Patent Publication Number: US-2020292035-A1

Title: Unlocking mechanism for a variable camshaft phaser

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims one or more inventions which were disclosed in Provisional Application No. 62/855,239, filed May 31, 2019, entitled “UNLOCKING MECHANISM FOR A VARIABLE CAMSHAFT PHASER”. The benefit under 35 U.S.C. § 119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention pertains to the field of variable cam timing. More particularly, the invention pertains to an unlock mechanism for a variable camshaft timing phaser. 
     Description of Related Art 
     Internal combustion engines have employed various mechanisms to vary the relative timing between the camshaft and the crankshaft for improved engine performance or reduced emissions. The majority of these variable camshaft timing (VCT) mechanisms use one or more “vane phasers” on the engine camshaft (or camshafts, in a multiple-camshaft engine). Vane phasers have a rotor assembly with one or more vanes, mounted to the end of the camshaft, surrounded by a housing assembly with the vane chambers into which the vanes fit. It is possible to have the vanes mounted to the housing assembly, and the chambers in the rotor assembly, as well. The housing&#39;s outer circumference forms the sprocket, pulley or gear accepting drive force through a chain, belt, or gears, usually from the crankshaft, or possible from another camshaft in a multiple-cam engine. 
     Apart from the camshaft torque actuated (CTA) variable camshaft timing (VCT) systems, the majority of hydraulic VCT systems operate under two principles, oil pressure actuation (OPA) or torsional assist (TA). In the oil pressure actuated VCT systems, an oil control valve (OCV) directs engine oil pressure to one working chamber in the vane phaser while simultaneously venting the opposing working chamber defined by the housing assembly, the rotor assembly, and the one or more vanes. This creates a pressure differential across one or more of the vanes to hydraulically push the vane phaser in one direction or the other. Neutralizing or moving the oil control valve to a null position puts equal pressure on opposite sides of the one or more vanes and holds the vane phaser in any intermediate position. If the vane phaser is moving in a direction such that valves of the engine will open or close sooner, the vane phaser is said to be advancing and if the vane phaser is moving in a direction such that valves will open or close later, the vane phaser is said to be retarding. 
     The torsional assist (TA) systems operates under a similar principle with the exception that it has one or more check valves to prevent the vane phaser from moving in a direction opposite than being commanded, should it incur an opposing force such as torque. 
     The problem with OPA or TA systems is that the oil control valve defaults to a position that exhausts all the oil from either the advance or retard working chambers and fills the opposing chamber. In this mode, the vane phaser defaults to moving in one direction to an extreme stop where a lock pin engages, locking the movement of the rotor assembly relative to the housing assembly. The OPA or TA systems are unable to direct the vane phaser to any other position during the engine start cycle when the engine is not developing any oil pressure. This limits the vane phaser to being able to move in one direction only in the engine shut down. In the past this was acceptable because at engine shut down and during engine start the vane phaser would be commanded to lock at one of the extreme travel limits (either full advance or full retard). 
     Most engines with an intake phaser place the phaser in the retard position in engine shutdown using a lock pin or a series of lock pins, in preparation for the next start of a “stop-start mode” which automatically stops and automatically restarts the internal combustion engine to reduce the amount of time the engine spends idling when the vehicle is stopped, for example at a stop light or in traffic. This stopping of the engine is different than a “key-off” position or manual stop via deactivation of the ignition switch in which the user of the vehicle shuts the engine down or puts the car in park and shuts the vehicle off. In “stop-start mode”, the engine stops as the vehicle is stopped, then automatically restarts in a manner that is nearly undetectable to the user of the vehicle. In the past, vehicles have been designed primarily with cold starts in mind, since that is the most common situation. In a stop-start system, because the engine had been running until the automatic shutdown, the automatic restart occurs when the engine is in a hot state. It has long been known that “hot starts” are sometimes a problem because the engine settings necessary for the usual cold start—for example, a particular valve timing position—are inappropriate to a warm engine. 
     Unlocking the lock pin is dependent upon engine oil pressure available at start up. 
