| 摘要 |
A unit fuel injector includes a body. The body incorporates a pump mechanism, an injection nozzle mechanism for injecting fuel fed thereto from the pump mechanism, and an electromagnetic valve mechanism for relieving high pressure fuel from the pump mechanism. The electromagnetic valve mechanism includes a poppet-type valve member. Immediately when an abutment portion of the valve member is disengaged from a valve seat during a pump stroke, the pressurized fuel is spilled into a spill chamber from the pump mechanism. The fuel injector further includes a mechanism for propelling the valve member in such a direction that said abutment portion is moved away from the valve seat, utilizing the spill fuel pressure. The propelling mechanism includes a bore formed in said body, and a flange provided on a stem portion of the valve member, the flange being slidably fitted in the bore to divide the bore into a pressure introduction chamber and a low pressure chamber along the axis of the valve member. The pressure introduction chamber is connected to the spill chamber so as to receive the spill fuel pressure in the spill chamber whereas the low pressure chamber is connected to a low pressure source disposed exteriorly of the body. With this construction, the valve member is propelled in such a direction that said abutment portion is moved away from the valve seat due to a pressure differential across the flange when the pressure introduction chamber receives the spill fuel pressure.
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