| 摘要 |
A fuel injector of the open nozzle type, which is capable of achieving SAC pressures in excess of 30,000 psi during injection. The injector assembly of the preferred embodiments includes a plunger assembly having three plungers arranged to form a hydraulic, variable timing fluid chamber between upper and intermediate plungers and an injection chamber below a lower plunger. To prevent leakage from the injection chamber, the fuel supply passage is provided, along with the injection chamber, within a one-piece injector cup and a predetermined minimum seal length, at commencement of injection, between a land portion of an injection plunger and a wall surface defined by a bore of the injector within which it reciprocates is coordinated to the dimensions of the bore below the land and a predetermined maximum solid fuel height for the injector to result in the minimum seal length being at least one-half of the maximum solid fuel height. To obtain an increase in SAC pressures under low speed operating conditions without exceeding pressure capabilities under high speed conditions, some embodiments have valve arrangements for draining timing fluid from the timing chamber whenever the pressure of the timing fluid therein exceeds a predetermined value.
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