High pressure unit fuel injector

• Main Author: PERR, JULIUS P
• Format: Patent
• Language: English; French; German
• Published: 26.01.1994
• Edition: 5
• Subjects: BLASTING; COMBUSTION ENGINES; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; LIGHTING; MECHANICAL ENGINEERING; SUPPLYING COMBUSTION ENGINES IN GENERAL, WITH COMBUSTIBLEMIXTURES OR CONSTITUENTS THEREOF; WEAPONS

A fuel injector of the open nozzle type, which is capable of achieving SAC pressures (i.e. the pressure of the fuel in the injection chamber just in front of the injector spray holes) in excess of 30,000 psi during injection. The injector assembly (11) of the preferred embodiments includes a plunger assembly (7) having three plungers (9,11,13) arranged to form a hydraulic, variable timing fluid chamber between upper (13) and intermediate (11) plungers and an injection chamber below a lower plunger (9). To prevent leakage from the injection chamber, the fuel supply passage (31) is provided, along with the injection chamber, within a one-piece injector cup (5) and a predetermined minimum seal length, at commencement of injection, between a land portion (9b) of an injection plunger (9) and a wall surface defined by a bore (6) 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.