     SUMMARY OF THE INVENTION 
     A vane phaser with an unlocking and relocking mechanism coupled to the lock pin, which through the use of at least one solenoid can lock and unlock the vane phaser. The at least one solenoid associated with the lock pin is distinct from the solenoid used for the phaser control valve. When the at least one solenoid is energized and during rotation of the camshaft, the at least one solenoid pin makes contact with a lever attached to the lock pin, causing the lock pin to rotate. A helical feature on the lock pin itself or on the lever causes the lock pin to move axially, unlocking the phaser. 
     Since the mechanism is mechanical and is not dependent upon oil engine pressure, the vane phaser can be unlocked at any time the camshaft is rotating. The advantage of being independent of engine oil pressure is that the vane phaser can be unlocked prior to oil pressure build up, which can be an issue in vane phasers. Furthermore, by unlocking the vane phaser to allow early phasing, engine emissions and engine vibration can be reduced during engine startup. 
     A lock pin assembly received within a rotor assembly or housing assembly of a vane phaser. The lock pin comprising: a body having a first closed head end, a second end and a recessed portion between the first closed head end and the second end, a shaft having a first end and a second end, the first end attached to the second surface of the second end of the body and a second end connected to a gear having at least one tooth; a spring surrounding the shaft and adjacent the second surface of the second end of the body for biasing the first closed head end towards the recess of the housing assembly; and a pin having a first end spring biased towards the at least two axially extending grooves in the recessed portion, the pin being perpendicular to the body of the lock pin. The first closed head end having a first surface for mating with the recess of the housing assembly, and a second surface adjacent the recessed portion; the second end of the body has a first surface adjacent the recessed portion and a second surface, the first surface of the second end of the body comprising at least two repeats of a sequence of a first radiused edge, a flat, and a second radiused edge. The recessed portion is defined between the second surface of the first closed and the first surface of the second end of the body and has at least a first axially extending groove and a second axially extending groove, the first and second axially extending grooves each aligned with the flats of the first surface of the second end of the body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  shows a front view of a phaser of a first embodiment with a single solenoid pin and a lock pin in the locked position. 
         FIG. 2  shows a front view of a phaser of the first embodiment with a single solenoid pin, with the lock pin moving between the locked position and unlocked position. 
         FIG. 3  shows a front view of a phaser of the first embodiment with a single solenoid pin and the lock pin in the unlocked position. 
         FIG. 4  shows an isometric view of a lock pin in the locked position and the position of the pin and the solenoid pin. 
         FIG. 5  shows a cutaway of the phaser showing the lock pin and solenoid pin in the locked position. 
         FIG. 6  shows a sectional view of the phaser with the lock pin in the locked position. 
         FIG. 7  shows an isometric view of a lock pin in the unlocked position and the position of the pin and the solenoid pin. 
         FIG. 8  shows a cutaway of the phaser showing the lock pin and the solenoid pin in the unlocked position. 
         FIG. 9  shows a sectional view of the phaser with the lock pin in the unlocked position. 
         FIG. 10  shows a lock pin between a locked and unlocked position and the position of the solenoid pin and the pin. 
         FIG. 11  shows a cutaway of the phaser moving between the locked and unlocked position. 
         FIG. 12  shows a sectional view of the phaser with the lock pin being between locked and unlocked. 
         FIG. 13  shows a sectional view of the phaser just prior to the locked position. 
         FIG. 14  shows sectional view of the detent on the lock pin. 
         FIG. 15  shows a front view of a phaser of the second embodiment with dual solenoid pins and the lock pin in the locked position. 
         FIG. 16  shows a front view of a phaser of the second embodiment with dual solenoid pins, with the lock pin moving between the locked position and unlocked position. 
         FIG. 17  shows a front view of a phaser of the second embodiment with dual solenoid pins and the lock pin in the unlocked position. 
         FIG. 18  shows a sectional view of the phaser with the lock pin in the locked position. 
         FIG. 19  shows a sectional view of the phaser with the lock pin in between a locked and an unlocked position. 
         FIG. 20  shows a sectional view of the phaser with the lock pin in the unlocked position. 
         FIG. 21  shows a sectional view of the phaser with the lock pin just prior to the locked position. 
         FIG. 22  shows a sectional view of the detent on the lock pin. 
         FIG. 23  shows an isometric view of a lock pin in a locked position and the position of the pin and the solenoid pin. 
         FIG. 24  shows an isometric view of a lock pin between a locked and an unlocked position and the position of the solenoid pin and pin. 
