Actuator and Control Method For Variable Valve Timing (Vvt) Mechanism

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

BACKGROUND OF THE INVENTION

1. Field of the Invention

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.

2. Description of Related Art

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.

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.

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.

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.

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.

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

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.

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

FIG. 1 a shows a schematic of an actuator and the valves.

FIG. 1 b shows a schematic of the contact between the lifters and the camshaft.

FIG. 2 a shows a schematic of the variable valve timing (VVT) actuator of the first embodiment in a first position.

FIG. 2 b shows a schematic of the variable valve timing (VVT) actuator of the first embodiment in a second position.

FIG. 2 c shows a schematic of the variable valve timing (VVT) actuator of the first embodiment in a third, null position.

FIG. 3 a shows a variable valve timing (VVT) actuator of the second embodiment in a first position.

FIG. 3 b shows a variable valve timing (VVT) actuator of the second embodiment in a second position.

FIG. 3 c shows a variable valve timing (VVT) actuator of the second embodiment in a third, null position.

FIG. 4 a shows an actuator of the third embodiment in a first position.

FIG. 4 b shows an actuator of the third embodiment in a second position.

FIG. 5 shows a control loop of the present invention.

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.

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.

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.

FIG. 7 shows an alternate cam profile and actuation of the lifters.

DETAILED DESCRIPTION OF THE INVENTION

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 107a 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. 2a and 2b, actuator 250, shown in FIGS. 3a and 3b, actuator 450 shown in FIGS. 4a and 4b, or actuator 350 shown in FIGS. 6a, 6b, and 6c.

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 107a. The lifter'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.

In a first embodiment, shown in FIGS. 2a, 2b, and 2c, one end of the rack 107, opposite the end including teeth 107a 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 101a, 101b. Fluid can not directly flow between the chambers 101a, 101b. Seals 110a on the entry and exit points of the rack 107 and housing 110 interface prevent fluid leakage from the chambers 101a, 101b as the rack 107 moves linearly back and forth. The end of the rack opposite the end with teeth 107a 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 109a, 109b, and 109c 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.

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 101a, 101b 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 101a, 101b to the other chamber 101a, 101b.

The pressurization of the first chamber 101a causes fluid in the first chamber 101a to move into the second chamber 101b, moving the piston 108 to the position shown in FIG. 2a. 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 109b blocks second line 113, extending from the spool valve 104 to the second chamber 101b and a first line 112, extending from the spool valve 104 to the first chamber 101a and central line 116 are open. Fluid exiting the first chamber 101a moves through first line 112 and into spool valve 104 between spool lands 109a and 109b. 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 101b. As fluid enters the second chamber 101b, the piston 108 and thus the rack 107 are further moved to the left in the figure.

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 101a or the second chamber 101b.

The pressurization of the second chamber 101b causes fluid in the second chamber 101b to move into the first chamber 101a, moving the piston 108 to the position shown in FIG. 2b. 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 109a blocks first line 112, and second line 113 and central line 116 are open. Fluid exiting the second chamber 101b moves through second line 113 and into spool valve 104 between spool lands 109a and 109b. 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 101a. As fluid enters the first chamber 101a, the piston 108 and thus the rack 107 are moved further to the right in the figure.

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 101a or the second chamber 101b.

FIG. 2 c shows the actuator in a third position or null position. In this position, spool land 109a blocks line 112 and spool land 109b blocks line 113, locking the actuator in position.

The combination of the pressurization of the chambers 101a, 101b by the motion of the rack 107 and spool position allows fluid to recirculate between the first and second chamber, adjusting the valve timing.

FIGS. 3 a, 3b, and 3c 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 110a and a second housing 110b. The equivalent of teeth 107a of the rack 107 are present on a tooth body 240 coupled to a first rack portion and a second rack portion 107b, 107c on either side of the tooth body 240. Along the length of the tooth body 240 are teeth 107a that mesh with the gear teeth 132 of the concentric sleeve 128 of the lifter 130. The first rack portion 107b extends between tooth body 240 and first housing 110a, 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 110a forming a first chamber 101a. The second rack portion 107c extends between the tooth body 240 and the second housing 110b, 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 110b forming a second chamber 101b, such that the first piston 234 is connected to the second piston 236 and moveable as one whole structure through the first rack portion 107b, the tooth body 240 and the second rack portion 107c. Seals (not shown) are preferably present in the first and second housings 110a, 110b to prevent leakage as the first and second rack portions 107b, 107c move linearly back and forth, with the first piston 234 connected to the second piston 236 through a first rack portion 107b, the tooth body 240, and the second rack portion 107c. If either piston 234, 236, moves, the other piston moves in a corresponding manner.

The linear or reciprocating movement of the racks 107b, 107c 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 107b, 107c, and tooth body 240 have to resist the torsional force from the camshaft and other valve train components. The position of the racks 107b, 107c 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.

When the rack 107b, 107c 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 107b, 107c pressurize one of the chambers 101a, 101b in either the first or second housing 110a, 110b 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.

