WO2006127348A1

WO2006127348A1 - Check valve to reduce the volume of an oil chamber

Info

Publication number: WO2006127348A1
Application number: PCT/US2006/019053
Authority: WO
Inventors: Roger T. Simpson
Original assignee: Borgwarner Inc
Priority date: 2005-05-23
Filing date: 2006-05-16
Publication date: 2006-11-30

Abstract

A check valve (71, 73) in the vane of the phase (41) allows direct one-way fluid communication between the advance chamber (47, 49) and the retard chamber (51,53) in a cam-torque actuated variable cam timing system. The direct fluid communication decreases the fluid path and the volume of fluid required in the system. Furthermore, the direct fluid communication improves response time and decreases the package and cost of the assembly.

Description

CHECK VALVE TO REDUCE THE VOLUME OF AN OIL CHAMBER

REFERENCE TO RELATED APPLICATIONS

This application claims an invention which was disclosed in Provisional Application Number 60/683,600, filed May 23, 2005, entitled "CHECK VALVE TO REDUCE THE VOLUME OF AN OIL CHAMBER". The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The invention pertains to the field of variable cam timing systems. More particularly, the invention pertains to a check valve in the vane of a phaser for reduced chamber size.

DESCRIPTION OF RELATED ART

Various mechanisms have been employed with internal combustion engines to vary the angle between the camshaft and the crankshaft for improved engine performance or reduced emissions. The majority of these variable camshaft timing (VCT) mechanisms use one or more "vane phasers" on the engine camshaft (or camshafts, in a multiple- camshaft engine). In most cases, the phaser has a rotor with one or more vanes, mounted to the end of the camshaft, surrounded by a housing with the vane chambers into which the vanes fit. The vanes may also be mounted to the housing, and the chambers may be in the rotor. The outer circumference of the housing forms the sprocket-, pulley-, or gear- accepting drive force through a chain, belt, or gears, usually from the camshaft, or from another camshaft in a multiple-cam engine.

Fig. 1 through Fig. 3 show a prior art cam torque actuated (CTA) phaser. In a CTA phaser, torque reversals in the camshaft caused by the forces of opening and closing the valves move the vane 6. In a CTA system, the control valve, which usually includes a spool valve 4 with a spool 9, allows the vanes 6 in the phaser to move by permitting fluid flow from the advance chamber 8 to the retard chamber 10 or vice versa, depending on the desired direction of movement. The spool valve 4 is internally mounted and includes a sleeve 17 for receiving a spool 9 with lands 9a, 9b. Positive cam torsionals are used to retard the phaser and negative cam torsionals are used to advance the phaser. During operation of the CTA phaser, the spool valve 4 directs oil circulation to and from the chambers 8, 10. Typically, two fluid lines 12, 13 provide fluid communication between the spool valve 4 and the chambers 8, 10, and two check valves 14, 15 allow flow from a central fluid line 16 to the other fluid lines 12, 13, respectively, but prevent fluid flow in the opposite direction.

More specifically, in the null position, as shown in Fig. 1, the spool lands 9a, 9b block the fluid lines 12, 13, respectively, and the vane 6 is locked into position by fluid pressure. With both fluid lines 12, 13 blocked, fluid is prevented from flowing from the advance chamber 8 to the retard chamber 10 and vice versa. The inlet flow check valve 9 maintains system pressure by allowing additional fluid to the phaser from an external source through a supply line 18 to make up for losses due to leakage. In some engines the cam torque energy dissipates at high speeds, and the CTA VCT is not able to move without cam torque energy, because by the nature of the CTA hydraulic circuit, equal source pressure is applied to both sides of the vane such that the vane does not move. To move the phaser toward retard, as shown in Fig. 2, the spool 9 is moved to the left, so that the spool lands 9a, 9b do not block the advance and central fluid lines 12, 16. Only the retard fluid line 13 is blocked. In this spool position, fluid exits the advance chamber 8 through the advance fluid line 12 then travels through the spool 9 between the lands 9a, 9b and into the central line 16. The fluid then feeds into the retard fluid line 13 through the open check valve 15, thereby supplying fluid to the retard chamber 10. The spool 9 and a check valve 14 prevent return flow from the retard fluid line 13. This movement of fluid causes the vane 6 to move in a retard direction 20. In order to transfer fluid from the advance chamber 8 to the retard chamber 10, the fluid must travel through the advance line 12, past the spool 9, through the central line 16, through the retard check valve 15, and finally through the retard line 13 before reaching the retard chamber 10. This long path requires a larger volume of fluid and slows response time.

