Concepts and Evolution of Injector for Common Rail System 2012-01-1753
Diesel injection equipment is required to be more accurate and higher in pressure to meet the increasingly strict emission, fuel consumption regulations and higher engine performance. It also needs to achieve a number of requirements such as robustness against diversified market fuels, pressure maintenance characteristics in the idle stop system (ISS), easy installation to engine, etc. One of the key component to meet these demands is injector. DENSO has been working to develop injector according to the following five concepts which are seemingly conflicting, since several years.
Increase injection pressure from 200 MPa to 300 MPa aiming at better spray characteristics
Develop a new control valve to achieve zero static leakage and minimized switching leakage aiming at higher fuel robustness, higher fuel efficiency, ISS capability.
Develop a new control valve capable of individual setting of nozzle open/close speed aiming at higher injection flexibility.
Make the actuator and control valve small size aiming at easier installation to engine.
Locate the actuator and control valve near the nozzle to reduce the mass of movement aiming at higher injection responsiveness accuracy.
DENSO launched 200 MPa piezo injector for passenger cars and light duty trucks based on the above concepts in 2008. After that, a solenoid-actuated injector which is capable of up to 250 MPa was developed to assure longer lifespan not only for passenger cars and light duty trucks but also for commercial, agricultural, industrial and construction vehicles subject to stricter service environment. This solenoid injector has potential to achieve 300 MPa, and our trial product has already been applied to some laboratories, which are demonstrating the effects of increased pressure. 
This paper reports the new concept solenoid injector structure and performance combining high pressure up to 250 MPa comparable with the piezo injector, as well as excellent fuel robustness and reliability.