Lash adjustment in lost motion engine systems
Systems for valve actuation in internal combustion engines provide configurations for hydraulic lash adjusters and valve actuation valvetrain components that are particularly suitable for prevention of HLA jacking in lost motion cam environments and in valve bridge environments. In one implementation, a rocker arm may transmit motion from a lost motion cam having main event and auxiliary event lobes. Main event motion is transmitted to two engine valves through the rocker arm, a lash adjuster, lash adjuster loading component and valve bridge, which define part of a first load path. Braking motion is transmitted to one of the engine valves through an inboard valve actuator and bridge pin, which define part of a second load path. The HLA is thus disposed in a separate load path from the braking valve load and the lash adjuster loading component keeps the lash adjuster under a constant compressive force to prevent jacking.
1. An apparatus for actuating at least one of two or more engine valves in an internal combustion engine, comprising:
a valve bridge operatively associated with the two or more engine valves;
a rocker arm for transmitting motion from a motion source to the valve bridge through a first load path;
a valve actuator for transmitting motion from the motion source to one of the two or more engine valves through a second load path;
a lash adjuster disposed in the first load path;
a lash adjuster loading assembly disposed in the first load path and adapted to prevent overextension of the lash adjuster when the valve actuator transmits motion to the one engine valve.
2. The apparatus of claim 1 , wherein the lash adjuster is g hydraulic lash adjuster disposed in the rocker arm.
3. The apparatus of claim 2 , wherein the lash adjuster loading assembly comprises a piston located in the valve bridge and is biased in a direction that compresses the lash adjuster.
4. The apparatus of claim 1 wherein the lash adjuster loading assembly comprises a piston, a biasing element for biasing the piston in a direction that compresses the lash adjuster, and a stroke-limiter for limiting the stroke of the piston.
5. The apparatus of claim 2 , wherein the lash adjuster loading assembly comprises a piston disposed on a bore in the rocker arm and a biasing element for biasing the piston in a direction that compresses the lash adjuster.
6. The apparatus of claim 1 , wherein the lash adjuster is disposed within a bore in the valve bridge.
7. The apparatus of claim 6 , wherein the lash adjuster loading assembly comprises a piston disposed the bore in the valve bridge for biasing the piston in direction that compresses the lash adjuster.
8. The apparatus of claim 1 , wherein the motion source is a lost-motion cam lobe having a main event portion of the cam lobe and an auxiliary event portion of the same cam lobe.
9. The apparatus of claim 8 , where the main event portion of the cam lobe represents a primary motion source and the secondary portion of the same cam lobe represents an aux motion source.
10. The apparatus of claim 1 , wherein the valve actuator is a lost motion device.
11. The apparatus of claim 10 , further comprising a rocker shaft for the rocker arm, wherein the valve actuator is located closer to the rocker shaft than the lash adjuster.
12. The apparatus of claim 1 , wherein the lash adjuster is housed in the rocker arm.
13. The apparatus of claim 12 , wherein the lash adjuster loading assembly is housed in the valve bridge.
14. The apparatus of claim 1 , wherein the lash adjuster is housed in the valve bridge.
15. The apparatus of claim 14 , wherein the lash adjuster loading assembly is housed in the valve bridge.
16. The apparatus of claim 1 , wherein the lash adjuster loading assembly is a lost motion device.
17. The apparatus of claim 1 , wherein the lash adjuster loading assembly includes a stroke-limited piston.
18. The apparatus of claim 1 , wherein the first load path and second load path are coextensive, the lash adjuster and valve actuator being disposed in the same load path.
19. An apparatus for actuating at least one of two or more engine valves in an internal combustion engine, comprising:
a rocker arm operatively associated with one or more engine valves and configured for transmitting motion from a motion source to one or more engine valves;
a lash adjuster disposed in the rocker arm;
a lash adjuster loading assembly disposed in the rocker arm and configured to apply compressive load to the lash adjuster,
wherein the lash adjuster loading assembly is adapted to permit lost motion;
and wherein the lash adjuster loading assembly may be selectively locked in an extended state to activate an auxiliary lift profile on the motion source.
20. An apparatus for actuating at least one of two or more engine valves in an internal combustion engine, comprising:
a valve bridge operatively associated with the two or more engine valves;
a rocker arm for transmitting motion from a motion source to the valve bridge through a first load path;
a valve actuator for transmitting motion from the motion source to one of the two or more engine valves through a second load path;
a lash adjuster disposed in the first load path, the lash adjuster being adapted to automatically extend to take up lash in the first load path; and
a lash adjuster loading assembly disposed in the first load path for applying a load to the lash adjuster to prevent overextension thereof.