Abstract:
A variable valve timing system includes a toothed rotating sleeve, a rack, and an actuator. The rack has a first end, a second end with a plurality of teeth in meshing contact with the teeth of rotating sleeves of the valve and being linearly moveable to rotate the sleeves. The actuator includes a housing, a control valve, and at least one check valve. The housing slidably receives a piston coupled to the rack separating a chamber in the housing into first and second chambers. The control valve selectively directs fluid from the first to the second chamber or vice versa. When the rack is shifted linearly by vibrational impulses from the engine, the piston moves linearly within the housing, pressurizing the first or the second chamber and under control of the control valve, fluid recirculates from the first or the second chamber to the other chamber.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims an invention which was disclosed in Provisional Application No. 60/694,172, filed Jun. 27, 2005, entitled “ACTUATOR AND CONTROL METHOD FOR VARIABLE VALVE TIMING (VVT) MECHANISM”. The benefit under 35 USC § 119(e) of the U.S. provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention pertains to the field of variable valve timing mechanisms. More particularly, the invention pertains to an actuator and control method for a variable valve timing mechanism. 
         [0004]    2. Description of Related Art 
         [0005]    Internal combustion engines have employed various mechanisms to vary the valve timing. Examples of varying the valve timing include varying the shape of the cam; varying the relationship of the cam lobes to the cam, such as in a camshift device disclosed in U.S. Pat. No. 5,913,292; varying the relationship between the valve actuators and cam or valves; or individually controlling the valves themselves using electrical or hydraulic actuators. 
         [0006]    SAE Paper No. 2003-01-0037, entitled “Application of a Simple Mechanical Phasing Mechanism for Independent Adjustment of Valves in a Pushrod Engine,” discloses a valve timing mechanism that uses an eccentric sleeve to alter the geometric relationship between the lifter roller and the cam lobe. As the eccentric sleeve is rotated by a worm drive, the lifter translates relative to the cam lobe. This movement either advances or retards the valve timing. The eccentricity and the sleeve rotation angle determine the range of the phasing. 
         [0007]    U.S. Pat. No. 5,111,781 discloses a rocker shaft in which rotation is caused by a hydraulic cylinder actuated by oil pressure. The hydraulic cylinder has two ports, a low speed oil port and a high speed oil port. Within the hydraulic cylinder is a piston coupled to a rack meshed with a pinion formed on the end of the rocker shaft. The rocker shaft, rack and pinion are all located in a central chamber of the cylinder head. When the engine is running at low speed, oil enters the low speed oil port and retracts the rack, causing the pinion to rotate counterclockwise. When the engine is running at intermediate/high speed, oil enters the high speed oil port and extends the rack, causing the pinion to rotate clockwise. 
         [0008]    U.S. Pat. No. 5,666,913 discloses a cam follower lever assembly which includes a timing control lever and a force transmitting lever mounted for pivotal movement on a common pivot shaft. The timing control lever is also mounted to non-pivotal movement relative to the pivot shaft by a hydraulic actuation device. The actuation device includes actuator cavities formed in the levers and a control valve arrangement including a plunger with lands biased by a coil spring in a valve cavity. A pressure regulator is also present in the force transmitting lever. An increase in the force on the pressure regulator causes fluid to move the plunger, allowing fluid to flow to or from actuator cavities, advancing or retarding the timing of the fuel injection and causing the timing control lever to shift along the outer surface of the cam in either a counterclockwise or clockwise direction. The control valve and the timing control lever act as a hydraulic servo type valve. 
         [0009]    U.S. Pat. No. 6,155,216 discloses a rotatable eccentric sleeve that allows the position of the cam follower to be altered and thus alter the timing of the opening and closing of the valve events. In one embodiment, the eccentric sleeves have gear teeth incorporated around the outside and a toothed rack moves fore and aft to rotate the sleeves. In another embodiment, the eccentric sleeve has worm gear teeth incorporated around the outside and a worm drive rotates the sleeves. 
         [0010]    Japanese Publication No. 07-026926 discloses a valve that is opened and closed by a cam plunger with the use of hydraulic oil pressurized by reciprocation of the cam plunger in association with the rotation of a cam. A sleeve, formed therein with a central hole, has an inclined surface and is fitted on the outer periphery of the cam plunger. This sleeve is rotated by axially sliding a rack, which is meshed with a gear part formed on the outer peripheral surface of the lower part of the sleeve. 
