The challenge for the diesel engines today is to reduce harmful emissions, such as particulate matter (PM) and Nitrogen oxides (NOx), and enhance the fuel efficiency and power, which are its main advantages. To meet this challenge, DENSO has developed an advanced common rail system (CRS) that uses piezo actuated fuel injectors capable of delivering up to five injection events per combustion cycle at 180MPa, currently the world's highest commercially available diesel fuel injection pressure.
The DENSO piezo injector incorporates an internally developed piezoelectric element that energizes quicker than its solenoid counterpart, thereby reducing the transition time for the start and end of the fuel injection event. The piezoelectric element and unique passage structure of the DENSO injector combine to provide a highly reliable and responsive fuel injection event. The DENSO piezo injector reduced the minimum injection interval delay from electronic activation to mechanical delivery from 0.4ms with the conventional solenoid actuated fuel injector to 0.1ms. This reduced response time is possible in part to the control valve actuation in less than 150us and leads to achieving precise injection quantity, timing control, and finer spray atomization. Currently the DENSO piezo CRS has been jointly developed with TOYOTA and is now in production on various TOYOTA vehicles. With this partnership, the world is able to realize a diesel engine with increased power output and reduced PM and NOx emissions.