Engine block construction with skeletal frame

Abstract

A cylinder block as a main part of an engine block includes a cylinder barrel assembly block, a skeleton-like frame surrounding the outer periphery of the cylinder barrel assembly block and a plate-like rigid film member, within a fluid passage in the skeleton-like frame. The skeleton-like frame is integrally joined to the outer surfaces of left and right side walls of the assembly block along the crankshaft axis and includes crossbeam bone members, longitudinal beam bone members and post bone members which are rigid and unitarily assembled into a three-dimensional latticework structure. A cylinder head is integrally coupled to the deck surface of the cylinder block and a lower case is integrally coupled to the lower surface of the cylinder block, lateral outer surfaces of the block and lower case along the crankshaft axis being formed flush with each other in parallel with the cylinder bore axis. The lower case includes a lower case frame of three-dimensional latticework structure and rigid film members at least on the lateral outer surfaces of the lower case frame along the crankshaft axis. Moreover, the lower case is secured to the lower surface of the cylinder block by bolts and an oil pan is floatingly carried on the lower surface of the lower case via resilient members. The cylinder block has at its one end surface along the crankshaft axis a square, transmission mating surface and a divergent bulged portion extending from a rear part of the cylinder block toward the mating surface.