Development of direct fuel injection technology based on piezoceramic actuation

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Global demand for better fuel economy, low engine emissions, and better vehicle response speed require engine manufacturers to continue to seek better combustion systems. In the past decade, the common rail direct fuel injection technology in engines which features a high-pressure fuel rail and electric controls of individual valves led to a significant improvement in emissions, fuel consumption and power density. The key constituent of the common rail system is the fuel injector. A conventional direct fuel injector uses a solenoid coil that drives a valve to move the injector needle through a hydraulic circuit. The solenoid actuator cannot meet stringent future emission requirements (US 2012, Euro 6). Piezoelectric fuel injectors are gradually replacing the solenoid injectors and typically consist of a multi-layer piezoelectric stack actuator acting on a nozzle with a speed 4~5 times faster than its solenoid counterpart. Current piezoelectric engine fuel injectors use a