WO2008042621A1

WO2008042621A1 - Cushioned stop valve event duration reduction device

Info

Publication number: WO2008042621A1
Application number: PCT/US2007/079107
Authority: WO
Inventors: James Sisson
Original assignee: Borgwarner Inc
Priority date: 2006-09-29
Filing date: 2007-09-21
Publication date: 2008-04-10
Also published as: WO2008042622A1

Abstract

A phaser with a first connecting port having a first check valve and a first port valve to transfer hydraulic fluid from the advance chamber to the retard chamber and a second connecting port having a second check valve and a second port valve to transfer hydraulic fluid from the retard chamber to the advance chamber. When the vane of the phaser reaches a pre-set point in travel towards the advance or retard wall of the housing, the a port valve closes and the a check valve prevents hydraulic fluid from exiting the advance chamber or retard chamber, retaining a specific amount of hydraulic fluid in the advance chamber or retard chamber between the vane and the advance wall or the vane and the retard wall to prevent the vane from forcefully slamming into the advance or retard wall of the housing.

Description

CUSHIONED STOP VALVE EVENT DURATION REDUCTION DEVICE

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The invention pertains to the field of cam phasing devices for internal combustion engines. More particularly, the invention pertains to an apparatus and method for using hydraulic fluid to reduce the noise resulting from oscillations within the components of the phasing device that can occur during high engine revolutions.

DESCRIPTION OF RELATED ART

The performance of an internal combustion engine is improved by the use of dual camshafts, one to operate the intake valves of the various cylinders of the engine and the other to operate the exhaust valves. Typically, one of the camshafts may be driven by the crankshaft of the engine, through a sprocket and chain drive or a belt drive, and the other of such camshafts would be driven by the first, through a second sprocket and chain drive or a second belt drive. Alternatively, both of the camshafts are driven by a single crankshaft powered chain drive or belt drive. Engine performance in an engine with dual camshafts can be further improved, in terms of idle quality, fuel economy, reduced emissions or increased torque, by changing the positional relationship of one of the camshafts, usually the camshaft which operates the intake valves of the engine, relative to the other camshaft and relative to the crankshaft, to thereby vary the timing of the engine in terms of the operation of intake valves relative to its exhaust valves or in terms of the operation of its valves relative to the position of the crankshaft.

It has become more common for variable camshaft timing ("VCT") mechanisms to be made in a vane and housing format. Working hydraulic chambers are created by imposing either single or multiple vanes of a rotor attached to the camshaft into a cavity in a housing that is attached to the camshaft sprocket. The circumferential length of the pocket or cavity in the housing determines the relative phase travel of the camshaft relative to the sprocket/housing. The control is accomplished by exhausting fluid such as oil from one chamber while simultaneously filling the opposing chamber. This causes the variable camshaft timing mechanism to move the camshaft relative to the crankshaft manifested in a phase position.

The rate of change of the camshaft phasing is determined in part by how fast the oil can exhaust from the resisting or draining hydraulic chamber. As the rotor and vane of the VCT reaches the end of its travel, which is limited by the cavity of the housing, the rotor and vane will impact the housing and cause undesirable noise. As can be seen, there is need to reduce the noise at the end of vane's travel, while maintaining a suitable rate of change camshaft phasing.

Numerous attempts have been made to alleviate this problem. For example, U.S. Patent No. 4,601,231 shows a rotary actuator that restricts oil flow to prevent leakage without using the sealing members of the vane and reduces the velocity of the vane as it approaches impact with the housing, thus cushioning the impact of the vane against the stops. Multiple passages and switches are used to move oil to separate passages as the vane nears the stop. The vane is used to block the primary passage and switch to the bypass circuit. Specifically, the vane blocks a main path and oil is supplied to a subpath. A small amount of oil flows into the bypath and the majority of the oil flows and pushes against a ball valve, which is in opposition to a spring. The force of the oil overcomes the spring and pushes the ball valve from its seat and oil behind the ball valve moves into a passage which leads the oil to bear against a cutout of the vane. When the pressure is great enough, the vane separates from the stopper so that a new oil chamber is formed therebetween. At the same time, oil passes through a path and reaches a boundary between the other vane and stopper and effects a similar separation when the vane advances, opening a main oil path. The oil from the main path is fed directly into a second diametrically opposed newly opened oil chamber from the main path. Simultaneously, oil the other chamber is discharged from the oil port via the main path as the rotation of the vanes takes place. A cushion effect is created so that the impact or shock of the vane against the spring is moderate.

