Pressure-controlled fuel injection for internal combustion engines

Abstract

An electronically controlled fuel supply system for an internal combustion engine. The timing of the commencement of fuel injection into each combustion chamber is not fixed relative to the rotational position of the camshaft or other engine components. A unit injector assembly associated with each combustion chamber includes a control module and an accumulator type injector module. The control module contains a solenoid valve and, in some embodiments, a hydraulic pressure intensifier. The accumulator type injector module contains an injector nozzle, a hydraulic accumulator, and a non-return valve for admitting liquid fuel under pressure into the accumulator. In operation, an electrical control system supplies an electrical signal to the control module an appreciable portion of the engine cycle in advance of the time when fuel injection is to be initiated in the particular combustion chamber. In response to that electrical signal, the solenoid valve admits liquid fuel under pressure into the hydraulic pressure intensifier. The output of the intensifier provides a metering and intensifying chamber in which the pressure of the fuel continues to increase until near the time when fuel injection is to commence. As pressure builds up, fuel flows through the non-return valve into the accumulator. Under control of the electrical signal the solenoid valve then shuts off the flow of liquid fuel into the intensifier. The transfer of fuel under high pressure from the intensifier chamber to the accumulator is discontinued due to the non-return valve, and the injector nozzle then fires. Alternatively, the solenoid valve admits liquid fuel under pressure directly through the non-return valve into the accumulator, with the turn-off of the solenoid valve causing the injector nozzle to fire. The control system may be utilized for operating the engine in a modified engine cycle in which firing cycles are selectively eliminated. The control system may also be utilized for controlling different cylinders of an engine differently from each other. The control of engine power is accomplished by either electrical or hydraulic means, or a combination thereof, and does not involve any mechanical adjustments within the unit injector assemblies.