Insulated composite piston

Claim 1

A piston for an internal combustion engine, said piston comprising: a crown portion of temperature resistant material, said crown portion having a circular periphery; a one piece aluminum piston body having a circular periphery, said crown portion and said piston body having opposed planar surfaces, the opposed planar surface of said crown portion being the sole surface facing said piston body, and the opposed planar surface of said piston body being defined by a recess in said piston body facing said crown portion; a plurality of stacked steel discs having a relatively low conductivity planar interface between adjacent discs and positioned between the opposed planar surfaces of said crown portion and piston body for forming a low effective thermal conductivity interface, the planar surface of said crown portion extending radially outward at least as far as the periphery of said discs, means for fastening said crown portion to said piston body, thereby sandwiching said discs between the crown portion and the piston body, said discs being freely separable from one another in the absence of the fastening means, whereby the temperature gradient across said crown is minimized, wherein said crown, said discs, and said piston body have aligned holes, the one in said piston body terminating in an interior recess thereof, and wherein said fastening means comprises a bolt extending through said holes and having a head positioned on said crown portion and a threaded portion extending through said piston body to said interior recess, a nut threaded onto said bolt, and a plurality of belleville washers positioned between said nut and said piston body for yieldably urging said piston body and crown portion towards one another, said piston body has a larger diameter hole than the one through said crown, said piston further comprises a steel sleeve-like insert supported in said hole of said piston body, said insert having a flange which abuts the interior recess of said piston body, said washers acting between said insert and said nut; and wherein said discs do not extend to the periphery of the interface between the crown portion and the piston body, the overall thickness of said stacked discs being selected so that the crown portion and said piston body are maintained out of contact with one another.