Internal-combustion engines – Poppet valve operating mechanism – Tappet
Patent
1980-09-19
1983-01-04
Feinberg, Craig R.
Internal-combustion engines
Poppet valve operating mechanism
Tappet
F01L 114
Patent
active
043667856
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to tappets for use in internal combustion engines and more particularly to tappets having inserts designed to resist wear resulting from cam contact.
BACKGROUND ART
The cam contacting face of tappets used in internal combustion engines is subjected to the significant abrading and heat inducing action of a cam repeatedly striking and rubbing across it. As this face becomes worn, tappet travel is changed causing valve motion to be altered consequently affecting engine performance. Eventually, engine performance is decreased to the point where rectification of this problem is mandatory. Wear of the tappet can also result in damage to the cam that drives it.
Extensive efforts have been made to minimize tappet wear so as to avoid the consequent problems. Most attempts at a solution to this wear have centered on providing a hardened face for cam contact. In U.S. Pat. No. 2,817,144 issued to Zeller on May 25, 1953 there is disclosed a tappet with a carbide facing attached thereto by brazing. This development and refinements thereof are commonly used improvements on the standard tappet. All suffer the defect of relying on a brazed joint for adherence of the wear resisting face to the tappet proper. Stresses on this joint due to differing coefficients of thermal expansion between the joined surfaces can result in separation of the wear resisting surface from the tappet.
Many other schemes for joining hardened surfaces to tappets have been proposed, none of which yield a totally satisfactory product. Robinson et al in U.S. Pat. No. 3,198,182 issued Aug. 3, 1965 describe a tappet including a hardened wear face formed and bonded to the tappet by techniques of powder-metallurgy. Such tappets are very expensive and consequently are not widely used.
German Pat. No. 2,209,926 issued to Bertinetti on Sept. 14, 1972 discloses a tappet formed of a steel wear face implanted in a plastic or nylon main body. In this invention, the wear face is embedded in the tappet during the molding of the plastic main body. Such a tappet would be limited in application to engines in which the tappet temperature and mechanical loadings are sufficiently low so as to be within the material limitations of the synthetic substance from which the main body is fabricated.
French Pat. No. 1,020,632, issued to Robig on Feb. 9, 1953, relates to a tappet with a hardened cam contacting wear face made of cast iron or some ceramic material. In this invention the insert is retained in place by a dovetailed joint, the tappet main body being cast with the prefashioned dovetailed wear surface in place. A drawback of this invention is the expense of casting the tappet with the wear resisting insert in place. Also, if the insert is metallic, detrimental metallurgic changes can occur within it should its temperature be sufficiently elevated in the process of casting the tappet main body around it.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention a tappet for use in an internal combustion engine has a main body and a cam contacting face that is especially wear resistant. This cam contacting face includes an annular rim extending outward from the tappet main body, this rim defining a recess in which is set a wear resisting insert retained by an interference fit and being preferably fashioned of a ceramic material. The face of the rim and the wear resisting insert are substantially flush.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, reference may be had to the accompanying drawings in which:
FIG. 1 is a diagrammatic side view of an embodiment of the present invention and its corresponding cam;
FIG. 2 is a cross sectional view of the present invention taken along line II--II of FIG. 1; and
FIG. 3 is a bottom view of the present invention taken along line III--III of FIG. 1.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring to the drawings a tappet 10 i
REFERENCES:
patent: 1402226 (1922-01-01), Germonprez
patent: 2817144 (1957-12-01), Zeller
patent: 2891525 (1959-06-01), Moore
patent: 2987815 (1961-06-01), Zeller
patent: 3073292 (1963-01-01), Behnke et al.
patent: 3198182 (1965-08-01), Robinson et al.
Goloff Alexander
Staebler Paul J.
Caterpillar Tractor Co.
Feinberg Craig R.
Wolfe W. R.
Woloch Anthony N.
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