Hydraulically actuated VCT system with spool-type valve

Abstract

A hydraulically actuated variable camshaft timing (VCT) system includes a spool valve including a sleeve and a valve stem received in the sleeve, the valve stem having a plurality of radially outwardly extending shoulders; a sleeve fluid passage extending axially along the sleeve and formed in the sleeve, the valve stem being configured to receive fluid from a fluid supply; an advance port in the sleeve in fluid communication with an advance chamber of a hydraulically actuated camshaft phaser; a retard port in the sleeve in fluid communication with a retard chamber of the hydraulically actuated camshaft phaser; a first fluid supply port formed in the sleeve; a second fluid supply port formed in the sleeve; and a drain port axially positioned in the sleeve between the first and second fluid supply ports or between the advance and retard ports, wherein the drain port is configured to selectively receive fluid from the advance chamber or the retard chamber depending on an axial position of the valve stem relative to the sleeve.

Description

Technical Field

[0001] The present application relates to fluid control, and more particularly, to a linear motion valve that controls the flow of fluid in a hydraulically actuated VCT system. Background Art

[0002] Internal combustion engines (ICEs) selectively control the flow of fluids in a variety of ways. An ICE may use a spool valve, which includes a sleeve and a spool having a land that slides linearly within the sleeve to selectively allow and stop the flow of a fluid, such as oil. Spool valves on ICEs have many different applications, such as controlling the flow of fluid to a hydraulically actuated variable camshaft timing (VCT) device (commonly referred to as a camshaft phaser). The spool includes one or more lands positioned at precise axial positions along the spool, extending radially outward from an elongated body to engage a radially inwardly facing surface of the sleeve to form a fluid seal. As the spool moves linearly relative to the sleeve, the land also moves, exposing different fluid passages to transfer fluid from a source to the exposed fluid passages. Flow through the fluid passages can be controlled by moving the land relative to the sleeve to expose or cover a fluid port in the sleeve that provides access to the fluid passages. However, the location of the fluid supply port relative to the fluid outlet port can involve performance challenges. Careful placement of the fluid supply port relative to the fluid exhaust port can improve the performance of the spool-type valve. Summary of the invention

[0003] In one embodiment, a hydraulically actuated variable camshaft timing (VCT) system includes a spool-type valve including a sleeve and a spool received in the sleeve, the spool having a plurality of radially outwardly extending shoulders; a sleeve fluid passage extending axially along the sleeve and formed in the sleeve and configured to receive fluid from a fluid supply; an advancing port in the sleeve in fluid communication with an advancing chamber of a hydraulically actuated camshaft phaser; a retarding port in the sleeve in fluid communication with a retarding chamber of the hydraulically actuated camshaft phaser; a first fluid supply port formed in the sleeve; a second fluid supply port formed in the sleeve; and a drain port axially positioned in the sleeve between the first and second fluid supply ports or between the advancing and retarding ports, wherein the drain port is configured to selectively receive fluid from the advancing chamber or the retarding chamber depending on an axial position of the spool relative to the sleeve.

[0004] In another embodiment, a hydraulically actuated VCT system includes a spool valve configured to receive fluid from a fluid supply, including a spool received in a sleeve and a spool cavity, the spool having a plurality of shoulders extending radially outward; an advance port in the sleeve in fluid communication with an advance chamber of a hydraulically actuated camshaft phaser; a retard port in the sleeve in fluid communication with a retard chamber of the hydraulically actuated camshaft phaser; a first fluid supply port formed in the sleeve; a second fluid supply port formed in the sleeve; and a drain port axially positioned in the sleeve between the first and second fluid supply ports or between the advance and retard ports, wherein the drain port is configured to selectively receive fluid from the advance chamber or the retard chamber depending on an axial position of the spool relative to the sleeve, and wherein the spool valve directs fluid from the fluid supply to the advance / retard chamber, from one of the advance chamber or the retard chamber to the other of the advance chamber or the retard chamber, or both. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1a is a schematic diagram depicting an embodiment of a hydraulically actuated variable camshaft timing (VCT) system;

[0006] FIG. 1 b is a cross-sectional view depicting a portion of an embodiment of a hydraulically actuated VCT system;

