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 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 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 located coaxially within the rotor to control the flow of oil into and out of the chambers. A lock pin oil passage communicates oil to and from the lock pin based on input from a lock pin control valve located outside of the camshaft phaser. The control valves are operational independent of each other.

Description:
TECHNICAL FIELD OF INVENTION 
     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 phase relationship control valve located coaxially within the camshaft phaser for varying the phase relationship between the crankshaft and the camshaft and a lock pin oil passage for communicating oil to and from a lock pin using a lock pin oil control valve located outside of the camshaft phaser. 
     BACKGROUND OF INVENTION 
     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 venting oil from the intermediate lock pin and supplying pressurized oil to the intermediate lock pin respectively. 
     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 are 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. 
     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 works well for oil control valves that supply oil only to the advance and retard chambers, controlling a lock pin with the same valve provides disadvantages. One example of such a camshaft phaser is shown in United States Patent Application Publication number 2004/0055550. One disadvantage of 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 is the increased camshaft phaser thickness that is needed 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. 
     What is needed is an axially compact camshaft phaser with valving for controlling the phase relationship and for controlling the lock pin which does not require three separate supply passages in the camshaft bearing. What is also needed is such a camshaft phaser which allows for control of the oil used for changing the phase relationship independent of the oil used for controlling the lock pin. 
     SUMMARY OF THE INVENTION 
     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 is 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 the other of the rotor and stator for preventing a change in phase relationship 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 and 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 is located coaxially within the rotor for controlling the flow of oil into and out of the advance and retard chambers. A lock pin oil passage is provided for communicating oil to and from the lock pin. The lock pin oil passage is connectable to a lock pin oil control valve located outside of the camshaft phaser when the camshaft phaser is attached to the internal combustion engine. The lock pin control valve controls the flow of oil to and from the lock pin and is operated independently of the phase relationship control valve. 
     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 
       This invention will be further described with reference to the accompanying drawings in which: 
         FIG. 1  is an exploded isometric view of a camshaft phaser in accordance with the present invention; 
         FIG. 2  is an axial cross-section of the camshaft phaser of  FIG. 1 ; 
         FIG. 3  is a radial cross-section of the camshaft phaser in accordance with the present invention taken in the direction of arrows  3  in  FIG. 2 ; 
         FIG. 4A  is an axial cross-section of the camshaft phaser of  FIG. 1  taken through section line  4 - 4  as shown in  FIG. 3  and showing the phase relationship control valve in a first position for supplying pressurized oil to the retard chambers and for venting oil from the advance chambers; 
       FIG.  4 A′ is an enlarged view of the pertinent elements of  FIG. 4A  without reference numbers to clearly shown the oil flow through the camshaft phaser; 
         FIG. 4B  is the axial cross section of  FIG. 4A  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; 
       FIG.  4 B′ is an enlarged view of the pertinent elements of  FIG. 4B  without reference numbers to clearly shown the oil flow through the camshaft phaser; 
         FIG. 5A  is an enlarged isometric view of a bushing adaptor of the camshaft phaser of  FIG. 1 ; 
         FIG. 5B  is an isometric cross-section of the bushing adaptor of  FIG. 5A ; 
         FIG. 6  is an enlarged view of circle  6  from  FIG. 2 ; 
         FIG. 7A  is an axial cross-section of the camshaft phaser of  FIG. 1  taken through section line  7 - 7  as shown in  FIG. 3  and showing the lock pin control valve in an oil supplying position for supplying pressurized oil to the primary and secondary lock pins; and 
         FIG. 7   b  the an axial cross-section of the  FIG. 7A  showing the lock pin control valve in an oil venting position for venting oil from the primary and secondary lock pins. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     In accordance with a preferred embodiment of this invention and referring to  FIGS. 1 ,  2 , and  3 , 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. 
     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. 
     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. 
     Rotor  28  includes central hub  30  with a plurality of vanes  32  extending radially outward therefrom and central through bore  34  extending 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 . 
