System and method of retaining hydraulic fluid in a hydraulic valve actuation system

1. A hydraulic valve actuation system adapted to be installed on an internal combustion engine, comprising:

a plurality of hydraulic passages connecting a piston bore, an accumulator, and a trigger valve;

a retaining passage connecting a hydraulic fluid supply to the hydraulic passages, the retaining passage having at least one portion elevated above at least one portion of the hydraulic passages;

an air vent provided along said retaining passage; and

means for selectively opening and closing the trigger valve during engine shut-off to maintain some hydraulic fluid in the hydraulic valve actuation system.

2. The system of claim 1 , wherein the retaining passage further comprises at least one u-shaped bend.

3. The system of claim 1 , further comprising a check valve disposed within the retaining passage.

4. The system of claim 1 , wherein the means for selectively opening and closing is adapted to close the trigger valve during at least a substantial portion of a main valve event.

5. A hydraulic valve actuation system adapted to be installed on an internal combustion engine, comprising:

a plurality of hydraulic passages connecting a piston bore, an accumulator, and a trigger valve to a hydraulic fluid supply;

a retaining passage connecting the hydraulic fluid supply to the hydraulic passages, the retaining passage having at least one portion elevated above at least one portion of the hydraulic passages; and

means for air to enter the retaining passage.

6. The system of claim 5 , wherein the retaining passage is elevated above a lower portion of the accumulator.

7. The system of claim 5 , wherein the retaining passage is elevated above a lower portion of the piston bore.

8. The system of claim 5 , wherein the retaining passage further comprises at least one u-shaped bend.

9. The system of claim 5 , further comprising a check valve disposed within the retaining passage.

10. A hydraulic valve actuation system adapted to be installed on an internal combustion engine, comprising:

a hydraulic fluid supply;

a fluid accumulator;

a passage connecting the fluid supply with the accumulator, the passage having at least one portion elevated above a point at which the passage connects to the accumulator; and

means for air to enter the passage at a point between the fluid supply and the accumulator.

11. The system of claim 10 , wherein the passage further comprises at least one u-shaped bend.

12. The system of claim 10 , further comprising a check valve disposed in the passage between the fluid supply and the fluid accumulator.

13. A hydraulic valve actuation system of an internal combustion engine, comprising:

a hydraulic fluid supply;

an accumulator; and

a passage connecting the fluid supply with the accumulator, the passage including a non-valve means for retarding the drainage of hydraulic fluid from the accumulator towards the hydraulic fluid supply.

14. A hydraulic valve actuation system adapted to be installed on an internal combustion engine, comprising:

a plurality of hydraulic passages connecting a piston bore, an accumulator, and a trigger valve to a hydraulic fluid supply; and

means for selectively opening and closing the trigger valve during engine shut-off to maintain some hydraulic fluid in the hydraulic valve actuation system.

15. The system of claim 14 , wherein the means for selectively opening and closing is adapted to close the trigger valve during at least a substantial portion of a main valve event.

16. The system of claim 14 , further comprising a check valve disposed within the hydraulic passages.

17. A method of retaining hydraulic fluid in a hydraulic valve actuation system used to actuate an engine valve, comprising the steps of:

providing hydraulic fluid to the hydraulic valve actuation system through a trigger valve during engine operation;

initiating engine shut-off; and

maintaining the trigger valve closed during a substantial portion of a main valve event responsive to initiation of engine shut-off,

wherein the hydraulic valve actuation system is operatively connected to a cam having at least a main event lobe and a base circle portion, said method further comprising the step of maintaining the trigger valve open during at least a substantial portion of the base circle cam portion.

18. A method of maintaining hydraulic fluid in a hydraulic valve actuation system operatively connected to a cam having one or more lobes, the method comprising the steps of:

providing hydraulic fluid to the hydraulic valve actuation system through a trigger valve during engine operation;

initiating engine shut-off; and

closing the trigger valve during one or more periods corresponding to one or more cam lobes responsive to initiation of engine shut-off,

wherein the trigger valve is closed during an exhaust gas recirculation event cam lobe.

19. A method of maintaining hydraulic fluid in a hydraulic valve actuation system operatively connected to a cam having one or more lobes, the method comprising the steps of:

providing hydraulic fluid to the hydraulic valve actuation system through a trigger valve during engine operation;

initiating engine shut-off; and

closing the trigger valve during one or more periods corresponding to one or more cam lobes responsive to initiation of engine shut-off,

wherein the trigger valve is closed during a braking event cam lobe.