The challenges for diesel engines are how to control emissions of harmful substances including NO{sub}x and PM in response to global mandates for reduced diesel emissions and how much fuel efficiency advantages they can provide compared to gasoline engines. Further enhanced output and torque are also expected for diesel vehicles to improve the engine performance. In order to solve these issues, a lot of studies have been conducted regarding engine combustion system, air intake system, fuel injection system and exhaust air after-treatment system. Among them, the fuel injection system plays a major role to find solutions. The third generation solenoid common rail system, successfully developed by DENSO, employs the solenoid injector that can provide up to nine separate injection events per combustion cycle at the increased maximum injection pressure. In particular, the injector, the key device of the common rail system, features not only the injection pressure (max. 200 MPa) higher than that of the second-generation system (max. 180 MPa) but also the improved injection accuracy, which was achieved by employing improved magnetic material as hardware and pilot injection quantity learning control as software.
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