[0007] FIG. 2a is a schematic diagram depicting an embodiment of a hydraulically actuated variable camshaft timing (VCT) system;

[0008] FIG2 b is a cross-sectional view depicting a portion of an embodiment of a hydraulically actuated VCT system;

[0009] FIG3 a is a schematic diagram depicting an embodiment of a hydraulically actuated variable camshaft timing (VCT) system;

[0010] FIG3 b is a cross-sectional view depicting a portion of an embodiment of a hydraulically actuated VCT system;

[0011] Figure 4 is a schematic diagram depicting another embodiment of a hydraulically actuated VCT system;

[0012] Figure 5 is another schematic diagram depicting another embodiment of a hydraulically actuated VCT system; and

[0013] Figure 6 is another schematic diagram depicting another embodiment of a hydraulically actuated VCT system. DETAILED DESCRIPTION

[0014] The hydraulically actuated VCT system has a spool valve, which includes a valve column that slides relative to a sleeve to control the flow of fluid from multiple supply ports through a common exhaust port. The spool valve may include a sleeve (or stud) that receives fluid from a fluid source and a valve column that slides axially in the stud to control the flow of fluid into a VCT device (also known as a camshaft phaser) and out of the VCT device. Specifically, the fluid can be supplied to the stud from the fluid source, and then guided to both the first supply port and the second supply port in the stud, and the fluid can be provided to the VCT device through the first supply port and the second supply port. The fluid exhaust port can be axially positioned at a position between the first supply port and the second supply port along the spool valve. The fluid exhaust port can also be axially positioned between the advance port and the exhaust port along the valve column. In one embodiment, the fluid manifold in the stud can transmit the fluid to the first supply port and the second supply port formed in the stud on the opposite side of the fluid exhaust port. In another embodiment, the spool valve receives fluid from a fluid supply device and guides the fluid to an advance port or a lag port. At the same time, the spool valve can direct fluid from one of the advance chamber or the retard chamber to the other of the advance chamber or the retard chamber. With respect to this embodiment, the spool valve can direct fluid from a fluid supply to an advance / retard chamber, from one of the advance chamber or the retard chamber to the other of the advance chamber or the retard chamber, or both. This embodiment of the spool valve can use fluid pressure from a fluid supply and fluid pressure from camshaft torque to facilitate phase adjustment of the camshaft. In contrast, previous spool valves used more than one exhaust port to exhaust fluid from the valve. In a hydraulically actuated VCT system that uses both an oil pump and camshaft torque assist to provide fluid to the VCT device, previous spool valves with more than one exhaust port may also involve more than one check valve, thereby increasing complexity.

[0015] One embodiment of a hydraulically actuated variable camshaft timing (VCT) system 10 is shown in FIGS. 1-3 . The system includes a hydraulically actuated camshaft phaser 12, a spool valve 14 having a spool 16 and a sleeve 18 or a plunger receiving the spool 16, a fluid pump 20 supplying pressurized fluid to the spool valve 14, and a fluid tank 22 supplying fluid and receiving exhaust fluid. The system 10 also includes a variable force solenoid (VFS) 24 that axially moves the spool 16 relative to the sleeve 18 in opposition to a spring 25 to control the flow of fluid within the system 10. The phaser 12 includes a rotor 26 and a stator housing 32 receiving the rotor 26, and in this embodiment, the rotor has a plurality of vanes 28 extending radially outward from a hub 30. The vanes 28 can extend into a fluid chamber 34 formed in the stator housing 32, thereby dividing the fluid chamber 34 into an advance chamber 36 and a retard chamber 38. The advance fluid passage 40 can be in fluid communication with the advance chamber 36, and the retard fluid passage 42 can be in fluid communication with the retard chamber 36. Fluid flowing into and out of the advance fluid passage 40 and the retard fluid passage 42 can exert force on the rotor 26 through the vanes 28, thereby selectively rotating or holding the rotor 26 relative to the stator housing 32. An example of a hydraulically actuated camshaft VCT system is described in application number 14 / 840,683, which was ultimately published as U.S. Patent No. 9,695,716, the contents of which are incorporated herein by reference. The hydraulically actuated VCT system 10 can adjust the camshaft phaser in response to fluid under pulsation from camshaft rotation, fluid pressurized by the fluid pump 20, or both. One or more check valves can control the flow of fluid under pulsation. The check valve can be implemented in various ways, such as as a ball valve or a reed valve.

