Hydraulically-actuated electronically-controlled unit injector fuel system having variable control of actuating fluid pressure

A hydraulically-actuated electronically-controlled unit injector fuel system comprising:

• at least one hydraulically-actuated electronically-controlled unit injector;
• means for supplying fuel at a relatively low pressure to the unit injector;
• means for supplying hydraulically actuating fluid, separate from said fuel, to the unit injector, at a pressure that is relatively higher than the relatively low pressure of said fuel, said supplying means including an actuating fluid pump communicating with the unit injector and having an output pressure, said unit injector including means for intensifying the relatively low pressure of said fuel supplied to the unit injector, said intensifying means being actuated by the hydraulically actuating fluid applied to the unit injector;
• a manifold communicating between the pump and the unit injector;
• means for detecting the pressure of the hydraulically actuating fluid in the manifold and generating a pressure indicative signal indicative of said pressure detected;
• means for detecting at least one other parameter and generating a parameter indicative signal indicative of said parameter detected;
• and
• means for electronically controlling the output pressure of the pump in response to the at least one parameter indicative signal and for correcting said pressure amount based on the pressure indicative signal, said pressure controlling means directly controlling the intensified pressure of said fuel injected by the unit injector independent of the quantity of said fuel injected by the unit injector.

A method of operating a hydraulically-actuated electronically-controlled unit injector fuel system having at least one unit injector comprising the steps of:

• pressurizing fuel at a first pressure;
• supplying said fuel at the first pressure to the unit injector;
• pressurizing hydraulically actuating fluid, separate from said fuel, at a pressure that is relatively higher than the first pressure of said fuel;
• supplying the pressurized hydraulically actuating fluid to the unit injector;
• intensifying the first pressure of said fuel with the pressure of the hydraulically actuating fluid;
• detecting the pressure of the hydraulically actuating fluid supplied to the unit injector and generating a pressure indicative signal indicative of the pressure detected;
• detecting at least one other parameter and generating a parameter indicative signal indicative of the parameter detected;
• and
• electronically controlling the pressure of the hydraulically actuating fluid supplied to the unit injector in response to the at least one parameter indicative signal;
• controlling the intensified pressure of said fuel injected by the unit injector in response to the pressure of the hydraulically actuating fluid supplied to the unit injector independent of the quantity of said fuel injected by the unit injector;
• correcting said pressure amount based on the pressure indicative signal.