Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
1999-04-23
2001-05-15
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090360, C074S559000
Reexamination Certificate
active
06230676
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to rocker arm assemblies for internal combustion engines and, in particular, to internal combustion engines for motor vehicles. The rocker arm assemblies of the present invention have unique lubrication systems and also permit both a bearingless and a roller bearing type rocker arm shaft assembly to be interchangeably mounted in a same engine.
BACKGROUND OF THE INVENTION
Rocker arm assemblies are utilized in internal combustion engines for alternately actuating intake and exhaust valves. As an engine cam shaft rotates, a push rod is selectively actuated by cams located on the cam shaft. The push rods, in turn, direct an upward force on one end of a rocker arm to cause the rocker arm to pivot about a mounting shaft. As the rocker arm pivots, its opposite end generates a downward force to selectively open an intake or exhaust engine valve.
Typically, rocker arms are integral, one-piece parts having a generally U-shaped cross-section including a pair of opposing side walls separated by a bottom wall and a pair of end walls disposed between the side walls. Rocker arms are conventionally either stamped or cast. The above described U-shaped rocker arms are commonly referred to as “boat-type” rocker arms. U-shaped rocker arms generally have adequate stiffness. However, the increased mass and width of U-shaped rocker arms negatively affects the moment of inertia, which is important for engine components reciprocating at very high frequencies. Increased mass also decreases vehicle fuel efficiency. Some other disadvantages of U-shaped rocker arms include loud operating noise, vibration, and undesirable levels of friction.
Lubrication in conventional U-shaped rocker arm assemblies is provided through hollow push rods that channel lubricant up to a lubricant aperture in one end of an adjacent rocker arm. Then lubricant flows onto the bottom wall in between the side walls of the rocker arm.
The previously known rocker arm assemblies include variations having so-called “frictionless” bearings and assemblies without bearings. However, none of the prior known devices allow a bearingless rocker arm shaft assembly to be interchanged with a frictionless bearing rocker arm shaft assembly within the same basic engine design configuration. The incompatibility of the prior art decreases engine manufacturer flexibility by forcing a selection between the higher costs associated with multiple engine design configurations or only being able to offer a single engine design with only one type of rocker arm s haft assembly.
Further, the prior art rocker arm designs lack the ability to have a rocker arm supplier provide a fully pre-assembled rocker arm shaft assembly that can be shipped to and installed at the engine manufacturer's assembly plant. Instead, the prior art designs require the engine manufacturer to pre-assemble the components. Thus, the prior art designs are more susceptible to having loose, individual component parts lost during shipping and handling. Moreover, the prior art designs increase inventory burden on the engine manufacturer and often result in inadequate rotation of parts in inventory.
SUMMARY OF THE INVENTION
The present invention is directed to a rocker arm assembly including a central mounting shaft having at least one rocker arm rotatably mounted to the central shaft. The rocker arm has a generally planar main body with first and second ends and first and second side surfaces and a central aperture that receives a tubular section. In addition, the first end of the rocker includes a convex surface for contacting a valve stem. The convex surface extends laterally beyond at least one of the first and second side surfaces of the planar main body.
The second end of the rocker arm includes a generally hollow recess formed adjacent an edge of the planar main body such that an outer projection is formed on each of the first and second side surfaces of the planar main body. The hollow recess receives an end of a push rod for transmission of forces from an engine cam shaft. Also, the tubular section of the rocker arm surrounds the central shaft and intersects the main body at a predetermined angle.
The present invention further provides an improved lubrication system for efficiently distributing lubricant to the valve stem contact surface of the rocker arm. In one embodiment of the present invention, a hollow central shaft has lubricant apertures that align with a lubricant bore provided in the rocker arm. The lubricant bore of the rocker arm extends from the central aperture of the rocker arm to a top edge of the rocker arm, near a high point or apex thereof Thus, lubricant is channeled up from the hollow central shaft through the rocker arm to an apex on its top edge before flowing downwardly toward the valve stem contact surface via a groove located on the outer edge of the rocker arm. Such a lubrication system permits fast delivery of lubricant because the lubricant flows over a shorter distance from an approximate center of the rocker arm to the valve stem contact surface.
According to a second embodiment of the present invention, another improved lubrication system is provided. In the second embodiment, a central mounting shaft is formed from a series of relatively short, hardened shafts connected together at respective adjoining ends by a joining spacer sleeve. The joining spacer sleeve includes a split for increasing clamping load to retain the adjoining ends of the shafts. Further, a lubrication flow channel is provided on the joining spacer sleeve to collect and direct lubricant toward an interface between the rocker arm and the central mounting shaft. In the second embodiment, lubricant flows through a hollow push rod, up through a lubricant aperture in one end of the rocker arm, and then to the valve stem contact end of the rocker arm via a groove in the rocker arm top surface. Lubricant also overflows from the groove and is caught in the channel of the joining spacer sleeve to direct lubricant toward roller bearing elements on which the rocker arms are mounted.
In addition, a thrust washer is optionally located on the central mounting shaft and has a central aperture for receiving the central shaft. The thrust washer has a recessed portion on an inside diameter to form a lubricant passageway through the thrust washer to lubricate a set of roller bearings that mount the rocker arm onto the central mounting shaft.
The rocker arm assemblies of the present invention have two piece rocker arms that are relatively thin, stamped plates connected to a tubular element. The different configuration of the present rocker arms, (e.g., they are relatively thin compared to the prior art), allows a greater number of engine towers to be provided on an engine, resulting in greater overall system stiffness. In addition, lighter weight rocker arms have less reciprocating mass about the intake and exhaust valves, providing a lower moment of inertia and increased engine efficiency. Thus, the present rocker arm design reduces weight and noise and has a better moment of inertia than traditional U-shaped rocker arms.
In addition, a rocker arm subassembly is disclosed having a relatively short shaft with first and second ends and a plurality of through bores for attaching the shaft to an engine. Only first and second rocker arms are spaced apart on the short shaft and positioned for rotational movement. A spacer is located on the shaft between the first and second rocker arms to accurately position the first and second rocker arms. At least two of the relatively short shafts are connected together to form an engine rocker arm assembly.
Further, the present invention contemplates a complete assembly of rocker arms mounted on one or more shafts that can be shipped in a fully pre-assembled condition to an engine maker for ready installation into a cylinder head of an engine. The component parts of the rocker arm shaft assembly are securely held together, preventing unwanted loss of parts during shipping and handling. Further, the present inventi
DeLong Rodney E.
Pryba Stanley J.
Shook Terry R.
Denion Thomas
Nguyen Tu M.
Rader & Fishman & Grauer, PLLC
Toledo Technologies Inc.
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