Design and Development of a Battery-Voltage-Driven Fuel Injector for Direct-Injection Gasoline Engines

The conventional fuel injector for direct-injection gasoline engines is driven by voltage step-up circuitry and current control circuitry. The voltage step-up circuitry boosts the battery voltage to near 100 volts. This conventional system is fairly large and a more compact system is preferable. We have developed a mass producible battery-voltage-driven fuel injector for direct-injection gasoline engines. The injector has a dual-coil structure that enables the injector to operate at the battery voltage, thus eliminating the need for either voltage step-up circuitry or current control circuitry. Deviation in battery voltage and changes in harness resistance are fully compensated through opening-coil energization-time control. In addition, with this control method, the injector can be used with a wide range of fuel pressures. In this paper, the design concept and the dynamic characteristics of the battery-voltage-driven fuel injector with a dual-coil structure and the opening-coil energized time control method is discussed in detail.