Abstract:
A variable cam timing system for an engine with at least one camshaft comprising: a housing, a rotor, and a controlled bypass. The housing has an outer circumference for accepting drive force and chambers. The rotor has a connection to a camshaft coaxially located within the housing. The housing and the rotor define at least one vane separating a chamber in the housing into advance and retard chambers. The vane is capable of rotation to shift the relative angular position of the housing and the rotor. The controlled bypass provides fluid communication between the chambers. When the valve is closed, the valve blocks passage between the chambers and when the valve is open fluid flows through the passage extending between the advance chamber to the retard chamber. A method for reducing the valve event is also disclosed.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention pertains to the field of valve event reduction. More particularly, the invention pertains to valve event reduction through operation of a fast-acting cam phaser.  
         [0003]     2. Description of Related Art  
         [0004]     For engines with a fixed geometry camshaft actuated inlet and exhaust valves, a variable cam timing (VCT) phaser is useful for improving engine operation. Since most VCT phasers are relatively slow acting devices, they can advance or retard the camshaft, but to change between the positions, will take numerous engine cycles to accomplish, even at engine cranking speeds.  
         [0005]     To vary the valve event or more specifically, shorten the effective intake or exhaust valve event, numerous methods have been implemented in the prior art, for example U.S. Pat. No. 5,297,507 discloses a method of reducing the valve event by varying the angular velocity of the camshaft. A variable event timing mechanism has a flexible lost motion coupling (valve spring) interposed between the drive wheel and the camshaft. For the camshaft to open normally and close early, the camshaft rotates at substantially the same speed as the drive wheel during opening and closing of the valve. The camshaft is accelerated by the valve spring to lead the drive wheel and thereby reduce the duration of the valve event. For the camshaft to open late and close normally, the camshaft is retarded by the valve spring to lag behind the drive wheel, and during closing of the valve, the camshaft rotates at substantially the same speed as the drive wheel, thereby reducing the duration of the valve event.  
         [0006]     U.S. Pat. No. 6,405,694 discloses an exhaust valve advanced-closing control for controlling the valve closing timing of the exhaust valve to the advance side without using valve overlap of a valve timing control means. In a second embodiment, a changeover may be made between the exhaust valve advanced-closing control for controlling the timing to close the exhaust valve to the advance side of the intake TDC and the retarded exhaust valve closing control for controlling the timing to close the exhaust valve to the retard side of the TDC.  
         [0007]     US 2003/0121484A1 discloses a method of altering the continuously variable valve timing, lift, and duration by altering the location of the pivot of a rocker arm. The overlap and valve lift duration increases when the valve lift increases. The chain timing, lift and duration are continuous and a function of engine speed.  
         [0008]     SAE Technical Paper No. 930825 discloses a variable event timing system that varies both the event length and phasing to optimize the breathing cycle of the engine. A drive shaft replaces an existing camshaft and uses the original drive flange configuration to drive each of the camshafts via a peg that engages with a drive slot in each of the camshafts. The drive shaft transmits torque and runs in its own bearing housings that are moved offset from the drive centerline relative to the camshaft centerline. By applying the offset drive shaft to drive the camshafts, the force applied is of a variable velocity, which accelerates and decelerates the individual camshafts during a single cam revolution. By adjusting the relationship of the drive shaft and the camshaft, the valves open late and close early, shortening the intake valve duration.  
       SUMMARY OF THE INVENTION  
       [0009]     A variable cam timing system for an engine with at least one camshaft comprising: a housing, a rotor, and a controlled bypass. The housing has an outer circumference for accepting drive force and chambers. The rotor has a connection to a camshaft coaxially located within the housing. The housing and the rotor define at least one vane separating a chamber in the housing into advance and retard chambers. The vane is capable of rotation to shift the relative angular position of the housing and the rotor. The controlled bypass provides fluid communication between the chambers. When the valve is closed, the valve blocks passage between the chambers and when the valve is open, fluid flows through the passage extending between the advance and the retard chamber, allowing the phaser to be rapidly actuated to a full retard position prior to peak valve lift, which then causes the camshaft torque to rapidly advance the phaser during the closing half of the valve event or zero lift.  
         [0010]     A method for varying the phase of the camshaft relative to the crankshaft with a variable cam timing phaser for an internal combustion engine is also disclosed. In a first step the duration, the phase of the cams camshaft relative to the crankshaft is changed, such that the duration of the valve opening is varied and the valve reaches a first center. In a second step, the phase is shifted in an opposite direction by operating the phaser during valve closing until the valve reaches a second center. The phase may be lengthened or shortened. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0011]      FIG. 1  is a graph showing valve timing characteristics.  
         [0012]      FIG. 2  shows a flowchart of the steps associated with cold-start cranking of the engine.  
         [0013]      FIG. 3  shows a flowchart of the steps associated with initial cold running of the engine.  
         [0014]      FIG. 4  shows a flowchart of the steps associated with hot idle condition of the engine.  
