PROBLEM TO BE SOLVED: To provide a technology capable of achieving both of improvement of heater performance and proper opening/closing control of a thermostat.;SOLUTION: Cooling water inlets 70a, 70b are disposed at one side in an extension direction of a water jacket HWJ for a head, and cooling water outlets 72, 74a, 74b, 76a, 76b are disposed at the other side in the extension direction of the water jacket HWJ for the head. The cooling water from the cooling water inlet 70a, 70b is allowed to flow to lower and upper flow channels 62a, 64a for cooling a combustion chamber, lower and upper flow channels 62b, 64b for cooling an exhaust passage, and lower and upper flow channels 62c, 64c for cooling an intake passage, and the cooling water after cooling is mixed at a mixing portion 92. Further the cooling water outlets 74a, 74b connected to a pipe to a heater HT, is positioned corresponding to an extension line in an extension direction of the lower and upper flow channels 62b, 64b for cooling the exhaust passage. According to this constitution, both of improvement of heater performance and proper opening/closing control of a thermostat TM can be achieved.;SELECTED DRAWING: Figure 9;COPYRIGHT: (C)2019,JPO&INPIT
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