     Central hub  30  includes a plurality of oil passages  42 A,  42 R formed radially therethrough (best visible as hidden lines in  FIG. 3 ). 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. 
     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. 
     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 , 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 , 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 . 
     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 , 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 , 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 . 
     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  respectively toward camshaft phaser cover  50 . 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. 
     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. 
     Now referring to  FIGS. 1 ,  2 ,  5   a , and  5 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  of central through bore  34  which is defined 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. 
     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 . 
     Annular oil chamber  80  is formed radially between camshaft phaser attachment bolt  74  and pocket  70  for receiving oil from camshaft phasing 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. 
     Now referring to  FIGS. 1 ,  3 ,  4 A,  5 A, and  5 B, 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 . 
     Supply passage  90  may be further defined by axial grooves  96  which extend axially part way into central hub  30  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 . 
     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 . 
     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 . 
     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 . 
     Check valve assembly  112  may be disposed axially between first radial drillings  108  and second radial drillings  110  in order to allow pressurized oil to be supplied from internal combustion engine  10  to phase relationship control valve  92  while preventing oil from back-flowing from phase relationship control valve  92  to internal combustion engine  10 . Check valve assembly  112  includes filter  114  in order to prevent any foreign matter that may present in the pressurized oil from reaching phase relationship control valve  92 . Check valve assembly  112  is describe in more detail in U.S. patent application Ser. No. 12/912,338 which is commonly assigned to Applicant and which is incorporated herein by reference in its entirety. 
     Camshaft phaser attachment bolt  74  includes supply drillings  116  extending radially therethrough for providing fluid communication between first annular groove  94  and blind bore  106 . Supply drillings  116  allow pressurized oil to be supplied to phase relationship control valve  92 . 
     In addition to defining at least in part supply passage  90 , bushing adaptor  68  also defines at least in part advance passage  118  for selectively communicating pressurized oil from phase relationship control valve  92  to advance chambers  36  and for venting oil therefrom. Advance passage  118  may be defined at least in part by fourth annular groove  120  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  122 , fourth annular groove  120  is in fluid communication with oil passages  42 A that are in fluid communication advance chambers  36 . Advance oil connecting passages  122  extend axially from fourth annular groove  120  through bushing adaptor  68 . 
     Camshaft phaser attachment bolt  74  includes advance drillings  124  extending radially therethrough for providing fluid communication between fourth annular groove  120  and blind bore  106 . Advance drillings  124  allow pressurized oil to be selectively supplied from phase relationship control valve  92  to advance chambers  36 . 
     In addition to defining at least in part supply passage  90  and advance passage  118 , bushing adaptor  68  also defines at least in part retard passage  126  for selectively communicating pressurized oil from phase relationship control valve  92  to retard chambers  38 . Retard passage  126  may be defined by axial space  128  formed axially between axial end  130  of bushing adapter  68  and head  86 . Axial end  130  may be defined by reduced diameter section  132  of bushing adapter  68  which provides radial clearance between central through bore  34  of rotor  28  and reduced diameter section  132 . Axial space  128  is further defined radially between rotor  28  and camshaft phaser attachment bolt  74 . Axial space  128  is in fluid communication with oil passages  42 R that are in fluid communication with retard chambers  38 . 
     Camshaft phaser attachment bolt  74  includes retard drillings  134  extending radially through camshaft phaser attachment bolt  74  for providing fluid communication between axial space  128  and blind bore  106 . Retard drillings  134  allow pressurized oil to be selectively supplied from phase relationship control valve  92  to retard chambers  38 . 
     Phase relationship control valve  92  is disposed within camshaft phaser attachment bolt  74  and retained therein by retaining ring  136  which fits within groove  138  of camshaft phaser attachment bolt  74 . Phase relationship control valve  92  includes valve spool  140  with body  142  that is generally cylindrical, hollow and dimensioned to provide annular clearance between body  142  and blind bore  106  of camshaft attachment bolt  74 . 
     Valve spool  140  also includes advance land  144  extending radially outward from body  142  for selectively blocking fluid communication between supply drillings  116  and advance drillings  124 . Advance land  144  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  144  and blind bore  106 . 