U.S. Patent No. 5,002,023 describes a VCT system within the field of the invention in which the system hydraulics includes a pair of oppositely acting hydraulic cylinders with appropriate hydraulic flow elements to selectively transfer hydraulic fluid from one of the cylinders to the other, or vice versa, to thereby advance or retard the circumferential position of a camshaft relative to a crankshaft. The control system utilizes a control valve in which the exhaustion of hydraulic fluid from one or another of the oppositely acting cylinders is permitted by moving a spool within the valve one way or another from its centered or null position. The movement of the spool occurs in response to an increase or decrease in control hydraulic pressure, P_c, on one end of the spool and the relationship between the hydraulic force on such end and an oppositely direct mechanical force on the other end which results from a compression spring that acts thereon.

U.S. Patent No. 5,107,804 describes an alternate type of VCT system within the field of the invention in which the system hydraulics include a vane having lobes within an enclosed housing which replace the oppositely acting cylinders disclosed by the aforementioned U.S. Patent No. 5,002,023. The vane is oscillatable with respect to the housing, with appropriate hydraulic flow elements to transfer hydraulic fluid within the housing from one side of a lobe to the other, or vice versa, to thereby oscillate the vane with respect to the housing in one direction or the other, an action which is effective to advance or retard the position of the camshaft relative to the crankshaft. The control system of this VCT system is identical to that divulged in U.S. Patent No. 5,002,023, using the same type of spool valve responding to the same type of forces acting thereon.

U.S. Patent Nos. 5,172,659 and 5,184,578 both address the problems of the aforementioned types of VCT systems, created by the attempt to balance the hydraulic force exerted against one end of the spool and the mechanical force exerted against the other end. The improved control system disclosed in both U.S. Patent Nos. 5,172,659 and 5,184,578 utilizes hydraulic force on both ends of the spool. The hydraulic force on one end results from the directly applied hydraulic fluid from the engine oil gallery at full hydraulic pressure, P_s. The hydraulic force on the other end of the spool results from a hydraulic cylinder or other force multiplier which acts thereon in response to system hydraulic fluid at reduced pressure, Pc, from a PWM solenoid. Because the force at each of the opposed ends of the spool is hydraulic in origin, based on the same hydraulic fluid, changes in pressure or viscosity of the hydraulic fluid will be self -negating, and will not affect the centered or null position of the spool. U.S. Patent No. 5,657,725 shows a control system which utilizes engine oil pressure for actuation. The system includes a camshaft having a vane secured to an end thereof for non-oscillating rotation therewith. The camshaft also carries a housing which can rotate with the camshaft but which is oscillatable with the camshaft. The vane has opposed lobes which are received in opposed recesses, respectively, of the housing. The recesses have greater circumferential extent than the lobes to permit the vane and housing to oscillate with respect to one another, and thereby permit the camshaft to change in phase relative to a crankshaft. The camshaft tends to change direction in reaction to engine oil pressure and/or camshaft torque pulses which it experiences during its normal operation, and it is permitted to either advance or retard by selectively blocking or permitting the flow of engine oil through the return lines from the recesses by controlling the position of a spool within a spool valve body in response to a signal indicative of an engine operating condition from an engine control unit. The spool is selectively positioned by controlling hydraulic loads on its opposed end in response to a signal from an engine control unit. The vane can be biased to an extreme position to provide a counteractive force to a unidirectionally acting frictional torque experienced by the camshaft during rotation.