       SUMMARY OF THE INVENTION 
       [0011]    A variable valve timing system for altering valve timing of an internal combustion engine having at least one camshaft and a plurality of valves having a valve stem with a valve head including a toothed rotating sleeve, a rack, and an actuator. The rotating sleeve has a plurality of teeth around at least part of its circumference; rotatably mounted on each valve stem about an axis and has an a valve lifter mounted on an upper surface off of an axis of rotation. The rack has a first end, a second end with a plurality of teeth in meshing contact with the teeth of the rotating sleeves and being linearly moveable to rotate the sleeves. The actuator includes a housing, a control valve and at least one check valve. The housing has a chamber for slidably receiving a piston coupled to the rack. The piston separates the chamber into a first fluid chamber and a second fluid chamber. The control valve directs fluid flow between the first and second chambers, selectively directing fluid from the first chamber to the second chamber or vice versa. In between the first and second chambers and the control valve is at least one check valve for blocking reverse fluid flow. 
         [0012]    When the rack is shifted linearly by vibrational impulses from the engine, the piston moves linearly within the housing, pressurizing the first chamber or the second chamber and under control of the control valve, fluid recirculates from the first chamber or the second chamber to the other chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1   a  shows a schematic of an actuator and the valves. 
           [0014]      FIG. 1   b  shows a schematic of the contact between the lifters and the camshaft. 
           [0015]      FIG. 2   a  shows a schematic of the variable valve timing (VVT) actuator of the first embodiment in a first position. 
           [0016]      FIG. 2   b  shows a schematic of the variable valve timing (VVT) actuator of the first embodiment in a second position. 
           [0017]      FIG. 2   c  shows a schematic of the variable valve timing (VVT) actuator of the first embodiment in a third, null position. 
           [0018]      FIG. 3   a  shows a variable valve timing (VVT) actuator of the second embodiment in a first position. 
           [0019]      FIG. 3   b  shows a variable valve timing (VVT) actuator of the second embodiment in a second position. 
           [0020]      FIG. 3   c  shows a variable valve timing (VVT) actuator of the second embodiment in a third, null position. 
           [0021]      FIG. 4   a  shows an actuator of the third embodiment in a first position. 
           [0022]      FIG. 4   b  shows an actuator of the third embodiment in a second position. 
           [0023]      FIG. 5  shows a control loop of the present invention. 
           [0024]      FIG. 6   a  shows an actuator of a fourth embodiment with the position setter on the control sleeve in a first position and the spool in the null position. 
           [0025]      FIG. 6   b  shows the actuator of the fourth embodiment with the position setter on the control sleeve in a second position and the spool in a second position. 
           [0026]      FIG. 6   c  shows the actuator of the fourth embodiment with the position setter on the control sleeve in a second position and the spool in the null position. 
           [0027]      FIG. 7  shows an alternate cam profile and actuation of the lifters. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]      FIG. 1   a  shows a camshaft  126  with a plurality of lobes  129  spaced apart a distance that contact the lifters  130  mounted off of an axis of rotation on the upper surface of concentric sleeves  128 , which are rotatably mounted on valve stems  134  with valve heads  136  about an axis. The outer circumference of the concentric sleeves  128  have gear teeth  132  that mesh with teeth  107   a  of rack  107 . Rack  107  is connected to an actuator  100 . The actuator  100  in combination with the position of the rack  107  changes the valve timing. The linear or reciprocating movement of the rack  107  back and forth between a first position and a second position provides the energy needed to move the oil from a first chamber to a second chamber or vice versa. Since the sleeve  128  is adjusting the position of the lifter  130 , the sleeve  128  and rack  107  both have to resist the torsional force from the camshaft and other valve train components. The position of the rack  107  is controlled using oscillatory, vibrational, or reciprocating force of the sleeve  128  acting on the rack  107 , which moves the rack  107  linearly and the actuator  100 . The actuator  100  is preferably chosen from the actuators including actuator  150 , shown in  FIGS. 2   a  and  2   b , actuator  250 , shown in  FIGS. 3   a  and  3   b , actuator  450  shown in  FIGS. 4   a  and  4   b , or actuator  350  shown in  FIGS. 6   a ,  6   b , and  6   c.    
