Patent ID: 8776735

Claim:
A cooling device of a water-cooled engine, in which plural cylinders are arranged in line, and a cylinder head with cross-flow type of intake-and-exhaust arrangement includes at least one intake-valve opening and at least one exhaust-valve opening which are arranged for each cylinder, all of the intake-valve openings for the plural cylinders being disposed on one side of the cylinder head relative to an engine's center along a cylinder line direction, all of the exhaust-valve openings for the plural cylinders are arranged at the other side of the cylinder head, intake ports and exhaust ports which connect to respective combustion chambers of the plural cylinders through the intake-valve openings and the exhaust-valve openings, respectively, and an exhaust collective portion which connects to the exhaust ports for the plural cylinders via a connection portion, the cooling device comprising: a main cooling jacket portion of a cooling jacket formed in the cylinder head, the main cooling jacket portion including an intake-side space formed around the intake-valve openings and an exhaust-side lower space formed around the exhaust-valve openings, the intake-side space and the exhaust-side lower space being connected to each other; a sub cooling jacket portion of the cooling jacket formed in the cylinder head, the sub cooling jacket portion including an exhaust-side upper space formed at a level above said exhaust-side lower space; and a connecting passage extending vertically to connect said main cooling jacket portion and said sub cooling jacket portion, the connecting passage connecting a portion located between the cylinders of said main cooling jacket portion and a portion located between the cylinders of said sub cooling jacket portion, the connecting passage being comprised of a cylindrical hole, a diameter size of which is set at 1/10 of a diameter of a cylinder bore formed at a cylinder block of the engine or larger and ⅕ of the diameter of the cylinder bore or smaller, wherein said exhaust-side upper space of the sub cooling jacket portion is configured to expand along the cylinder line direction over substantially a half area, in a plan view, of the cylinder head which is located on the other side of the cylinder head where the exhaust-valve openings for the plural cylinders are arranged so as to cover over the exhaust ports, the connection portion, and the exhaust collective portion of the cylinder head, without covering over the intake ports, and said main cooling jacket portion and said sub cooling jacket portion are separate from each other vertically via a wall portion in another area than said connecting passage.