         FIG. 25  shows an isometric view of a lock pin in an unlocked position and the position of the solenoid pin and pin. 
         FIG. 26  shows an isometric view of the lock pin just prior to a locked position and the position of the pin and solenoid pin. 
         FIG. 27  shows a front view of a phaser with the lock pin in the unlocked position. 
         FIG. 28  shows a front view of the phaser relocking the lock pin. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In an embodiment of the present invention, rotation of the camshaft and a linear solenoid is used to mechanically lock and unlock a lock pin by changing rotational energy to linear energy, therefore circumventing hydraulic issues at startup of the engine and addressing immediate phasing needs of a vane phaser at startup without relying on hydraulic fluid to unlock the lock pin. 
     Referring to  FIGS. 1-14 , vane phasers (herein referred to as “phasers”) have a rotor assembly  105  with one or more vanes  104 , mounted to the end of the camshaft (not shown), surrounded by a housing assembly  100  with vane chambers  171  into which the vanes  104  fit. It is possible to have the vanes  104  mounted to the housing assembly  100 , and the chambers in the rotor assembly  105 , as well. The housing assembly  100  includes a first end plate  100   a  and a second end plate  100   b . The first end plate  100   a  has an outer circumference  101  which forms the sprocket, pulley or gear accepting drive force through a chain, belt, or gears, usually from the crankshaft, or possible from another camshaft in a multiple-cam engine. 
     The rotor assembly  105  is connected to the camshaft (not shown) and is coaxially located within the housing assembly  100 . The rotor assembly  105  has a vane  104  separating a chamber  171  formed between the housing assembly  100  and the rotor assembly  105  into an advance chamber and a retard chamber. The vane  104  is capable of rotation to shift the relative angular position of the housing assembly  100  and the rotor assembly  105 . 
     An oil control valve  170  can be located remotely from the phaser, within a bore  172  in the rotor assembly  105  which pilots in the camshaft, or in a center bolt of the phaser and controls the movement of the vane  104  to control the timing of the engine. 
     Within at least one vane  104  of the rotor assembly  105  is a lock pin  125 . The lock pin  125  is slidably housed in a bore  108  of at least one vane  104  of the rotor assembly  105 . The lock pin  125  is moveable from a first locked position in which the lock pin  125  engages a recess  127  in a first end plate  100   a  of the housing assembly  100 , preventing movement of the rotor assembly  105  relative to the housing assembly  100  and an unlocked position in which the lock pin  125  does not engage the recess  127  in the first end plate  100   a  of the housing assembly  100  and the rotor assembly  105  can rotate relative to the housing assembly  100 . 
     The lock pin  125  has a body  126  with a first closed head end  126   a , a second end  126   b  and a recessed portion  126   c  between the first closed head end  126   a  and the second end  126   b . The first closed head end  126   a  has a first surface  128   a  which can mate with the recess  127  and a second surface  128   b  which is adjacent the recessed portion  126   c . The second end  126   b  of the body  126  of the lock pin  125  has a first surface  129   a  adjacent the recessed portion  126   c  and a second surface  129   b  which receives a shaft  130 . The first surface  129   a  of the second end  126   b  has a first radiused edge  131  and a second radiused edge  132  with flats  137   a - 137   n . Travel distance of the lock pin  125  is defined between a first set of flats  137   a  to the second set of flats  137   b  with the first and second radiused edges  131 ,  132  between the first and second set of flats  137   a - 137   b . The recessed portion  126   c  is therefore defined between the second surface  128   b  of the closed head end  126   a  and the first surface  129   a  of the second end  126   b . The recessed portion  126   c  additionally contains two or more detent grooves  133   a - 133   n  which run axially relative to a centerline C-C as shown in  FIGS. 4, 7, 10, and 14 . The flats  137   a - 137   n  are aligned with a detent groove  133   a - 133   n . Adjacent detent grooves  133   a - 133   n  in the recessed portion  126   c  correspond to a locked position of the lock pin  125  and an unlocked position of the lock pin  125 . The sequence around the radiused edge includes a repeat of a first radiused edge  131 , a second radiused edge  132 , a flat  137   a - 137   n , a second radiused edge  132  and a first radiused edge  131 . 