         [0029]      FIG. 1   b  shows the movement of the lifter  130  from a first position shown by a solid line circle to a second position indicated in the figure by a dashed circle. The movement of the lifter  130 , moves the rack  107  through the meshing of gear teeth  132  and rack teeth  107   a . The lifter&#39;s range of movement relative to the cam lobe  129  is shown by distance D. The lifter  130  travels a rotational distance of D and moves perpendicular to the axis of rotation  160 . 
         [0030]    In a first embodiment, shown in  FIGS. 2   a ,  2   b , and  2   c , one end of the rack  107 , opposite the end including teeth  107   a  meshed with the gear teeth  132  of the concentric sleeves  128  of the lifters is connected to a piston  108  slidably received in housing  10 . The piston  108  divides the housing into two chambers  101   a ,  101   b . Fluid can not directly flow between the chambers  101   a ,  101   b . Seals  110   a  on the entry and exit points of the rack  107  and housing  110  interface prevent fluid leakage from the chambers  101   a ,  101   b  as the rack  107  moves linearly back and forth. The end of the rack opposite the end with teeth  107   a  is preferably connected to a position sensor  106 . The position sensor  106  is connected to the engine control unit (ECU)  102 , which influences the variable force solenoid  103 , biasing the control valve  104 , preferably a spool valve in a first direction. The spool  109  with lands  109   a ,  109   b , and  109   c  is slidably received in a bore  125  of an engine block. A spring  105  biases the spool in a second direction, opposite the first direction. 
         [0031]    When the rack  107  is linearly moved to a first position by the rotational force of the concentric sleeves  128 , piston  108  coupled to the rack  107  is also moved. The position and the reciprocating motion of the rack  107  pressurizes one of the chambers  101   a ,  101   b  on either side of the piston  108 . The position of the rack  107  is then reported to the ECU  102  by the position sensor  106  on the rack  107 . The ECU  102  uses the position sensor  106  information to influence the variable force solenoid (VFS)  103 . The VFS  103  in turn may or may not bias the spool  109  of the control valve  104  against the force of spring  105 , allowing the flow of fluid from one chamber  101   a ,  101   b  to the other chamber  101   a ,  101   b.    
         [0032]    The pressurization of the first chamber  101   a  causes fluid in the first chamber  101   a  to move into the second chamber  101   b , moving the piston  108  to the position shown in  FIG. 2   a . The position of the rack  107  is then reported to the ECU  102  and the spool  109  is moved by the force of the spring  105 , which is greater than the force of the variable force solenoid  103 , biasing the spool to the left in the figure until the force of the spring  105  balances the force of the VFS  103 . In the position shown, spool land  109   b  blocks second line  113 , extending from the spool valve  104  to the second chamber  101   b  and a first line  112 , extending from the spool valve  104  to the first chamber  101   a  and central line  116  are open. Fluid exiting the first chamber  101   a  moves through first line  112  and into spool valve  104  between spool lands  109   a  and  109   b . From the spool valve  104 , fluid moves back into central line  116 , through check valve  115  and into second line  113  supplying and recirculating fluid to the second chamber  101   b . As fluid enters the second chamber  101   b , the piston  108  and thus the rack  107  are further moved to the left in the figure. 
         [0033]    Makeup oil is supplied to the actuator  150  from supply S to make up for leakage only and enters line  118  and moves through inlet check valve  119  to the spool valve  104 . From the spool valve fluid, enters center line  116  through either of the check valves  114 ,  115 , depending on which is open to either the first chamber  101   a  or the second chamber  101   b.    
