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An engine valve actuation system includes an engine valve moveable between first and second positions, a valve actuation assembly connected to move the engine valve between the first and second positions, a fluid actuator configured to selectively modify a timing of the engine valve in moving from t

An engine valve actuation system includes an engine valve moveable between first and second positions, a valve actuation assembly connected to move the engine valve between the first and second positions, a fluid actuator configured to selectively modify a timing of the engine valve in moving from the second to the first position, a source of fluid, and a pair of passages in the cylinder that allow fluid to flow from the chamber to the fluid source. The fluid actuator includes a cylinder and a piston at least partly defining a chamber. The piston is slidably movable in the cylinder between a first position and a second position, and blocks at least a portion of one of the passages at an intermediate position between the second position and the first position to reduce fluid flow from the chamber when the piston moves from the second position toward the first position.

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What is claimed is: 1. An engine valve actuation system, comprising: an engine valve moveable between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; a valve actuation assembly operably connected to move the engine valve between the first position and

What is claimed is: 1. An engine valve actuation system, comprising: an engine valve moveable between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; a valve actuation assembly operably connected to move the engine valve between the first position and the second position; a separate fluid actuator configured to selectively modify a timing of the engine valve in moving from the second position to the first position, the separate fluid actuator including a cylinder having a longitudinal direction and a piston cooperating to at least partly define a chamber, the piston having at least one fluid passage and being slidably movable in the cylinder between a first position and a second position; a source of fluid in communication with the separate fluid actuator; and first, second, and third passages longitudinally spaced apart in the cylinder, each of the first, second, and third passages structured and arranged to allow fluid to flow from the source of fluid to the chamber at a time when the piston is moving from the first position to the second position, said piston blocking at least a portion of one of the first, second, and third passages at an intermediate position between the second position and the first position so as to reduce the flow of fluid from the chamber at a time when the piston is moving from the second position toward the first position, the at least one fluid passage of the piston being in communication with at least one of the first, second, and third passages. 2. The engine valve actuation system of claim 1, further including a check valve configured to prevent fluid flow through at least one of the first, second, and third passages during movement of the piston from the second position toward the first position. 3. The engine valve actuation system of claim 1, further including a stop member cooperating with the actuator cylinder to retain at least a portion of the piston in the actuator cylinder. 4. The engine valve actuation system of claim 3, further including a flow path configured to prevent hydraulic lock of the piston. 5. The engine valve actuation system of claim 1, further including an accumulator configured to reduce the impact of pressure fluctuations within the system. 6. The engine valve actuation system of claim 1, further including a fluid rail having a first end and a second end, the fluid rail being configured to supply fluid to the fluid actuator; and a fluid tank in selective fluid communication with the fluid rail. 7. The engine valve actuation system of claim 1, further including a directional control valve configured to control a flow of fluid between the source of fluid and the fluid actuator. 8. The engine valve actuation system of claim 1, wherein the source of fluid provides fluid having a pressure of between about 210 KPa and 620 KPa to the fluid rail. 9. A method of operating an engine valve actuation system, comprising: moving an engine valve, according to an engine timing, between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; directing fluid flow from a source of fluid to a chamber of a fluid actuator via first, second, and third longitudinally spaced apart passages in an actuator cylinder to slideably move an actuator piston in the actuator cylinder between a first position and an second position, the actuator piston having at least one passage in fluid communication with at least one of the first, second, and third passages; operatively engaging the fluid actuator with the engine valve when the piston is in the second position to modify the timing of moving the engine valve from the second position to the first position; passing fluid from the chamber to the source of fluid at a first rate at a time when the piston is moving from the second position toward the first position; and throttling said passing of fluid from the chamber to a second rate less than the first rate by blocking one of the first, second, and third passages from the chamber with said piston at a time when the piston is moving from the second position toward the first position. 10. The method of claim 9, further including: preventing fluid flow through at least one other of the first, second, and third passages during at least a portion of movement of the piston from the second position toward the first position. 