The pressurization of the first chamber 101a causes fluid in the first chamber 101a formed between the first piston 234 and the first housing 110a to move into the second chamber 101b formed between the second piston 236 and the second housing 110b, moving the first and second pistons 234, 236 to the positions shown in FIG. 3a. 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 109b blocks second line 113, extending from the spool valve 104 to the second chamber 101b and first line 112, extending from the spool valve to the first chamber 101a and central line 116 are open. Fluid exiting the first chamber 101a moves through first line 112 and into spool valve 104 between spool lands 109a and 109b. 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 101b. As fluid enters the second chamber 101b, the pistons 234, 236 and thus the tooth body 240 are further moved to the left in this figure.

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 101a or the second chamber 101b.

The pressurization of the second chamber 101b, formed between the second piston 236 and the second housing 110b causes fluid in the second chamber 101b to move into the first chamber 101a, formed between the first piston 234 and the first housing 110a, moving the pistons 234, 236 to the positions shown in FIG. 3b. 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 109a blocks first line 112, and second line 113 and central line 116 are open. Fluid exiting the second chamber 101b moves through second line 113 and into spool valve 104 between spool lands 109a and 109b. 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 101a. As fluid enters the first chamber 101a, the pistons 234, 236 and the tooth body 240 are further moved to the right in the figure.

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 101a or the second chamber 101b.

FIG. 3 c shows the actuator in a third position or null position. In this position, spool land 109a blocks line 112 and spool land 109b blocks line 113, locking the actuator in position.

It should be noted that the force from the concentric sleeve 128 pushes on rack 107b and 107c to pressurize either of the chambers 101a, 101b. 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.

In a fourth embodiment, actuator 450 is shown in a first position in FIG. 4a and a second position in FIG. 4b. In this embodiment, the control valve 104 is split into a first control valve 104a and a second control valve 104b. One end of the rack 107, opposite the end including teeth 107a 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 101a, 101b, separated by the piston 108. Fluid can not directly flow from one chamber to the other. Seals 110a on the housing prevent fluid leakage from the chambers as the rack 107 moves back and forth.

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 101a. Fluid flows from the first chamber through line 412 to the first one way valve 442. From the first control valve 104a, fluid flows into line 411, through check valve 415 to the second chamber 101b defined between the piston 108 and the housing 110. The fluid aids in moving the piston 108 to the left as shown in FIG. 4a. Check valve 414 in line 409 prevents fluid from entering the second control valve 104b. Fluid is prevented from exiting chamber 101b through line 413 since the second control valve 104b 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.

When the rack is moved to a second position, shown in FIG. 4b, the second chamber 101b is pressurized. Fluid flows from the second chamber 101b through line 413 through the second control valve 104b. From the second control valve 104b, fluid flows into line 409, through check valve 414 to the first chamber 101a defined between the piston 108 and the housing 110. The fluid aids in moving the piston 108 to the right as shown in FIG. 4b. Check valve 415 in line 411 prevents fluid from entering the first control valve 104a. Fluid is prevented from exiting chamber 101a through line 412 since the first control valve 104b 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.

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.

FIGS. 6 a through 6c 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 302a, 302b, 302c, and 302d. 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.

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 301a and a second fluid chamber 301b. One end of the rack 107 has teeth 107a 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 107d extending a length of the rack. Within the bore 107d, 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 107d along the length and through the piston 309 to a third chamber 301c formed between a groove 302e in the inner circumference 302f 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 302a, 302b, 302c, 302d, allowing a position setter 300, preferably formed of a first coil 300a and a second coil 300b staggered from the first coil 300a to linearly move the control sleeve 302 to the left or right in the Figures.

Referring to FIG. 6a, the position setter 300 is in a first position with the first coil 300a of the position setter 300 adjacent to pull piece 302c and the second coil 300b between pull pieces 302b and 302c 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 302f of the control sleeve 302. The central passage 316 is open to the third chamber 301c formed between the piston 309 and the groove 302e on the inner circumference 302f of the control sleeve 302. Passage 107f leading from the first fluid chamber 301a to the bore 107d of the rack 107 is open to the first fluid chamber 301a, however, fluid is blocked from exiting the first fluid chamber 301a through the first passage 312 by the inner circumference 302f of the control sleeve 302 and from entering the central passage 316 by check valve 314. Passage 107e leading from the second fluid chamber 301b to the bore 107d of the rack 107 is open to the second fluid chamber 301b, however fluid is blocked from exiting the second fluid chamber 301b through the second passage 313 by the inner circumference 302f of the control sleeve 302 and the from entering the central passage 316 by check valve 315. Therefore, fluid in the first fluid chamber 301a cannot flow to the second fluid chamber 301b and vice versa.

