A bearing structure of a crankshaft in an internal combustion engine supports a crankshaft on a crankcase with rolling bearings includes a play absorbing device for absorbing the play in the radial direction generated between an outer race of the rolling bearing and a bearing hole of the crankcase. The play absorbing device includes a push plug which pushes an outer race of the ball bearing in the direction perpendicular to an axis of the crankshaft. The push plug is arranged in parallel to the crankshaft between the cylinder and the crankshaft. The outer race of the ball bearing is resiliently biased toward a side of the bearing hole of the crankcase which receives an explosion pressure. As a result, the generation of a hitting sound which is attributed to the above-mentioned "play" can be largely reduced even with respect to an internal combustion engine with a high explosion pressure.

The present invention provides a cylinder block which can reduce the vibrations and noises produced from the engine at high temperatures and has a light weight, as well as a method of making such a cylinder block. Specifically, the cylinder block of the present invention comprises a main body (5, 21) of the cylinder block, a bearing (11, 17) attached to the underside of the main body (5, 21), and a crankshaft supported rotatably in a bearing section (13, 25) formed by the underside of the main body (5, 21) and the bearing (11, 17). In this cylinder block, an aluminum alloy layer (33) is formed in the sliding portion of the bearing section (13, 25), the region adjacent to the aluminum alloy layer (33) consists of a composite material (35), and the coefficient of thermal expansion of the composite material (35) is lower than that of the aluminum alloy layer (33) formed in the sliding portion.

An internal combustion engine comprises an aluminum alloy engine block housing pistons in cylinders and having a lower face including an upper semi-circular bearing surface. A lower bearing support has a lower semi-circular bearing surface to complement the upper semi-circular bearing surface in the engine block to define a crankshaft bore to rotatably support a ferrous crankshaft. The lower bearing support is formed of a single beryllium-aluminum alloy having a coefficient of thermal expansion comparable to the ferrous crankshaft to promote a consistent clearance between the lower bearing support and the crankshaft. Such a beryllium-aluminum alloy may be comprised of approximately 60-65% by weight beryllium and the balance is aluminum.

A main bearing cap (20) for an internal combustion engine consists of an aluminum alloy with an iron alloy core (10). The cap has a supporting surface (22) for a bearing shell. The iron alloy core has a central portion (13) with two spaced apart through-channels (15) filled with an aluminum alloy (24) forming a coherent mass with an aluminum layer (23) the outer limiting surface of which forms the supporting surface (22).

A core member has a core member side journal portion and a core member bolt hole on both sides of the core member side journal portion and is provided in a separation state from a surface of a casting mold through a cast-off pin including a step portion in a vertical direction in the casting mold. A radius of curvature of the core member side journal portion of the core member is made greater than a radius of curvature of the cap side journal portion of the bearing cap in such a manner that a clearance between the cap side journal portion and the core member side journal portion is larger than a clearance between the core member bolt hole and the cast-off pin. A pouring gate is provided on a side surface of the casting mold to inject a base material along the bonding portion of the bearing cap.