11. An engine valve actuation system, comprising: an engine valve moveable between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; a valve actuation assembly operably connected to move the engine valve between the first position and the second position; a separate fluid actuator configured to selectively modify a timing of the engine valve in moving from the second position to the first position, the separate fluid actuator including a cylinder having a longitudinal direction, a piston, and a chamber, the cylinder including a snubbing orifice and first, second, and third passages longitudinally spaced apart in the cylinder, the piston having at least one passage in fluid communication with at least one of the first, second, and third passages and being slidably movable in the cylinder between a first position and a second position; and a source of fluid in fluid communication with the separate fluid actuator, the source of fluid being in fluid communication with the chamber via the snubbing orifice and the first, second, and third passages when the piston moves from the first position toward the second position, and fluid flow through at least one of the first, second, and third passages being prevented during at least a portion of movement of the piston from the second position toward the first position. 12. An engine valve actuation system, comprising: an engine valve moveable between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; a valve actuation assembly operably connected to move the engine valve between the first position and the second position; a fluid actuator configured to selectively modify a timing of the engine valve in moving from the second position to the first position, the fluid actuator including a cylinder and a piston cooperating to at least partly define a chamber, the piston being slidably movable in the cylinder between a first position and a second position; a source of fluid in communication with the fluid actuator; a pair of passages in the cylinder, said passages structured and arranged to allow fluid to flow from the chamber to the source of fluid at a time when the piston is moving from the second position toward the first position, said piston blocking at least a portion of one of said passages at an intermediate position between the second position and the first position so as to reduce the flow of fluid from the chamber at a time when the piston is moving from the second position toward the first position; a stop member cooperating with the actuator cylinder to retain at least a portion of the piston in the actuator cylinder; and a flow path configured to prevent hydraulic lock of the piston, wherein the flow path includes at least one flow passage in the stop member in fluid communication with a tank. 13. The engine valve actuation system of claim 12, wherein the cylinder includes at least one additional passage longitudinally spaced from said pair of passages, the source of fluid being in fluid communication with the chamber via the at least one additional passage when the piston moves from the first position toward the second position. 14. The engine valve actuation system of claim 13, further including a check valve configured to prevent fluid flow through the at least one additional passage during movement of the piston from the second position toward the first position. 15. The engine valve actuation system of claim 12, further including an accumulator configured to reduce the impact of pressure fluctuations within the system. 16. The engine valve actuation system of claim 12, further including: a fluid rail having a first end and a second end, the fluid rail being configured to supply fluid to the fluid actuator; and a fluid tank in selective fluid communication with the fluid rail. 17. The engine valve actuation system of claim 12, further including a directional control valve configured to control a flow of fluid between the source of fluid and the fluid actuator. 18. The engine valve actuation system of claim 12, wherein the source of fluid provides fluid having a pressure of between about 210 KPa and 620 KPa to the fluid rail. 19. An engine valve actuation system, comprising: an engine valve moveable between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; a valve actuation assembly operably connected to move the engine valve between the first position and the second position; a fluid actuator configured to selectively modify a timing of the engine valve in moving from the second position to the first position, the fluid actuator including a cylinder and a piston cooperating to at least partly define a chamber, the piston being slidably movable in the cylinder between a first position and a second position; a source of fluid in communication with the fluid actuator; a pair of passages in the cylinder, said passages structured and arranged to allow fluid to flow from the chamber to the source of fluid at a time when the piston is moving from the second position toward the first position, said piston blocking at least a portion of one of said passages at an intermediate position between the second position and the first position so as to reduce the flow of fluid from the chamber at a time when the piston is moving from the second position toward the first position; an accumulator configured to reduce the impact of pressure fluctuations within the system; and a restrictive orifice associated with the accumulator. 20. The engine valve actuation system of claim 19, wherein the cylinder includes at least one additional passage longitudinally spaced from said pair of passages, the source of fluid being in fluid communication with the chamber via the at least one additional passage when the piston moves from the first position toward the second position. 21. The engine valve actuation system of claim 20, further including a check valve configured to prevent fluid flow through the at least one additional passage during movement of the piston from the second position toward the first position. 22. The engine valve actuation system of claim 19, further including a stop member cooperating with the actuator cylinder to retain at least a portion of the piston in the actuator cylinder. 23. The engine valve actuation system of claim 22, further including a flow path configured to prevent hydraulic lock of the piston. 24. The engine valve actuation system of claim 19, further including an accumulator configured to reduce the impact of pressure fluctuations within the system. 25. The engine valve actuation system of claim 19, further including a directional control valve configured to control a flow of fluid between the source of fluid and the fluid actuator. 