[0016] The rotor 26 may be mechanically attached to the camshaft by fasteners (not shown), such as studs, and the camshaft may be mounted in the head of the internal combustion engine. The hydraulic lock 44 may be positioned in the stator housing 32 and biased so that it releasably engages the rotor 26 to maintain a fixed angular position of the rotor 26 relative to the stator housing 32. The fluid pump 20 supplies pressurized fluid to the spool valve 14 through a fluid supply device 46 at an axial end of the spool valve 14. The fluid supply device 46 may be in fluid communication with one or more fluid passages of the spool valve 14. For example, in this embodiment, the fluid supply device 46 fluidly delivers the supply fluid with a fluid supply port 48 that receives fluid from the fluid pump 20. The exhaust port 54 may be positioned axially along the sleeve 18 between the advance port 50 and the retard port 52. The advance chamber 36 of the phaser 12 may be in fluid communication with the advance fluid passage 40 and the advance port 50, while the retard chamber 38 may be in fluid communication with the retard fluid passage 42 and the retard port 52. Fluid may flow from the spool valve 14 to the advance chamber 36 through the advance port 50, or alternatively from the advance chamber 36 to the exhaust port 54 through the advance port 50. Similarly, fluid may flow from the spool valve 14 to the retard chamber 38 through the retard port 52, or alternatively from the retard chamber 38 to the exhaust port 54 through the retard port 52.

[0017] The valve plunger 60 can be concentrically received by the valve spool 16 in the valve spool cavity 62. The valve spool 16 can have a plurality of shoulders 58 extending radially outward from the valve plunger 60 and helping to direct fluid flow from the fluid supply 46 to the advance port 50, the retard port 52, and the exhaust port 54. In addition, the valve spool 16 can include one or more check valves 64 that can control the flow of fluid from the advance chamber 36 to the retard chamber 38 or from the retard chamber 38 to the advance chamber 36, as shown in FIG. 1b. In this embodiment, the check valve 64 is a reed valve carried by the valve plunger 60 and is oppositely biased to engage with the inner surface 66 of the valve spool 16. The valve plunger 60 can also include a plug cavity 68 within the valve plunger 60 to help drain fluid from the spool valve 14. The outer surface of the valve plunger 60 may include one or more valve stops 70 extending radially outward from the valve plunger 60 to regulate the travel of a flapper used in a reed valve of the check valve 64. This will be described in more detail below. In addition, this embodiment of the valve spool 16 may be applied to a hydraulically actuated VCT system that is capable of regulating a camshaft phaser in response to a fluid under pulsation in response to camshaft rotation as discussed above, a fluid pressurized by a fluid pump 20, or both.

[0018] The valve stem 16 of the spool valve 14 is concentrically positioned relative to the sleeve 18 (also called a stud) and is received in the sleeve cavity 56. The valve stem 16 includes an elongated body and a plurality of shoulders 58 positioned at axial positions along the body, and the plurality of shoulders extend radially outward from the body. The radial outer surface of the shoulder 58 has a shape corresponding to the inner surface of the sleeve cavity 56, so that the surface of the shoulder 58 closely matches the inner surface to prevent the fluid from flowing axially from one side of the shoulder 58 to the other side of the shoulder 58. The cross-sectional shape of the valve stem 16 and the shoulder 58 can be annular or circular, or another shape consistent with the inner surface of the sleeve 18 in the sleeve cavity 56. Both the valve stem 16 and the shoulder 58 can be made of one of many different types of materials, such as a metal alloy. In this embodiment, the fluid supply device 46 can be in fluid communication with the advance chamber 36, the retardation chamber 38 and the exhaust port 54. That is, the exhaust port 54 can be in fluid communication with both the advance port 50 and the retard port 52 and with a reservoir of fluid drawn by the fluid pump 20. The spool 16 includes a spool advance port 72, a spool retard port 74, and a spool exhaust port 76. The first check valve 64a can releasably engage the inner surface of the spool cavity 62 to control fluid flow through the spool advance port 72, while the second check valve 64b can control fluid flow through the spool retard port 74.