         [0034]    The pressurization of the second chamber  101   b  causes fluid in the second chamber  101   b  to move into the first chamber  101   a , moving the piston  108  to the position shown in  FIG. 2   b . The position of the rack  107  is then reported to the ECU  102  and the spool  109  is moved by the force of variable force solenoid  103 , which is greater than the force of spring  105 , biasing the spool to the right in the figure, until the force of the spring  105  balances the force of the VFS  103 . In the position shown, spool land  109   a  blocks first line  112 , and second line  113  and central line  116  are open. Fluid exiting the second chamber  101   b  moves through second line  113  and into spool valve  104  between spool lands  109   a  and  109   b . From the spool valve  104 , fluid moves back into central line  116 , through check valve  114  and into first line  112  supplying and recirculating fluid to the first chamber  101   a . As fluid enters the first chamber  101   a , the piston  108  and thus the rack  107  are moved further to the right in the figure. 
         [0035]    Makeup oil is supplied to the actuator  150  from supply S to make up for leakage only and enters line  118  and moves through inlet check valve  119  to the spool valve  104 . From the spool valve, fluid enters central line  116  through either of the check valves  114 ,  115 , depending on which is open to either the first chamber  101   a  or the second chamber  101   b.    
         [0036]      FIG. 2   c  shows the actuator in a third position or null position. In this position, spool land  109   a  blocks line  112  and spool land  109   b  blocks line  113 , locking the actuator in position. 
         [0037]    The combination of the pressurization of the chambers  101   a ,  101   b  by the motion of the rack  107  and spool position allows fluid to recirculate between the first and second chamber, adjusting the valve timing. 
         [0038]      FIGS. 3   a ,  3   b , and  3   c  show an actuator  250  of a second embodiment. In this embodiment, the housing  110 , defined as encasing the pistons and forming fluid chambers is split into a first housing  110   a  and a second housing  110   b . The equivalent of teeth  107   a  of the rack  107  are present on a tooth body  240  coupled to a first rack portion and a second rack portion  107   b ,  107   c  on either side of the tooth body  240 . Along the length of the tooth body  240  are teeth  107   a  that mesh with the gear teeth  132  of the concentric sleeve  128  of the lifter  130 . The first rack portion  107   b  extends between tooth body  240  and first housing  110   a , with one end connected to the tooth body  240  and the other end connected to a first piston  234  slidably received in a first housing  110   a  forming a first chamber  101   a . The second rack portion  107   c  extends between the tooth body  240  and the second housing  110   b , with one end connected to the tooth body  240  and the other end connected to a second piston  236  slidably received in a second housing  110   b  forming a second chamber  101   b , such that the first piston  234  is connected to the second piston  236  and moveable as one whole structure through the first rack portion  107   b , the tooth body  240  and the second rack portion  107   c . Seals (not shown) are preferably present in the first and second housings  110   a ,  110   b  to prevent leakage as the first and second rack portions  107   b ,  107   c  move linearly back and forth, with the first piston  234  connected to the second piston  236  through a first rack portion  107   b , the tooth body  240 , and the second rack portion  107   c . If either piston  234 ,  236 , moves, the other piston moves in a corresponding manner. 
         [0039]    The linear or reciprocating movement of the racks  107   b ,  107   c  back and forth between a first position and a second position aids in controlling the flow of oil in the actuator and the valve timing. Since the sleeve  128  is adjusting the position of the lifter  130 , the sleeve  128 , racks  107   b ,  107   c , and tooth body  240  have to resist the torsional force from the camshaft and other valve train components. The position of the racks  107   b ,  107   c  and the tooth body  240  are controlled using oscillatory, vibrational, or reciprocating force of the sleeve  128  acting on the racks, which move the racks linearly. 
         [0040]    When the rack  107   b ,  107   c  are linearly moved to a first position by the rotational force of the concentric sleeves  128 , pistons  234 ,  236  are also moved. The position and the reciprocating motion of the racks  107   b ,  107   c  pressurize one of the chambers  101   a ,  101   b  in either the first or second housing  110   a ,  110   b  with pistons  234 ,  236 , respectively. A position sensor may be present as in the first embodiment to report the position of the rack to the ECU  102 . The ECU  102  influences the variable force solenoid (VFS)  103 , which may or may not bias the control valve, preferably a spool valve  104  against the force of spring  105 . 
