Abstract:
A spool valve for variable cam timing phaser comprising a spool, a plurality of check valves and passages from the advance chamber and the retard chamber to a port in the spool valve. The spool having at least two lands separated by a central spindle, slidably mounted within a bore. When the spool is in the first position, fluid from the advance chamber flows through the passage and the port to the bore surrounding the central spindle of the spool valve and through a check valve and port to the passage to the retard chamber. When the spool is in the second position, fluid from the retard chamber flows through the passage and the port to the bore surrounding the central spindle of the spool valve and through a check valve and port to the passage to the advance chamber.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention pertains to the field of variable cam timing. More particularly, the invention pertains to controlling the phaser to vary the timing of the cam using the spool valve. 
   2. Description of Related Art 
   U.S. Pat. No. 5,002,023 shows a single check valve in a spool valve which is present in the rotor. 
   U.S. Pat. No. 5,172,659 shows dual check valves in the rotor between the chambers and the spool valve. A single check valve is present in the spool itself. 
   U.S. 2003/0070713A1 discloses a valve arrangement having a valve member in a cylindrical sleeve, where the sleeve has several bores in which hydraulic medium can flow through. A rectangular strip-shaped member made of springs steel surrounds a bore of the sleeve, sealing the bore. The strip-shaped member expands when the hydraulic pressure reaches a certain pressure. 
   JP11013430A discloses a selector mechanism in the middle of an oil pressure passage in the camshaft. Two check valves are present in the selector mechanism. Each check valve has a ball, received by a seat in a body that is slanted. A slidable selecting piston slides back and forth between the two check valves and first with the slant present on the check valve body, allowing fluid to move through only one check valve at a time to a hydraulic chamber. 
   The “Pictorial Handbook of Technical Devices” by Grafstein &amp; Schwarz on pages 376–377 shows a shuttle valve, identified by “d”. As shown in “d”, the valve has two inlets and one outlet. Two check valves block low pressure from the sides of the valve. Shuttle valves are commonly used to isolate a normal operating system from an alternate/emergency system. So, one of the inlets is to the normal operating system and the other is for the emergency system. The shuttle slides and blocks the emergency inlet during normal operation by normal system pressure. The emergency inlet remains blocked until the emergency system is activated. At this time, the shuttle moves, blocking the normal system inlet, allowing free flow from the emergency inlet to the outlet. 
   The 2 nd  edition of the “Automotive Handbook” by Bosch, pages 634–636 discloses a spool valve comprising a valve body, a load, metering notches, a spool a, a check valve, and a return spring. The check valve is located in the body of the spool and acts as a one way flow device for the inlet line of the spool valve. On pages 636 &amp; 637, a hydraulically unlockable double check valve is shown. The valve comprises a poppet valve, an unlockable piston and two check valves. The check valve may be opened mechanically, hydraulically, or electrically. 
   SUMMARY 
   A spool valve for variable cam timing phaser comprising a spool, a plurality of check valves and passages from the advance chamber and the retard chamber to a port in the spool valve. The spool having at least two lands separated by a central spindle, slidably mounted within a bore in the rotor. When the spool is in the first position, fluid from the advance chamber flows through the passage and the port to the bore surrounding the central spindle of the spool valve and through a check valve and port to the passage to the retard chamber. When the spool is in the second position, fluid from the retard chamber flows through the passage and the port to the bore surrounding the central spindle of the spool valve and through a check valve and port to the passage to the advance chamber. 
   Additionally, the spool valve may also by externally or internally connected to a stationary rotary actuator. In the rotary actuator, the housing does not have an outer circumference for accepting drive force and motion of the housing is restricted. The restriction of the housing ranges from not moving the housing at all to the housing having motion restricted to less than 360°. All movement, other than the twisting of the shaft is done by the rotor. The rotor and the vane moves or swings through the distance as defined and limited by the housing. All of the cyclic load is on the rotor and the rotor accepts all of the drive force. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1   a  shows a schematic of an oil pressure actuated (OPA) phaser shifting to retard.  FIG. 1   b  shows a schematic of an oil pressure actuated (OPA) phaser shifting to advance.  FIG. 1   c  shows a schematic of an oil pressure actuated (OPA) phaser in the null position. 
       FIG. 2   a  shows a schematic of a cam torque actuated (CTA) phaser shifting to retard.  FIG. 2   b  shows a schematic of a cam torque actuated (CTA) phaser shifting to advance.  FIG. 2   c  shows a schematic of a cam torque actuated (CTA) phaser in the null position. 
