Lost-motion variable valve actuation system with cam phaser
Devices and related methods are disclosed that generally involve variable actuation of engine valves. In one embodiment, a valve train for a split-cycle internal combustion engine or an air hybrid split-cycle engine is provided that includes a cam phaser, a dwell cam, an adjustable mechanical element for performing a variable valve actuation function, and/or a valve seating control device. The devices and methods disclosed herein also have application in conventional internal combustion engines and can actuate inwardly-opening and/or outwardly-opening valves.
1. A rocker assembly, comprising:
a rocker mounted to a rocker pedestal having an adjustable height;
a wedge-shaped bearing element slidably disposed between first and second portions of the rocker pedestal;
wherein withdrawing the wedge-shaped bearing element from between the first and second portions is effective to decrease the height of the pedestal.
2. The rocker assembly of claim 1 , wherein the rocker is rotatably mounted on a rocker shaft having an aperture formed therein in which a projection of a fixed rocker support is slidably received.
3. The rocker assembly of claim 2 , wherein the projection has a fixed position relative to a cam configured to actuate the rocker such that the projection guides vertical movement of the rocker and limits the degree to which a pivot point of the rocker can be adjusted.
4. The rocker assembly of claim 1 , wherein sliding movement of the bearing element relative to the rocker pedestal is effective to adjust a height of the rocker pedestal.
5. The rocker assembly of claim 1 , further comprising a plurality of bearings disposed between the bearing element and the rocker pedestal to facilitate sliding movement of the bearing element relative to the rocker pedestal.
6. The rocker assembly of claim 1 , wherein the bearing element has a wedge angle of about 0 degrees to about 25 degrees.
7. The rocker assembly of claim 1 , further comprising an actuator configured to vary the degree to which the bearing element is inserted between the first and second portions of the rocker pedestal to adjust a height of the rocker pedestal and thereby vary the degree to which motion of a cam is imparted to the rocker.
8. The rocker assembly of claim 7 , further comprising a connecting arm that is rotatably coupled to the actuator and non-rotatably coupled to the bearing element.
9. The rocker assembly of claim 7 , wherein the actuator is collapsible along a length thereof to allow the bearing element to be pushed away from the rocker pedestal.
10. The rocker assembly of claim 7 , wherein the actuator has a stroke that is greater than or equal to an amount of valve lift lost by collapsing the rocker pedestal and that is less than or equal to three times the amount of valve lift lost by collapsing the rocker pedestal.
11. A rocker assembly comprising:
a rocker rotatably mounted about a rocker shaft;
a support housing having a first portion and a second portion, the rocker shaft being supported by the first portion;
a femur having a first end and an opposed second end, the first end of the femur being rotatably coupled to the first portion of the support housing;
a shin having a first end and an opposed second end, the first end of the shin being rotatably coupled to the second end of the femur at a knee joint, the second end of the shin being rotatably coupled to the second portion of the support housing; and
an actuator configured to vary the angle of the knee joint to adjust a height of the rocker shaft and thereby vary the degree to which motion of a cam is imparted to the rocker.
12. The rocker assembly of claim 11 , wherein the first portion of the support housing includes a hemi-cylindrical slot that receives a corresponding hemi-cylindrical edge formed at the first end of the femur.
13. The rocker assembly of claim 11 , wherein the first portion of the support housing includes a hemi-cylindrical protrusion that is received in a first hemi-cylindrical slot formed in the first end of the femur.
14. The rocker assembly of claim 11 , wherein the femur includes a reduced-thickness central portion disposed between the first and second ends of the femur.
15. The rocker assembly of claim 11 , wherein the shin includes a hemi-cylindrical slot that receives a corresponding hemi-cylindrical edge formed at the second end of the femur.
16. The rocker assembly of claim 15 , wherein the actuator bears against a leading edge of the hemi-cylindrical slot such that the leading edge acts as a lever to provide a mechanical advantage.
17. The rocker assembly of claim 11 , wherein the knee joint is positionable in at least a fully-extended configuration and a fully-collapsed configuration.
18. The rocker assembly of claim 17 , wherein:
when the knee joint is positioned in the fully-extended configuration, an angle between a longitudinal axis of the femur and a longitudinal axis of the support housing is about 8 degrees; and
when the knee joint is positioned in the fully-collapsed configuration, an angle between a longitudinal axis of the femur and a longitudinal axis of the support housing is about 23 degrees.
19. The rocker assembly of claim 11 , wherein the actuator comprises:
a cylinder in which a hydraulic actuation piston is reciprocally disposed; and
a control valve configured to selectively allow fluid to be drained from the cylinder such that the piston can be driven into the cylinder away from the rocker pedestal.
20. The rocker assembly of claim 19 , wherein the cylinder is in fluid communication with the control valve via one or more orifices which are progressively occluded as the piston is driven into the cylinder.
21. The rocker assembly of claim 19 , wherein the piston bears against the shin such that, when the control valve is closed, the piston holds the knee joint in an extended configuration and, when the control valve is opened, the knee joint drives the piston into the cylinder and transitions to a collapsed configuration.
22. The rocker assembly of claim 21 , wherein, when the piston is driven into the cylinder by the knee joint, the rocker is lowered by a distance that is less than the distance the piston travels.