There is such a conventionally known engine block of which cylinder block is comprised of a cylinder block body made of an aluminum alloy, and one or two or more cylinder sleeves of a cast iron formed by casting in the cylinder block body, and to which engine block a cylinder head and bearing caps for a crankshaft are assembled through a plurality of stud bolts provided on the cylinder block.
The conventional engine block suffers from the following problem: An explosion force applied to the cylinder head is received by the cylinder block, and the cylinder block is a member to which the cylinder head and the bearing caps are assembled. Therefore, in order to increase the strength of the cylinder block and thus the strengths of the cylinder block body and the cylinder sleeves, the thickness of them is increased. For this reason, the weight of the cylinder block is increased and hence, it is impossible to meet the demand for a reduction in weight of the engine block.
In a waste heat recovering device for an internal combustion engine utilizing a Rankin cycle, the following problem is encountered: If an exhaust gas from the internal combustion engine is used as a heat source, the higher the temperature of the exhaust gas is, the higher the waste heat recovering efficiency is. If each of the cylinder sleeves of the cast iron is formed by casting in the cylinder block body, as described above, the area of contact of both the members with each other is increased. For this reason, the heat of the exhaust gas is partially diffused from the cylinder sleeves through the cylinder block body, and as a result, the temperature of the exhaust gas dropps.