         [0041]    The pressurization of the first chamber  101   a  causes fluid in the first chamber  101   a  formed between the first piston  234  and the first housing  110   a  to move into the second chamber  101   b  formed between the second piston  236  and the second housing  110   b , moving the first and second pistons  234 ,  236  to the positions shown in  FIG. 3   a . The spool  109  of the spool valve  104  is moved by the force of the spring  105 , which is greater than the force of the variable force solenoid  103 , biasing the spool to the left in the figure until the force of the spring  105  balances the force of the VFS  103 . In the position shown, spool land  109   b  blocks second line  113 , extending from the spool valve  104  to the second chamber  101   b  and first line  112 , extending from the spool valve to the first chamber  101   a  and central line  116  are open. Fluid exiting the first chamber  101   a  moves through first line  112  and into spool valve  104  between spool lands  109   a  and  109   b . From the spool valve  104 , fluid moves back into central line  116 , through check valve  115  and into second line  113  supplying and recirculating fluid to the second chamber  101   b . As fluid enters the second chamber  101   b , the pistons  234 ,  236  and thus the tooth body  240  are further moved to the left in this figure. 
         [0042]    Makeup oil is supplied to the actuator  250  from supply S to make up for leakage only and enters line  118  and moves through inlet check valve  119  to the spool valve  104 . From the spool valve, fluid enters central line  116  through either of the check valves  114 ,  115 , depending on which is open to either the first chamber  101   a  or the second chamber  101   b.    
         [0043]    The pressurization of the second chamber  101   b , formed between the second piston  236  and the second housing  110   b  causes fluid in the second chamber  101   b  to move into the first chamber  101   a , formed between the first piston  234  and the first housing  110   a , moving the pistons  234 ,  236  to the positions shown in  FIG. 3   b . The spool  109  is moved by the force of variable force solenoid  103 , which is greater than the force of spring  105 , biasing the spool to the right in the figure until the force of the spring  105  balances the force of the VFS  103 . In the position shown, spool land  109   a  blocks first line  112 , and second line  113  and central line  116  are open. Fluid exiting the second chamber  101   b  moves through second line  113  and into spool valve  104  between spool lands  109   a  and  109   b . From the spool valve  104 , fluid moves back into central line  116 , through check valve  114  and into first line  112  supplying and recirculating fluid to the first chamber  101   a . As fluid enters the first chamber  101   a , the pistons  234 ,  236  and the tooth body  240  are further moved to the right in the figure. 
         [0044]    Makeup oil is supplied to the actuator  250  from supply S to make up for leakage only and enters line  118  and moves through inlet check valve  119  to the spool valve  104 . From the spool valve, fluid enters central line  116  through either of the check valves  114 ,  115 , depending on which is open to either the first chamber  101   a  or the second chamber  101   b.    
         [0045]      FIG. 3   c  shows the actuator in a third position or null position. In this position, spool land  109   a  blocks line  112  and spool land  109   b  blocks line  113 , locking the actuator in position. 
         [0046]    It should be noted that the force from the concentric sleeve  128  pushes on rack  107   b  and  107   c  to pressurize either of the chambers  101   a ,  101   b . The spool valve  109  either allows or blocks the flow of oil from one chamber to the other, moving pistons  234  and  236 , adjusting the valve timing. 
         [0047]    In a fourth embodiment, actuator  450  is shown in a first position in  FIG. 4   a  and a second position in  FIG. 4   b . In this embodiment, the control valve  104  is split into a first control valve  104   a  and a second control valve  104   b . One end of the rack  107 , opposite the end including teeth  107   a  meshed with the gear teeth  132  of the concentric sleeves  128  of the lifters is connected to a piston  108  slidably received in the housing  110 . The piston  108  divides the housing into two chambers  101   a ,  101   b , separated by the piston  108 . Fluid can not directly flow from one chamber to the other. Seals  110   a  on the housing prevent fluid leakage from the chambers as the rack  107  moves back and forth. 
         [0048]    When the rack  107  is linearly moved to a first position by the rotational force of the concentric sleeves  128 , piston  108  is also moved. The position and the reciprocating motion of the rack  107  pressurizes the first chamber  101   a . Fluid flows from the first chamber through line  412  to the first one way valve  442 . From the first control valve  104   a , fluid flows into line  411 , through check valve  415  to the second chamber  101   b  defined between the piston  108  and the housing  110 . The fluid aids in moving the piston  108  to the left as shown in  FIG. 4   a . Check valve  414  in line  409  prevents fluid from entering the second control valve  104   b . Fluid is prevented from exiting chamber  101   b  through line  413  since the second control valve  104   b  allows fluid to flow in the opposite direction only. 