U.S. Patent No. 6,250,265 shows a variable valve timing system with actuator locking for an internal combustion engine. The system consists of a variable camshaft timing system comprising a camshaft with a vane secured to the camshaft for rotation with the camshaft but not for oscillation with respect to the camshaft. The vane has a circumferentially extending plurality of lobes projecting radially outwardly therefrom and is surrounded by an annular housing that has a corresponding plurality of recesses each of which receives one of the lobes and has a circumferential extent greater than the circumferential extent of the lobe received therein to permit oscillation of the housing relative to the vane and the camshaft while the housing rotates with the camshaft and the vane. Oscillation of the housing relative to the vane and the camshaft is actuated by pressurized engine oil in each of the recesses on opposed sides of the lobe therein, the oil pressure in such recess being preferably derived in part from a torque pulse in the camshaft as it rotates during its operation. An annular locking plate is positioned coaxially with the camshaft and the annular housing and is moveable relative to the annular housing along a longitudinal central axis of the camshaft between a first position, where the locking plate engages the annular housing to prevent its circumferential movement relative to the vane and a second position where circumferential movement of the annular housing relative to the vane is permitted. The locking plate is biased by a spring toward its first position and is urged away from its first position toward its second position by engine oil pressure, to which it is exposed by a passage leading through the camshaft, when engine oil pressure is sufficiently high to overcome the spring biasing force, which is the only time when it is desired to change the relative positions of the annular housing and the vane. The movement of the locking plate is controlled by an engine electronic control unit either through a closed loop control system or an open loop control system.

SUMMARY OF THE INVENTION

The present invention employs check valves and ports to provide a cushioned stop for the vanes of the rotor of a phaser against the walls of the chambers that house each vane. As the rate of movement of the phaser between advance and retard positions increases, the increasing speed of the vanes slamming into the retard and advance walls of the housing chamber creates increasingly louder noise.

A phaser of the present invention has a first connecting port having a first check valve and a first port valve to transfer hydraulic fluid from the advance chamber to the retard chamber and a second connecting port having a second check valve and a second port valve to transfer hydraulic fluid from the retard chamber to the advance chamber. When the phaser is moved towards the retard position, the first port valve is open allowing hydraulic fluid from the advance chamber to travel through the first check valve to fill the retard chamber, and when the vane reaches a pre-set point in travel towards the advance wall of the housing, the first port valve closes and the second check valve prevents hydraulic fluid from exiting the advance chamber, retaining a specific amount of hydraulic fluid in the advance chamber between the vane and the advance wall to prevent the vane from forcefully slamming into the advance wall of the housing. When the phaser is moved towards the advance position, the second port valve is open, allowing hydraulic fluid from the retard chamber to travel through the second check valve to fill the advance chamber, and wherein when the vane reaches a pre-set point in travel towards the retard wall of the housing, the second port valve closes and the first check valve prevents fluid from exiting the retard chamber, retaining a specific amount of hydraulic fluid in the retard chamber between the vane and the retard wall to prevent the vane from forcefully slamming into the retard wall of the housing.

The check valves and ports may also be included and used in a rotary actuator to also prevent the slamming of vane into the walls of the advance and retard chambers.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1 shows a schematic of a vane type VCT phaser.

Fig. 2 shows a flow chart of the operation of the present invention in a VCT phaser.

Fig. 3a shows a schematic representation of one embodiment of the present invention in a cam torque actuated (CTA) phaser in the null position.

Fig. 3b shows a schematic of the chambers of the phaser when the phaser is moving towards the retard position.

Fig. 3c shows a schematic of the chambers of the phaser when the phaser is moving towards the advance position.

Fig. 4 shows a schematic representation of a second embodiment of the present invention in a CTA phaser.

Fig. 5 shows a schematic of a rotary actuator with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It will be recognized by one skilled in the art that this description is common to vane phasers in general, and the specific arrangement of vanes, chambers, passages and valves shown in Figure 1 may be varied within the teachings of the invention. For example, the number of vanes and their location can be changed, some phasers may have only a single vane, others may have as many as a dozen, and the vanes might be located on the housing and reciprocate within chambers on the rotor. The housing might be driven by a chain or belt or gears, and the sprocket teeth might be gear teeth or a toothed pulley for a belt.