     A pin  140  having a first end  141  is spring  143  biased into contact with at least one of the detent grooves  133   a - 133   n  of the recessed portion  126   c  so that the pin  140  is perpendicular to the centerline C-C. The pin  140  is received within a recess  173  in the vane  104  and is perpendicular to the lock pin body  126 . A plug  142  maintains the spring biased pin  140  in the recess  173 . The force of spring  143  is tuned such that the pin  140  can be moved between the detent grooves  133   a - 133   n  and control overshoot of the lock pin rotation about the centerline C-C. The placement of the detent grooves  133   a - 133   n  additionally ensures that the lock pin  125  does not rotate once it is moved to the new position (locked or unlocked). 
     The shaft  130  has a first end  130   a  connected to the second surface  129   b  of the second end  126   b  of the lock pin body  126  and a second end  130   b  connected to a gear  136 . The shaft  130  is received by and protrudes from a slot  147  of the second end plate  100   b.    
     The gear or lever  136  has a plurality of radially extending teeth  136   a - 136   n . The teeth  136   a - 136   n  are spaced apart relative to each other to allow a solenoid pin  150  to seat between the teeth  136   a - 136   n . The number of teeth  136   a - 13   n  of the gear  136  corresponds to the number of detent grooves  133   a - 133   n . A detent groove  133   a - 133   n  is present for each position and the number of positions is dictated by the number of teeth  136   a - 136   n  on the gear  136 . The solenoid pin  150  position is stationary relative to the rotation of the phaser in the clockwise direction indicated by the arrow in  FIGS. 1-3 . The position of the solenoid pin  150  relative to interfacing with the teeth  136   a - 136   n  of the gear  136  is controlled by a solenoid  175 . The solenoid  175  is preferably an on/off linear solenoid. 
     Adjacent the second surface  129   b  of the second end  126   b  of the lock pin body  126  is a lock pin spring  145  for biasing the first closed head end  126   a  of the lock pin  125  towards the recess  127  in the first end plate  100   a  of the housing assembly  100  as shown in  FIGS. 5, 6, 8, 9, and 11-13 . 
     In an alternate embodiment, a ramp could be used to return the solenoid pin  150  to the retracted position if a latching solenoid were used. The ramp ensures that the solenoid pin  150  is retracted within a single phaser rotation. If ramp is not present, the lock pin  125  is rotated again and returned to the previous lock/unlock position. 
     Referring to  FIGS. 1 and 4-6 , which shows the lock pin  125  in a locked position. In this position, the lock pin  125  interfaces with the recess  127  of the housing assembly  100  and the rotor assembly  105  is prevented from rotating relative to the housing assembly  100 . 
     The housing assembly  100  of the phaser rotates in a clockwise direction as shown by the arrow as it is driven by the chain or belt. It should be noted that in the Figures, all elements except for the solenoid pin  150  of the solenoid  175  rotate with the phaser. 
     During the full rotation of the phaser 360°, the solenoid pin  150  of the linear solenoid  175  interfaces with gear tooth  136   a  of the gear  136 , causing the gear  136  to turn counterclockwise. It should be noted that the solenoid pin  150  interacts with the gear  136  only once during 360° or full rotation of the phaser. 
     Referring to  FIGS. 2 and 10-12 , the rotation of the gear  136  is translated through the shaft  130  to the lock pin body  126 , causing the lock pin body  126  to rotate in the counterclockwise direction 90° per full rotation (360°) of the housing assembly  100 . The rotation of the lock pin body  126  causes the spring biased pin  140  to travel between detent grooves  133   a - 133   n  at each of the 90° rotation increments (see  FIG. 14 ) along the first and second radiused edges  131 ,  132  of the first surface  129   a  of the second end  126   b  of the body until the spring biased pin  140  interfaces with the flats  137   a - 137   n  of the first surface  129   a  adjacent the detent groove  133   a - 133   n , causing the spring biased pin  140  to seat in the detent groove  133   a - 133   n , limiting the rotation of the lock pin  125 . In the unlocked position, the closed head end  126   a  of the lock pin  125  does not interface with the recess  127  and the rotor assembly  105  can rotate relative to the housing assembly  100 . 