         [0015]      FIG. 5  shows a flowchart of the steps associated with low speed part-throttle condition of the engine.  
         [0016]      FIG. 6  shows a flowchart of how the conditions of the engine are related.  
         [0017]      FIG. 7   a  shows a schematic of a phaser with a pressure-actuated valve in the closed position.  FIG. 7   b  shows of a phaser with a pressure actuated valve in the open position.  
         [0018]      FIG. 8   a  shows a schematic of a phaser with a centrifugal valve in the vane in the closed position.  FIG. 8   b  shows a schematic of a phaser with a centrifugal valve in the vane in the open position.  
         [0019]      FIG. 9   a  shows a schematic of a phaser with high pressure and high response in the null position.  FIG. 9   b  shows a schematic of the phaser in the retard position.  FIG. 9   c  shows a schematic of the phaser in the advance position.  
         [0020]      FIG. 10   a  shows a schematic of a phaser with a centrifugal valve in a closed position connected to the advance and retard chambers outside of the vane.  FIG. 10   b  shows a schematic of a phaser with a centrifugal valve in an open position connected to the advance and retard chambers outside of the vane.  
         [0021]      FIG. 11   a  shows a schematic of a cam torque actuated phaser with passages or a bypass between the lands of the spool in the null position.  FIG. 11   b  shows a schematic of a cam torque actuated phaser with passages or a bypass between the lands of the spool in the advanced position.  FIG. 11   c  shows a schematic of a cam torque actuated phaser with passages or a bypass between the lands of the spool in the retard position.  FIG. 11   d  shows a schematic of a cam torque actuated phaser with passages or a bypass between the lands of the spool in a valve event duration reduction position.  
         [0022]      FIG. 12   a  shows a schematic of an oil pressure actuated phaser with passages or a bypass between the lands of the spool in the null position.  FIG. 12   b  shows a schematic of an oil pressure actuated phaser with passages or a bypass between the lands of the spool in the advanced position.  FIG. 12   c  shows a schematic of an oil pressure actuated phaser with passages or a bypass between the lands of the spool in the retard position.  FIG. 12   d  shows a schematic of an oil pressure actuated phaser with passages or a bypass between the lands of the spool in the valve event duration reduction position.  
         [0023]      FIG. 13   a  shows a schematic of a torsion assist phaser with passages or a bypass between the lands of the spool in the null position.  FIG. 13   b  shows a schematic of a torsion assist phaser with passages or a bypass between the lands of the spool in the advanced position.  FIG. 13   c  shows a schematic of a torsion assist phaser with passages or a bypass between the lands of the spool in the retard position.  FIG. 13   d  shows a schematic of a torsion assist phaser with passages or a bypass between the lands of the spool in the valve event duration reduction position.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     Referring to  FIGS. 1 through 6 , the steps for reducing the valve event duration are disclosed using a variable cam timing (VCT) phaser that may be actuated rapidly enough, such that the camshaft is set to the fully retard position prior to peak valve lift, which then causes the camshaft torque, oil pressure or a combination of both to rapidly advance the camshaft during the closing half of the valve event. Therefore, as shown in  FIG. 1 , the reduced valve event curve (shown by the dashed, dotted line) results and the opening of the valve is retarded the closing is advanced within one valve event.  
         [0025]     If no alterations were made to the valve event, typical opening and closing of the valve is shown by the normal valve event curve line illustrated as the unbroken line. If the opening of the valve is advanced, the valve opens earlier than the normal curve, and closes prior to the normal curve, as illustrated by the dotted line. If the opening of the valve is retarded, the valve opens later than the normal curve and closes after the normal curve, as illustrated by the dashed line. The reduced valve event curve that results from the method of the present invention is a combination of the retard valve event curve opening of the valve and the advance valve event closing of the valve, illustrated by the dashed, dotted line. As shown by the reduced valve event curve, the duration of the valve event is significantly shorter than the normal valve event, the reduced valve event, or the advance valve event.  
         [0026]      FIG. 6  shows the engine conditions and the relationship among the conditions. The first engine condition is cold-start cranking  100 . This condition occurs when the engine is started when it is “cold” and trying to turn over. After the engine has started, the engine is in initial cold running  200 , which includes the first several firing engine cycles. After the engine has been running for sometime, the engine is in hot idle condition  300 . In this condition, the engine is warm enough to vaporize liquid fuel droplets and an increase in speed is not present. Next, the engine is in low speed part-throttle condition  400 , which applies to the engine during an increase in speed, until the top speed of the engine is reached and valve event reduction may be accomplished.  
