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 and includes vanes interspersed with the stator lobes to define alternating advance and retard chambers. A primary lock pin is provided for selective engagement with a primary lock pin seat for limiting rotation between the rotor and stator to a range between full advance and full retard. A secondary lock pin is provided for selective engagement with a secondary lock pin seat for preventing rotation between the rotor and the stator at a predetermined position within the range. A cap is disposed axially adjacent the rotor to define a bridging lock pin oil passage therebetween. The bridging lock pin oil passage provides fluid communication between the primary lock pin and the secondary lock pin.

Description:
TECHNICAL FIELD OF INVENTION 
       [0001]    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 still more particularly to a vane-type camshaft phaser which includes a primary lock pin, a secondary lock pin, and an oil passage within the camshaft phaser providing fluid communication of the primary lock pin with the secondary lock pin. 
       BACKGROUND OF INVENTION 
       [0002]    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 two intermediate lock pins which selectively prevent relative rotation between the rotor and the stator at an angular position that is intermediate of a full advance and a full retard position. One example of such a camshaft phaser is described in United States Patent Application Publication number US 2009/0266322-A1. In this example, a primary lock pin is selectively seated in a primary lock pin seat which is elongated to allow relative rotation between the rotor and the stator in a range that is between full advance and full retard. The secondary lock pin is selectively seated in a secondary lock pin seat in order to substantially prevent relative rotation between the rotor and the stator at a predetermined position that is within the range. The primary lock pin assists in engagement of the secondary lock pin with the secondary lock pin seat by limiting rotation of the rotor to a small range when the primary lock pin is seated in the primary lock pin seat. With the primary lock pin constraining rotation of the rotor to a small range, it is easier to precisely align the secondary lock pin with the secondary lock pin seat which fit together very closely in order to substantially prevent relative rotation between the rotor and the stator. 
         [0003]    Now referring to  FIG. 1 , it is known to use pressurized oil from the internal combustion engine to disengage the primary and secondary lock pins from the primary and secondary lock pin seats respectively. Pressurized oil is supplied to annular groove  10  of camshaft  12 . Primary lock pin camshaft oil passage  14  extends axially into camshaft  12  and is in fluid communication with annular groove  10  through primary lock pin camshaft connecting passage  16  which extends radially into camshaft  12 . Primary lock pin camshaft oil passage  14  is aligned with primary lock pin rotor oil passage  18  which extends axially into rotor  20 . Primary lock pin rotor oil passage  18  is in fluid communication with primary lock pin  22  through primary lock pin rotor connecting passage  24  which extends radially into rotor  20 . Similarly, secondary lock pin camshaft oil passage  26  extends axially into camshaft  12  and is in fluid communication with annular groove  10  through secondary lock pin camshaft connecting passage  28  which extends radially into camshaft  12 . Secondary lock pin camshaft oil passage  26  is aligned with secondary lock pin rotor oil passage  30  which extends axially into rotor  20 . Secondary lock pin rotor oil passage  30  is in fluid communication with secondary lock pin  32  through secondary lock pin rotor connecting passage  34  which extends radially into rotor  20 . 
         [0004]    While this arrangement of one axial lock pin oil passage in the camshaft for each lock pin may be satisfactory for some applications, it may be unsatisfactory for other applications. For example, an internal combustion engine manufacturer that had previously employed a camshaft phaser with a single lock pin, and consequently only one axial lock pin oil passage in the camshaft for communication with the lock pin, may wish to switch to a camshaft phaser with a dual lock pin arrangement. A redesign of the camshaft would be required to include a second axial lock pin oil passage in the camshaft in order to accommodate the second lock pin of the camshaft phaser. This redesign may be costly and time intensive. 
         [0005]    This arrangement of one axial lock pin oil passage in the camshaft for each lock pin may also be unsatisfactory for some applications due to a limited availability of space in the camshaft. More specifically, the camshaft may include a plurality oil passages for supplying oil to and from the advance and retard chambers of the camshaft phaser. This plurality of oil passages for supplying oil to and from the advance and retard chambers may leave insufficient space for multiple axial lock pin oil passages in the camshaft. 
         [0006]    What is needed is a camshaft phaser having primary and secondary lock pins and a single hydraulic interface with the internal combustion engine for communication of oil to and from both the primary and secondary lock pins. What is also needed is such a camshaft phaser which includes a rotor and a cap disposed axially adjacent to the rotor to define a lock pin passage therebetween which provides fluid communication between the primary and secondary lock pins. 
