To prevent deterioration of cooling efficiency by providing a wind screening plate for screening the opposing wind on the flow path of wind generated by a cooling fan of an engine and a cooling fan of a gear unit such that opposite directed cooling winds do not impinge with each other and ventilation is not prevented.

A cooling fan A11 is disposed between an engine 3 and a radiator for supplying wind. A cooling fan B19 that prevents the rise in the fluid temperature is disposed in a gear unit 10 for supplying wind. The engine 3 and the gear unit 10 are arranged such that opposing winds do not directly impinge with each other. However, the flow of the opposite diffusing winds may impinge to prevent ventilation. Therefore, the opposing wind path is divided by a wind screening plate 14 disposed thereon. As a result, the aforementioned structure prevents deterioration of cooling efficiency resulting from insufficient ventilation owing to the decrease in wind speed under the influence of opposing wind flows.