     It should be noted that while the detent grooves  133   a - 133   n  are described as being 90° apart within the recessed portion  126   c  of the lock pin body  126 , the spacing between the detent grooves  133   a - 133   n  can be altered. 
       FIG. 13  shows a sectional of the phaser just prior to moving towards a locked position. 
     The spring biased pin  140  is seated in a detent groove  133   a - 133   n  of the recessed portion  126   c  of the lock pin body  126  of the lock pin  125 . The pin  140  is adjacent the second surface  128   b  of the closed head end  126   a  of the lock pin body  126  of the lock pin  125  and not the first surface  129   a  of the second end  126   b  of the lock pin body  126 . 
       FIGS. 2 and 10-12  show the lock pin  125  just prior to unlock (e.g. prior to fully disengaging from the recess  127  of the housing assembly  100 ) and between the locked and unlocked position. 
     Referring to  FIGS. 3 and 7-9 , where the lock pin  125  is in an unlocked position, and during the full rotation of the phaser 360°, the solenoid pin  150  is adjacent and in contact with a single tooth. The contact of the solenoid pin  150  with the single gear tooth  136   a  rotates the lock pin body  126 , such that the spring biased pin  140  is unseated from any detent groove  133   a - 133   n  it may have been seated in and the spring biased pin  140  is forced to travel along the first and second radiused edges  131 ,  132  of the first surface  129   a  of the second end  126   b  of the lock pin body  126 . The travel of the spring biased pin  140  along the first and second radiused edges  131 ,  132  moves the lock pin  125  axially away from the recess  127  of the housing assembly  100 . 
       FIGS. 1 and 4-6  shows the lock pin  125  in a locked position. In the locked position, the housing assembly  100  is fixed relative to the rotor assembly  105  and the phaser rotates in the clockwise direction as indicated by the arrow. During the full rotation of the phaser 360°, the solenoid pin  150  of the linear solenoid  175  interfaces with the gear tooth  136   a  of the gear  136 , causing the gear  136  to turn counterclockwise. The rotation of the gear  136  is translated through the shaft  130  to the lock pin body  126 , causing the lock pin body  126  to rotate in the counterclockwise direction 90° per full rotation (360°) of the housing assembly  100 . The rotation of the lock pin body  126  causes the spring biased pin  140  to travel between detent groove  133   n  to detent groove  133   a  at each of the 90° rotation increments (see  FIG. 14 ) along the first and second radiused edges  131 ,  132  of the first surface  129   a  of the second end  126   b  of the body until the pin  140  interfaces with the flat  137   a  of the first surface  129   a  adjacent the detent groove  133   a , causing the pin  140  to seat in the detent groove  133   a , limiting the rotation of the lock pin  125 . In the locked position, the closed head end  126   a  of the lock pin interfaces with the recess  127  and the rotor assembly  105  cannot rotate relative to the housing assembly  100 . 
     Therefore, in a locked position of the lock pin  125 , spring bias pin  140  is in detent groove  133   a  and interfaces with flat  137   a  of the first surface  129   a . In an unlocked position of the lock pin  125 , spring bias pin  140  is in detent groove  133   n  and interfaces with flat  137   n  of the first surface  129   a.    
     Between the locked and unlocked positions of the lock pin  125 , spring bias pin  140  moves between detent grooves  133   n  and  133   a  along the first surface  129   a.    
     Upon the next commanded lock pin change, the following detent grooves  133   b ,  133   c  would be used and  133   a ,  133   b ,  133   c ,  133   n  are used sequentially as locked or unlocked commands are received and the lock pin  125  will continue to rotate such that the detent grooves  133   n  and  133   a  are used for the next commanded lock pin change. 
       FIGS. 15-28  show an alternate embodiment in which two solenoid pins are present to engage a lock pin  225  use to lock the vane phaser. 
     Within at least one vane  104  of the rotor assembly  105  is a lock pin  225 . The lock pin  225  is slidably housed in a bore  108  of the vane  104  of the rotor assembly  105 . The lock pin  225  is moveable from a first locked position in which the lock pin  225  engages a recess  127  in a first end plate  100   a  of the housing assembly, preventing movement of the rotor assembly  105  relative to the housing assembly  100  and an unlocked position in which the lock pin  225  does not engage the recess  127  in the first end plate  100   a  of the housing assembly  100 , and the rotor assembly  105  can rotate relative to the housing assembly  100 . 