         [0027]      FIGS. 2 through 5  show individual steps of each of the engine conditions necessary to reduce the valve event duration.  FIG. 2  shows the steps for reducing the valve event duration during cold-start cranking  100 . During cold-start cranking of a conventional phaser, a compromise between the benefit of enhanced mixture preparation from the retarded intake valve opening and the deterioration of the combustion quality due to the reduced compression ratio from the retarded intake closing occurs. In the present invention, an emissions benefit is present for at least the first few cranking and firing cycles. The first step of when the engine is in the cold-start cranking condition  100  is to retard the intake valve opening (IVO) to the maximum limit of the phaser, such that the intake valve opening occurs after top dead center (TDC). This allows a period of high air velocity to move past the intake valve seat as the valve opens and the piston velocity is increasing, resulting in enhancement of fuel-air mixing when the engine components are too cold to thermally vaporize liquid fuel drops, yielding an improvement in hydrocarbon emissions during the first firing engine cycles. During the same engine cycle, the intake valve closing (IVC) is advanced, such that the closing of the valve is near bottom dead center (BDC). By closing the valve near bottom dead center, as much of the effective compression ratio is preserved as possible, which helps combustion since it maximizes the peak mixture temperature prior to ignition. If the engine is equipped with an exhaust cam phaser, the exhaust valve opening is retarded. This will reduce the valve overlap further and therefore the burned gas fraction, aiding in combustibility of the fuel/air mixture. The closing of the exhaust valve may also need to be advanced. If the engine has not sufficiently warmed enough to proceed to initial cold running, the steps shown in  FIG. 2  are repeated.  
         [0028]      FIG. 3  shows the steps for reducing the valve event duration during initial cold running  200  of the engine. The first step is to partially advance the intake valve opening to promote blowback or the back flow of the charge due to the movement of the air/fuel mixture through the intake valve and into the intake port. The intake valve closing would also be advanced partially. Assuming that the engine is equipped with an exhaust cam phaser, the exhaust valve closing is advanced. By promoting the blowback of the charge, which contains a portion of burned gas from the previous cycle, heating of the intake valve and vaporization of the fuel/air mixture is increased. If the engine is not sufficiently warmed enough to thermally vaporize liquid fuel droplets, the steps shown in  FIG. 3  are repeated.  
         [0029]      FIG. 4  shows the steps for reducing the valve event duration during hot idle  300  of the engine. The first step is to retard the intake valve opening (IVO) to the maximum limit of the phaser such that the intake valve opening occurs after top dead center (TDC). If the intake valve opening (IVO) occurs at or near top dead center, the intake valve closing (IVC) is advanced, such that the closing of the valve is near bottom dead center (BDC). By retarding the intake valve opening and advancing the intake valve closing, the combustion stability and fuel consumption, due to pumping losses, is improved. If the engine is equipped with an exhaust cam phaser, the exhaust valve opening is retarded. Next, the exhaust valve closing is advanced. The combination of the retarded exhaust valve opening and the advanced exhaust valve closing provides increased fuel economy and minimization of the burned gas fraction leading to good combustion stability. If the engine is still idling, the steps shown in  FIG. 4  are repeated, if not then the engine moves to the low speed part-throttle condition.  
         [0030]      FIG. 5  shows the steps for reducing valve event duration during the low speed part-throttle  400  condition of the engine. The low speed part-throttle condition of the engine applies up until the top speed of the reduction of the valve event duration may be accomplished, since it is limited by the dynamics of response of the phaser and the camshaft. First, the intake valve opening is retarded to the maximum limit of the phaser, such that the intake valve opening occurs after top dead center (TDC). During the same engine cycle, the intake valve closing (IVC) is advanced, such that the closing of the valve is near bottom dead center (BDC). Once the intake valve closing (IVC) occurs at or near bottom dead center (BDC), the exhaust valve opening is retarded. The exhaust valve closing is also retarded, thereby increasing valve overlap, which increases the exhaust gas ratio or high burn gas fraction reduces hydrocarbon emissions and improves fuel consumption  
         [0031]     The above steps for reducing the valve event duration may be applied to and carried out by the phasers shown in  FIGS. 7   a  through  13   d . The variable cam timing phasers shown in  FIGS. 7   a  through  13   d  may be actuated rapidly enough, such that the camshaft is moved to the full retard position prior to peak valve lift, which then causes the camshaft torque, oil pressure or a combination of both to rapidly advance the camshaft during the closing half of the valve event or zero lift.  
         [0032]      FIG. 7   a  shows a schematic of a cam torque actuated phaser in the null position with a pressure-actuated valve in the vane  506  in the closed position. In a conventional cam torque actuated phaser (CTA) torque reversals in the camshaft  530  caused by the forces of opening and closing engine valves move the vanes  506 . The control valve  536  in a CTA system allows the vanes  506  in the phaser to move by permitting fluid flow from the advance chamber  502  to the retard chamber  504  or vice versa, depending on the desired direction of movement. Cam torsionals are used to advance and retard the phaser (not shown). In the null position, the vane is locked in position. Makeup fluid is supplied to the phaser as is necessary.  