       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 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 primary lock pin is disposed within one of the rotor and the stator for selective engagement with a primary lock pin seat for limiting a change in phase relationship between the rotor and the stator to a range between full advance and full retard when the primary lock pin is engaged with the primary lock pin seat. Pressurized oil is selectively supplied to the primary lock pin in order to disengage the primary lock pin with the primary lock pin seat, and oil is selectively vented from the primary lock pin in order to engage the primary lock pin with the primary lock pin seat. A secondary lock pin is disposed within one of the rotor and the stator for selective engagement with a secondary lock pin seat for preventing a change in phase relationship between the rotor and the stator at a predetermined position within the range when the secondary lock pin is engaged with the secondary lock pin seat. Pressurized oil is selectively supplied to the secondary lock pin in order to disengage the secondary lock pin with the secondary lock pin seat, and oil is selectively vented from the secondary lock pin in order to engage the secondary lock pin with the secondary lock pin seat. A cap is disposed axially adjacent the rotor to define a bridging lock pin oil passage therebetween. The bridging lock pin oil passage provides fluid communication between the primary lock pin and the secondary lock pin. 
         [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 isometric axial cross-section of a prior art camshaft phaser with separate oil passages for each lock pin; 
           [0011]      FIG. 2  is an exploded isometric view of a camshaft phaser in accordance with the present invention; 
           [0012]      FIG. 3  is an isometric axial cross-section of the camshaft phaser of  FIG. 2 ; 
           [0013]      FIG. 4  is an radial cross-section of the camshaft phaser of  FIG. 2 ; 
           [0014]      FIG. 5  is an isometric axial cross-section of the camshaft phaser of  FIG. 2  without the camshaft phaser attachment bolt; 
           [0015]      FIG. 6  is an exploded isometric view of a portion of a camshaft phaser in accordance with a second embodiment of the present invention; and 
           [0016]      FIG. 7  is an axial cross-section of the camshaft phaser of the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0017]    In accordance with a preferred embodiment of this invention and referring to  FIGS. 2-5 , internal combustion engine  50  is shown which includes camshaft phaser  52 . Internal combustion engine  50  also includes camshaft  54  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  54  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  52  allows the timing between the crankshaft and camshaft  54  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. 
         [0018]    Camshaft phaser  52  includes sprocket  56  which is driven by a chain or gear (not shown) driven by the crankshaft of internal combustion engine  50 . Alternatively, sprocket  56  may be a pulley driven by a belt. Sprocket  56  includes a central bore  58  for receiving camshaft  54  coaxially therethrough which is allowed to rotate relative to sprocket  56 . Sprocket  56  is sealingly secured to stator  60  with sprocket bolts  62  in a way that will be described in more detail later. 
         [0019]    Stator  60  is generally cylindrical and includes a plurality of radial chambers  64  defined by a plurality of lobes  66  extending radially inward. In the embodiment shown, there are four lobes  66  defining four radial chambers  64 , however, it is to be understood that a different number of lobes  66  may be provided to define radial chambers  64  equal in quantity to the number of lobes  66 . 
         [0020]    Rotor  68  includes central hub  70  with a plurality of vanes  72  extending radially outward therefrom and central through bore  74  extending axially therethrough. The number of vanes  72  is equal to the number of radial chambers  64  provided in stator  60 . Rotor  68  is coaxially disposed within stator  60  such that each vane  72  divides each radial chamber  64  into advance chambers  76  and retard chambers  78 . The radial tips of lobes  66  are mateable with central hub  70  in order to separate radial chambers  64  from each other. Preferably, each of the radial tips of vanes  72  includes one of a plurality of wiper seals  80  to substantially seal adjacent advance and retard chambers  76 ,  78  from each other. Although not shown, each of the radial tips of lobes  66  may include a wiper seal similar in configuration to wiper seal  80 . 
         [0021]    Central hub  70  includes a plurality of oil passages  82 A,  82 R formed radially therethrough (best visible as hidden lines in  FIG. 4 ). Each one of the plurality of oil passages  82 A is in fluid communication with one of the advance chambers  76  for supplying oil thereto and therefrom while each one of the plurality of oil passages  82 R is in fluid communication with one of the retard chambers  78  for supplying oil thereto and therefrom. 
