Rocker assembly having improved durability
A durable system is disclosed for controlling variable valve actuation of an engine valve corresponding to a cylinder of an automobile engine. The system is designed to have a durability that exceeds the expected life of a conventional automobile engine. The system includes first crowned cam having a first lift profile, a second crowned cam having a second lift profile, and a rocker arm assembly. The rocker assembly includes a first arm having an end connected to said engine valve, having a high impact roller following the first crowned cam operating the engine valves according to a first lift profile. The rocker arm assembly also includes a second arm having slider pads riding on the second crowned cam to operate said engine valve according to a second lift profile. The slider pads have a sliding surface covered with an impact-resistant multilayer coating with its outermost coating being a wear-resistant coating. A latch having adjustable latch lash secures the second arm relative to the first arm when in a latched position causing the valve to operate according to a second lift profile when the latch is in a latched position, and the valve is operated according to a first lift profile when the latch is not in a latched position.
1. A system for controlling variable valve actuation of an engine valve corresponding to a cylinder of an automobile engine having a durability exceeding the expected life of a conventional automobile engine, the system comprising:
a first crowned cam having a first lift profile;
a second crowned cam having a second lift profile; and
a rocker arm assembly comprising:
a first arm having an end connected to said engine valve, the first arm riding on the first crowned cam and having a high impact roller following the first crowned cam adapted to operate said engine valve according to the first lift profile;
a second arm having at least one slider pad adapted to ride on the second crowned cam to operate said engine valve according to the second lift profile; and
a latch adapted to have an adjustable latch lash and secure the second arm relative to the first arm when in a latched position;
wherein the valve is operated according to the second lift profile when the latch is in a latched position and
the valve is operated according to the first lift profile when the latch is not in a latched position.
2. The system of claim 1 wherein the high impact roller employs a hardened axle.
3. The system of claim 1 wherein the at least one slider pad comprises: two substantially parallel curved slider pads manufactured to have less than a predetermined included angle.
4. The system of claim 3 wherein: the substantially parallel curved slider pads have less than a +/−0.8 degree angle deviation.
5. The system of claim 3 wherein: the substantially parallel curved slider pads have less than a +/−0.4 degree angle deviation.
6. The system of claim 1 wherein: the at least one slider pad is coated with a multilayer wear-resistant coating including a layer exhibiting increased ductility as compared with that of the slider pad to absorb impact.
7. The system of claim 6 wherein: the at least one slider pad comprises a polished curved surface beneath the wear-resistant coating.
8. The system of claim 7 wherein: the at least one slider pad comprises an adhesion layer between the polished surface and the layer exhibiting increased ductility.
9. The system of claim 1 wherein the crowned cam is polished.
10. The system of claim 1 wherein the crowned cam comprises: a hardened cam having a raised center crown which reduces edge loading of the slider pads.
11. The system of claim 1 wherein crowned cam comprises: a crowned cam made of steel having a polished engagement surface.
12. The system of claim 1 , wherein the adjustable latch lash is adjustable within limits such that the adjustable latch lash and a cam lash comprise a total mechanical lash.
13. The system of claim 1 , wherein the adjustable latch lash comprises a spacing between a latch pad surface of the latch and an arm engaging surface of the second arm.
14. A system for controlling variable valve actuation of an engine valve corresponding to a cylinder of an automobile engine having a durability exceeding the expected life of a conventional automobile engine, the system comprising:
a first crowned cam having a first lift profile;
a second crowned cam having a second lift profile; and
a rocker arm assembly comprising:
a first arm having an end connected to said engine valve, the first arm riding on the first crowned cam and having a high impact roller following the first crowned cam adapted to operate said engine valve according to the first lift profile;
a second arm having at least one slider pad adapted to ride on the second crowned cam to operate said engine valve according to the second lift profile; and and
a latch adapted to have an adjustable latch lash and secure the second arm relative to the first arm when in a latched position,
wherein the at least one slider pat has a sliding surface covered with an impact-resistant multilayer coating with its outermost coating being a wear-resistant coating, and
wherein the valve is operated according to the second lift profile when the latch is in a latched position and the valve is operated according to the first lift profile when the latch is not in a latched position.
15. The system of claim 14 , wherein the impact-resistant multilayer coating comprises: a ductile layer between the wear-resistant coating and the at least one slider pad to absorb impacts and prevent the wear-resistant coating from cracking.
16. The system of claim 14 , wherein the sliding surface is polished before the impact-resistant multi-layer coating is applied.
17. The system of claim 14 , wherein the impact-resistant multilayer coating comprises: an adhesive layer between the ductile layer and the sliding surface.
18. The system of claim 14 , wherein the adjustable latch lash and an adjustable cam lash comprise a total mechanical lash that remains constant over a life of the engine valve for an engine using the system for controlling variable valve actuation of the cylinder.
19. The system of claim 14 , wherein the adjustable latch lash comprises a clearance or spacing between a latch pad surface of the latch and an arm engaging surface of the second arm.
20. The system of claim 14 , wherein the adjustable latch is a component of a dual feed hydraulic lash adjuster and further comprising remaining components of the dual feed hydraulic lash adjuster.