| 摘要 |
PURPOSE:To obtain an appropriate injection quantity of fuel, by constituting a fuel injection valve in a double-needle valve structure having two coaxial needle valves which are closed at different pressures, in order to promote atomization of fuel at the time oif low-load opera tion of an engine by injecting fuel from a first nozzle hole having a small opening area and to inject fuel also from a second nozzle hole having a large opening area at the time of high-load operation of the engine. CONSTITUTION:When a fuel injection pump starts supply of fuel under pressure, pressure rise of fuel at first acts on the pressure receiving surface 14a of a first needle valve 14 via a first fuel passage and then acts on the prssur receiving surface 15a of a second needle valve 15 via a connecting port 25a at the top of the first needle valve 143 and a second fuel passage 25. Here, since the pressure at which the first needle valve 14 is opened by a spring 20 is set lower than the pressure at which the second needle valve 15 is opened by a spring 23, the first needle valve 14 is at first raised upward and a first nozzle hole 12 having a smaller diameter is opened for injecting fuel. At the time of low-load operation of an engine, fuel pressure is not raised sufficiently, so that the second needle valve 15 is kept closed. On the other hand, when fuel pressure is raised siffuciently at the time of high- load operation of the engine, the second needle valve 15 is also opened and fuel is injected also from a second nozzle hole 13 having a larger diameter.
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