| 摘要 |
An internal combustion engine component assembly including piston, wrist pin, and cylinder sleeve, all constructed of a matching carbon-carbon composite is disclosed. The piston is a two-piece assembly divided in crown and skirt, each fabricated individually to optimize the most desirable properties in the respective cylinder areas in which they operate. The crown is fabricated by placing the fiber and binder into a compression mold and pyrolizing(heating) the resulting preform at a high temperature in the range of 1500 to 2000 degrees C. to achieve high temperature strength, and high thermal conductivity that continue after machining to the finished crown part. The skirt, a separate piece, on the other hand is fabricated differently to seek higher lubricity and better wear resistance along the cylinder wall with lower thermal conductivity to minimize heat loss. The skirt preform is fabricated by wrapping the fiber around a mandrel and subsequently heating and pyrolizing at temperatures far less than the heat treatment temperature of the crown preform resulting in significant time and cost saving. The skirt precursor is machined and then assembled to the crown to complete the piston. The piston skirt, the wrist pin and the cylinder sleeve are also fabricated using similar composition matching techniques to minimize tolerances between these parts. All three of these parts are separately preformed on mandrels utilizing the same wrapping angles to equate wrap strength. Then, the resulting preforms of each are preheated and pyrolized at the same temperatures to almost similar elevated temperature strength and, most importantly, coefficients of thermal expansion. This technique permits the engine designer to reduce the clearance between these parts, thereby minimize blow by, reduce lubrication requirements, and increase engine horsepower.
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