       FIG. 3  shows an externally mounted spool valve with check valves in the sleeve of the spool valve. 
       FIG. 4  shows an internally mounted spool valve with check valves in the sleeve of the spool valve. 
       FIG. 5  shows a close-up of the spool valve. 
       FIG. 6   a  shows a schematic of the spool with the check valve in the sleeve mounted to an oil pressure actuated phaser in the null position.  FIG. 6   b  shows a schematic of the spool with the check valve in the sleeve mounted to an oil pressure actuated phaser shifting to retard.  FIG. 6   c  shows a schematic of the spool with the check valve in the sleeve mounted to an oil pressure actuated phaser shifting to advance.  FIG. 6   d  shows a schematic of the spool with the check valve in the sleeve mounted to an oil pressure actuated phaser when oil needs to be supplied to a chamber (retard in this instance) due to leakage.  FIG. 6   e  shows a schematic of the spool with the check valve mounted in a sleeve mounted to a rotary actuator. 
       FIG. 7  shows an externally mounted spool valve with check valves in between the spool lands of a second embodiment. 
       FIG. 8  shows an internally mounted spool valve with check valves in between the spool lands of a second embodiment. 
       FIG. 9  shows a close-up of the spool valve. 
       FIG. 10  shows a cross-section of the spool valve along line  10 — 10  in  FIG. 9 . 
       FIG. 11   a  shows a schematic of the spool valve of the second embodiment with a cam torque actuated phaser in the null position.  FIG. 11   b  shows a schematic of the spool valve of the second embodiment with a cam torque actuated phaser in the advanced position.  FIG. 11   c  shows a schematic of the spool valve of the second embodiment with a cam torque actuated phaser in the retard position. 
       FIG. 12  shows an externally mounted spool valve with check valves in the spool body of a third embodiment. 
       FIG. 13  shows an internally mounted spool valve with check valves in the spool body of a third embodiment. 
       FIG. 14  shows an exploded view of the spool valve of the third embodiment. 
       FIG. 15   a  shows a schematic of the spool valve of the third embodiment with a cam torque actuated phaser in the null position.  FIG. 15   b  shows a schematic of the spool valve of the third embodiment with a cam torque actuated phaser in the retard position.  FIG. 15   c  shows a schematic of the spool valve of the third embodiment with a cam torque actuated phaser in the advanced position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1   a  through  1   c , a conventional oil pressure actuated phaser, where engine oil pressure is applied to a chamber  108 ,  110  on one side of the vane  106  or the other by a control valve  104 ,  109 . The housing  111  has an outer circumference for accepting drive force. The rotor  107  is connected to the camshaft  126  coaxially located in the housing  111 . The housing  111  and the rotor  107  define at least one vane  106  separating a chamber in the housing  111  into an advance chamber  108  and a retard chamber  110 . The vane  106  is capable of rotation to shift the relative angular position of the housing  111  and the rotor  107 . The control valve  104 ,  109  may be internally or externally mounted and may consist of a variable force solenoid (VFS) controlled by an ECU  102 , the spool valve  104 ,  109 , also known as a four-way valve, and sleeve (not shown). In this case, the spool valve is mounted remotely. Oil from an opposing chamber  108 ,  110  is exhausted back to the oil sump through lines  112 ,  113 . The applied engine oil pressure alone is used to move the vane  106  in the advance direction or the retard direction. To retard the phaser, as shown in  FIG. 1   a , pressure is applied to the retard chamber  110  to the retard the camshaft and simultaneously exhausting chamber  108 . Higher oil pressure increases the retard actuation rate. To advance the phaser, as shown in  FIG. 1   b , pressure is applied to the advance chamber  108  to advance the camshaft. Higher oil pressure increases the advance actuation rate. The oil that is controlled by the four-way valve  104 ,  109  communicates with the chambers via the two lines  112 ,  113  in the camshaft, one for retarding the vane  106 , as shown in  FIG. 1   a  and one for advancing the vane  106 , as shown in  FIG. 1   b .  FIG. 1   c  shows the phaser in the null position where the phase angle is being maintained and pressure and fluid are blocked from both the advance and retard chambers  108 ,  110 . Because of torque reversals in the camshaft, the graph of movement of an OPA phaser looks similar to a sine wave. One of the disadvantages of the OPA phaser is that the performance of the phaser is directly related to the oil pump capacity and requires a constant supply of oil. 