         [0022]    Bias spring  84  is disposed within annular pocket  86  formed in rotor  68  and within central bore  88  of camshaft phaser cover  90 . Bias spring  84  is grounded at one end thereof to camshaft phaser cover  90  and is attached at the other end thereof to rotor  68 . When internal combustion engine  50  is shut down, bias spring  84  urges rotor  68  to a predetermined angular position within stator  60  in a way that will be described in more detail in the subsequent paragraph. 
         [0023]    Camshaft phaser  52  includes a staged dual lock pin system for selectively preventing relative rotation between rotor  68  and stator  60  at the predetermined angular position which is between the extreme advance and extreme retard positions. Primary lock pin  92  is slidably disposed within primary lock pin bore  94  formed in one of the plurality of vanes  72  of rotor  68 . Primary lock pin seat  96  is formed in camshaft phaser cover  90  for selectively receiving primary lock pin  92  therewithin. Primary lock pin seat  96  is larger than primary lock pin  92  to allow rotor  68  to rotate relative to stator  60  in a range of about 5° on each side of the predetermined angular position when primary lock pin  92  is seated within primary lock pin seat  96 . The enlarged nature of primary lock pin seat  96  allows primary lock pin  92  to be easily received therewithin. When primary lock pin  92  is not desired to be seated within primary lock pin seat  96 , pressurized oil is supplied to primary lock pin  92 , thereby urging primary lock pin  92  out of primary lock pin seat  96  and compressing primary lock pin spring  98 . Conversely, when primary lock pin  92  is desired to be seated within primary lock pin seat  96 , the pressurized oil is vented from primary lock pin  92 , thereby allowing primary lock pin spring  98  to urge primary lock pin  92  toward camshaft phaser cover  90 . In this way, primary lock pin  92  is seated within primary lock pin seat  96  by primary lock pin spring  98  when rotor  68  is positioned within stator  60  to allow alignment of primary lock pin  92  with primary lock pin seat  96 . 
         [0024]    Secondary lock pin  100  is slidably disposed within secondary lock pin bore  102  formed in one of the plurality of vanes  72  of rotor  68 . Secondary lock pin seat  104  is formed in camshaft phaser cover  90  for selectively receiving secondary lock pin  100  therewithin. Secondary lock pin  100  fits within secondary lock pin seat  104  in a close sliding relationship, thereby substantially preventing relative rotation between rotor  68  and stator  60  at the predetermined angular position within the range when secondary lock pin  100  is received within secondary lock pin seat  104 . When secondary lock pin  100  is not desired to be seated within secondary lock pin seat  104 , pressurized oil is supplied to secondary lock pin  100 , thereby urging secondary lock pin  100  out of secondary lock pin seat  104  and compressing secondary lock pin spring  106 . Conversely, when secondary lock pin  100  is desired to be seated within secondary lock pin seat  104 , the pressurized oil is vented from the secondary lock pin  100 , thereby allowing secondary lock pin spring  106  to urge secondary lock pin  100  toward camshaft phaser cover  90 . In this way, secondary lock pin  100  is seated within secondary lock pin seat  104  by secondary lock pin spring  106  when rotor  68  is positioned within stator  60  to allow alignment of secondary lock pin  100  with secondary lock pin seat  104 . 
         [0025]    When it is desired to prevent relative rotation between rotor  68  and stator  60  at the predetermined angular position, the pressurized oil is vented from both primary lock pin  92  and secondary lock pin  100 , thereby allowing primary lock pin spring  98  and secondary lock pin spring  106  to urge primary and secondary lock pins  92 ,  100  respectively toward camshaft phaser cover  90 . In order to align primary and secondary lock pins  92 ,  100  with primary and secondary lock pin seats  96 ,  104  respectively, rotor  68  may be rotated with respect to stator  60  by one or more of supplying pressurized oil to advance chambers  76 , supplying pressurized oil to retard chambers  78 , urging from bias spring  84 , and torque from camshaft  54 . Since primary lock pin seat  96  is enlarged, primary lock pin  92  will be seated within primary lock pin seat  96  before secondary lock pin  100  is seated within secondary lock pin seat  104 . With primary lock pin  92  seated within primary lock pin seat  96 , rotor  68  is allowed to rotate with respect to stator  60  by about 10°. Rotor  68  may be further rotated with respect to stator  60  by one or more of supplying pressurized oil to advance chambers  76 , supplying pressurized oil to retard chambers  78 , urging from bias spring  84 , and torque from camshaft  54  in order to align secondary lock pin  100  with secondary lock pin seat  104 , thereby allowing secondary lock pin  100  to be seated within secondary lock pin seat  104 . Supply and venting of oil to and from advance chambers  76  and retard chambers  78  through oil passages  82 A,  82 R respectively is provided by an oil control valve (not shown) as is well known in the art of camshaft phasers. Supply and venting of oil to and from and primary and secondary lock pins  92 ,  100  will be described in more detail later. 
