| 摘要 |
PURPOSE: A water jacket of a cylinder head is provided to evenly cool down an exhaust port of each of cylinder of the cylinder head and improve cooling performance by additionally forming a section sudden reducing part on an exhaust side of the water jacket to reduce flowing sectional area and induce depression so as to induce even flowing of coolant for each of the cylinders. CONSTITUTION: A section sudden reducing part(28) is formed on a part of a lower flowing channel(24) which is an upper stream of a part of the lower flowing channel merged with a middle flowing channel(26) to reduce flowing sectional area of the lower flowing channel for each of cylinders of a water jacket(10). Flow rate of coolant in the lower flowing channel is increased in the downstream of the section sudden reducing part with the section sudden reducing part as a starting point. Pressure in the downstream is reduced relatively with the upper stream centering on the section sudden reducing part. The other section sudden reducing part(30) is formed on a part of an upper flowing channel(22) which is the downstream of a part of the upper flowing channel merged with the middle flowing channel to reduce flowing sectional area of the upper flowing channel so as to induce falling of pressure only for a first combustion chamber nearest to a coolant inlet(12).
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