         [0033]      FIGS. 7   a  and  7   b  show the phaser in the null position, Fluid from a pressurized source supplies line  518 , through check valve  520  to the spool valve or the control valve  536  with makeup fluid only. The spool valve  536  may be internally or externally mounted and comprises a sleeve  524  for receiving a spool  509  with lands  509   a ,  509   b  and a biasing spring  522 . An actuator  503 , which is controlled by the ECU  501 , moves the spool  509  within the sleeve  524 . From the spool valve  536 , fluid enters supply line  516 , which branches and leads to advance line  512  and retard line  513  and to the chambers  502 ,  504  through check valves  514 ,  515 .  
         [0034]     A pressure actuated valve, including a piston  526  biased by spring  528  is housed in an axial bore  532  of the vane  506 . The vane  506  also includes a passage  534  extending across the vane  506  from the advance chamber  502  to the retard chamber  504 , with the axial bore  532  connected to the passage  534  between the chambers  502 , 504 . The pressure actuated valve is supplied by an on/off solenoid valve  510  connected to a pressurized source. The control of the pressure-actuated valve is independent of spool valve  509  control and position of the vane  506  itself. When the pressure-actuated valve is closed, no fluid is supplied from the on/off solenoid  510  to the axial bore  532  in the vane  506  through line  508 . Furthermore, piston  526  of pressure actuated valve blocks the passage  534  and prevents any fluid from traveling between the advance chamber  502  and the retard chamber  504  through the passage  534 .  
         [0035]      FIG. 7   b  shows of a schematic of a phaser with a pressure-actuated valve in the open position. To open the pressure-actuated valve, the on/off solenoid  510  provides fluid to the axial bore  532  of the vane  506  via line  508 . The pressure of the fluid is greater than the force of the spring  528  and the piston  526  retracts, allowing fluid passage between the advance chamber  502  and the retard chamber  504  through passage  534 . When fluid passage is allowed between the advanced chamber  502  and the retard chamber  504 , the camshaft  530  is retarded by negative cam torque prior to the valve opening and fluid is allowed to flow from the retard chamber  504  to the advance chamber  502 . After the peak valve lift, the positive cam torque, due to the valve spring acting on the cam lobe (not shown), advances the cam during the closing half of the valve event and fluid flows from the advance chamber  502  back to the retard chamber  504 . In other words, the phaser is actuated rapidly enough such that the camshaft is moved to the full retard position prior to peak valve lift, which then causes the camshaft torque to rapidly advance the camshaft during the closing half of the valve event or zero lift.  
         [0036]     The pressure-actuated valve may also be added to the vane of an oil pressure actuated phaser and a torsion assist phaser.  
         [0037]      FIG. 8   a  shows a schematic of a cam torque actuated phaser in the null position with a centrifugal valve in the vane  606  in the closed position. In a conventional cam torque actuated phaser (CTA) torque reversals in the camshaft  630  caused by the forces of opening and closing engine valves move the vanes  606 . The control valve in a CTA system allows the vanes  606  in the phaser to move by permitting fluid flow from the advance chamber  602  to the retard chamber  604  or vice versa, depending on the desired direction of movement. Cam torsionals are used to advance and retard the phaser (not shown). In the null position, the vane is locked in position. Makeup fluid is supplied to the phaser as is necessary.  
         [0038]      FIGS. 8   a  and  8   b  show the phaser in the null position. Fluid from a pressurized source supplies line  618 , through check valve  620  to the spool valve or control valve  636  with makeup fluid only. The spool valve  636  may be internally or externally mounted and comprises a sleeve  624  for receiving a spool  609  with lands  609   a ,  609   b  and a biasing spring  622 . An actuator  603 , which is controlled by the ECU  601 , moves the spool  609  within the sleeve  624 . From the spool valve  636 , fluid enters supply line  616 , which branches and leads to advance line  612  and retard line  613  and to the chambers  602 ,  604  through check valves  614 ,  615 .  
         [0039]     A centrifugal valve, including a piston  626  biased by a spring  628  is housed in an axial bore  632  of the vane  606 . The vane  606  also includes a passage  634  extending across the vane  606  from the advance chamber  602  to the retard chamber  604 , with the axial bore  632  connected to the passage  634  between the chambers  602 , 604 . The centrifugal valve remains closed during high engine speeds, since the centrifugal force, indicated by arrow F, is great enough to bias spring  628 . When the centrifugal valve is closed, piston  626  blocks the passage  634  and prevents any fluid from traveling between the advance chamber  602  and the retard chamber  604  through the passage  634 .  
         [0040]     The centrifugal valve is open during low engine speeds, since the centrifugal force is not greater than the biasing force of spring  628 , as shown in  FIG. 8   b . With the centrifugal valve in the open position, fluid may pass between the advance chamber  602  and the retard chamber  604  through passage  634 . When fluid passage is allowed between the advanced chamber  602  and the retard chamber  604 , the camshaft  630  is retarded by negative cam torque prior to the valve opening and fluid is allowed to flow from the retard chamber  604  to the advance chamber  602 . After the peak valve lift, the positive cam torque, due to the valve spring acting on the cam lobe (not shown), advances the cam during the closing half of the valve event and fluid flows from the advance chamber  602  back to the retard chamber  604 . In other words, the phaser is actuated rapidly enough such that the camshaft is moved to the full retard position prior to peak valve lift, which then causes the camshaft torque to rapidly advance the phaser during the closing half of the valve event or zero lift. The position of the spool  609  is independent of whether the centrifugal valve is open or closed.  
