Hybrid-Optimized Engine Cooling Concept

Abstract

An increasing level of hybridization in modern passenger car powertrains creates new challenges concerning the internal combustion engine. Primarily affected are turbo-/supercharging system, start performance, oil deterioration and exhaust aftertreatment. But thermal management faces new demands and requirements as well. A significantly more frequent intermitting operation mode of the ICU, which even includes frequent instantaneous switching from high load operation to a shut-off engine and vice versa, requires the cooling concept to be capable of suppling full cooling performance independently from engine rpm. Apart from the ICU itself, several peripheral components as e.g. cabin heater and EGR cooler demand an engine-rpm-independent supply of heating or cooling power. Additionally, a rapid warm-up phase after cold start further gains in importance as ICU operation time decreases and number of cold starts increases. A critical target conflict arises between the above mentioned, additional technical requirements on the one hand and an increased cost pressure on the other hand. The later one occurs due to a growing overall complexity of any hybridized powertrain and a therefore increased cost optimization pressure on the ICU and its periphery. This target conflict was solved by developing a cooling system concept combining maximum thermal management functionality, including an electric main water pump, with a highly reduced system complexity, including e.g. the complete abandonment of any active valves.