To move the phaser toward advance, as shown in Fig. 3, the spool 9 is moved to the right, so that the spool lands 9a, 9b do not block the retard and central fluid lines 13, 16. Only the advance fluid line 12 is blocked. In this spool position, fluid exits the retard chamber 10 through the retard fluid line 13 then travels through the spool 9 between the lands 9a, 9b and into the central line 16. The fluid then feeds into the advance fluid line 12 through the open check valve 14, thereby supplying fluid to the advance chamber 8. The spool 9 and a check valve 15 prevent return flow from the advance fluid line 12. This movement of fluid causes the vane 6 to move in an advance direction 22. In order to transfer fluid from the retard chamber 10 to the advance chamber 8, the fluid must travel through the retard line 13, past the spool 9, through the central line 16, through the advance check valve 14, and finally through the advance line 12 before reaching the advance chamber 8. This long path requires a larger volume of fluid and slows response time.

Check valves are commonly used in variable cam timing to introduce fluid to the chambers but prevent fluid from exiting the chamber.

U.S. Patent No. 6,761,138, VALVE TIMING CONTROL APPARATUS FOR INTERNAL COMBUSTION ENGINE, issued July 13, 2004, discloses a valve timing control apparatus for an internal combustion engine. A locking mechanism locks a second rotor to a first rotor at an angle. As part of this locking mechanism, a vane is provided with a check valve. The check valve allows fluid communication between either the advance chamber and a locking pin or the retard chamber and the locking pin, depending on which chamber has a higher fluid pressure.

There is a need in the art for a CTA system with a shorter fluid path for reduced sizing of the system and a reduced response time.

SUMMARY OF THE INVENTION

A check valve in the vane of the phaser allows direct one-way fluid communication between the advance chamber and the retard chamber in a cam-torque actuated variable cam timing system. The direct fluid communication decreases the fluid path and the volume of fluid required in the system. Furthermore, the direct fluid communication improves response time and decreases the package and cost of the assembly.

The variable cam timing phaser for an internal combustion engine includes a housing, a rotor, an oil supply line, and an inlet check valve. The housing has an outer circumference and accepts drive force. The rotor is connected to a camshaft coaxially located within the housing. The housing and the rotor define at least two vanes. A first vane separates a first chamber into a first advance chamber and a first retard chamber. A second vane separates a second chamber into a second advance chamber and a second retard chamber. The rotor is capable of rotation within the housing to shift the relative angular position of the housing and the rotor.

The first check valve is located in the first vane for one-way fluid communication directly through the first vane from the first advance chamber to the first retard chamber. The second check valve is located in the second vane for one-way fluid communication directly through the second vane from the second retard chamber to the second advance chamber.

The spool valve includes a spool in a spool sleeve in direct fluid communication with the first retard chamber by a first retard passageway, the second retard chamber by a second retard passageway, the first advance chamber by a first advance passageway, and the second advance chamber by a second advance passageway.

When the spool is in a first position, fluid flows through the first retard passageway, fluid flow through the second advance passageway is blocked, and the phaser moves toward an advance position. When the spool is in a second position, fluid flows through the second advance passageway, fluid flow through the first retard passageway is blocked, and the phaser moves toward a retard position,

The variable cam timing phaser is preferably actuated by cam torque. In a preferred embodiment, the vane includes a check valve seat for the check valve. The phaser preferably includes an inlet check valve for allowing fluid flow in an oil supply line only into the phaser. In a preferred embodiment, when the spool is in a third position, fluid flow through the second advance passageway and the first retard passageway is blocked, and the rotor does not rotate with respect to the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a prior art vane phaser in a null position.

Fig. 2 shows a prior art vane phaser moving toward a retard position.

Fig. 3 shows a prior art vane phaser moving toward an advance position.

Fig. 4 shows an embodiment of the present invention in a null position with check valves in the vanes.

Fig. 5 shows an embodiment of the present invention in a retard position.

Fig. 6 shows an embodiment of the present invention in an advance position.

Fig. 7 shows an embodiment of the present invention in a null position with check valves in the rotor near the bases of the vanes.

Fig. 8 shows an embodiment of the present invention in a null position with four vanes. DETAILED DESCRIPTION OF THE INVENTION

Since a cam torque-actuated (CTA) phaser requires less volume of oil in the chambers than an oil pressure-actuated (OPA) phaser, the chambers can be smaller and there can be fewer of them. In the present invention, the check valves are located in the . vanes of the rotor to reduce the package space of a CTA further. The check valve may be a complete check valve assembly, or preferably, the check valve is made using the rotor itself as a check valve seat to reduce the package and cost of the assembly further. Locating the check valve in the vane also shortens the oil flow path on the rotor vane to allow the oil to flow right through the rotor vane check valve directly to the other side of the vane. A check valve of the present invention has high response and high flow for quick response.