         [0041]     The centrifugal valve may also be added to the vane of an oil pressure actuated phaser and a torsion assist phaser.  
         [0042]      FIGS. 9   a - 9   c  show an extremely high pressure, high response, oil pressure actuated phaser in the null position, the retard position, and the advance position. The high pressure and high response of the phaser allows the phaser to be actuated rapidly enough, such that the camshaft is moved to the full retard position prior to peak valve lift, which then causes the camshaft torque to rapidly advance the camshaft during the closing half of the valve event or zero lift. In oil pressure actuated phasers, engine oil pressure is applied to the advance chamber or the retard chamber, moving the vane. The control valve  721  may be internally or externally mounted and includes an actuator  703 , which is controlled by an ECU (not shown), that moves the spool  709  with lands  709   a ,  709   b  within the sleeve  724  against the force of spring  722 . Fluid from a highly pressurized, high response pump is supplied to the control valve by supply line  718 . In the case of the null position, as shown in  FIG. 9   a , spool lands  709   a  and  709   b  block lines  714 ,  715 ,  716 ,  717  to the advance and retard chambers  702 ,  704 .  
         [0043]     When the phaser is in the retard position, shown in  FIG. 9   b , fluid from the spool valve enters  721  line  717  which leads to retard line  713  and the retard chamber  704 . As the retard chamber  704  fills, the vane  706  moves to the left (as shown in this figure), causing the fluid in the advance chamber  702  to exit by advance line  712  to line  714  and to sump via line  719 . Line  715  and line  720  to sump are blocked by spool land  709   b . Line  716  is blocked by spool land  709   a.    
         [0044]     When the phaser is in the advance position, shown in  FIG. 9   c , fluid from the spool valve  721  enters line  716 , which leads to advance line  712  and the advance chamber  702 . As the advance chamber  702  fills, the vane  706  moves to the right (as shown in this figure), causing the fluid in the retard chamber  704  to exit by retard line  713  to line  715  and to sump via line  720 . Line  714  and line  719  to sump are blocked by spool land  709   a . Line  717  is blocked by spool land  709   b.    
         [0045]     Alternatively, a check valve may be added to supply line  718 .  
         [0046]      FIG. 10   a  shows a schematic of a cam torque actuated phaser in the null position with a centrifugal valve located in the housing  850  or outside of the phaser in the closed position. In a conventional cam torque actuated phaser (CTA) torque reversals in the camshaft  830  caused by the forces of opening and closing engine valves move the vanes  806 . The control valve in a CTA system allows the vanes  806  in the phaser to move by permitting fluid flow from the advance chamber  802  to the retard chamber  804  or vice versa, depending on the desired direction of movement. Cam torsionals are used to advance and retard the phaser (not shown). In the null position, the vane is locked in position. Makeup fluid is supplied to the phaser as is necessary.  
         [0047]      FIGS. 10   a  and  10   b  show the phaser in the null position. Fluid from a pressurized source supplies line  818  through check valve  820  to the spool valve  836  with makeup fluid only. The spool valve  836  may be internally or externally mounted and comprises a sleeve  824  for receiving a spool  809  with lands  809   a ,  809   b , and a biasing spring  822 . An actuator  803 , which is controlled by the ECU  801 , moves the spool  809  within the sleeve  824 . From the spool valve  836 , fluid enters supply line  816 , which branches and leads to advance line  812  and retard line  813 , and to the chambers  802 ,  804  through check valves  814 ,  815 .  
         [0048]     A centrifugal valve, including a piston  826  biased by a spring  828  is housed in a bore  832  in the housing  850  or outside of the phaser. A passage or bypass  834  extends from the centrifugal valve to the advance chamber  802  and from the valve to the retard chamber  804 . The centrifugal valve remains closed during high engine speeds, since the centrifugal force, indicated by arrows F, is great enough to bias spring  828 . When the centrifugal valve is closed, piston  826  blocks the passage  834  and prevents any fluid from traveling between the advance chamber  802  and the retard chamber  804  through passage  834 .  