26. The engine valve actuation system of claim 19, further including: a fluid rail having a first end and a second end, the fluid rail being configured to supply fluid to the fluid actuator; and a fluid tank in selective fluid communication with the fluid rail. 27. The engine valve actuation system of claim 26, further including a restrictive orifice disposed between the source of fluid and the fluid rail. 28. The engine valve actuation system of claim 19, wherein the source of fluid provides fluid having a pressure of between about 210 KPa and 620 KPa to the fluid rail. 29. An engine valve actuation system, comprising: an engine valve moveable between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; a valve actuation assembly operably connected to move the engine valve between the first position and the second position; a fluid actuator configured to selectively modify a timing of the engine valve in moving from the second position to the first position, the fluid actuator including a cylinder and a piston cooperating to at least partly define a chamber, the piston being slidably movable in the cylinder between a first position and a second position; a source of fluid in communication with the fluid actuator; a pair of passages in the cylinder, said passages structured and arranged to allow fluid to flow from the chamber to the source of fluid at a time when the piston is moving from the second position toward the first position, said piston blocking at least a portion of one of said passages at an intermediate position between the second position and the first position so as to reduce the flow of fluid from the chamber at a time when the piston is moving from the second position toward the first position; a fluid rail having a first end and a second end, the fluid rail being configured to supply fluid to the fluid actuator; a fluid tank in selective fluid communication with the fluid rail; and a control valve configured to control a flow of fluid from the fluid rail to the fluid tank, the control valve being moveable between a first position that blocks a flow of fluid from the fluid rail to the fluid tank and a second position that allows a flow of fluid from the fluid rail to the fluid tank. 30. The engine valve actuation system of claim 29, wherein the cylinder includes at least one additional passage longitudinally spaced from said pair of passages, the source of fluid being in fluid communication with the chamber via the at least one additional passage when the piston moves from the first position toward the second position. 31. The engine valve actuation system of claim 30, further including a check valve configured to prevent fluid flow through the at least one additional passage during movement of the piston from the second position toward the first position. 32. The engine valve actuation system of claim 29, further including a stop member cooperating with the actuator cylinder to retain at least a portion of the piston in the actuator cylinder. 33. The engine valve actuation system of claim 32, further including a flow path configured to prevent hydraulic lock of the piston. 34. The engine valve actuation system of claim 29, further including an accumulator configured to reduce the impact of pressure fluctuations within the system. 35. The engine valve actuation system of claim 29, further including a directional control valve configured to control a flow of fluid between the source of fluid and the fluid actuator. 36. The engine valve actuation system of claim 29, further including a restrictive orifice disposed between the source of fluid and the fluid rail. 37. The engine valve actuation system of claim 29, wherein the source of fluid provides fluid having a pressure of between about 210 KPa and 620 KPa to the fluid rail. 38. An engine valve actuation system, comprising: an engine valve moveable between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; a valve actuation assembly operably connected to move the engine valve between the first position and the second position; a fluid actuator configured to selectively modify a timing of the engine valve in moving from the second position to the first position, the fluid actuator including a cylinder and a piston cooperating to at least partly define a chamber, the piston being slidably movable in the cylinder between a first position and a second position; a source of fluid in communication with the fluid actuator; a pair of passages in the cylinder, said passages structured and arranged to allow fluid to flow from the chamber to the source of fluid at a time when the piston is moving from the second position toward the first position, said piston blocking at least a portion of one of said passages at an intermediate position between the second position and the first position so as to reduce the flow of fluid from the chamber at a time when the piston is moving from the second position toward the first position; a fluid rail having a first end and a second end, the fluid rail being configured to supply fluid to the fluid actuator; a fluid tank in selective fluid communication with the fluid rail; and a restrictive orifice disposed between the source of fluid and the fluid rail. 39. The engine valve actuation system of claim 38, wherein the cylinder includes at least one additional passage longitudinally spaced from said pair of passages, the source of fluid being in fluid communication with the chamber via the at least one additional passage when the piston moves from the first position toward the second position. 40. The engine valve actuation system of claim 39, further including a check valve configured to prevent fluid flow through the at least one additional passage during movement of the piston from the second position toward the first position. 41. The engine valve actuation system of claim 38, further including a stop member cooperating with the actuator cylinder to retain at least a portion of the piston in the actuator cylinder. 42. The engine valve actuation system of claim 41, further including a flow path configured to prevent hydraulic lock of the piston. 43. The engine valve actuation system of claim 38, further including an accumulator configured to reduce the impact of pressure fluctuations within the system. 44. The engine valve actuation system of claim 38, further including a directional control valve configured to control a flow of fluid between the source of fluid and the fluid actuator. 