Combustion Monitoring by use of the Spark Plug for DI Engine 2001-01-0994

To meet the recent emission standard and fuel economy, it is required to scale down engine component sizes. For the ignition system, we would like to reduce the physical size of an ignition coil as well. However the present direct-ignition (DI) engine requires long spark duration time, and which makes difficult to reduce the physical size of the ignition coil. NTK developed a special method to achieve the goal.

The presented paper introduces size reduction of the ignition coil and shortening the spark duration time for good ignition performance with the carbon fouling detection capability. Occurrence of the carbon fouling accompanies abnormal spark around the spark nose area always. Accordingly, this paper describes also a method detecting the abnormal spark, by using discharge current method or spark plug voltage. Furthermore, this paper describes the method of early detection of misfire and evasive control by detecting the abnormal spark. On the other hand, it is necessary for the SI engine to accurately detect the combustion condition of an engine in real time in order to maintain high efficiency and low emission. To monitor the information, the presented paper discusses the method of detecting the combustion condition by detecting ions generated from combustion, with aid of electrodes of the spark plug. The paper also describes how the miniaturization of ignition coil mentioned above is useful to detect combustion condition by using the ion current method.