     Valve spool  140  also includes retard land  146  extending radially outward from body  142  for selectively blocking fluid communication between supply drillings  116  and retard drillings  134 . Retard land  146  is positioned axially away from advance land  144  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  146  and blind bore  106 . 
     Now referring to  FIGS. 1 ,  4 A, and  6 , valve spool  140  is axially moveable within blind bore  106  with input from phase relationship control valve actuator  148  and spool spring  150 . Spool spring  150  is grounded to camshaft phaser attachment bolt  74  by seat  152  which is sealingly fixed within blind bore  106  between second radial drillings  110  and advance drillings  124 . Seat  152  sealingly separates blind bore  106  into spool section  154  and check valve section  156 . A first end of spool spring  150  is seated within annular recess  158  of seat  152  while a second end of spool spring  150  is seated within spring pocket  160  formed in an end of valve spool  140 . In this way, spool spring  150  biases valve spool  140  away from seat  152  when phase relationship control valve actuator  148  is not energized, thereby positioning valve spool  140  within spool section  154  such that pressurized oil is supplied to retard drillings  134  from supply drillings  116  while oil is vented from advance drillings  124  through central passage  162  of valve spool  140  and through the end of blind bore  106  that is adjacent to head  86 . In contrast, when phase relationship control valve actuator  148  is energized, the biasing force of spool spring  150  is overcome to position valve spool  140  within spool section  154  such that pressurized oil is supplied to advance drillings  124  while oil is vented from retard drillings  134  to the end of blind bore  106  that is adjacent to head  86 . 
     Now referring to  FIGS. 4A ,  7 A, and  7 B; lock pin control valve  164  is shown schematically and which is a conventional 3-way valve which is known in the art. Lock pin control valve  164  is located outside and remote from camshaft phaser  12  and is preferably located within internal combustion engine  10 . Lock pin control valve  164  received pressurized oil from pump  166  which preferably also supplies pressurized oil to phase relationship control valve  92 . Lock pin control valve actuator  168  moves lock pin control valve  164  between an oil supplying position and an oil venting position. 
     In the oil supplying position, as shown in  FIG. 7A , pressurized oil from pump  166  is passed through lock pin control valve  164  and is supplied to annular lock pin oil groove  170  formed circumferentially around camshaft  14  and which is in fluid communication with camshaft primary lock pin oil passage  172  and camshaft secondary lock pin oil passage  174  formed axially through camshaft  14 . Camshaft primary lock pin oil passage  172  is aligned with rotor primary lock pin oil passage  176  which is formed through rotor  28  and which is in fluid communication with primary lock pin  52 . Similarly, camshaft secondary lock pin oil passage  174  is aligned with rotor secondary lock pin oil passage  178  which is formed through rotor  28  and which is in fluid communication with secondary lock pin  60 . 
     In the oil venting position, as shown in  FIG. 7B , pressurized oil from pump  166  is prevented from passing through lock pin control valve  164  to annular lock pin oil groove  170 . At the same time, fluid communication is provided between annular lock pin oil grooved  170  and oil reservoir  180  in order to vent oil from primary and secondary lock pins  52 ,  60 . 
     In operation and referring to  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  where the path taken by the pressurized oil is represented by arrows P. This is accomplished by placing lock pin control valve  164  in the oil supplying position using lock pin control valve actuator  168 . In this way, pressurized oil is supplied from pump  166  to camshaft primary and secondary lock pin oil passages  172 ,  174  through annular lock pin oil groove  170 . From camshaft primary and secondary lock pin oil passages  172 ,  174 , the pressurized oil is supplied to primary and secondary lock pins  52 ,  60  respectively through rotor primary and secondary lock pin oil passages  176 ,  178  respectively. The pressurized oil supplied to primary and secondary lock pins  52 ,  60  causes primary and secondary lock pins  52 ,  60  to retract from primary and secondary lock pin seats  56 ,  64  respectively. 