     The lock pin  225  has a body  226  with a first closed head end  226   a , a second end  226   b  and a recessed portion  226   c  between the first closed head end  226   a  and the second end  226   b . The first closed head end  226   a  has a first surface  228   a  which can mate with the recess  127  and a second surface  228   b  which is adjacent the recessed portion  226   c . The second end  226   b  of the body  226  of the lock pin  225  has a first surface  229   a  adjacent the recessed portion  226   c  and a second surface  229   b  which receives a shaft  230 . 
     The first surface  229   a  of the second end  226   b  has at least two sequences of a first radiused edge  231 , a second radiused edge  232  and a flat  237  that define travel distance of the lock pin  225 . The recessed portion  226   c  is therefore defined between the second surface  228   b  of the closed head end  226   a  and the first surface  229   a  of the second end  226   b . The recessed portion  226   c  additionally contains two detent grooves  233   a ,  233   b  which run axially relative to a centerline C-C as shown in  FIGS. 23-26 . The first detent groove  233   a  corresponds to a locked position of the lock pin  225  and the second detent groove  233   b  corresponds to an unlocked position of the lock pin  225 . The flats  237  are aligned with detent grooves  233   a ,  233   b . Therefore, a first flat  237   a  is aligned with detent groove  233   a  and a second flat  237   b  is aligned with detent groove  233   b.    
     A pin  140  having a first end  141  and a spring  143  are received within a bore  173  of the vane  104  of the rotor assembly  105 . The pin  140  is spring biased into contact with the recessed portion  226   c  of the lock pin  225  so that the pin  140  is perpendicular to the centerline C-C. A plug  142  maintains the spring biased pin  140  in the recess  173 . The force of spring  143  is tuned such that the pin  140  can be moved between the detent grooves  233   a ,  233   b  and control overshoot of the lock pin  225  rotation about the centerline C-C. The placement of the detent grooves  233   a - 233   b  additionally ensures that the lock pin  225  does not rotate once it is moved to the new position (locked or unlocked). Adjacent the second surface  229   b  of the second end  226   b  of the lock pin body  226  is a lock pin spring  245  for biasing the first closed head end  228   a  of the lock pin  225  towards the recess  127  in the first end plate  100   a  of the housing assembly  100 . 
     A shaft  230  has a first end  230   a  connected to the second surface  229   b  of the second end  226   b  of the lock pin body  226  and a second end  230   b  connected to a gear  236 . The shaft  230  is received by and protrudes from a slot  147  of the second end plate  100   b.    
     The gear or lever  236  has at least two radially extending teeth  236   a ,  236   b . The teeth  236   a ,  236   b  are spaced apart relative to each other to allow first and second solenoid pins  150 ,  152  to interact with the teeth  236   a ,  236   b . The position of the first and second solenoid pins  150 ,  152  is stationary relative to the rotation of the vane phaser in the clockwise direction indicated by the arrow in  FIGS. 15-17 . The position of the first and second solenoid pins  150 ,  152  relative to interfacing with the teeth  236   a ,  236   b  of the gear  236  is controlled by a solenoid  175 . The first and second solenoids controlling the first and second solenoid pins  150 ,  152  are preferably on/off linear solenoids  175 . 
     The spacing of the first and second solenoid pins  150 ,  152  relative to each other can be set based on the application and is irrelevant as long as both solenoid pins  150 ,  152  do not interact with both teeth  236   a ,  236   b  of the gear  236  at the same time. 
     In an alternate embodiment, a ramp could be used to return at least one of the solenoid pins  150 ,  152  to the retracted position if a latching solenoid were used. The ramp ensures that at least one of the solenoid pins  150 ,  152  is retracted from interaction with the gear teeth  236   a ,  236   b  of the gear  236  in preparation for the second solenoid pin  152  to be extended. If the ramp is not present and the first solenoid pin  150  is still extended when the second solenoid pin  152  extends, the lock pin  225  is rotated again and returned to the previous lock/unlock position. 