         [0049]     The centrifugal valve is open during low engine speeds, since the centrifugal force F is not greater than the biasing force of the spring  828 , as shown in  FIG. 10   b . With the centrifugal valve in the open position, fluid may pass between the advance chamber  802  and the retard chamber  804  through passage  834 . When fluid passage is allowed between the advanced chamber  802  and the retard chamber  804 , the camshaft  830  is retarded by negative cam torque prior to the valve opening and fluid is allowed to flow from the retard chamber  804  to the advance chamber  802 . After the peak valve lift, the positive cam torque, due to the valve spring acting on the cam lobe (not shown), advances the cam during the closing half of the valve event and fluid flows from the advance chamber  802  back to the retard chamber  804 . In other words, the phaser is actuated rapidly enough such that the camshaft is moved to the full retard position prior to peak valve lift, which then causes the camshaft torque to rapidly advance the camshaft during the closing half of the valve event or zero lift. The position of the spool  809  is independent of whether the centrifugal valve is open or closed.  
         [0050]     The centrifugal valve may also be added to the housing or outside of an oil pressure actuated phaser or a torsion assist phaser.  
         [0051]      FIGS. 11   a - 11   d  shows schematics of a cam torque actuated phaser with an extended spool position or a valve event duration reduction (VEDR) position that reduces the valve event, by allowing rapid actuation of the camshaft to a full retard position and prior to peak valve lift, which then causes the camshaft torque to rapidly advance the camshaft during the closing half of the valve event. The housing, the rotor, the vane and the actuating means for the spool valve have not been shown.  
         [0052]      FIG. 11   a  shows the phaser in the null position. In the null position, fluid is prevented from flowing out of the advanced chamber  902  and the retard chamber  904  by spool lands  909   a  and  909   b  respectively. In a conventional cam torque actuated phaser, torque reversals in the camshaft caused by the forces of opening and closing engine valves move the vanes. The control valve  936  in a CTA system allows the vanes in the phaser to move by permitting fluid flow from the advance chamber  902  to the retard chamber  904  or vice versa, depending on the desired direction of movement. Cam torsionals are used to advance and retard the phaser (not shown). In the null position, the vane is locked in position. Makeup fluid is supplied to the phaser as is necessary.  
         [0053]     In the VEDR position, shown in  FIG. 11   d , the phaser is moved to a full retard position prior to peak valve lift, which then causes the camshaft torque to rapidly advance the camshaft during the closing half of the valve event or zero lift without having to move the spool position shown by the flow of fluid.  
         [0054]     For the retarding of the phaser, fluid moves from the advance chamber  902  through line  912  to the spool valve  926 . Fluid can flow to the retard chamber  904  by two different routes. In one route, fluid enters line  916  and through check valve  915  to line  913  and the retard chamber  904 . In another route, fluid moves into a series of passages or a spool bypass  911 , which routes fluid to line  913  and to the retard chamber  904 . The spool bypass  911  extends from the spool body  909   c  defined between the first land  909   a  and the second land  909   b , to the second spool land  909   b . The spool bypass  911  is comprised of a first spool bypass portion  911   a  along the center of the spool body  909   c  extending the entire circumference of the spool body  909   c . The first spool bypass portion  911   a  is in fluid communication with a second spool bypass portion  911   b  that extends from the first spool bypass portion  911   a  to a third bypass portion  911   c  in the second land  909   b . The third spool bypass portion  911   c  extends the entire circumference of the second spool land  909   b . From the third spool bypass portion  911   c  fluid flows to line  913  and to the retard chamber  904 .  
         [0055]     The phaser is then rapidly actuated to an advanced position. Fluid can flow to the advance chamber  902  by two different routes. In one route, fluid exits the retard chamber  904  through line  913  to the third spool bypass portion  911   c . Fluid moves from the third spool bypass portion  911   c  to the second spool bypass portion  911   b  and to the first spool bypass portion  911   a . From the first spool bypass portion  911   a , fluid moves into line  916 , through check valve  914  to line  912  and the advance chamber  902 . In another route, fluid moves through the third spool bypass portion  911   c  to the second spool bypass portion  911   b  to the first spool bypass portion  911   a . From the first spool bypass portion  911   a  fluid moves into line  912  and to the advance chamber  902 .  
         [0056]     In  FIG. 11   b , the advanced position shown does not receive fluid from the spool bypass  911 . As in a conventional cam torque actuated phaser, the spool is positioned such that spool land  909   a  blocks the exit of fluid from line  912 , and lines  913  and  916  are open. Camshaft torque pressurizes the advance chamber  902 , causing fluid in the retard chamber  904  to move into the advance chamber  902 . Fluid exiting the retard chamber  904  moves through line  913  and into the spool valve  936  between lands  909   a  and  909   b . From the spool valve, the fluid enters line  916  and travels through open check valve  914  and into line  912  to the advance chamber  902 .  
         [0057]      FIG. 11   c  shows the retard position, which also does not receive fluid from the spool bypass  911 . As in a conventional cam torque actuated phaser, the spool is positioned such that spool land  909   b  blocks the exit of fluid from line  913 , and lines  912  and  916  are open. Camshaft torque pressurizes the retard chamber  904 , causing fluid in the advance chamber  902  to move into the retard chamber  904 . Fluid exiting the advance chamber  902  moves through line  912  and into the spool valve  936  between spool lands  909   a  and  909   b . From the spool valve, the fluid enters line  916  and travels through open check valve  915  and into line  913  to the retard chamber  904 .  
