| 摘要 |
PURPOSE:To prevent noise and deterioration of exhaust N emission by decreasing injection pressure of fuel in the low-load operation of a diesel engine. CONSTITUTION:In a variable injection characteristic nozzle 1, a cam 12 is attached on the upper end of a needle 3 capable of being vertically moved in a nozzle body 2, and a passage inner weir 14 energized by a spring 15 is in contact with the cam. Since the lift amount of the needle 3 is decreased in the low-load operation of an engine, the passage inner weir 14 is brought in contact with a first perpendicular surface 12b and an inclined surface 12a of the cam 12 and projects into a fuel passage 6, so as to increase resistance of flow in the passage 6 and pressure loss. Accordingly, fuel pressure in a fuel reserving part, for pushing up the needle 3 can be restrained to lower, and the initial injection rate of fuel injection is decreased, and rising of pressure and temperature in a combustion chamber is slowed. The passage inner weir 14 is retreated from the inside of the fuel passage 6 in the high-load operation, and injection pressure is sufficiently increased.
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