Referring to Figure 1, a schematic of a typical vane-type VCT phaser is shown. It consists of a housing 201, the outside of which has sprocket teeth 208 that mesh with and are driven by timing chain 209. Coaxially located within the housing 201, free to rotate relative to the housing 201, is a rotor 202 with vanes 206 projecting from the rotor's circumference. The vanes 206 separate chambers in the housing defined by an arcuate outer wall. The vanes 206 separate the chambers in the housing into advance and retard chambers 205 and 207, respectively, and are limited in movement between advance wall 215 and retard wall 217 within the chamber of the housing 201. Radially projecting outward from a central control valve 204 in the rotor 202 are advance passages 213 and retard passages 212. The central control valve 204 routes pressurized fluid to the advance and retard chambers 205 and 207 by the advance and retard passages 213 and 212, respectively. The central control valve 204 is preferably a spool valve 203 including a spool with cylindrical lands 203a, 203b slidably received in a sleeve or a bore in the camshaft or the rotor. The position of the spool of the spool valve 203 of the central control valve 204 is influenced by a spring 219 and a solenoid 218 (as shown in Figure 3). The position of the spool in the spool valve 203 controls the motion (e.g. to move towards the advance position or the retard position) of the phaser.

In order to advance or retard the timing of the camshaft(s) with respect to the drive shaft, hydraulic fluid is directed to either the advance chamber 205 or the retard chamber 207 via the appropriate passages. The fluid entering the retard chamber 207 via passage 212, forces the vane 206 to move counterclockwise, or to the retard position. Conversely, when advance timing is required, fluid is directed to the advance chamber 205, via passage 213, forcing the vane 206 to move clockwise, or to the advance position. As discussed in the background, undesirable noise occurs when the vane 206 slams into the advance wall 215 or the retard wall 217 of the housing 201.

As discussed previously, the rate of change of the phasing of the camshaft is determined, in part, by how fast hydraulic fluid can exhaust from the resisting hydraulic chamber. As the rotor 202 of the VCT reaches the end of its travel, as limited by the walls of the chambers of the housing 201, the vanes 206 will impact the walls of housing 201 and cause undesirable noise.

Figure 2 is a schematic block diagram that describes the operation of the present invention. Two independent connecting ports 102, 113 connect the retard chambers 207 to the advance chambers 205. Within the first independent connecting port 102 is a first check valve 101 and a first port valve 103. Within the second independent connecting port 113 is a second check valve 111 and a second port valve 113.

When the phaser moves towards the advance position, the second port valve 113 is open in the second connecting port 110, allowing fluid from the retard chamber 207 to travel through the second connecting port 110 and through the second check valve 111 to enter and fill the advance chamber 205. The first port valve 103 is closed. As the fluid enters the advance chamber 205, the vane 206 is moved clockwise (see Figure 3c). When the vane 206 reaches a predetermined point in its travel toward the retard wall 217, the second port valve 113 closes, and the first check valve 101 prevents fluid from exiting the retard chamber 207, and traps a specific amount of fluid in the retard chamber 207 to cushion the impact of the vane 206 against the retard wall 217. Once the rotor and vane stop moving towards the retard wall, the phaser is in the advance stop position. To overcome the problem of having a slow actuation rate off of the advance stop position, the first port valve 103 is opened and the first check valve 101 provides fluid through the first connecting port 102 directly to the retard chamber 207.

Conversely, when the phaser moves towards the retard position, the first port valve 103 is open in the first connecting port 102, allowing fluid from the advance chamber 205 to travel through the first connecting port 102 and through the first check valve 101 to enter and fill the retard chamber 207. The second port valve 113 is closed. As the fluid enters the retard chamber 207, the vane 206 is moved counterclockwise (see Figure 3b). When the vane 206 reaches a predetermined point in its travel toward the advance wall 215, the first port valve 103 closes and the second check valve 111 prevents fluid from exiting the advance chamber 205, and traps a specific amount of fluid in the advance chamber 205 to cushion the impact of the vane 206 against the advance wall 215. Once the rotor and vane stop moving towards the advance wall 215, the phaser is in the retard stop position. To overcome the problem of having a slow actuation rate off of the retard stop position, the second port valve 113 is opened and the second check valve 111 provides fluid through the second connecting port 110 directly to the advance chamber 205.

Additional fluid may be provided by the advance and retard passages 213 and 212.

Figures 3a through 3c are schematic depictions that show the operation of a first embodiment of the present invention in a cam torque actuated (CTA) phaser 300. Figure 3a shows the null position, figure 3b shows only the chambers and the vane moving towards the retard position, and figure 3c shows only the chambers and the vane moving towards the advance position.

