Sliding contact for electrically actuated rocker arm
A valvetrain for an internal combustion engine of the type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft includes a rocker arm assembly, a pivot providing a fulcrum for a rocker arm of the rocker arm assembly, and a latch assembly. An electrical device mounted to the rocker arm assembly receives power or communicates through a circuit that includes an electrical connection formed by abutment between surfaces of two distinct parts. The rocker arm assembly is operative to move one of the two abutting surfaces relative to the other in response to actuation of the cam follower. Forming an electrical connection through abutting surfaces that are free to undergo relative motion may reduce or eliminate the need to run wires to a mobile portion of the rocker arm assembly.
1. A valvetrain for an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft, the valvetrain comprising:
a rocker arm assembly comprising a rocker arm and a cam follower configured to engage a cam mounted on the camshaft as the camshaft rotates; and
an electrical circuit comprising an electrical device mounted to the rocker arm;
wherein the electrical circuit includes an electrical connection made by abutment between a first surface belonging to a first part and a second surface belonging to a second part; and
the rocker arm assembly is operative to move the first surface relative to the second surface in response to actuation of the cam follower.
2. A valvetrain according to claim 1 , wherein:
the first part is mounted to the rocker arm; and
mountings for the second part consist of mountings to structures that are not part of the rocker arm assembly.
3. A valvetrain according to claim 2 , wherein the second part is mounted to a frame that has a base that fits around a pivot that provides a fulcrum for the rocker arm assembly.
4. A valvetrain according to claim 2 , wherein the second part is mounted to a frame that has a base that abuts two or more pivots that provide fulcrums for rocker arm assemblies of the valvetrain.
5. A valvetrain according to claim 1 , wherein:
the rocker arm assembly is configured to pivot in a plane; and
at least one of the first surface and the second surface is parallel to the plane.
6. A valvetrain according to claim 1 , further comprising:
a lash adjuster that provides a fulcrum for the rocker arm assembly;
wherein one of the first surface and the second surface runs parallel to a direction in which the lash adjuster extends to adjust lash.
7. A valvetrain according to claim 1 , further comprising:
a lash adjuster that provides a fulcrum for the rocker arm assembly;
wherein the first surface and the second surface are configured to slide relative to one another while remaining in contact as the lash adjuster extends and retracts to adjust lash.
8. A valvetrain according to claim 1 , further comprising:
a hydraulic lash adjuster that provides a fulcrum for the rocker arm assembly;
wherein the first surface and the second surface are configured to maintain the electrical connection as the hydraulic lash adjuster extends and retracts between pumped up and depressurized states.
9. A valvetrain according to claim 1 , wherein:
the rocker arm assembly is configured to pivot on a fulcrum when actuated through the cam follower; and
the electrical connection is made proximate the fulcrum.
10. A valvetrain according to claim 1 , wherein the electrical connection is isolated from ground.
11. A valvetrain according to claim 1 , wherein the electrical device is a coil forming part of an electromagnetic latch assembly.
12. A valvetrain according to claim 11 , wherein:
the electromagnetic latch assembly switches the rocker arm assembly between first and second configurations;
in the first configuration, the rocker arm assembly is operative to actuate a moveable valve in response to rotation of the camshaft to produce a first valve lift profile; and
in the second configuration, the rocker arm assembly is operative to actuate the moveable valve in response to rotation of the camshaft to produce a second valve lift profile, which is distinct from the first valve lift profile, or the moveable valve is deactivated.
13. A valvetrain according to claim 1 , wherein the first surface and the second surface are biased against the each other by a spring.
14. A valvetrain according claim 13 , wherein the spring is a leaf spring.
15. A valvetrain according to claim 1 , wherein the first part is a contact held to a side of the rocker arm by a contact frame that is supported within an opening at a back end of the rocker arm.
16. A valvetrain according to claim 15 , wherein the contact frame is secured to two opposite sides of the rocker arm.
17. A valvetrain according to claim 1 , wherein the rocker arm assembly is operative to cyclically break or vary a resistance of the electrical connection in relation to actuation of the cam follower.
18. A valvetrain according to claim 17 , wherein one of the first surface and the second surface is operative to abut a third surface to form a second electrical connection over a period when the first surface and the second surface are not abutting.
19. A valvetrain according to claim 17 , wherein:
one of the first surface and the second surface is a partially coated surface that is partially coated with a material that increases electrical resistance; and
the valvetrain is operable to move the electrical connection between a coated portion of the partially coated surface and an uncoated portion of the partially coated surface, whereby the resistance of the electrical connection varies.
20. A valvetrain according to claim 1 , wherein a load-bearing structure of the valvetrain forms a part of the electrical circuit.
21. A valvetrain according to claim 1 , wherein the electrical circuit is completed by a mechanical interface between two load-bearing structures of the valvetrain.
22. An internal combustion engine comprising:
a combustion chamber;
a moveable valve having a seat formed in the combustion chamber;
a camshaft; and
a valvetrain comprising a rocker arm assembly that comprises a rocker arm and a cam follower configured to engage a cam mounted on the camshaft as the camshaft rotates and an electrical circuit that comprises an electrical device mounted to the rocker arm;
wherein the electrical circuit includes an electrical connection made by abutment between a first surface belonging to a first part and a second surface belonging to a second part;
the rocker arm assembly is operative to move the first surface relative to the second surface in response to actuation of the cam follower; and
the first surface and the second surface are electrically isolated from the combustion chamber.
23. The engine of claim 22 , wherein:
the first part is mounted to the rocker arm;
the second part is mounted to a frame that has a base that rests against a cylinder head in which the combustion chamber is formed and abuts a pivot that provides a fulcrum for the rocker arm assembly.
24. The engine of claim 23 , wherein the frame rests against the cylinder head at a point on the cylinder head that is higher above the combustion chamber than the rocker arm assembly and at a point on the cylinder head that is less high above the combustion chamber than the rocker arm assembly.
25. The engine of claim 22 , wherein:
the first surface and the second surface are biased against each other by a leaf spring; and
an end of the leaf spring is held stationary relative to the combustion chamber.
26. A method of operating an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, a camshaft on which a cam is mounted, and a valvetrain that includes a rocker arm assembly comprising a rocker arm and a cam follower configured to engage the cam mounted on the camshaft as the camshaft rotates and an electrical circuit comprising an electrical device mounted to the rocker arm and an electrical connection made by abutment between a first surface belonging to a first part and a second surface belonging to a second part, the method comprising:
configuring the electrical connection to cyclically break or vary in resistance in relation to movement of the rocker arm;
actuating the rocker arm assembly using the cam follower;
assessing a status of the electrical connection via the circuit;
monitoring movement of the rocker arm based on the status assessment to acquire information related to movement of the rocker arm; and
performing an engine management operation or making a diagnostic determination using the information.