A spool valve controls the direction of flow. The spool valve may be mounted in the rotor, and its position is controlled to direct fluid flow. By measuring the position of the camshaft and the crankshaft, a phaser angle is measured by an electronic controller. The phase angle of the phaser is controlled to a desired position.

A phaser 41 of the present invention is shown in Fig. 4 through Fig. 6. The phaser 41 includes a rotor 43 with vanes 45, 46 extending as lobes from the rotor 43. The vanes 45, 46 are preferably 180 degrees apart. Advance chambers 47, 49 and retard chambers 51, 53 are formed between the housing 55 and the rotor 43. An inlet check valve 57 maintains fluid pressure in the system and allows fluid to enter the system to compensate for loss due to leakage. A spool valve 59 with a spool 61 controls movement of the vanes. The position of the spool valve is controlled by an actuator including, but not limited to, a regulated pressure control system (RPCS) or a variable force solenoid (VFS) such as the solenoid disclosed in U.S. Patent No. 5,497,738, hereby incorporated herein by reference. The spool valve 59 is preferably located in the rotor 43. Four passageways 63, 65, 67, 69 permit fluid communication between the inlet check valve 57, the spool 61, and the chambers 47, 49, 51, 53. A vane check valve 71 in one vane 45 allows fluid to flow through the vane 45 directly from the retard chamber 51 to the advance chamber 47. A vane check valve 73 in the other vane 46 allows fluid to flow through the vane 46 directly from the advance chamber 49 to the retard chamber 53. Referring to Fig. 4, the phaser 41 is shown in a null position, where the vanes 45, 46 are stationary relative to the housing. The inlet check valve 57 maintains fluid pressure by making up for losses due to leakage. Although the inlet check valve 57 supplies oil to one of the retard fluid passageways 67 in the embodiment of Fig. 4, the inlet check valve could alternatively be placed to supply oil to one of the advance fluid passageways 65.

The spool 61 is positioned such that the lands 61a and 61b block an advance passageway 63 and a retard passageway 69, respectively. The inlet check valve could also be alternatively placed in one of the other passageways 63, 69, if the passageways were shifted so that the other two passageways 65, 67 were the ones blocked by the spool 61. Fluid pressure is equalized in the chambers by flow through the vane check valves 45, 46. Blockage of the top advance passageway 63 by the spool prevents counterclockwise movement of the rotor with respect to the housing, because the fluid can not go back across the top check valve 45 from the advance chamber 47. Blockage of the bottom retard passageway 69 by the spool prevents clockwise move of the rotor with respect to the housing, because the fluid can not go back across the bottom check valve 46 from the retard chamber 49. Although the rotor does not rotate with respect to the housing in this spool position, the arrows in Fig. 4 indicate the direction of minimal flow of fluid to make up for losses due to leakage.

Referring to Fig. 5, the position of the spool 61 is adjusted to the left to direct fluid to move the vanes counterclockwise 75 toward the retard position. The right spool land 61b continues to block one of the retard passageways 69, but the left spool land 61a no longer blocks an advance passageway 63. Counterclockwise movement of the rotor with respect to the housing is no longer inhibited when the top advance passageway 63 is opened. This allows fluid to move from one advance chamber 47 to its respective retard chamber 51 by passing through its advance passageway 63, past the spool 61 , through the retard passageway 67, and into the retard chamber 51. For the other set of chambers, however, the fluid flows directly from the advance chamber 49 to the retard chamber 53 by passing through the vane check valve 73. The arrows in Fig. 5 indicate the direction of fluid flow during retardation of the rotor.

Referring to Fig. 6, the position of the spool 61 is adjusted to the right to direct fluid to move the vanes clockwise 77 toward the advance position. The left spool land 61a blocks one of the advance passageways 63, but the right spool land 61b no longer blocks a retard passageway 69. Clockwise movement of the rotor with respect to the housing is no longer inhibited when the bottom retard passageway 69 is opened. This allows fluid to move from one retard chamber 53 to its respective advance chamber 49 by passing through its retard passageway 69, past the spool 61, through the advance passageway 65, and into the advance chamber 49. For the other set of chambers, however, the fluid flows directly from the retard chamber 51 to the advance chamber 47 by passing through the other vane check valve 71. The arrows in Fig. 6 indicate the direction of fluid flow during advancement of the rotor.

