Internal-combustion engines – Poppet valve operating mechanism – Rocker
Reexamination Certificate
1999-06-10
2001-04-10
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Rocker
C123S090330, C123S090500, C123S090510, C123S508000
Reexamination Certificate
active
06213075
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a roller follower assembly for a reciprocating engine and more particularly to an axle pin for use with the roller follower assembly.
BACKGROUND ART
Engine manufacturers strive to improve performance of internal combustion engines by maximizing the conversion of chemical energy to mechanical energy. The conversion efficiency may be improved when losses of energy used to overcome friction between moving parts in the engine are reduced. Mechanical design along with oil and other lubricants aid in reducing these losses.
Roller follower assemblies are mechanical design improvements that reduce friction losses between a cam and a rocker arm. Past systems used a sliding contact between the cam and rocker arm. These systems resulted in large frictional losses. Also, these systems experienced increased wear. Roller follower assemblies reduce friction between the cam and rocker arm by changing the sliding contact to a rolling contact. However, roller follower assemblies may still have a problem with wear.
Each roller rotates about an axle pin. Typically, oil reduces sliding friction between a roller and an axle pin. Oil also provides an additional and equally important role of cleaning the engine. Oil along with an oil filter system may remove particles above a particular size. However, the roller and axle pin may ingest smaller particles. At some point these small particles may cause sliding between the roller and axle pin to cease. The interruption in sliding stops the rolling contact between the cam and roller and causes sliding contact between the cam and roller. The sliding contact between the roller and cam may cause a tearing damage at their respective surfaces.
The present invention is directed to overcoming one or more of the problems set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention a roller follower assembly for an internal combustion engine comprises a roller having a central bore. An axle pin is positioned within the central bore. A hard coating is disposed between the axle pin and the roller.
In another aspect of the present invention a method for improving wear of a roller follower assembly on an internal combustion engine includes lubricating an axle pin and a roller. Particles present during the lubricating step are reduced. Remaining particles are pulverized between the axle pin and the roller.
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Ajayi Oyelayo O.
Becker, Jr. Theodore H.
Dam Chuong Q.
Zhang Jian
Caterpillar Inc.
Lo Weilun
Roberson Keith P.
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