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 highpressure 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.

Evaluation of electron beam welding technique for the integration of robust sensor elements into high-pressure automotive systems

“…Therefore, it is concluded that the radial bending of the nozzle tip caused by the EBW process is amplified when integrating in addition to the injection quantity sensor. This result is confirmed with the measurements of the injected fuel quantity (Schmid and Seidel 2005b) as well as on the optical investigation on the formation of spray cones (see Figs. 7,10) showing in both cases a lower deviation from the original state when only a welding seam is applied.…”

“…It is therefore reasonable to assume that at these welding conditions, the angular distortion dominates the deformation of the work piece in contrast to transverse and longitudinal shrinkage effects. In comparison with the strong dependence of the injected fuel volume V IAI determined with the injection amount indicator (IAI) on electron beam welding parameters (Schmid and Seidel 2005b), it is confirmed that the geometrical distortion induced by the welding seam leads to a radial bending of the nozzle tip in the direction of the sealed access hole. The six injection holes are uncovered nonuniformly when the needle is lifted due to the perturbed axial symmetry along the nozzle axis.…”

“…Challenging, however, is the sensor implementation without influencing the hydraulic performance of the nozzle which is fabricated with mechanical tolerances in the lm-range. In a previous study (Schmid and Seidel 2005b), the basic steps for integrating the thermal injection quantity sensor are presented using electro-discharge machining (EDM) and electron-beam welding (EBW). To determine in an application-oriented way the geometrical distortion associated with the integration procedure the injected fuel quantity V i as a function of implementation parameters was evaluated within a standardized measurement procedure.…”

“…This is due to both a targeted resolution of about 1 lm and the request for a screening of a large number of modified devices. In a previous study (Schmid and Seidel 2005b), the injected fuel quantity as a function of injection pressure and drive pulse was investigated as an indirect indicator for the determination of the geometrical distortion introduced into the nozzle during welding. Beside these characteristic numbers being of utmost importance for the design and operation of engines the direct observation of spray pattern is more significant due to a direct correlation between the location of the welding seam and the asymmetry in spray pattern formation.…”

LTCC: a fascinating technology platform for miniaturized devices

“…The sensor fabrication and the corresponding integration process into the nozzle are described in detail elsewhere [14][15][16]. Basically, the device consists of a metallic thin film element on a pressure-stable LTCC substrate with integrated electrical feed-throughs.…”