Referring to Fig. 7, in an alternate embodiment of the present invention, the phaser

141 includes a rotor 143 with vanes 145, 146 extending as lobes from the rotor 143. Advance chambers 147, 149 and retard chambers 151, 153 are formed between the housing 155 and the rotor 143. An inlet check valve 157 maintains fluid pressure in the system and allows fluid to enter the system to compensate for loss due to leakage. A spool valve 159 with a spool 161 controls movement of the vanes. The position of the spool valve is controlled by an actuator including, but not limited to, a regulated pressure control system (RPCS) or a variable force solenoid (VFS) such as the solenoid disclosed in U.S. Patent No. 5,497,738. The spool valve 159 is preferably located in the rotor 143. Four passageways 163, 165, 167, 169 permit fluid communication between the inlet check valve 157, the spool 161, and the chambers 147, 149, 151, 153. In this embodiment, the check valves 171, 173 are located in the rotor 143, but preferably near the bases of the vanes 145, 146, respectively. A check valve 171 near one vane 145 allows fluid to flow through a passage in the rotor 143 from near the retard chamber 151 to near the advance chamber 147. A check valve 173 near the other vane 146 allows fluid to flow through a passage in the rotor 143 from near the advance chamber 149 to near the retard chamber

153. The phaser 141 is shown in a null position in Fig. 7. Control of the phaser of Fig. 7 is similar to control of the phaser of Fig. 4 through Fig. 6.

Referring to Fig. 8, in another alternate embodiment of the present invention, the phaser 241 includes a rotor 243 with four vanes 245 A, 245B, 246A, 246B extending as lobes from the rotor 243. The vanes 245 A, 245B, 246A, 246B are preferably all 90 degrees apart. Advance chambers 247A, 247B, 249 A, 249B and retard chambers 25 IA, 25 IB, 253 A, 253B are formed between the housing 255 and the rotor 243. An inlet check valve 257 maintains fluid pressure in the system and allows fluid to enter the system to compensate for loss due to leakage. A spool valve 259 with a spool 261 controls movement of the vanes. The position of the spool valve is controlled by an actuator including, but not limited to, a regulated pressure control system (RPCS) or a variable force solenoid (VFS) such as the solenoid disclosed in U.S. Patent No. 5,497,738. The spool valve 259 is preferably located in the rotor 243. Four passageways 263, 265, 267, 269 permit fluid communication between the inlet check valve 257, the spool 261, and the chambers 247 A, 247B, 249A, 249B, 25 IA, 25 IB, 253 A, 253B.

A vane check valve 271 A in one vane 245 A allows fluid to flow through the vane

245A directly from the retard chamber 25 IA to the advance chamber 247 A. A vane check valve 27 IB in another vane 245B allows fluid to flow through the vane 245B directly from the retard chamber 25 IB to the advance chamber 247B. A vane check valve 273 A in another vane 246A allows fluid to flow through the vane 246 A directly from the advance chamber 249 A to the retard chamber 253 A. A vane check valve 273B in another vane

246B allows fluid to flow through the vane 246B directly from the advance chamber 249B to the retard chamber 253B. The vanes may be arranged with similar vanes paired next to each other, as shown in Fig. 8, or with similar vanes across from each other. The phaser 241 is shown in a null position in Fig. 8. Control of the phaser of Fig. 8 is similar to control of the phaser of Fig. 4 through Fig. 6.

The present invention simplifies fluid communication relative to the prior art by using only one passageway for connecting each chamber to the central spool valve. Placing a check valve in each vane decreases the path length of fluid flow and eliminates the need for any further check valves for the system other than an inlet check valve. Although the inlet check valve is shown as attached to a retard passageway, it may alternatively be attached to an advance passageway. The inlet check valve may be attached to any passageway that does not get blocked by the spool valve during operation of the phaser. Although two vanes are described in Fig. 4 through Fig. 6, alternative embodiments of the present invention, such as shown in Fig. 8, have more than two vanes. The phaser may have an odd number of vanes, but an even number of vanes is preferred to balance the torque on the phaser. Although the check valves are shown as being all in the vanes or all in the rotor below the vanes, check valves may be found in one vane and in the rotor below another vane within the same rotor within the spirit of the present invention. Both locations of the check valve allow fluid to flow from one chamber to another chamber along a shorter path without fluid flow all the way back through the spool valve.