45. The engine valve actuation system of claim 38, wherein the source of fluid provides fluid having a pressure of between about 210 KPa and 620 KPa to the fluid rail. 46. An engine valve actuation system, comprising: an engine valve moveable between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; a valve actuation assembly operably connected to move the engine valve between the first position and the second position; a fluid actuator configured to selectively modify a timing of the engine valve in moving from the second position to the first position, the fluid actuator including a cylinder and a piston cooperating to at least partly define a chamber, the piston being slidably movable in the cylinder between a first position and a second position; a source of fluid in communication with the fluid actuator; a pair of passages in the cylinder, said passages structured and arranged to allow fluid to flow from the chamber to the source of fluid at a time when the piston is moving from the second position toward the first position, said piston blocking at least a portion of one of said passages at an intermediate position between the second position and the first position so as to reduce the flow of fluid from the chamber at a time when the piston is moving from the second position toward the first position; a directional control valve configured to control a flow of fluid between the source of fluid and the fluid actuator; and a check valve, wherein the check valve and the directional control valve are disposed in parallel between the fluid actuator and the source of fluid. 47. The engine valve actuation system of claim 46, wherein the cylinder includes at least one additional passage longitudinally spaced from said pair of passages, the source of fluid being in fluid communication with the chamber via the at least one additional passage when the piston moves from the first position toward the second position. 48. The engine valve actuation system of claim 47, further including a check valve configured to prevent fluid flow through the at least one additional passage during movement of the piston from the second position toward the first position. 49. The engine valve actuation system of claim 46, further including a stop member cooperating with the actuator cylinder to retain at least a portion of the piston in the actuator cylinder. 50. The engine valve actuation system of claim 49, further including a flow path configured to prevent hydraulic lock of the piston. 51. The engine valve actuation system of claim 46, further including an accumulator configured to reduce the impact of pressure fluctuations within the system. 52. The engine valve actuation system of claim 46, further including a fluid rail having a first end and a second end, the fluid rail being configured to supply fluid to the fluid actuator; and a fluid tank in selective fluid communication with the fluid rail. 53. The engine valve actuation system of claim 52, further including a directional control valve configured to control a flow of fluid between the source of fluid and the fluid actuator. 54. The engine valve actuation system of claim 46, further including an air bleed valve disposed between the check valve and the fluid actuator. 55. The engine valve actuation system of claim 46, wherein the source of fluid provides fluid having a pressure of between about 210 KPa and 620 KPa to the fluid rail. 56. A method of operating an engine valve actuation system, comprising: moving an engine valve, according to an engine timing, between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; directing fluid flow between a source of fluid and a chamber of a fluid actuator to slideably move an actuator piston in an actuator cylinder between a first position and an second position; operatively engaging the fluid actuator with the engine valve when the piston is in the second position to modify the timing of moving the engine valve from the second position to the first position; passing fluid from the chamber to the source of fluid at a first rate at a time when the piston is moving from the second position toward the first position; throttling said passing of fluid from the chamber to a second rate less than the first rate by blocking a fluid passage from the chamber with said piston at a time when the piston is moving from the second position toward the first position; and retaining at least a portion of the actuator piston in the actuator cylinder with a stop member coupled with the actuator cylinder, the stop member defining at least a portion of a flow path configured to prevent hydraulic lock of the actuator piston. 57. The method of claim 56, further including: allowing fluid flow from the source of fluid to the chamber via at least one additional passage longitudinally spaced from said fluid passage when the piston moves from the first position toward the second position; and preventing fluid flow through the at least one additional passage during at least a portion of movement of the piston from the second position toward the first position. 58. A method of operating an engine valve actuation system, comprising: moving an engine valve, according to an engine timing, between a first position that blocks a flow of fluid and a second position that allows a flow of fluid; directing fluid flow between a source of fluid and a chamber of a fluid actuator to slideably move an actuator piston in an actuator cylinder between a first position and an second position; operatively engaging the fluid actuator with the engine valve when the piston is in the second position to modify the timing of moving the engine valve from the second position to the first position; passing fluid from the chamber to the source of fluid at a first rate at a time when the piston is moving from the second position toward the first position; throttling said passing of fluid from the chamber to a second rate less than the first rate by blocking a fluid passage from the chamber with said piston at a time when the piston is moving from the second position toward the first position; and reducing the impact of pressure fluctuations within the system with at least one of an accumulator and a restrictive orifice. 59. The method of claim 58, further including: allowing fluid flow from the source of fluid to the chamber via at least one additional passage longitudinally spaced from said fluid passage when the piston moves from the first position toward the second position; and preventing fluid flow through the at least one additional passage during at least a portion of movement of the piston from the second position toward the first position.