Hydraulically-actuated electronically-controlled unit injector having stroke-controlled piston and methods of operation

A method of operating a hydraulically-actuated electronically-controlled unit injector adapted for starting an engine comprising the steps of:

• detecting the viscosity of actuating fluid used to actuate the unit injector;
• applying an electrical fuel delivery command signal of a selected first pulsewidth to an electrically-actuated valve of the unit injector to open the valve during the first pulsewidth, said first pulsewidth selected in accordance with the detected viscosity of the actuating fluid;
• supplying pressurized actuating fluid to the unit injector in response to the valve being opened during the first pulsewidth;
• hydraulically displacing a piston of the unit injector over a first displacement to effect a first fuel injection quantity in response to the pressurized actuating fluid being supplied to the unit injector during the first pulsewidth;
• discontinuing the electrical fuel delivery command signal of the selected first pulsewidth to close the valve and end the first fuel injection quantity;
• applying another electrical fuel delivery command signal of a selected second pulsewidth to the electrically-actuated valve of the unit injector after the engine is started to open the valve during the second pulsewidth, said second pulsewidth being less than the first pulsewidth and selected in accordance with the detected viscosity of the actuating fluid;
• supplying pressurized actuating fluid to the unit injector in response to the valve being opened during the second pulsewidth;
• hydraulically displacing the piston of the unit injector over a second displacement to effect a second fuel injection quantity in response to the pressurized actuating fluid being supplied to the unit injector during the second pulsewidth, said second displacement of the piston being less than the first displacement;
• and
• discontinuing the electrical fuel delivery command signal of the selected second pulsewidth to close the valve and end the second fuel injection quantity.

A method of operating a hydraulically-actuated electronically-controlled unit injector adapted for starting an engine comprising the steps of:

• detecting the temperature of actuating fluid used to actuate the unit injector;
• applying an electrical fuel delivery command signal of a selected first pulsewidth to an electrically-actuated valve of the unit injector to open the valve during the first pulsewidth, said first pulsewidth selected in accordance with the detected temperature of the actuating fluid;
• supplying pressurized actuating fluid to the unit injector in response to the valve being opened during the first pulsewidth;
• hydraulically displacing a piston of the unit injector over a first displacement to effect a first fuel injection quantity in response to the pressurized actuating fluid being supplied to the unit injector during the first pulsewidth;
• discontinuing the electrical fuel delivery command signal of the selected first pulsewidth to close the valve and end the first fuel injection quantity;
• applying another electrical fuel delivery command signal of a selected second pulsewidth to the electrically-actuated valve of the unit injector after the engine is started to open the valve during the second pulsewidth, said second pulsewidth being less than the first pulsewidth and selected in accordance with the detected temperature of the actuating fluid;
• supplying pressurized actuating fluid to the unit injector in response to the valve being opened during the second pulsewidth;
• hydraulically displacing the piston of the unit injector over a second displacement to effect a second fuel injection quantity in response to the pressurized actuating fluid being supplied to the unit injector during the second pulsewidth, said second displacement of the piston being less than the first displacement;
• and
• discontinuing the electrical fuel delivery command signal of the selected second pulsewidth to close the valve and end the second fuel injection quantity.

A method of operating a hydraulically-actuated electronically-controlled unit injector adapted for starting an engine comprising the steps of:

• applying an electrical fuel delivery command signal of a selected first pulsewidth to an electrically-actuated valve of the unit injector to open the valve during the first pulsewidth;
• supplying pressurized actuating fluid of a selected first pressure to the unit injector in response to the valve being opened during the first pulsewidth;
• hydraulically displacing a piston of the unit injector over a first displacement to effect a first fuel injection quantity in response to the pressurized actuating fluid being supplied to the unit injector during the first pulsewidth;
• discontinuing the electrical fuel delivery compound signal of the selected first pulsewidth to close the valve and end the first fuel injection quantity;
• applying another electrical fuel delivery command signal of a selected second pulsewidth to the electrically-actuated valve of the unit injector after the engine is started to open the valve during the second pulsewidth;
• supplying pressurized actuating fluid of a selected second pressure to the unit injector in response to the valve being opened during the second pulsewidth, said second pressure being less than the first pressure;
• hydraulically displacing the piston of the unit injector over a second displacement to effect a second fuel injection quantity in response to the pressurized actuating fluid being supplied to the unit injector during the second pulsewidth, and
• discontinuing the electrical fuel delivery command signal of the selected second pulsewidth to close the valve and end the second fuel injection quantity.

A method of operating a hydraulically-actuated electronically-controlled unit injector adapted for starting an engine comprising the steps of:

• applying an electrical fuel delivery command signal of a selected first pulsewidth to an electrically-actuated valve of the unit injector to open the valve during the first pulsewidth;
• supplying pressurized actuating fluid of a selected first pressure to the unit injector in response to the valve being opened during the first pulsewidth;
• hydraulically displacing a piston of the unit injector over a first displacement to effect a first fuel injection quantity in response to the pressurized actuating fluid being supplied to the unit injector during the first pulsewidth;
• discontinuing the electrical fuel delivery command signal of the selected first pulsewidth to close the valve and end the first fuel injection quantity;
• applying another electrical fuel delivery command signal of a selected second pulsewidth to the electrically-actuated valve of the unit injector after the engine is started to open the valve during the second pulsewidth, said second pulsewidth being less than the first selected pulsewidth;
• supplying pressurized actuating fluid of a selected second pressure to the unit injector in response to the valve being opened during the second pulsewidth, said second pressure being less than the first pressure;
• hydraulically displacing the piston of the unit injector over a second displacement to effect a second fuel injection quantity in response to the pressurized actuating fluid being supplied to the unit injector during the second pulsewidth, said second displacement of the piston being less than the first displacement;
• and
• discontinuing the electrical fuel delivery command signal of the selected second pulsewidth to close the valve and end the second fuel injection quantity.

A method of operating a hydraulically-actuated electronically-controlled unit injector adapted for starting an engine comprising the steps of:

• applying a series of electrical fuel delivery command signals of selected pulsewidths to an electrically-actuated valve of the unit injector to open the valve during the pulsewidths;
• supplying pressurized actuating fluid of a selected pressure to the unit injector in response to the valve being opened during the pulsewidths;
• hydraulically displacing a piston of the unit injector over a selected displacement to effect selected fuel injection quantities in response to supplying pressurized actuating fluid to the unit injector during the pulsewidths;
• discontinuing the electrical fuel delivery command signals to close the valve and end the respective fuel injection quantities;
• and
• varying the pressure of the actuating fluid so that the pressure gradually decreases from one selected magnitude to another selected magnitude during startup of the engine.