Figure 3a shows the phaser is in a null position. In this position, the force of the solenoid 218 on one end of the spool of the spool valve 203 equals the force of the spring 219 on the opposite end of the spool. The lands 203a and 203b block the flow of fluid to lines 212 and 213 respectively. Makeup oil is supplied to the phaser from supply S to makeup for leakage and enters line 220 and moves through inlet check valve Vl to the spool valve 203. From the spool valve 203, fluid enters the central supply line Sl and through the check valves 222, 221, depending on which is open to the chambers 205, 207.

In moving towards the advance position, as shown in Figure 3c, the force of the solenoid 218 was greater than the force of the spring 219 on the spool of the spool valve 203, and the spool was moved by the solenoid 218, until the force of the spring 219 balanced the force of the solenoid 203 (not shown). In this position, spool land 203a blocks the advance line 213, and central supply line Sl and line 212 are open. Camshaft torque pressurizes the retard chamber 207, causing fluid in the retard chamber 207 to move into the advance chamber 205 through line 213, moving the vane 206 clockwise. Fluid exits the retard chamber 207 through line 212 to the spool 203 and recirculates back to the central supply line Sl, through check valve 222 to line 213 leading to the advance chamber 205. As discussed with reference to Figure 2, additionally, the second port valve 113 is open in the second connecting port 110, allowing fluid from the retard chamber 207 to travel through the second connecting port 110 and through the second check valve 111 to enter and fill the advance chamber 205. The first port valve 103 is closed. As the fluid enters the advance chamber 205, the vane 206 is moved clockwise. When the vane 206 reaches a predetermined point in its travel toward the retard wall 217, the second port valve 113 closes, and the first check valve 101 prevents fluid from exiting the retard chamber 207, and traps a specific amount of fluid in the retard chamber 207 to cushion the impact of the vane 206 against the retard wall 217. Once the rotor and vane stop moving towards the retard wall, the phaser is in the advance stop position. To overcome the problem of having a slow actuation rate off of the advance stop position, the first port valve 103 is opened and the first check valve 101 provides fluid through the first connecting port 102 directly to the retard chamber 207.

In moving towards the retard position, as shown in Figure 3b, the force of the solenoid 218 was less than the force of the spring 219 on the spool of the spool valve 203, and the spool was moved by the spring 219, until the force of the spring 219 balanced the force of the solenoid 218 (not shown). In this position, spool land 203b blocks the retard line 212 and central supply line Sl and line 213 are open. Camshaft torque pressurizes the advance chamber 205, causing fluid in the advance chamber 205 to move into the retard chamber 207 through line 212, moving the vane 206 counterclockwise. Fluid exits the advance chamber 205 through line 213 to the spool 203 and recirculates back to the central supply line Sl, through check valve 221 to line 212 leading to the retard chamber 207. As discussed with reference to Figure 2, additionally, the first port valve 103 is open in the first connecting port 102, allowing fluid from the advance chamber 205 to travel through the first connecting port 102 and through the first check valve 101 to enter and fill the retard chamber 207. The second port valve 113 is closed. As the fluid enters the retard chamber 207, the vane 206 is moved counterclockwise. When the vane 206 reaches a predetermined point in its travel toward the advance wall 215, the first port valve 103 closes and the second check valve 111 prevents fluid from exiting the advance chamber 205, and traps a specific amount of fluid in the advance chamber 205 to cushion the impact of the vane 206 against the advance wall 215. Once the rotor and vane stop moving towards the advance wall 215, the phaser is in the retard stop position. To overcome the problem of having a slow actuation rate off of the retard stop position, the second port valve 113 is opened and the second check valve 111 provides fluid through the second connecting port 110 directly to the advance chamber 205. Makeup oil us supplied to the phaser from supply S to make up for leakage and enters line 220 and moves through the inlet check valve Vl to the control valve 204. From the valve, fluid enters the central supply line Sl and through the check valves 221, 222, depending on which is open to the chambers 205, 207.

A second embodiment of the present invention is shown in Figure 4. In this embodiment, the first port 102 and the second port 110 are located in at least one vane 206 of the rotor 202. The function of this system is identical to the system previously described with the ports and their attendant valves incorporated into the housing 201 as described with reference to Figures 2 and 3a-3c and is repeated herein by reference.

