I. Field of the Invention
The present invention relates generally to reciprocating piston mechanisms as are used in internal combustion engines and more particularly to the construction of a piston pin used for connecting the piston to a connecting rod.
II. Description of the Prior Art
Piston pins are commonly employed to pivotally connect a piston to a connecting rod for reciprocating movement of the piston in response to rotation of the crank shaft or the like. While some previously known piston pins have been made of a solid shank of metal, such piston pins unduly increase the weight of the piston assembly. Moreover, such pins may not dissipate heat as quickly as is necessary to avoid fracturing or fatigue in the piston pin.
In addition, some previously known piston pins have been formed from a tubular body so that the pins are hollow to reduce the mass of the piston assembly. However, tubular piston pins can be deformed during reciprocal movement of the piston, especially when subjected to the high pressures and temperatures existing within the cylinder and the mechanical stresses associated with reciprocating displacement due to combustion. As a result, it has previously been known to completely fill the entire tubular chamber of the piston pin to close the ends of the piston pin. However, such a construction can still result in an unduly massive piston assembly, and the operation of filling the chamber of tubular piston pin can be extremely expensive. For example, formation of a one-piece filler within a tubular pin requires highly controlled introduction of the filler so as to avoid cavities and incomplete filling of the tubular pin.
In order to avoid these complications, some previously known tubular piston pins have been enclosed by end caps which frictionally engage the inner periphery of the pin. Such end caps are substantially easier to manufacture and install than previously known means for sealing the ends of a tubular piston pin. However, such end caps have been known to loosen during operation of the piston, probably due to the pressures in the cylinder and mechanical forces which cause deformation of the piston pin during reciprocatory movement of the piston. Unfortunately, end plugs which loosen can cause extensive engine damage.