| 摘要 |
A two-stage, hydraulic, electronic unit fuel injector powered by lubricating oil from the engine crankcase includes a housing, a pilot valve disposed in the housing and connected to an electronically-controlled solenoid for movement with the armature thereof, a slidable poppet valve disposed in the housing beneath the pilot valve and controlled by the action of the pilot valve, and a fixed intensifier dump valve disposed within the poppet valve. An intensifier piston, controlled by the action of the poppet valve, is disposed within the housing below the intensifier dump valve which upon receiving high pressure fluid, in this case, lubricating oil, is forced downwardly to inject fuel received in the lower end of the injector from a common rail out of the injector tip under very high pressure. Both the pilot valve and the poppet valve are provided with valving arrangements, in the form of valve seats. internal passages, and registering annular grooves to provide and relieve the pressure acting respectively on the poppet valve and on the intensifier piston at various times during the injection cycle. Prior to the start of injection, the pilot valve provides high pressure to the top of the poppet valve forcing the poppet against its seat, relieving the pressure on the intensifier piston by dumping the pressurized oil externally of the injector onto the top of the cylinder head. When the pilot valve moves to start injection, it closes the high pressure source and dumps the pressurized oil above the poppet externally so that differential pressure acting upwardly on the poppet valve opens the poppet and exposes the intensifier piston to the high pressure source, causing injection. At the end of injection, the pilot valve closes, forcing the poppet down against its seat and dumping the oil from the intensifier piston causing injection to end.
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