It is noted that the present invention contemplates application in any type VCT phaser including a Cam Torque Actuated (CTA) phaser as disclosed in U.S. Patent No. 5,104,804, issued on April 28, 1992, entitled "Variable Camshaft Timing For Internal Combustion Engine" which is herein incorporated by reference, torsion assist (TA) phaser as disclosed in U.S. Patent No. 6,883,481, issued April 26, 2005, entitled "Torsional Assisted Multi-Position Cam Indexer Having Controls Located in Rotor", which discloses a single check valve TA, and is herein incorporated by reference and U.S. Patent No. 6,763,791, issued July 20, 2004, entitled "Cam Phaser for Engines Having Two Check Valves in Rotor Between Chambers and Spool Valve", which discloses two check valve TA, and is herein incorporated by reference, an oil pressure actuated (OPA) phaser, or any other type of phaser.

Additionally, the present invention may be used with a rotary actuator as shown in Figure 5. In a rotary actuator, the housing 411 does not have an outer circumference for accepting drive force and the motion of the housing 411 is restricted (see range of motion 450). In other words, gear teeth are not present to accept a chain, which would normally cause the housing to rotate 360 degrees, as in a vane phaser. The restriction of the housing 411 ranges from not moving the housing 411 at all, to the housing 411 having motion restricted to less than 360 degrees. This may be accomplished by having the housing 411 shaped to interfere with the movement of the rotor 402. Since the housing 411 does not accept drive force, the rotor 402 does instead. All movement, other than the twisting of the shaft in which the rotor 402 is connected, is done by the rotor. The rotor 402 and the vanes 406 move or swing through the distance 450 as defined and limited by the housing walls 415, 417. All of the cyclic load is on the rotor 402 and the rotor accepts all of the drive force, instead of the housing 411, as in a vane phaser.

In order to advance or retard the timing with a rotary actuator, hydraulic fluid is directed to either the advance chamber 405 or the retard chamber 407 via the appropriate passages by the control valve 404. The fluid entering the retard chamber 407 forces the vane 406 to move to the left, or the retard position. Conversely, when advance timing is required, fluid is directed to the advance chamber 405, via passage 413, forcing the vane 406 clockwise, or the advance position. As discussed in the background, undesirable noise occurs when the vane 406 slams into the advance wall 415 or the retard wall 417 of the housing 401.

The independent ports 102 and 113 as shown in Figure 2 and Figures 3a-3c may also be present in a rotary actuator. The two independent 102, 113 ports connect the retard chambers 407 to the advance chambers 405 of the rotary actuator (not shown in Figure 5). Within the first independent connecting port 102 is a first check valve 101 and a first port valve 103. Within the second independent connecting port 113 is a second check valve 111 and a second port valve 113.

When the rotary actuator moves towards the advance position, the second port valve 113 is open in the second connecting port 110, allowing fluid from the retard chamber 407 to travel through the second connecting port 110 and through the second check valve 111 to enter and fill the advance chamber 405. The first port valve 103 is closed. As the fluid enters the advance chamber 405, the vane 406 is moved clockwise. When the vane 406 reaches a predetermined point in its travel toward the retard wall 417, the second port valve 113 closes, and the first check valve 101 prevents fluid from exiting the retard chamber 407, and traps a specific amount of fluid in the retard chamber 407 to cushion the impact of the vane 406 against the retard wall 417. Once the rotor and vane stop moving towards the retard wall 417, the rotary actuator is in the advance stop position. To overcome the problem of having a slow actuation rate off of the advance stop position, the first port valve 103 is opened and the first check valve 101 provides fluid through the first connecting port 102 directly to the retard chamber 407. Conversely, when the rotary actuator moves towards the retard position, the first port valve 103 is open in the first connecting port 102, allowing fluid from the advance chamber 405 to travel through the first connecting port 102 and through the first check valve 101 to enter and fill the retard chamber 407. The second port valve 113 is closed. As the fluid enters the retard chamber 407, the vane 406 is moved counterclockwise. When the vane 406 reaches a predetermined point in its travel toward the advance wall 415, the first port valve 103 closes and the second check valve 111 prevents fluid from exiting the advance chamber 405, and traps a specific amount of fluid in the advance chamber 405 to cushion the impact of the vane 406 against the advance wall 415. Once the rotor and vane stop moving towards the advance wall 415, the rotary actuator is in the retard stop position. To overcome the problem of having a slow actuation rate off of the retard stop position, the second port valve 113 is opened and the second check valve 111 provides fluid through the second connecting port 110 directly to the advance chamber 405.

