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In recent years, in association with the increase of the development of higher turbocharged diesel engines for commercial vehicles, the requirements for the gas sealing ability of cylinder head gaskets have been getting more severe. This paper introduces the requirements of the optimum design of a cylinder head gasket having the structure that minimizes: 1)the amplitude of motion between a cylinder head and a block and 2)the contact pressure fluctuation of the cylinder head gasket. Both of these are caused by the internal pressure change in the bore of the running engine. In order to examine the relationship of the structure of the various sealing areas with the amplitude of motion and the contact pressure change in cylinder head gaskets, the amplitude between the head and block and the contact pressure changes were empirically observed at three different locations.

Three types of cylinder head gaskets which were different in their structures and materials, were adopted for experimental study to describe cylinder head motions due to thermal cycle conditions. The experimental studies were conducted by measuring (1) the temperatures on the cylinder head gasket, the cylinder head, the cylinder block and head bolts,(2) the relative displacements of the cylinder head and block, (3) the axial tensions on the cylinder head bolts, and (4) the indicator diagram, on the engine testing with a specific thermal cycle. Following conclusions were obtained as the results; The effect of the change in circulating water temperature on the sealing function of cylinder head gaskets has become clear through this experimental study. The mutual relationship between the deflection of the cylinder head and the temperature at the gasket and its peripheral region, has been able to estimate sufficiently from the results of the measurement.