| 摘要 |
PROBLEM TO BE SOLVED: To prevent the tip of a nozzle from being thermally damaged, by restraining combustion gas from entering an air chamber. SOLUTION: In a fuel injection device of an engine, a heat insulating cap 2 is mounted on a nozzle tip part 7 of a fuel injection nozzle 1, an air chamber 9 is formed between a nozzle tip surface 8 and the heat insulating cap 2, a fuel injection port 10 of the nozzle tip surface 8 is exposed from an opening part 5 of the heat insulating cap 2, and a seal part 6 of the heat insulating cap 2 is brought into pressure-contact with the nozzle tip surface 8. The nozzle tip surface 8 is formed into such a spherical surface as to project in the tip direction. Accordingly, since any corner part to be partially increased in the temperature is not formed in a part of the nozzle tip surface 8 with which the seal part 6 is to be brought into contact, thermal distortion is not easily generated on the part. Therefore, the contact area of the seal part 6 is properly maintained, and sealing force of the seal part 6 can be highly maintained. Therefore, combustion gas is restrained from entering the air chamber 9, and the nozzle tip part 7 is not easily thermally damaged.
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