     FIGS. 2   a  through  2   c  show a conventional cam torque actuated phaser (CTA). Torque reversals in the camshaft caused by the forces of opening and closing engine valves move the vanes  106 . The control valve in a CTA system allows the vanes  106  in the phaser to move by permitting fluid flow from the advance chamber  108  to the retard chamber  110  or vice versa, depending on the desired direction of movement as shown in  FIGS. 2   a  and  2   b . Positive cam torsionals are used to retard the phaser, as shown in  FIG. 2   a . Negative cam torsionals are used to advance the phaser, as shown in  FIG. 2   b . A null or central position, as shown in  FIG. 2   c , stops the flow of fluid, locking the vane in position. 
   More specifically, in the retard position of the phaser, as shown in  FIG. 2   a , hydraulic fluid from the supply enters line  118  and moves through check valve  119  to the spool valve  104 . As shown in the schematic, the spool valve  104  is internally mounted and comprises a sleeve  117  for receiving a spool  109  with lands  109   a ,  109   b ,  109   c  and a biasing spring  105 . One of the advantages of locating the hydraulic control inside of the phaser, is the decrease in the amount of modification of the engine required. A VFS  103 , which is controlled by an ECU  102 , moves the spool  109  within the sleeve  117 . For the retard position, as shown in  FIG. 2   a , the spool  109  is moved to the left by spring  105 , and spool land  109   b  blocks line  113  and most of exhaust line  121 , spool land  109   c  blocks another exhaust line, and line  112  and  116  are open. From the spool  109 , fluid enters line  116  through open check valve  115  and moves into line  113  and to the retard chamber  110 . At the same time fluid is exiting the advance chamber through line  112  and the fluid moves through the spool between lands  109   a  and  109   b , and back into line  116  where it feeds into line  113  supplying fluid to the retard chamber. In addition, as stated earlier positive cam torsionals are used to aid in moving the vane  106 . 
   To advance the phaser, as shown in  FIG. 2   b , the spool is moved by the VFS  103  to the right, so that spool land  109   a  and  109   b  do not block line  113 , line  116 , or any exhaust lines and spool land  109   a  blocks the exit of fluid from line  112 . Fluid from the retard chamber  110  exits the chamber through line  113 , which routes the fluid through the spool  109  between lands  109   a  and  109   b . The fluid then enters line  116  and travels through open check valve  114  into line  112  and the advance chamber  108 . In addition, as stated earlier only cam torsionals are used to move the vane  106 . Additional fluid is supplied by the supply through line  118  and check valve  119  to the spool valve  104 . 
     FIG. 2   c  shows the phaser in null or a central position where the spool lands  109   a ,  109   b  block lines  112  and  113  and vane  106  is locked into position. Additional fluid is provided to the phaser to makeup for losses due to leakage. 
   The primary operation differences between an OPA phaser and a CTA phaser, is that the oil pressure actuated phaser exhausts oil back to the sump when the vane is actuating, whereas the cam torque actuated phaser exhaust oil from one chamber directly to the other chamber, and therefor recirculates the oil inside the phaser while it is actuated. Advantages of the CTA phaser over the OPA phaser are that the CTA phaser uses the cam torsionals to assist in moving the vane and reciruclates oil, increasing efficiency and performance of the phaser, so that the performance is not relying on the pump capacity. 
     FIGS. 3 through 6   d  shows a remotely mounted control valve for an oil pressure actuated phaser of the present invention. The control valve includes the variable force solenoid (VFS)  103 , the spool valve  104  and the sleeve  117 , which are replaced with the spool valve  204  shown in  FIG. 5 . The spool valve  204  may be externally mounted or internally mounted as shown in  FIGS. 3 and 4 .  FIGS. 3 and 4  do not show the supply line, or the VFS.  FIG. 4  shows the spool valve  204  mounted externally. Two lines,  212 ,  213  run from the spool valve  204  through the cam bearing  220  of the camshaft  226 , into the rotor  207  and housing  211  to the retard chamber  210  and the advance chamber  208 . The lines  212 ,  213  are usually present on either side of a bolt  200  when the spool valve  204  is externally mounted. One of the advantages of externally mounting the spool valve is that the room required or the room that the phaser takes up in the engine is smaller and is shorter overall in length. 