     Referring to  FIGS. 15, 18 and 23 , the lock pin  225  is in a locked position. The housing assembly  100  of the phaser rotates in a clockwise direction as shown by the arrow as it is driven by the chain or belt. In the locked position, the closed head end  226   a  of the lock pin  225  interfaces with the recess  127  and the rotor assembly  105  cannot rotate relative to the housing assembly  100 . 
     Referring to  FIGS. 16, 19 and 24 , the second solenoid pin  152  contacts the gear tooth  236   a . The contact of the second solenoid pin  152  with the gear tooth  236   a  begins to rotate the lock pin body  226  counterclockwise. The rotation of the gear  236  is translated through the shaft  230  to the lock pin body  226 , causing the lock pin body  226  to rotate in the counterclockwise direction 90° per full rotation (360°) of the housing assembly  100 . The rotation of the lock pin body  226  causes the spring biased pin  140  to travel between detent grooves  233   a  and  233   b  (see  FIG. 22 ) and more specifically, from the detent groove  233   a  along the first radiused edge  231  and the second radiused edge  232  of the first surface  229   a  of the second end  226   b  of the body until the pin  140  interfaces with the flat  237   b  of the first surface  229   a  adjacent the detent groove  233   b , causing the spring biased pin  140  to seat in the detent groove  233   b , limiting the rotation of the lock pin  225 . The travel of the pin  140  along the first radiused edge  231  and the second radiused edge  232  moves the lock pin axially away from the recess  127  of the housing assembly  100 . Referring to  FIGS. 17, 20 and 25 , the lock pin  225  has completed the 90° counterclockwise rotation and the phaser is in the unlocked position. In the unlocked position, the closed head end  226   a  of the lock pin  225  does not interface with the recess  127  and the rotor assembly  105  can rotate relative to the housing assembly  100 . 
       FIGS. 27 and 28  show the lock pin  225  starting in an unlocked position and moving back towards the locked position. During the full rotation of the phaser 360°, the first solenoid pin  150  of the first linear solenoid interfaces with the gear tooth  236   b  of the gear  236 , causing the gear  236  to turn clockwise. The rotation of the gear  236  is translated through the shaft  230  to the lock pin body  226 , causing the lock pin body  226  to rotate in the clockwise direction 90° per full rotation (360°) of the housing assembly  100 . If the rotor assembly  105  is positioned so that the lock pin  225  is in line with the recess  127 , the rotation of the lock pin body  226  causes the spring biased pin  140  to travel from the second detent groove  233   b  along the first radiused edge  231  and the second radiused edge  232  of the first surface  229   a  of the second end  226   b  of the body until the pin  140  interfaces with the flat  237   a  of the first surface  229   a  adjacent the first detent groove  233   a , causing the pin  140  to seat in the first detent groove  233   a , limiting the rotation of the lock pin  225 . In the locked position, the closed head end  226   a  of the lock pin  225  interfaces with the recess  127  and the rotor assembly  105  cannot rotate relative to the housing assembly  100 . 
     If the lock pin is rotated to the locked position before the rotor assembly  105  has moved to align the lock pin  225  with the recess  127  and no axial motion of the lock pin  225  is possible, the rotation of the lock pin body  226  causes the spring biased pin  140  to travel from the second detent groove  233   b  along the flat face  275  of the second surface  228   b  of the first end  226   a  of the body until the spring biased pin  140  seats in the first detent groove  233   a , limiting the rotation of the lock pin  225 .  FIGS. 21 and 26  show a sectional of the phaser just prior to moving towards a locked position (prelock) and an isometric view of the lock pin  225 . The spring biased pin  140  is seated in the detent groove  233   a  of the recessed portion  226   c  of the body  226  of the lock pin  225 . The spring biased pin  140  is adjacent the second surface  228   b  of the closed head end  226   a  of the body  226  of the lock pin  225  and not the first surface  229   a  of the second end  226   b  of the body  226 . Once the rotor assembly  105  has moved to align the lock pin  225  with the recess  127 , the spring  245  will move the closed head end  226   a  of the lock pin  225  to interface with the recess  127  and the rotor assembly  105  will not be able to rotate relative to the housing assembly  100 . 
     It should be noted that while the first and second detent grooves  233   a ,  233   b  are described as being 90° apart within the recessed portion  226   c  of the lock pin body  226 , the spacing between the detent grooves  233   a ,  233   b  can be altered. 
     Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.