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 phaser for an internal combustion engine comprising:

a housing with an outer circumference for accepting drive force;

a rotor for connection to a camshaft coaxially located within the housing, the housing and the rotor defining at least two vanes extending from the rotor and comprising a first vane separating a first chamber into a first advance chamber and a first retard chamber and a second vane separating a second chamber into a second advance chamber and a second retard chamber, the rotor being capable of rotation within the housing to shift the relative angular position of the housing and the rotor;

a first check valve located in the rotor for one-way fluid communication directly through the rotor from the first advance chamber to the first retard chamber;

a second check valve located in the rotor for one-way fluid communication directly through the rotor from the second retard chamber to the second advance chamber; and

a spool valve comprising a spool in a spool sleeve in direct fluid communication with the first retard chamber by a first retard passageway, the second retard chamber by a second retard passageway, the first advance chamber by a first advance passageway, and the second advance chamber by a second advance passageway;

such that:

when the spool is in a first position, fluid flows through the first retard passageway, fluid flow through the second advance passageway is blocked, and the phaser moves toward an advance position; and

when the spool is in a second position, fluid flows through the second advance passageway, fluid flow through the first retard passageway is blocked, and the phaser moves toward a retard position.

2. The variable cam timing phaser of claim 1, wherein the first check valve is located in the first vane of the rotor.

3. The variable cam timing phaser of claim 1, wherein the second check valve is located in the second vane of the rotor.

4. The variable cam timing phaser of claim 1, wherein the variable cam timing phaser is actuated by cam torque.

5. The variable cam timing phaser of claim 1, wherein the vane comprises a check valve seat for the check valve.

6. The variable cam timing phaser of claim 1 further comprising an inlet check valve for allowing fluid flow in an oil supply line only into the phaser.

7. The variable cam timing phaser of claim 1, wherein when the spool is in a third position, fluid flow through the second advance passageway and the first retard passageway is blocked, thereby preventing the rotor from rotating with respect to the housing.

8. The variable cam timing phaser of claim 1, wherein the housing and the rotor further define a third vane extending from the rotor and separating a third chamber into a third advance chamber and a third retard chamber and a fourth vane separating a fourth chamber into a fourth advance chamber and a fourth retard chamber, the variable cam timing phaser further comprising:

a third check valve located in the rotor for one-way fluid communication directly through the rotor from the third advance chamber to the third retard chamber; and a fourth check valve located in the rotor for one-way fluid communication directly through the rotor from the fourth retard chamber to the fourth advance chamber.

9. The variable cam timing phaser of claim 8, wherein the third check valve is located in the third vane of the rotor.

10. The variable cam timing phaser of claim 8, wherein the fourth check valve is located in the fourth vane of the rotor.

11. A variable cam timing phaser for an internal combustion engine comprising:

a housing with an outer circumference for accepting drive force;

a rotor for connection to a camshaft coaxially located within the housing, the housing and the rotor defining at least two vanes comprising a first vane separating a first chamber into a first advance chamber and a first retard chamber and a second vane separating a second chamber into a second advance chamber and a second retard chamber, the rotor being capable of rotation within the housing to shift the relative angular position of the housing and the rotor;

a first check valve located in the first vane for one-way fluid communication directly through the first vane from the first advance chamber to the first retard chamber;

a second check valve located in the second vane for one-way fluid communication directly through the second vane from the second retard chamber to the second advance chamber; and

a spool valve comprising a spool in a spool sleeve in direct fluid communication with the first retard chamber by a first retard passageway, the second retard chamber by a second retard passageway, the first advance chamber by a first advance passageway, and the second advance chamber by a second advance passageway; such that:

12. The variable cam timing phaser of claim 11 , wherein the variable cam timing phaser is actuated by cam torque.

13. The variable cam timing phaser of claim 11, wherein the vane comprises a check valve seat for the check valve.

14. The variable cam timing phaser of claim 11 further comprising an inlet check valve for allowing fluid flow in an oil supply line only into the phaser.

15. The variable cam timing phaser of claim 11 , wherein when the spool is in a third position, fluid flow through the second advance passageway and the first retard passageway is blocked, thereby preventing the rotor from rotating with respect to the housing.

16. The variable cam timing phaser of claim 11, wherein the housing and the rotor further define a third vane separating a third chamber into a third advance chamber and a third retard chamber and a fourth vane separating a fourth chamber into a fourth advance chamber and a fourth retard chamber, the variable cam timing phaser further comprising:

a third check valve located in the third vane for one-way fluid communication directly through the third vane from the third advance chamber to the third retard chamber; and a fourth check valve located in the fourth vane for one-way fluid communication directly through the fourth vane from the fourth retard chamber to the fourth advance chamber.