| 摘要 |
PURPOSE:To prevent the unreasonable lowering of an injection ratio due to the sticking of carbon in a Diesel engine and the like by forming several wide parts with different widths of opening in a circular gap between the periphery of a small-diameter cylindrical part at the top end of a needle valve and an injection nozzle. CONSTITUTION:On a peripheral face 7a of a small-diameter cylindrical part 7 of a needle valve 6, surface processing parts 91-94 tangentially cut are provided at fixed intervals, and in a circular gap 8 to an injection nozzle 5, wide parts 8a1-8a4 and a narrow part 8b are formed. Widths of opening W1-W4 of wide parts are set to select W4 at a value near to the maximum within the limit of a fixed value of combustion noise after the accumulated amount of carbon reaches to a stationary value and W1 at the minimum to prevent the complete blockage by carbon and keep W1<W2<W3<W4. Meanwhile, the opening width t of the narrow part 8b is set at the minimum value to prevent the needle valve 6 from abnormal operation due to the processing error respectively. This construction permits to prevent the unreasonable lowering of an injection ratio due to the sticking of carbon for reducing the possibility of complete blockage, and promote to atomize fuel for reducing the noise caused by the delay of ignition effectively. |