In FIG. 6b, the second coil 300b of the position setter is energized and moves from between pull pieces 302b and 302c to adjacent to pull piece 302b, at the same time moving the control sleeve 302 to the right in the figure, causing the de-energized first coil 300a to be between pull pieces 302b and 302c. 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 301b to flow through the piston 309 the first fluid chamber 301a, moving the piston 309 relative to the control sleeve 302 back to a null position as shown in FIG. 6c, with the first and second passages 312, 313 blocked by the inner circumference 302f of the control sleeve, the central passage 316 open to the third chamber 301c, and the flow of fluid between the first and second fluid chambers 301a, 301b prevented. The movement of the piston 309 also moves the rack 107 and rack teeth 107a 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. 6c.

The movement of the control sleeve to the right as shown in FIG. 6b, also causes fluid in the second fluid chamber 301b to enter passage 107e leading to the bore in the rack 107, thus moving the rack as stated above. Fluid travels through the bore 107d and into the second passage 313, which is now, due to the control sleeve movement, open to the third chamber 301c formed between the groove 302e in the inner circumference 302f 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 107d, through check valve 314 and the bore 107d to passage 107f and the first fluid chamber 301a. Fluid is prevented from exiting the first passage 312 since it is blocked by the inner circumference 302f of the control sleeve 302. The exit of fluid from the second chamber 301b to the first chamber 301a, 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.

While not shown, fluid may also flow from the first fluid chamber 301a to the second fluid chamber 301b by entering passage 107f leading to the bore 107d in the rack 107. Fluid then travels through the bore 107d and into the first passage 313 open to the third chamber 301c formed between the groove 302e in the inner circumference 302f of the control sleeve 302 and the piston 309. From the third chamber 301c, fluid flows into the central passage 316 leading to bore 107d between the two check valves 314, 315. Fluid flows through check valve 315 and bore to passage 107e and the second fluid chamber 301b. Fluid is prevented from exiting through the second passage 313 since it is blocked by the inner circumference 302f of the control sleeve 302. The exit of fluid from the first chamber 301a to the second chamber 301b will move the piston 309 to the left in the figures shown.

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.

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.

The variable force solenoid (VFS) shown in the figures may be replaced with a solenoid, DPCS, on/off solenoid or other similar device.

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.

Claims

1. 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, the valve timing system comprising: a toothed rotating sleeve having a plurality of teeth around at least part of its circumference, rotatably mounted on each valve stem about an axis, having a valve lifter mounted on an upper surface off of an axis of rotation;a rack having a first end, a second end comprising a plurality of teeth in meshing contact with the teeth of the rotating sleeves of the valves, and being linearly moveable to rotate the rotating sleeves;an actuator comprising: a housing having a chamber for slidably receiving a piston coupled to the rack, wherein the piston separates the chamber into a first chamber and a second chamber,a control valve in connection with the first chamber and the second chamber for directing fluid flow between the first chamber and the second chamber, selectively directing fluid from the first chamber to the second chamber or vice versa; andat least one check valve between the first chamber and the second chamber and the control valve for blocking reverse fluid flow;wherein when the rack is shifted linearly by vibrational impulses from the engine, the piston moves linearly within the housing, the first chamber or the second chamber is pressurized and under control of the control valve, and fluid recirculates from the first chamber or the second chamber to the other chamber.

2. The system of the claim 1, further comprising a passage in fluid communication with a pressurized fluid source for providing makeup fluid only.

3. The system of claim 2, further comprising a check valve in the passage.

4. The system of claim 1, wherein the housing is split into a first housing and a second housing.

5. The system of claim 4, further comprising a second piston.

6. The system of claim 1, wherein the control valve is spool valve.

7. The system of claim 1, wherein the control valve is split into a first control valve and a second control valve.

8. The system of claim 7, wherein the first control valve and the second control valve are solenoid valves.

9. The system of claim 1, wherein each lobe on the camshaft has a varying contour a long a length.

10. A method of altering the 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 using a valve timing system comprising: a toothed rotating sleeve having a plurality of teeth around at least part of its circumference, rotatably mounted on each valve stem about an axis, having a valve lifter mounted on an upper surface off of an axis of rotation; a rack having an end with a plurality of teeth in meshing contact with the teeth of the rotating sleeves of the valves being linearly moveable rotate the rotating sleeves; and an actuator having a housing having a chamber for slidably receiving a piston coupled to the rack, wherein the piston separates the chamber into a first chamber and a second chamber, a control valve in connection with the first chamber and the second chamber for directing fluid flow between the first chamber and the second chamber, selectively directing fluid from the first chamber to the second chamber or vice versa; and at least one check valve between the first chamber and the second chamber and the control valve for blocking reverse fluid flow, comprising the steps of: a) determining the position of rack;b) sending the position of the rack to an engine control unit;c) sending a signal based on the position of the rack from the engine control unit to the actuator and moving a control valve of the actuator to a first position, a second position, or a third position; andd) pressurizing a first chamber or a second chamber of the actuator based on the position of the rack and the control valve of the actuator, allowing flow of fluid from the pressurized chamber to the other chamber and blocking reverse flow.

11. The method of claim 10, wherein the third position of the spool is a null position.