     FIG. 4  shows the spool valve  204  mounted internally. The spool valve  204  is located in the center of the rotor  207 . Supply provides hydraulic fluid to spool valve  204  through line  218 , which enters the phaser through the cam bearing  220  of the camshaft  226  and into the in the rotor  207  where the spool valve  204  is present. One of the advantages of internally mounting the spool valve  204  is the reduction of leakage of the phaser. 
     FIG. 5  shows a close-up of the spool valve  204 . The spool  209  is comprised of lands  209   a  and  209   b  separated by a central spindle and is surrounded by a cylindrical sleeve  217 . Within the cylindrical sleeve  217  are at least two check valves, an advance check valve  228   a , and a retard check valve  228   b , each having one or more passages  230   a , and  230   d  for the advance check valve  228   a  and passages  230   b  and  230   c  for the retard check valve. Each of the check valves  228   a ,  228   b  is comprised of a disk  231   a ,  231   b , and a spring  232   a ,  232   b , respectively. Other types of check valves may be used, including band check valves, ball check valves, and cone-type. The VFS  203  actuates the spool valve  204  and is biased by a spring not shown. 
     FIGS. 6   a  through  6   d  show the spool valve  204  mounted to an oil pressure actuated phaser. By adding spool valve  204  containing the check valves  228 , the oil pressure actuated phaser (OPA) is converted to a cam torque actuated (CTA) phaser, gaining all of the advantages of CTA phaser, such as recirculation of oil, and better performance than present in the OPA system, since the performance is no longer related to pump capacity, as discussed earlier.  FIG. 6   a  shows the spool  209  in the null position. Spool lands  209   a  and  209   b , and check valves  228   a ,  228   b  block the entrance and exit of fluid from lines  212  and  213  leading to the advance and retard chambers  208 ,  210  respectively. 
     FIG. 6   b  shows the phaser shifting to the retard position. The VFS  203  moves the spool valve  204  to the left in the Figure, such that spool land  209   a  is no longer blocking the fluid flow to the center of the spool valve. The hydraulic fluid, which may be oil, enters the spool valve  204  through supply line  218 . Fluid exits the advancing chamber  208  through line  212  into the advance check valve  228   a  of the cylindrical sleeve  217 . Due to the position of the spool land  209   a , fluid can exit to the center of the spool valve. From the center of the spool valve, fluid moves into passage  230   b ,  230   c  and pushes the disk  231   b , against spring  232   b , so that fluid can enter line  213  to the retard chamber  210 . The fluid in the retard chamber moves the vane  206  to the left. 
     FIG. 6   c  shows the phaser shifting to the advance position. The VFS  203  moves the spool valve  204  to the right in the Figure, such that spool land  209   b  is no longer blocking the fluid flow to the center of the spool valve. The hydraulic fluid, which may be oil, enters the spool valve  204  through supply line  218 . Fluid exits the retard chamber  210  through line  213  into retard check valve  228   b  of the cylindrical sleeve  217 . Due to the position of the spool land  209   b , fluid can exit to the center of the spool valve. From the center of the spool valve, fluid moves into passages  230   a ,  230   d  and pushes disk  231   a  against spring  232   a , so that fluid can enter line  212  to the advance chamber  208 . The fluid in the advance chamber  208  moves the vane  206  to the right. 
     FIG. 6   d  shows replenishment of oil to the retard and advance chambers  210 ,  208  due to leakage. When source oil pressure at the center of the spool valve exceeds the pressure in the retard and advance lines  213 ,  212 , the pressure is greater than the force of spring  232   a ,  232   b  and moves disks  231   a ,  231   b  so that fluid can enter lines  213 ,  212 . The spool lands  209   a  and  209   b  block the outlet of the advance and retard check valves  228   a ,  228   b  closest to the supply line  218 . 
   Some of the advantages of the spool valve of the first embodiment is that the spool valve can be remotely mounted to an already existing oil pressure actuated phaser, improving performance, decreasing the overall size and area the phaser takes up in the engine, and breaking the relationship between performance and supply pump capacity. 
   Additionally, the spool valve  204  may also by externally or internally connected to a stationary rotary actuator.  FIG. 6   e  shows the spool valve  204  internally connected to a stationary rotary actuator. In the rotary actuator, the housing  211  does not have an outer circumference for accepting drive force and motion of the housing  211  is restricted. The restriction of the housing  211  ranges from not moving the housing  211  at all to the housing  211  having motion restricted to less than 360°. All movement, other than the twisting of the shaft is done by the rotor  207 . The rotor  207  and the vane moves or swings through the distance as defined and limited by the housing  211 . All of the cyclic load is on the rotor  207  and the rotor  207  accepts all of the drive force. The check valves may be located remotely from the sleeve. 