         [0026]    Camshaft phaser cover  90  is sealingly attached to stator  60  by sprocket bolts  62  that extend through sprocket  56  and stator  60  and threadably engage camshaft phaser cover  90 . In this way, stator  60  is secured between sprocket  56  and camshaft phaser cover  90  in order to axially and radially secure sprocket  56 , stator  60 , and camshaft phaser cover  90  to each other. Also in this way, advance and retard chambers  76 ,  78  are sealed axially between sprocket  56  and camshaft phaser cover  90 . 
         [0027]    Camshaft phaser  52  is angularly indexed to camshaft  54  using indexing slot  108  formed in the axial end of camshaft  54  and indexing pin  110  extending from rotor  68 . In this way, angular alignment between rotor  68  and camshaft  54  is achieved. In order to secure camshaft phaser  52  to camshaft  54  after being angularly indexed to each other, camshaft phaser attachment bolt  112  is inserted coaxially through central through bore  74  of rotor  68  and is threadably engaged with camshaft  54 . When camshaft phaser attachment bolt  112  is tightened to a predetermined torque, head  114  of camshaft phaser attachment bolt  112  applies an axial force to central hub  70  of rotor  68 . In this way, rotor  68  is securely clamped to camshaft  54  and rotation between camshaft  54  and rotor  68  is prevented. 
         [0028]    In order to supply and vent oil to and from and primary and secondary lock pins  92 ,  100  to position primary and secondary lock pins  92 ,  100  as desired and as described previously, annular oil groove  116  is provided in camshaft  54 . Annular oil groove  116  is in fluid communication with an oil gallery (not shown) of camshaft bearing  118 . Pressurized oil is supplied and vented from annular oil groove  116  by a lock pin oil control valve as is well known in the art of camshaft phasers. Annular oil groove  116  is in fluid communication with lock pin camshaft oil connecting passage  120  which extends radially into camshaft  54  from annular oil groove  116 . Lock pin camshaft oil connecting passage  120  intersects with lock pin camshaft oil passage  122  which extends axially through camshaft  54  from lock pin camshaft oil connecting passage  120  to the axial end of camshaft  54  which mates with rotor  68 . 
         [0029]    Lock pin camshaft oil passage  122  is aligned with lock pin rotor oil passage  124  which extends axially through rotor  68 . In order to provide fluid communication between lock pin rotor oil passage  124  and secondary lock pin bore  102 /secondary lock pin  100 , secondary lock pin connecting passage  126  extends radially from lock pin rotor oil passage  124  to secondary lock pin bore  102 . 
         [0030]    Lock pin rotor oil passage  124  is also in fluid communication with primary lock pin bore  94 /primary lock pin  92 . Fluid communication from lock pin rotor oil passage  124  and primary lock pin bore  94 /primary lock pin  92  is provided in part by bridging lock pin oil passage  128  which is formed as a groove in axial face  130  of rotor  68 . Bridging lock pin oil passage  128  is arcuate to fit radially in the space between central through bore  74  and annular pocket  86 . A cap is provided axially adjacent to rotor  68  to seal the axial end of bridging lock pin oil passage  128 . In  FIGS. 2 and 3 , the cap takes the form of flange  132  extending radially outward from head  114  of camshaft phaser attachment bolt  112 . In this way, bridging lock pin oil passage  128  is defined between rotor  68  and flange  132  when camshaft phaser attachment bolt  112  is tightened to the predetermined torque. While the cap is shown in  FIGS. 2-3  as an integral part of head  114 , it should be understood that the cap could also be a washer of separate construction from head  114 . Primary lock pin oil passage  134  extends axially through rotor  68  from bridging lock pin oil passage  128 . While primary lock pin oil passage  134  is shown in  FIGS. 3 and 5  as extending to the axial face of camshaft  54  where it is terminated and sealed by camshaft  54 , it should be understood that primary lock pin oil passage  134  may be truncated within rotor  68  and extend only part way into rotor  68  from bridging lock pin oil passage  128 . Finally, primary lock pin connecting passage  136  extends radially from primary lock pin rotor oil passage  134  to primary lock pin bore  94 . In this way, fluid communication between primary lock pin  92  and secondary lock pin  100  is provided within camshaft phaser  52 , thereby requiring only one hydraulic connection between camshaft  54  and camshaft phaser  52  for controlling primary and secondary lock pins  92 ,  100 . 