         [0058]     Makeup oil is supplied to the phaser by supply line  937 , which is connected to a pressurized source of fluid.  
         [0059]      FIGS. 12   a - 12   d  show schematics of an oil pressure actuated phaser with an extended spool position or a valve event duration reduction (VEDR) position that reduces the valve event, by allowing rapid actuation of the camshaft to a full retard position and prior to peak valve lift, which then causes the oil pressure to rapidly advance the camshaft during the closing half of the valve event. The housing, the rotor, the vane and the actuating means for the spool valve have not been shown.  
         [0060]      FIG. 12   a  shows the phaser in the null position. In the null position, fluid is prevented from flowing out of the advanced chamber  702  and the retard chamber  704  by spool lands  709   b  and  709   c  respectively. In a conventional oil pressure actuated phaser, fluid from the pressurized source is used to move the vanes.  
         [0061]     In the VEDR position, shown in  FIG. 12   d , the phaser is moved to a full retard position prior to peak valve lift, which then causes the oil pressure to rapidly advance the camshaft during the closing half of the valve event or zero lift without having to move the spool position without having to move the spool position shown by the flow of fluid.  
         [0062]     For retarding of the phaser, fluid moves from the advanced chamber  702  through line  712  to line  716 . From line  716  fluid enters a series of passages or a spool bypass  725 , which routes fluid to line  717  and to the retard chamber  704 . The spool bypass  725  extends from the spool body  709   d  defined between the second land  709   b  and the third land  709   c , to the second spool land  709   b . The spool bypass  725  is comprised of a first spool bypass portion  725   a  along the center of the spool body  709   c , defined between the second land  709   b  and the third land  709   c , extending the entire circumference of the spool body  709   d . The first spool bypass portion  725   a  is in fluid communication with a second spool bypass portion  725   b  that extends from the first spool bypass portion  725   a  to a third bypass portion  725   c  in the second land  709   b . The third spool bypass portion  725   c  extends the entire circumference of the second spool land  709   b . From the third spool bypass portion  725   c  fluid flows to line  717  and to the retard chamber  704 . Fluid is also supplied from the pressurized source through line  718 .  
         [0063]     The phaser is then rapidly actuated to an advanced position. Fluid exits the retard chamber  704  through line  713  to line  717  and the spool valve  721 . From line  717  fluid enters a series of passages or a spool bypass  725 , which routes fluid to line  716  and to the advance chamber  702 . Fluid moves from the third spool bypass portion  725   c  to the second spool bypass portion  725   b  and to the first spool bypass portion  725   a . From the first spool bypass portion  725   a , fluid moves into line  716  and to the advance chamber  702 . Spool land  709   a  blocks fluid from entering the spool valve  721  from line  714  and exhausting to sump through line  719  and spool land  709   c  blocks fluid from entering or exiting the spool valve  721  from line  715  and exhausting to sump through line  720 . Fluid is also supplied from the pressurized source through line  718 .  
         [0064]     In  FIG. 12   b , the advanced position shown does not receive fluid from the third spool bypass portion  725   c . Instead, fluid is supplied from a pressurized source through line  718  to the spool valve. In the spool valve, fluid travels through the first spool bypass portion to line  716  and  712  to the advance chamber  702 . Fluid in the retard chamber  704  exits the chamber through lines  713  and  715  to the spool valve  721  and then to line  720  leading to sump. Spool land  709   b  blocks fluid from entering or exiting the spool valve  721  from line  714  and exhausting to sump through line  719  and spool land  709   c  blocks fluid from entering or exiting the spool valve  721  from line  717 .  
         [0065]      FIG. 12   c  shows the oil pressure actuated phaser in the retard position. Fluid from supply line  718  enters the spool valve  721  and moves through the first portion of the spool bypass  725  to line  717  and then to line  713 , leading to the retard chamber  704 . Fluid from the advance chamber  702  exits the chamber through line  712  and  714  to the spool valve  721 . Fluid in the spool valve  721  moves through a first portion of an exhaust bypass  735   a  defined as the spool body  709   d  between the first land  709   a  and the second land  709   b . The exhaust bypass first portion is in fluid communication with an exhaust bypass second portion which extends through the center and leads to the end of spool land  709   a . Fluid moves through the exhaust bypass first portion  735   a  to line  719  and sump or through the exhaust bypass second portion  735   b  leading to atmosphere. Spool land  709   b  blocks fluid from entering or exiting line  716  and spool land  709   c  blocks fluid from entering or exiting line  715  or exhausting to sump through line  720 .  
         [0066]      FIGS. 13   a  through  13   d  show schematics of a torsion assist phaser with an extended spool position or a valve event duration reduction (VEDR) position that reduces the valve event, by allowing rapid actuation of the camshaft to a full retard position and prior to peak valve lift, which then causes a combination or both camshaft torque and oil pressure to rapidly advance the camshaft during the closing half of the valve event. The housing, the rotor, the vane and the actuating means for the spool valve have not been shown.  
