| 摘要 |
PURPOSE:To aim at miniaturization of an engine having an overhead camshaft on its cylinder by taking out driving force from the driving system of its overhead camshaft through providing the cylinder with a fan shaft to the end of which forced-air cooling fan is attached. CONSTITUTION:An overhead camshaft 50 is held at the cylinder head 38 of an engine 30. In addition, two pieces of sprockets 52, 54 are fixed on the camshaft 50, and the rotation of a sprocket 56 on a crankshaft 40 is transmitted through a timing chain 58 to the sprocket 52 on one side. In the above, a fan shaft 78 is held at the cylinder head 38 such that it rotates freely. The one end on the left side of the fan shaft 78 is projected from the rear of an intake valve to said chain 58 side, and then a sprocket 80 fixed on this projected part and the other sprocket 54 as above are wound together with a chain 82. In addition, the other end on the right side of the fan shaft 78 is projected from the cylinder head 38 to the outside, and then an axial fan 84 for forced-air cooling is fixed on this projected part.
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