Quantification of Diesel Engine Vibration Using Cylinder Deactivation for Exhaust Temperature Management and Recipe for Implementation in Commercial Vehicles

Commercial vehicles require continual improvements in order to meet fuel emission standards, improve diesel aftertreatment system performance and optimize vehicle fuel economy. Aftertreatment systems, used to remove engine NOx, are temperature dependent. Variable valve actuation in the form of cylinder deactivation (CDA) has been shown to manage exhaust temperatures to the aftertreatment system during low load operation (i.e., under 3-4 bar BMEP). During cylinder deactivation mode, a diesel engine can have higher vibration levels when compared to normal six cylinder operation. The viability of CDA needs to be implemented in a way to manage noise, vibration and harshness (NVH) within acceptable ranges for today’s commercial vehicles and drivelines. A heavy duty diesel engine (inline 6 cylinder) was instrumented to collect vibration data in a dynamometer test cell. Three degrees of linear vibration and one degree of rotational vibration were measured using accelerometers and rotational speed sensors. Historical data analysis showed that the remaining two rotational degrees of freedom were insignificant when considering driveline vibration. The engine was tested using a combination of deactivating two, three and four cylinders (of the six) up to engine loads of approximately 4 bar BMEP in order to quantify system vibration and resonance frequencies. These results were compared to driveline NVH standards to determine the modes of operation that were acceptable over the engine speed and load operating range. A variable CDA implantation strategy for operating the engine over transient engine operation is recommended for this dynamometer operation. Additionally, a theory is provided for operating cylinder deactivation in a commercial diesel vehicle.