ECU Structure Strategy to Detect Lift Timing of GDI Solenoid Injectors with High Precision

In gasoline direct injection (GDI) systems, various injection types are needed to reduce emissions and improve fuel consumption. This requires high-precision injection in the region in which the amount of injection is small. Achieving injection of a small amount of fuel using GDI solenoid injectors requires the use of the half-lift region. In this region, however, the variation in the injection amount tends to increase due to the variation in the lift behavior of the injectors, posing the problem of how to achieve high-precision injection. To reduce the variation, we analyzed the lift timing out of the injector current and voltage signal with the ECU in an attempt to adjust the amount of injection. To detect the injector needle-opening timing, we focused on the characteristic point of the injector current signal appearing when the injector needle opens, and to detect the injector needle-closing timing, we focused on the characteristic point of the injector voltage signal appearing when the injector needle closes. Using the ECU, we analyzed the current and voltage signal, developing an algorithm allowing the characteristic points of both signals to be detected. Detection requires a wide dynamic range and high precision. The application specific integrated circuit (ASIC) can acquire and process the current and voltage signal with high precision and at high sampling speed. Accordingly, we adopted a functional allocation based on the use of ASIC. As a result, the ECU has potential to detect the timing of the open-close needle with high precision without increasing the processing load of the micro-controller significantly.