′ before being communicated through axial through holes  226  of plunger guide  224 . The oil is then vented through the end of camshaft phaser attachment bolt  74  by passing through central passage  160 . Oil communicated through the end of camshaft phaser attachment bolt  74  is shown as hidden lines because the passages therethrough are not visible in this view. For clarity, FIG.  7 B′ is provided without reference numbers and without elements that do not define the oil passages to clearly show the path taken by the vented oil represented by arrows V. 
         [0089]    While internal combustion engine  10  has been described as having camshaft phaser  12  applied camshaft  14 , it should now be understood internal combustion engine  10  may include multiple camshafts and that each camshaft may include its own camshaft phaser. It should also be understood that one camshaft may use a camshaft phaser in accordance with the present invention, while the second camshaft phaser may be another type of camshaft phaser, for example, an electrically actuated camshaft phaser. It should also be understood that the present invention applies to both internal combustion engines with a single bank of cylinders and to internal combustion engines with multiple banks of cylinders. 
         [0090]    The operation of camshaft phaser  12  has been described as supplying pressurized oil to retard chambers  38  when phase relationship control valve actuator  152  is not energized, while at the same time venting oil from advance chambers  36 . It should now be understood that operation of camshaft phaser  12  could also be arranged to supply pressurized oil to advance chambers  36  when phase relationship control valve actuator  152  is not energized, while at the same time venting oil from retard chambers  38 . Similarly, the operation of camshaft phaser  12  has been described as supplying pressurized oil to advance chambers  36  when phase relationship control valve actuator  152  is energized, while at the same time venting oil from retard chambers  38 . It should now be understood that the operation of camshaft phaser  12  could also be arranged to supply pressurized oil to retard chambers  38  when phase relationship control valve actuator  152  is energized, while at the same time venting oil from advance chambers  36 . 
         [0091]    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.