Uncooled oilless internal combustion engine having uniform gas squeeze film lubrication

An apparatus for providing a gas phase film lubrication between a reciprocal piston and a cylinder of an uncooled oilless internal combustion engine, said piston being effective to drive a rotary crankshaft in response to an expanding gas charge, comprising:

• (a) means connecting said crankshaft to said piston for transferring reciprocal thrust into rotary thrust, said means aligning said piston concentrically within said cylinder wall to limit the imposition of side loads on said piston;
• (b) interfacing walls on said piston and cylinder (i) sized to provide a predetermined annular gap therebetween at ambient conditions that has a radial dimension in the range of 0.001.+-.0.0005 inches, (ii) consisting of silicon nitride that prevents closure of said gap due to thermal expansion under the maximum temperature differential to be experienced between said piston and cylinder wall, and (iii) are preshaped to anticipate any thermal growth of said interfacing walls for maintaining the annular gap substantially constant at elevated temperatures.

An apparatus for providing a gas phase film lubrication between a reciprocal piston and a cylinder of an uncooled oilless internal combustion engine, said piston being effective to drive a rotary crankshaft in response to an expanding gas charge, comprising:

• (a) means connecting said crankshaft to said piston for transferring reciprocal thrust into rotary thrust, said means aligning said piston concentrically within said cylinder wall to limit the imposition of side loads on said piston;
• (b) interfacing walls on said piston and cylinder (i) sized to provide a predetermined annular gap therebetween at ambient conditions that has a radial dimension in the range of 0.00 .+-.0.0005 inches, (ii) consisting of matched materials that prevent closure of said gap due to thermal expansion under the maximum temperature differential to be experienced between said piston and cylinder wall, and (iii) are preshaped to anticipate any thermal growth of said interfacing walls for maintaining the annular gap substantially constant at elevated temperatures, said interfacing walls being further delimited in that the material for said piston is silicon nitride and the material for the wall of the cylinder is selected from the group consisting of silicon nitride, silicon carbide and partially stabilized zirconia.

An apparatus for providing a gas phase film lubrication between a reciprocal piston and a cylinder of an uncooled oilless internal combustion engine, said piston being effective to drive a rotary crankshaft in response to an expanding gas charge, comprising:

• (a) means connecting said crankshaft to said piston for transferring reciprocal thrust into rotary thrust, said means aligning said piston concentrically within said cylinder wall to limit the imposition of side loads on said piston;
• (b) interfacing walls on said piston and cylinder (i) sized to provide a predetermined annular gap therebetween at ambient conditions that has a radial dimension in the range of 0.001.+-.0.0005 inches, (ii) consisting of matched materials that prevent closure of said gap due to thermal expansion under the maximum temperature differential to be experienced between said piston and cylinder wall, and (iii) are preshaped to anticipate any thermal growth of said interfacing walls for maintaining the annular gap substantially constant at elevated temperatures, said piston of said interfacing walls being preshaped to have a chamfer along the upper crown, and said cylinder wall being preshaped to have a radial taper with the smallest dimension of said taper being at the top end of said cylinder wall.