     With primary and secondary lock pins  52 ,  60  now retracted from primary and secondary lock pin seats  56 ,  64  respectively and referring to  FIGS. 4A and 4B , 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. Pressurized oil is supplied from pump  166  of internal combustion engine  10  to annular oil chamber  80  through camshaft phasing oil passages  82 . The pressurized oil is then passed through first radial drillings  108  to check valve section  156  of blind bore  106  before passing through check valve assembly  112  and filter  114 . The pressurized oil is then passed to second annular groove  100  through second radial drillings  110 . From second annular groove  100 , the pressurized oil is supplied to third annular groove  104  through second connecting passages  102 . The pressurized oil is then supplied to first annular groove  94  through axial grooves  96  and first connecting passages  98 . After reaching first annular groove  94 , the pressurized oil is supplied to phase relationship control valve  92  through supply drillings  116 . 
     If the pressurized oil is desired to be supplied to retard chambers  38 , phase relationship control valve actuator  148  is placed in an unenergized state of operation as shown in  FIG. 4A . In this state of operation, valve spool  140  is positioned within blind bore  106  to allow the pressurized oil to be communicated to retard drillings  134  from first connecting passages  98  where the path taken by the pressurized oil is represented by arrows P. Retard drillings  134  then communicate the pressurized oil to axial space  128  where the pressurized oil is then communicated to retard chambers  38  through oil passages  42 R. 
     At the same time, the pressurized oil is prevented from being communicated from first connecting passages  98  to advance drillings  124  by advance land  144 . Also at the same time, advance land  144  allows the oil to be vented from advance chambers  36  by placing advance drillings  124  in fluid communication with central passage  162  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  120  through advance oil connecting passages  122 . The oil is then communicated to central passage  162  through advance drillings  124  where the oil is then vented through the end of camshaft phaser attachment bolt  74 . For clarity, FIG.  4 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 represented by arrows P and the path taken by the vented oil represented by arrows V. 
     However, if the pressurized oil is desired to be supplied to advance chambers  36 , phase relationship control valve actuator  148  is placed in an energized state of operation as shown in  FIG. 4B . In this state of operation, valve spool  140  is positioned within blind bore  106  to allow the pressurized oil to be communicated to advance drillings  124  from first connecting passages  98  where the path taken by the pressurized oil is represented by arrows P. Advance drillings  124  then communicate the pressurized oil to fourth annular groove  120  where the pressurized oil is then communicated to advance chambers  36  through advance oil connecting passages  122  and oil passages  42 R. 
     At the same time, the pressurized oil is prevented from being communicated from first connecting passages  98  to retard drillings  134  by retard land  146 . Also at the same time, retard land  146  allows the oil to be vented from retard chambers  38  by placing retard drillings  134  in fluid communication with central passage  162  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  128  and then to central passage  162  through retard drillings  134 . The oil is then vented through the end of camshaft phaser attachment bolt  74 . For clarity, FIG.  4 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. 
     In operation and referring to  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  168  in the oil venting position. In the oil venting position, pressurized oil from pump  166  is prevented from passing through lock pin control valve  164  to annular lock pin oil groove  170 . At the same time, fluid communication is provided between annular lock pin oil groove  170  and oil reservoir  180 . In this way, oil is vented from primary and secondary lock pins  52 ,  60  where the path taken by the vented oil is represented by arrows V. The oil vented from primary and secondary lock pins  52 ,  60  first passes to camshaft primary and secondary lock pin oil passages  172 ,  174  through rotor primary and secondary lock pin oil passages  176 ,  178  respectively. The oil is then passed to oil reservoir  180  through annular lock pin oil groove  170 . 
     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  may 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 . 
     While internal combustion engine  10  has been described as having camshaft phaser  12  applied to camshaft  14 , it should now be understood that 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. 
     The operation of camshaft phaser  12  has been described as supplying pressurized oil to retard chambers  38  when phase relationship control valve actuator  148  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  148  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  148  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  148  is energized, while at the same time venting oil from advance chambers  36 . 
     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.