Diesel common rail injectors are required to utilize a higher injection pressure and to achieve higher injection accuracy in order to meet increasingly severe emissions, less fuel consumption, and higher engine performance demand. In addition to those requirements, in conjunction with optimized nozzle geometry, a more rectangular injection rate and stable multiple injections with shorter intervals are required for further emissions and engine performance improvement by optimizing the combustion efficiency. Following these requirements DENSO has been working on the development of the 4th generation piezo injector (G4P) according to the following concepts.
Increase the injection pressure capability up to 270MPa aiming for a better spray atomization.
Develop a new 3-way valve to achieve zero static leakage and minimized switching leakage which is aiming for a higher fuel robustness and higher energy efficiency.
Develop a new hydraulic circuit combining a 3-way valve operated by a fast piezo actuator and a pressure balanced control plate, which allows for an increase of the IN/OUT orifice flow for a fast nozzle opening/closing speed with maintaining injection stability and controllability, and aiming for a rectangular injection rate and short hydraulic injection intervals.
This paper reports the G4P injector concepts, structure and hydraulic performance with rectangular injection rate and shorter multiple injection intervals close to zero, and also reports engine performance improvement result with G4P.