     FIGS. 7 through 11   c  show a spool valve  304  of a second embodiment. Spool valve  304  may be externally mounted or internally mounted as shown in  FIGS. 7 and 8 .  FIGS. 7 and 8  do not show the supply line or the VFS.  FIG. 7  shows the spool valve  304  mounted externally. Two lines  312 ,  313  run from the spool valve  304  through the cam bearing  320  of the camshaft  326 , into the rotor  307  and housing  311  to the retard chamber  310  and the advance chamber  308 . The lines  312 ,  313  are usually present on either side of a bolt  300 , when the spool valve  304  is externally mounted. One of the advantages of externally mounting the spool valve is that the room required or the room that the phaser takes up in the engine is smaller and is shorter overall in length. 
     FIG. 8  shows the spool valve  304  mounted internally. The spool valve  304  is located in the center of the rotor  307 . Supply provides hydraulic fluid to the spool valve  304  through line  318 , which enters the phaser through the cam bearing  320  of the camshaft  326 . Line  318  continues from the camshaft into the in the rotor  307  where the spool valve  304  is present. One of the advantages of internally mounting the spool valve  304  is the reduction of leakage of the phaser. 
     FIG. 9  shows a close-up of the spool valve  304 . The spool  309  is comprised of lands  309   a ,  309   b ,  309   c , and  309   d  which are separated by a central spindle and is surrounded by a cylindrical sleeve  317 . Between the lands  309   a  and  309   b , is check valve  328   a . The check valve  328   a  is comprised of a disk  331   a , a spring  332   a , and multiple passages  330   b ,  330   b ′ that are present within land  309   b . Between lands  309   c  and  309   d  is check valves  328   d . The check valve  328   d  is comprised of a disk  331   d , a spring  332   d , and multiple passages  330   c ,  330   c ′ that are present within land  309   c . Other types of check valves may be used, including band check valves, ball check valves, and cone-type. The spool valve  304  is actuated by a VFS  303  (not shown) and biased by a spring  305 .  FIG. 10  shows a cross-section of the spool valve along line  10 — 10  in  FIG. 9 . As seen in the cross-section, the placement of the multiple passages  330   b ,  330   b ′,  330   c ,  330   c ′ are shown in regards to the cylindrical sleeve. The number and placement of the multiple passages may vary. 
     FIGS. 11   a  through  11   c  show spool valve  304  mounted to a cam torque actuated phaser.  FIG. 1   a  shows the spool valve in the null position. In this position, the edge of land  309   a  and land  309   b  and check valve  328   a  between the edges of lands  309   a  and  309   b  block inlet line  313 , and land  309   c  and the edge of land  309   d  and check valve  328   d  between the edges of lands  309   c  and  309   d  blocks inlet line  312 . Makeup fluid enters inlet lines  312 ,  313  through passages  330   b ′, and  330   c ′ respectively, moving disk  331   a  or  331   d  to allow for refilling of the phaser due to leakage. 
     FIG. 11   b  shows the spool valve  304  in the retard position. The VFS  303  (not shown) moves the spool to the left since the force of the spring  305  is greater than the force exerted by the VFS  303  (not shown) on the spool  309 . The spool is moved until land  309   d  blocks part of inlet line  313  and the check valve  328   d  is open to line  313  and spool land  309   b  is opening part of inlet line  312 . Fluid in the advance chamber  308  exits through inlet line  312  into the center of the spool valve. From the center of the spool valve, fluid moves into passage  330   c ′ and has enough pressure to move disk  331   d  of check valve  328   d  against the force of spring  332   d ′, allowing the fluid to enter line  313  to the retard chamber. 
     FIG. 11   c  shows the spool valve in the advance position. The VFS  303  (not shown) moves the spool to the right since the force of the VFS is greater than the force of the spring  305  on the spool  309 . The spool is moved until land  309   a  blocks part of inlet line  312  and check valve  328   a ′ is open to line  312  and spool land  309   c  is opening part of inlet line  313 . Fluid from the retard chamber  310  exits through inlet line  313  into the center of the spool valve, From the center of the spool valve, fluid moves into passage  330   b ′ and has enough pressure to move disk  331   a  of check valve  328   a  against the force of spring  332   a , allowing fluid to enter line  312  to the advance chamber. 