[0019] 1a and 1b depict the system 10 with the spool 16 positioned in a "fully retracted" position relative to the sleeve 18. In this embodiment, the fully retracted position of the spool 16 directs fluid from the advance chamber 36 to the exhaust port 54 through the advance port 50, the spool exhaust port 76, and the first check valve 64a. The hydraulic lock 44 can be in fluid communication with the advance port 56, and fluid exiting the advance chamber 36 through the advance fluid passage 40 can reduce the force of the bias spring that overcomes the hydraulic lock 44, thereby allowing the hydraulic lock 44 to engage the stator housing 32 and prevent rotational movement between the rotor 26 and the stator housing 32. The exhaust port 54 fluidly communicates the fluid exiting the advance chamber 36 to the tank 22. In addition, the fluid exiting the advance chamber 36 can enter the retard chamber 38 through the first check valve 64a, the spool exhaust port 76, and the spool retard port 74. Fluid from the fluid pump 20 enters the retard chamber 38 through the second check valve 64b to the retard port 52.

[0020] Turning to FIGS. 2a and 2b , the spool 16 can be moved to a “neutral position” where the shoulder 58 prevents fluid from passing from the fluid supply port 48 to the advance port 50 or the retard port 52. The neutral position can also prevent fluid from leaving the advance chamber 36 or the retard chamber 38, thereby maintaining the angular position of the rotor 26 relative to the stator housing 32. FIGS. 3a and 3b depict the system 10 with the spool 16 positioned in a “fully inserted” position relative to the sleeve 18. In this embodiment, the fully inserted position of the spool 16 directs fluid from the fluid pump 20, through the second check valve 64b, through the advance port 50 to the advance chamber 36. The hydraulic lock 44 can receive a fluid that can overcome the spring force of the hydraulic lock 44, thereby releasing the hydraulic lock 44 from the stator housing 32, allowing rotational movement between the rotor 26 and the stator housing 32. Fluid from the retard chamber 38 exits through the retard port 52 to the exhaust port 54. The exhaust port 54 communicates fluid exiting the retard chamber 38 to the tank 22. Additionally, fluid may flow from the retard port 52 through the advance port 50 into the advance chamber 36 via the first check valve 64a.

[0021] Another embodiment of the valve stem 16' and the sleeve 18' or the stud is Figures 4 to 6 . The sleeve 18' includes a sleeve fluid passage 78, which is a fluid manifold extending axially within the wall of the sleeve 18' from the fluid supply 46 to a first fluid supply port 80 and a second fluid supply port 82, which provide fluid to the sleeve cavity 56. The exhaust port 54 can be positioned axially along the sleeve 18' between the first fluid supply port 80 and the second fluid supply port 82. The exhaust port 54 can be positioned axially along the spool valve 14' between the advance port 50 and the retard port 52. The exhaust port 54 can also or alternatively be positioned axially along the spool valve 14' between the first fluid supply port 80 and the second fluid supply port 82. Figure 4 The system 10 is depicted with the valve stem 16' positioned in a "fully retracted" position relative to the sleeve 18', similar to that described above with respect to Figures 1a and 1b. Figure 5 The spool 16 is depicted in a "neutral position" where the shoulder 58 prevents fluid from passing from the fluid supply port 48 to the advance port 50 or the retard port 52. The neutral position also prevents fluid from leaving the advance chamber 36 or the retard chamber 38, thereby maintaining the angular position of the rotor 26 relative to the stator housing 32. Figure 6 The system 10 is depicted with the valve stem 16' positioned in a "fully inserted" position relative to the sleeve 18', similar to that described above with respect to Figures 3a and 3b.

[0022] It should be understood that the foregoing is a description of one or more embodiments of the present invention. The present invention is not limited to the specific embodiments disclosed herein, but is limited only by the following claims. In addition, the statements contained in the foregoing description relate to specific embodiments and should not be interpreted as limitations on the scope of the present invention or on the definitions of the terms used in the claims, unless the terms or phrases are clearly defined above. Various other embodiments and various changes and modifications to the disclosed embodiments are obvious to those skilled in the art. All of these other embodiments, changes and modifications are intended to fall within the scope of the appended claims.