         [0049]    Makeup fluid is supplied to the system to make up for leakage only from a supply not shown. 
         [0050]    When the rack is moved to a second position, shown in  FIG. 4   b , the second chamber  101   b  is pressurized. Fluid flows from the second chamber  101   b  through line  413  through the second control valve  104   b . From the second control valve  104   b , fluid flows into line  409 , through check valve  414  to the first chamber  101   a  defined between the piston  108  and the housing  110 . The fluid aids in moving the piston  108  to the right as shown in  FIG. 4   b . Check valve  415  in line  411  prevents fluid from entering the first control valve  104   a . Fluid is prevented from exiting chamber  101   a  through line  412  since the first control valve  104   b  allows fluid to flow in the opposite direction only. Makeup fluid is supplied to the system to make up for leakage only from a supply not shown. 
         [0051]      FIG. 5  shows a control loop that is preferably used with any of the actuators  150 ,  250 ,  350 , and  450 , described herein. A signal indicating position of either the rack  107  via a rack position sensor  106  attached to rack  107  or the lifter  130  via a valve sensor  141  is fed into a controller  140 . The controller  140  also obtains input from the ECU  102  regarding various engine conditions. From the controller  140 , a signal is sent to the variable force solenoid (VFS) or similar solenoid to influence the position of the spool valve. 
         [0052]      FIGS. 6   a  through  6   c  show an actuator  350  of the fourth embodiment. In this embodiment, the control valve  104  is formed on the outer circumference of a sleeve or housing  302  in the form of integral pull pieces  302   a ,  302   b ,  302   c , and  302   d . The control valve  104  is actuated using a position setter  300 . The control valve  104  has an inner circumference which acts as housing  110  for the piston  309  and forms fluid chambers within the housing between the housing and the piston. As the control sleeve/housing is shifted by the control valve, the piston will follow. 
         [0053]    The hollow control sleeve  302  with two open ends is closed off by seals  303  and the rack  107  at either end, forming a chamber. The piston  309  is coupled to rack  107  and separates the chamber into a first fluid chamber  301   a  and a second fluid chamber  301   b . One end of the rack  107  has teeth  107   a  for meshing with gear teeth  132  of the concentric sleeve  128  of the lifter  130 . The other end of the rack  107  is received and irreversibly connected to the piston  309 . The end of the rack  107  irreversibly connected to the piston  309  has a bore  107   d  extending a length of the rack. Within the bore  107   d , centered in the piston  309  are check valves  314 ,  315  allowing fluid in one direction and blocking the flow of fluid in an opposite direction. Extending from the bore  107   d  along the length and through the piston  309  to a third chamber  301   c  formed between a groove  302   e  in the inner circumference  302   f  of the hollow control sleeve  302  and the piston  309  are a first passage  312 , a central passage  316 , and a second passage  313 . The outer circumference of the hollow control sleeve  302  has integrally formed pull pieces  302   a ,  302   b ,  302   c ,  302   d , allowing a position setter  300 , preferably formed of a first coil  300   a  and a second coil  300   b  staggered from the first coil  300   a  to linearly move the control sleeve  302  to the left or right in the Figures. 
         [0054]    Referring to  FIG. 6   a , the position setter  300  is in a first position with the first coil  300   a  of the position setter  300  adjacent to pull piece  302   c  and the second coil  300   b  between pull pieces  302   b  and  302   c  on the outer circumference of the control sleeve  302 . Within the control sleeve  302 , the piston  309  is centrally positioned with the first and second passages  312 ,  313  blocked by the inner circumference  302   f  of the control sleeve  302 . The central passage  316  is open to the third chamber  301   c  formed between the piston  309  and the groove  302   e  on the inner circumference  302   f  of the control sleeve  302 . Passage  107   f  leading from the first fluid chamber  301   a  to the bore  107   d  of the rack  107  is open to the first fluid chamber  301   a , however, fluid is blocked from exiting the first fluid chamber  301   a  through the first passage  312  by the inner circumference  302   f  of the control sleeve  302  and from entering the central passage  316  by check valve  314 . Passage  107   e  leading from the second fluid chamber  301   b  to the bore  107   d  of the rack  107  is open to the second fluid chamber  301   b , however fluid is blocked from exiting the second fluid chamber  301   b  through the second passage  313  by the inner circumference  302   f  of the control sleeve  302  and the from entering the central passage  316  by check valve  315 . Therefore, fluid in the first fluid chamber  301   a  cannot flow to the second fluid chamber  301   b  and vice versa. 