Additional fluid may be provided by the advance and retard passages 413 and 412.

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

What is claimed is:

1. A variable cam timing system for a camshaft of an internal combustion engine comprising:

a phaser having:

a rotor having at least one radially extending vane, the rotor being securely affixed to the axis of the camshaft;

a housing surrounding the rotor having at least one chamber for receiving a single vane, the chamber divided into an advance chamber between the vane and an advance wall and a retard chamber between the vane and a retard wall, the vane radially moveable within the chamber in one direction toward an advance timing position or in a second, opposite direction toward a retard timing position;

a first connecting port having a first check valve and a first port valve to transfer hydraulic fluid from the advance chamber to the retard chamber; and

a second connecting port having a second check valve and a second port valve to transfer hydraulic fluid from the retard chamber to the advance chamber,

wherein when the phaser is moved towards the retard position, the first port valve is open allowing hydraulic fluid from the advance chamber to travel through the first check valve to fill the retard chamber; and wherein when the vane reaches a pre- set point in travel towards the advance wall of the housing, the first port valve closes and the second check valve prevents hydraulic fluid from exiting the advance chamber, retaining a specific amount of hydraulic fluid in the advance chamber between the vane and the advance wall to prevent the vane from forcefully slamming into the advance wall of the housing;

wherein when the phaser is moved towards the advance position, the second port valve is open, allowing hydraulic fluid from the retard chamber to travel through the second check valve to fill the advance chamber, and wherein when the vane reaches a pre-set point in travel towards the retard wall of the housing, the second port valve closes and the first check valve prevents fluid from exiting the retard chamber, retaining a specific amount of hydraulic fluid in the retard chamber between the vane and the retard wall to prevent the vane from forcefully slamming into the retard wall of the housing.

2. The variable cam timing system of claim 1 wherein the hydraulic fluid is engine oil.

3. The variable cam timing system of claim 1 wherein the first port and the second port are within the housing.

4. The variable cam timing system of claim 1 wherein the first port and the second port are within the vane of the rotor

5. The variable cam timing system of claim 1, wherein the phaser is cam torque actuated.

6. The variable cam timing system of claim 1, wherein the phaser is oil pressure actuated.

7. The variable cam timing system of claim 1, wherein the phaser is torsion assisted.

8. A rotary actuator for an internal combustion engine having at least one camshaft comprising:

a housing with motion restricted to less than 360 degrees;

a rotor for accepting drive force and connection to a shaft coaxially located within the housing, the rotor having at least one radially extending vane, the housing and the rotor forming at least one chamber for receiving the vane, the chamber divided into an advance chamber between the vane and an advance wall and a retard chamber between the vane and a retard wall, the vane radially moveable within the chamber in one direction toward an advance timing position or in a second or opposite direction toward a retard timing position;

wherein when the rotary actuator is moved towards the retard position, the first port valve is open allowing hydraulic fluid from the advance chamber to travel through the first check valve to fill the retard chamber; and wherein when the vane reaches a pre-set point in travel towards the advance wall of the housing, the first port valve closes and the second check valve prevents hydraulic fluid from exiting the advance chamber, retaining a specific amount of hydraulic fluid in the advance chamber between the vane and the advance wall to prevent the vane from forcefully slamming into the advance wall of the housing;

wherein when the rotary actuator is moved towards the advance position, the second port valve is open, allowing hydraulic fluid from the retard chamber to travel through the second check valve to fill the advance chamber, and wherein when the vane reaches a pre-set point in travel towards the retard wall of the housing, the second port valve closes and the first check valve prevents fluid from exiting the retard chamber, retaining a specific amount of hydraulic fluid in the retard chamber between the vane and the retard wall to prevent the vane from forcefully slamming into the retard wall of the housing.

9. The rotary actuator of claim 8 wherein the hydraulic fluid is engine oil.

10. The rotary actuator of claim 8 wherein the first port and the second port are within the housing.

11. The rotary actuator of claim 8 wherein the first port and the second port are within the vane of the rotor.