| 摘要 |
PURPOSE:To maintain an ideal injection ratio even if carbon is stuck in a Diesel engine and the like by providing surface processing parts on the periphery of a small diameter cylindrical part at the top of a needle valve and forming a wide part and a narrow part in a circular gap to an injection port. CONSTITUTION:On a periphery 7a of a small diameter cylindrical part 7 of a needle valve 6 in a fuel injection nozzle, four surface processing parts 9 are provided circumferentially at fixed intervals to keep a flat face with an inner arc part cut, and in a circular gap 8 to an injection port 5 of a nozzle main body 2, a wide part 8a and a narrow part 8b are formed. An opening width W of this wide part 8a is set between the maximum value within the limit of a fixed value of combustion noise after the accumulated amount of carbon comes to a stationary value and the minimum value to prevent the complete blocking by carbn, while a width t of the narrow part 8b is set at the minimum level to prevent the needle valve 6 from abnormal operation due to the processing error. This construction permits to maintain an ideal injection ratio even when carbon is stuck, and furthermore, shorten the period to stabilize the combustion noise at a desired level after the accumulated amount of carbon reaches to a stationary condition. |
