Study on an injection quantity sensor. I: Evaluation of the integration procedure

Abstract

For 'on board' diagnosis purposes of the injected fuel quantity, ceramic flow sensor chips with a diameter of 2.2 mm were integrated into finished Common Rail injection nozzles of the valve covered orifice (VCO) or mini-sac hole (MSH) class. The influence of this integration step on the hydraulic performance of the high-precision injector nozzles which led to an optimized process flow with a minimized disturbance of the fluidic properties was investigated. Electron-discharge machining and electron-beam welding technology proved to be the key technologies for this integration process, providing a reliable solution for injection pressures ranging up to 135 MPa (1350 bar). With a high-pressure hydraulic test bench the decrease in the injected fuel quantity as a function of welding parameters was determined for both nozzle classes. The geometrical distortion of the nozzle was mainly attributed to a radial bending of the nozzle tip and is dominated by the heat concentration during the welding process. In comparison, the integration of the ceramic sensor chip causes lower distortion values. By reducing the thermal energy input during welding a negligible influence of the complete integration process with respect to the hydraulic performance of original orifices is demonstrated at MSH injection nozzles.