Lost motion variable valve actuation systems and method
A compact, modular, lost motion variable valve actuation assembly includes a dry start hydraulic circuit to enable quick priming of a lost motion master-slave circuit from a dry start reservoir to the master piston chamber during engine start. Motion of the master piston on engine startup may draw in fluid from the dry start hydraulic circuit. The dry start components may be integrated into a compact modular rocker shaft pedestal package suitable for retrofit on existing engine head assemblies. The master piston may include a push tube interface that includes a deep push tube cavity and lubrication capabilities in the master piston that provides for improved wear, stability, easy installation and alignment. The slave piston may be provided with a valve catch to reduce valve closing velocity during cycles involving lost-motion.
1. An engine valve actuation assembly for controlling motion of at least one engine valve in an engine comprising:
a motion source;
an engine valve train for conveying motion from the motion source to the at least one engine valve, the engine valve train including a housing;
a master piston bore defined in the housing;
a master piston cooperating with the master piston bore to define a master piston chamber; the master piston having a motion receiving interface for receiving motion from the motion source;
a slave piston bore defined in the housing;
a slave piston cooperating with the slave piston bore to define a slave piston chamber; the slave piston having a motion transferring interface for transferring motion to a motion receiving component in the engine valve train and to the at least one engine valve, the slave piston chamber being in hydraulic communication with the master piston chamber;
a control piston bore defined in the slave piston;
a control piston cooperating with the control piston bore to define an auto-lashing chamber;
a control pin operatively connected to the control piston, the control pin having multiple control pin ports arranged to permit flow from the slave piston chamber to the master piston chamber;
a check disk cooperating with the control pin such that the check disk progressively occludes flow through at least one of the multiple control pin ports in response to motion of the slave piston during engine valve closing; and
a valve catch seat having a common seating surface for the control pin and check disk, wherein the common seating surface facilitates precise positioning of the check disk relative to the control pin,
wherein at least one of the multiple control pin ports in the control pin is not occluded by the check disk when the at least one engine valve is in a seated position.
2. The engine valve actuation assembly of claim 1 , wherein the check disk is adapted to contact the valve catch seat when a lift of the at least one engine valve is below a threshold.
3. The engine valve actuation assembly of claim 2 , wherein the control pin is adapted to contact the valve catch seat just prior to seating of the at least one engine valve.
4. The engine valve actuation assembly of claim 1 , wherein at least one of the multiple control pin ports is a circular hole.
5. The engine valve actuation assembly of claim 1 , wherein a check disk stop on the control pin retains the check disk.
6. The engine valve actuation assembly of claim 1 , wherein a check disk spring is disposed between the control piston and the check disk.
7. The engine valve actuation assembly of claim 1 , wherein a control pin spring is disposed between the slave piston and the control pin.
8. The engine valve actuation assembly of claim 1 , further comprising a hydraulic passage between the master piston and slave piston.
9. The engine valve actuation assembly of claim 8 , wherein the hydraulic passage comprises a bellmouth at a top of the master piston bore.
10. The engine valve actuation assembly of claim 1 , wherein the control piston and control pin are operatively connected by means of a press fit.
11. The engine valve actuation assembly of claim 1 , further comprising a hydraulic control circuit in hydraulic communication with the master piston chamber.
12. The engine valve actuation assembly of claim 11 , wherein the hydraulic control circuit comprises an accumulator.
13. The engine valve actuation assembly of claim 11 , wherein the hydraulic control circuit comprises a dry start reservoir.
14. The engine valve actuation assembly of claim 11 , wherein the hydraulic control circuit comprises a solenoid valve for controlling flow of hydraulic fluid to and from the master piston chamber.
15. The engine valve actuation assembly of claim 11 , wherein the hydraulic control circuit is integrated into the housing.
16. The engine valve actuation assembly of claim 1 , wherein the housing is a rocker shaft pedestal adapted to be mounted to an engine overhead assembly.
17. The engine valve actuation assembly of claim 1 , wherein the housing is a rocker pedestal and wherein a hydraulic circuit is integrated into the rocker pedestal to provide a modular add-on assembly adapted to be attached to an engine head.
18. The engine valve actuation assembly of claim 1 , wherein the check disk includes an annular skirt defining a check disk seating surface.
19. The engine valve actuation assembly of claim 1 , wherein at least one of the multiple control pin ports extend radially through the control pin.
20. The engine valve actuation assembly of claim 1 , wherein the control piston comprises a control pin collar adapted to provide guided movement of the control pin.
21. The engine valve actuation assembly of claim 1 , further comprising a control pin spring arranged and adapted to provide a biasing force on the control pin relative to the slave piston.
22. The engine valve actuation assembly of claim 1 , further comprising a check disk spring arranged and adapted to bias the check disk relative to the control pin.
23. The engine valve actuation assembly of claim 1 , wherein the control pin defines an annular control pin seating surface.
24. The engine valve actuation assembly of claim 1 , wherein the check disk includes a metering edge arranged to progressively occlude at least one of the multiple control pin ports.
25. The engine valve actuation assembly of claim 1 , wherein at least one of the multiple control pin ports extend radially within the control pin and wherein the control pin defines an annular control pin seating surface.
26. An engine valve actuation assembly for controlling motion of at least one engine valve in an engine comprising:
a motion source;
an engine valve train for conveying motion from the motion source to the at least one engine valve, the engine valve train including a housing;
a master piston bore defined in the housing;
a master piston cooperating with the master piston bore to define a master piston chamber; the master piston having a motion receiving interface for receiving motion from the motion source;
a slave piston bore defined in the housing;
a slave piston cooperating with the slave piston bore to define a slave piston chamber; the slave piston having a motion transferring interface for transferring motion to a motion receiving component in the engine valve train and to the at least one engine valve, the slave piston chamber being in hydraulic communication with the master piston chamber;
a control piston bore defined in the slave piston;
a control piston cooperating with the control piston bore to define an auto-lashing chamber;
a control pin operatively connected to the control piston, the control pin having multiple control pin ports, arranged to permit flow from the slave piston chamber to the master piston chamber; and
a check disk cooperating with the control pin such that the check disk progressively occludes flow through at least one of the multiple control pin ports in response to motion of the slave piston during engine valve closing,
wherein at least one of the multiple control pin ports in the control pin is not occluded by the check disk when the at least one engine valve is in a seated position.