Patent ID: 7640898

Claim:
A water-cooled internal combustion engine comprising: a cylinder block provided with a plurality of cylinders aligned in a row; and a cylinder head defining combustion chambers respectively corresponding to the cylinders, and provided integrally therein with an exhaust manifold passage into which exhaust gas discharged from the combustion chambers flows through exhaust ports connected to the combustion chamber, and a cylinder head water jacket for cooling water including a combustion chamber water jacket surrounding the combustion chambers and an exhaust passage water jacket around the exhaust manifold passage; wherein said exhaust manifold passage extends in the cylinder head over the exhaust ports; wherein the exhaust passage water jacket is divided into an upstream water jacket and a downstream water jacket by a flow restriction which stops or restricts cooling water flow from the upstream water jacket into the downstream water jacket, said exhaust passage water jacket extending along the exhaust manifold passage; a part of the upstream water jacket on an upstream side of the flow restriction is connected to the combustion chamber water jacket to make the cooling water flow from the upstream water jacket into the combustion chamber water jackets; and the downstream water jacket is connected to the combustion chamber water jacket so that the cooling water flowing through the downstream water jacket flows from the downstream water jacket into the combustion chamber water jacket.