   Additionally, the spool valve  304  may also by externally or internally connected to a stationary rotary actuator similar to  FIG. 6   e . In the rotary actuator, the housing does not have an outer circumference for accepting drive force and motion of the housing is restricted. The restriction of the housing ranges from not moving the housing at all to the housing having motion restricted to less than 360°. All movement, other than the twisting of the shaft is done by the rotor. The rotor and the vane moves or swings through the distance as defined and limited by the housing. All of the cyclic load is on the rotor and the rotor accepts all of the drive force. The check valves may be located remotely from the spool. 
     FIGS. 12 through 15   c  show a spool valve  404  of a third embodiment. Spool valve  404  may be externally mounted or internally mounted as shown in  FIGS. 12 and 13 .  FIGS. 12 and 13  do not show the supply line or the VFS.  FIG. 12  shows the spool valve  404  externally mounted. Two lines  412 ,  413  run from the spool valve  404  through the cam bearing  420  of the camshaft  426 , into the rotor  407  and housing  411  to the retard chamber  410  and the advance chamber  408 . The lines  412 ,  413  are usually present on either side of a bolt  400  when the spool valve  404  is externally mounted. One of the advantages of externally mounting the spool valve is that the room required or the room that the phaser takes up in the engine is smaller and is shorter overall in length. 
     FIG. 13  shows the spool valve  404  mounted internally. The spool valve  404  is located in the center of the rotor  407 . Supply provides hydraulic fluid to the spool valve  404  through line  418 , which enter the phaser through the cam bearing  420  of the camshaft  426 . From the camshaft  426 , line  418  continues into the in the rotor  407  where the spool valve  404  is present. One of the advantages of internally mounting the spool valve  404  is the reduction of leakage of the phaser. 
     FIG. 14  shows an exploded view of the spool. The spool  409  has two lands  409   a  and  409   b  separated by a central spindle. Within each of the lands  409   a  and  409   b  are plugs  437   a ,  437   b  that house check valves  428   a  and  428   b . Each check valve is made up of a disk  431   a ,  431   b  and a spring  432   a ,  432   b . Other types of check valves may be used, including band check valves, ball check valves, and cone-type. The VFS  403 , not shown, actuates the spool valve  404  and biased by a spring  405 . 
     FIGS. 15   a  through  15   c  shows spool valve  404  mounted to a cam torque actuated phaser (not shown).  FIG. 15   a  shows the spool valve  404  in the null position. In this position, disks  431   a ,  431   b  of check valves  428   a ,  428   b  block the exit of the fluid from inlet lines  412 ,  413  into the middle of the spool  409 . A small amount of fluid is supplied from line  418  and allowed to refill the advance and retard chambers through lines  412 ,  413  due to leakage. 
     FIG. 15   b  shows the spool valve in the retard position. The VFS  403  moves the spool valve to the left since the force of the spring is greater than the force exerted by the VFS  403  on the spool  409 . When the spool is in this position, fluid from the advance chamber (not shown) exits to the spool valve through line  412 . Fluid passes through central hole  440   a  into the spool  409  moving the disk  431   b  against spring  432   b  of check valve  428   b , allowing fluid to enter line  413  to the retard chamber (not shown). 
     FIG. 15   c  shows the spool in the advance position. The VFS  403  moves the spool valve to the right since the force of VFS on the spool is greater than the force of spring  405  on the opposing end of the spool. When the spool is in this position, fluid from the retard chamber (not shown) exits to the spool valve through line  413 . Fluid passes through central hole  440   a  into the spool  409 , moving the disk  431   a  against spring  432   a  of check valve  428   a , allowing fluid to enter line  412  to the advance chamber (not shown). 
   Additionally, the spool valve  404  may also by externally or internally connected to a stationary rotary actuator similar to  FIG. 6   e . In the rotary actuator, the housing does not have an outer circumference for accepting drive force and motion of the housing is restricted. The restriction of the housing ranges from not moving the housing at all to the housing having motion restricted to less than 360°. All movement, other than the twisting of the camshaft is done by the rotor. The rotor and the vane moves or swings through the distance as defined and limited by the housing. All of the cyclic load is on the rotor and the rotor accepts all of the drive force. 
   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.