         [0055]    In  FIG. 6   b , the second coil  300   b  of the position setter is energized and moves from between pull pieces  302   b  and  302   c  to adjacent to pull piece  302   b , at the same time moving the control sleeve  302  to the right in the figure, causing the de-energized first coil  300   a  to be between pull pieces  302   b  and  302   c . Since the piston  309  does not receive any direct load from the position setter  300 , the piston  309  does not move immediately within the control sleeve  302 , instead, the movement of control sleeve  302  itself to the right in the figure causes fluid in the second fluid chamber  301   b  to flow through the piston  309  the first fluid chamber  301   a , moving the piston  309  relative to the control sleeve  302  back to a null position as shown in  FIG. 6   c , with the first and second passages  312 ,  313  blocked by the inner circumference  302   f  of the control sleeve, the central passage  316  open to the third chamber  301   c , and the flow of fluid between the first and second fluid chambers  301   a ,  301   b  prevented. The movement of the piston  309  also moves the rack  107  and rack teeth  107   a  meshed with the gear teeth  132  on the concentric sleeve  128  of the lifter  130 , moving the lifter  130  to a second position shown in  FIG. 6   c.    
         [0056]    The movement of the control sleeve to the right as shown in  FIG. 6   b , also causes fluid in the second fluid chamber  301   b  to enter passage  107   e  leading to the bore in the rack  107 , thus moving the rack as stated above. Fluid travels through the bore  107   d  and into the second passage  313 , which is now, due to the control sleeve movement, open to the third chamber  301   c  formed between the groove  302   e  in the inner circumference  302   f  of the control sleeve  302  and the piston  309  and the central passage  316 . The central passages  316  leads fluid to between the two check valves  314 ,  315  within the bore  107   d , through check valve  314  and the bore  107   d  to passage  107   f  and the first fluid chamber  301   a . Fluid is prevented from exiting the first passage  312  since it is blocked by the inner circumference  302   f  of the control sleeve  302 . The exit of fluid from the second chamber  301   b  to the first chamber  301   a , moves the piston  309  to the right, to a null position relative to the moved control sleeve  302 , where again the first and second passages  312 ,  313  are blocked by the inner circumference of the control sleeve  302 . 
         [0057]    While not shown, fluid may also flow from the first fluid chamber  301   a  to the second fluid chamber  301   b  by entering passage  107   f  leading to the bore  107   d  in the rack  107 . Fluid then travels through the bore  107   d  and into the first passage  313  open to the third chamber  301   c  formed between the groove  302   e  in the inner circumference  302   f  of the control sleeve  302  and the piston  309 . From the third chamber  301   c , fluid flows into the central passage  316  leading to bore  107   d  between the two check valves  314 ,  315 . Fluid flows through check valve  315  and bore to passage  107   e  and the second fluid chamber  301   b . Fluid is prevented from exiting through the second passage  313  since it is blocked by the inner circumference  302   f  of the control sleeve  302 . The exit of fluid from the first chamber  301   a  to the second chamber  301   b  will move the piston  309  to the left in the figures shown. 
         [0058]    Actuator  350  does not require a supply or sump, since it is self-contained and includes proper sealing. Alternatively, if the seals were removed, an additional line with an inlet check valve connected to a supply would provide makeup oil as necessary. 
         [0059]    Alternatively, actuator  100  may be used with valves that are actuated by altering the cam lobe profile and thus the relationship and interaction between the cam lobe  529  and the lifter  130 , altering the timing of the valves as shown in  FIG. 7 . 
         [0060]    The variable force solenoid (VFS) shown in the figures may be replaced with a solenoid, DPCS, on/off solenoid or other similar device. 
         [0061]    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.