         [0067]      FIG. 13   a  shows the phaser in the null position. In the null position, fluid is prevented from flowing out of the advanced chamber  702  and the retard chamber  704  by spool lands  709   b  and  709   c  respectively. In a conventional torsion assist phaser, fluid from the pressurized source and an inlet check valve  1001  is used to move the vanes.  
         [0068]     In the VEDR position, shown in  FIG. 13   d , the phaser is moved to a full retard position prior to peak valve lift, which then causes both camshaft torque and oil pressure to rapidly advance the camshaft during the closing half of the valve event or zero lift without having to move the spool position show by the flow of fluid.  
         [0069]     For retarding of the phaser, fluid moves from the advanced chamber  702  through line  712  to line  716 . From line  716  fluid enters a series of passages or a spool bypass  725 , which routes fluid to line  717  and to the retard chamber  704 . The spool bypass  725  extends from the spool body  709   d  defined between the second land  709   b  and the third land  709   c , to the second spool land  709   b . The spool bypass  725  is comprised of a first spool bypass portion  725   a  along the center of the spool body  709   c , defined between the second land  709   b  and the third land  709   c , extending the entire circumference of the spool body  709   d . The first spool bypass portion  725   a  is in fluid communication with a second spool bypass portion  725   b  that extends from the first spool bypass portion  725   a  to a third bypass portion  725   c  in the second land  709   b . The third spool bypass portion  725   c  extends the entire circumference of the second spool land  709   b . From the third spool bypass portion  725   c  fluid flows to line  717  and to the retard chamber  704 . Fluid is also supplied from the pressurized source through line  718  and inlet check valve  1001 .  
         [0070]     The phaser is then rapidly actuated to an advanced position. Fluid exits the retard chamber  704  through line  713  to line  717  and the spool valve  721 . From line  717  fluid enters a series of passages or a spool bypass  725 , which routes fluid to line  716  and to the advance chamber  702 . Fluid moves from the third spool bypass portion  725   c  to the second spool bypass portion  725   b  and to the first spool bypass portion  725   a . From the first spool bypass portion  725   a , fluid moves into line  716  and to the advance chamber  702 . Spool land  709   a  blocks fluid from entering the spool valve  721  from line  714  and exhausting to sump through line  719  and spool land  709   c  blocks fluid from entering or exiting the spool valve  721  from line  715  and exhausting to sump through line  720 . Fluid is also supplied from the pressurized source through line  718  and inlet check valve  1001 .  
         [0071]     In  FIG. 13   b , the advanced position shown does not receive fluid from the third spool bypass portion  725   c . Instead, fluid is supplied from a pressurized source through line  718  and an inlet check valve  1001  to the spool valve  721 . In the spool valve, fluid travels through the first spool bypass portion to line  716  and  712  to the advance chamber  702 . Fluid in the retard chamber  704  exits the chamber through lines  713  and  715  to the spool valve  721  and then to line  720  leading to sump. Spool land  709   b  blocks fluid from entering or exiting the spool valve  721  from line  714  and exhausting to sump through line  719  and spool land  709   c  blocks fluid from entering or exiting the spool valve  721  from line  717 .  
         [0072]      FIG. 13   c  shows the torsion assist phaser in the retard position. Fluid from supply line  718  and an inlet check valve  1001  enters the spool valve  721  and moves through the first portion of the spool bypass  725  to line  717  and then to line  713 , leading to the retard chamber  704 . Fluid from the advance chamber  702  exits the chamber through line  712  and  714  to the spool valve  721 . Fluid in the spool valve  721  moves through a first portion of an exhaust bypass  735   a  defined as the spool body  709   d  between the first land  709   a  and the second land  709   b . The exhaust bypass first portion  735   a  is in fluid communication with an exhaust bypass second portion  735   b  which extends through the center of and leads to the end of spool land  709   a . Fluid moves through the exhaust bypass first portion  735   a  to line  719  and sump or through the exhaust bypass second portion  735   b  leading to atmosphere. Spool land  709   b  blocks fluid from entering or exiting line  716  and spool land  709   c  blocks fluid from entering or exiting line  715  or exhausting to sump through line  720 .  
         [0073]     Alternatively, the valve event may be extended by advancing the opening of the valve and retarding the closing of the valve as shown in  FIG. 1  by the dotted, dashed line. Furthermore, during cold-start cranking the intake valve opening would be advanced and the intake valve closing would be retarded. During initial cold running, the intake valve opening is partially retarded. During hot idle, the intake valve opening would be advanced and the intake valve closing would be retarded. During low speed part-throttle, the intake valve opening would be advanced and the intake valve closing would be retarded.  
         [0074]     Any of the phasers shown in  FIGS. 7   a  through  13   d  may be used to lengthen or extend the valve event.  
         [0075]     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.