         [0031]    Now referring to  FIGS. 6 and 7 , camshaft phaser  52 ′ is shown as a second embodiment. Camshaft phaser  52 ′ is the same as camshaft phaser  52  described earlier with the exception of the cap used to seal the axial end of bridging lock pin oil passage  128 . In the second embodiment, the cap is shown as bushing  138  which is formed as a separate piece from camshaft phaser attachment bolt  112 ′. Camshaft phaser attachment bolt  112 ′ extends coaxially through bushing  138  and relative rotation between bushing  138  and camshaft phaser attachment bolt  112 ′ is allowed while camshaft phaser attachment bolt  112 ′ is being tightened to the predetermined torque. Relative rotation between bushing  138  and camshaft phaser attachment bolt  112 ′ is needed in this embodiment because bushing  138  is used to prevent rotation of rotor  68 /camshaft  54  while camshaft phaser attachment bolt  112 ′ is being tightened to the predetermined torque. 
         [0032]    Bushing  138  includes clocking features for radially orienting bushing  138  with rotor  68  and for preventing rotation of bushing  138  relative to rotor  68 . In  FIGS. 6 and 7 , the clocking features are shown as pins  140  which extend axially therefrom only part way into lock pin rotor oil passage  124  and primary lock pin oil passage  134  as to not prevent fluid communication of lock pin rotor oil passage  124  and primary lock pin oil passage  134  with bridging lock pin oil passage  128 . Pins  140  are sized to be close fitting with lock pin rotor oil passage  124  and primary lock pin oil passage  134  in order to prevent relative rotation between bushing  138  and rotor  68 . The width of bridging lock pin oil passage  128  may be smaller than the diameter of pins  140  to better prevent rotation between bushing  138  and rotor  68 . 
         [0033]    Bushing  138  also includes anti-rotation features used to prevent rotation of rotor  68 /camshaft  54  while camshaft phaser attachment bolt  112 ′ is being tightened to the predetermined torque. In  FIGS. 6 and 7 , these anti-rotation features are shown as tangs  142  which extend axially away from bushing  138 . In use, tangs  142  may be used to engage a holding tool which is used to hold bushing  138 /rotor  68 /camshaft  54  substantially stationary while camshaft phaser attachment bolt  112 ′ is tightened to the predetermined torque using a tightening tool (not shown). While the anti-rotation features used to prevent rotation of rotor  68 /camshaft  54  while camshaft phaser attachment bolt  112 ′ is being tightened to the predetermined torque are shown as tangs  142 , it should now be understood that other features may also be used, for example, but not limited to slots or holes extending into bushing  138 , or flats on the outer circumference of bushing  138 . 
         [0034]    While not shown, a third embodiment may include a cap of separate construction from the camshaft phaser attachment bolt. In this embodiment, the cap may include a cylindrical extension which is sealingly press fit within the central through bore of the rotor. The groove in the axial face of the rotor may now extend to the central through bore of the rotor. 
         [0035]    While bridging lock pin oil passage  128  has been shown as a groove formed in axial face  130  of rotor  68 , it should now be understood that the groove could instead be formed in the surface of the cap that faces rotor  68 . As a further alternative, a groove could be formed in both the rotor  68  and the cap. 
         [0036]    While bridging lock pin oil passage  128  has been shown as a semicircular groove, it should now be understood that lock pin oil passage  128  may be formed as a complete circle. In this arrangement, the width of the groove may be made smaller since the oil has two paths to follow. 
         [0037]    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.