[0023] As used in the specification and claims, the terms "such as," "for example," "for example," "such as," and "as," and the verbs "comprise," "have," "include," and other verb forms thereof, when used with a list of one or more components or other items, should be interpreted as open ended, meaning that the list should not be considered to exclude other additional components or items. Other terms should be interpreted using their broadest reasonable meaning unless used in a context that requires a different interpretation.

Claims

1. A hydraulically actuated variable camshaft timing (VCT) system comprising: A sliding-column valve comprising a single stud and a valve stem received in the stud, the valve stem having a plurality of shoulders extending radially outward; an advance port formed by the stud in fluid communication with an advance chamber of a hydraulically actuated camshaft phaser; a retard port formed by a stud in fluid communication with a retard chamber of the hydraulically actuated camshaft phaser; a first fluid supply port formed at least in part by a valve stem and a valve plunger concentrically received within the valve stem; a second fluid supply port formed at least in part by the valve spool and the valve plunger; as well as a drain port formed by a stud and axially positioned between the first fluid supply port and the second fluid supply port, or between the advance port and the retard port, wherein the spool valve is capable of: (a) directing from the first fluid supply port and the second fluid supply port to an advance port or a retard port; (b) directing from one of the advance port or the retard port to the other of the advance port or the retard port; and (c) Both (a) and (b) depend on the axial position of the valve column relative to the plunger so that a fluid passage exists between the surface of the valve column cavity and the valve plunger, wherein the surface of the valve column cavity is at least partially defined by the inner surface of the plunger facing the valve plunger.

2. The hydraulically actuated variable camshaft timing (VCT) system of claim 1, wherein: The hydraulically actuated VCT system directs fluid from the advance chamber to the retard chamber, or from the retard chamber to the advance chamber. 3 . The hydraulically actuated variable camshaft timing (VCT) system of claim 1 , further comprising one or more check valves.

4. The hydraulically actuated variable camshaft timing (VCT) system of claim 1, wherein: The exhaust port is in fluid communication with the inner surface of the rotor.

5. The hydraulically actuated variable camshaft timing (VCT) system of claim 1, wherein: A fluid supply port of the first fluid supply port or the second fluid supply port is positioned at an axial end of the plunger.

6. A hydraulically actuated variable camshaft timing (VCT) system comprising: A spool valve configured to receive fluid from a fluid supply, the spool valve comprising a valve stem received in a single stud and a valve stem cavity, the valve stem having a plurality of shoulders extending radially outward; an advance port in the stud in fluid communication with an advance chamber of a hydraulically actuated camshaft phaser; a retard port in the stud in fluid communication with a retard chamber of the hydraulically actuated camshaft phaser; a first fluid supply port formed in the stud; a second fluid supply port formed in the stud; a fluid passage formed in a single stud and within an outer wall of the stud and an inner wall of the stud, extending axially from the fluid supply device to the first fluid supply port and the second fluid supply port; a discharge port axially positioned in the stud between the first fluid supply port and the second fluid supply port or between the advance port and the retard port, wherein the fluid channel is a fluid manifold, wherein the exhaust port is configured to selectively receive fluid from the advance chamber and the retard chamber depending on an axial position of the valve stem relative to the stud, and wherein the spool valve directs fluid from the fluid supply device to the advance chamber, the spool valve directs fluid from the fluid supply device to the retard chamber, and the spool valve directs fluid from one of the advance chamber or the retard chamber to the other of the advance chamber or the retard chamber.

7. The hydraulically actuated variable camshaft timing (VCT) system of claim 6, further comprising one or more check valves.

8. The hydraulically actuated variable camshaft timing (VCT) system of claim 6, wherein: The exhaust port is in fluid communication with the inner surface of the rotor.

9. The hydraulically actuated variable camshaft timing (VCT) system of claim 6, wherein: The fluid supply ports of the first and second fluid supply ports are positioned at an axial end of the stud.

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