Valvetrain Solutions for Flexible Engine Families – Highest Optimization Potential for Varying Use Cases

Authors

Dr. M. Scheidt, Ing. P. Traversa, Dipl.-Ing. (FH) D. Wolf, Dipl.-Ing. S. Hardes, Schaeffler Technologies AG & Co. KG, Herzogenaurach:

Year

2021

Print Info

Production/Publication ÖVK

Summary

The increasing electrification of powertrains requires a flexible usage of the internal combustion engine in conventional, mild hybrid and full hybrid powertrains. At the same time the engine has to deliver maximum efficiency and lowest emissions in every configuration. Also, every engine family needs to be compatible with different vehicle and power classes at competitive costs. With the introduction of RDE it is mandatory to have an optimal behavior of the engine in transient operating conditions and in cold condition. The optimum behavior of the engine at start, cold operating conditions, in speed and load transients and the precise management of the aftertreatment system will be the key factor to fulfill future Euro 7 emission requirement. A key role to achieve these targets is the air path of an engine, which already today is equipped with different variabilities. Cam phasing systems are already state of the art. Also, switchable solutions or fully variable mechanical systems are used in several applications. Depending on the specific power required these systems are being applied or not. The structural design of the cylinder head, the required validation and the synchronization on these systems require significant development effort. Especially transient operation often requires a compromise due to the different response time of each system. Schaeffler has developed a portfolio of valve train systems to satisfy all possible OEM needs in valve actuation variability and packaging and is able to support the customer in the optimal integration and use of valve train systems. This portfolio is in continuous evolution and includes a new generation of the UniAir system, the eRocker, the Cam Shifting System, the eCP (Electric Cam Phaser) and smart hydraulic cam phasers. With the known fully variable valve train System UniAir, Schaeffler offers a system that allows a digital (cycle-by-cycle) response and at the same time allows a simplified cylinder head design by utilizing a SOHC layout, deleting one camshaft and both cam phasing systems. The latest evolution of the system described in this paper is characterized by a modular architecture, reduced friction and compact packaging. Furthermore, the developed control strategies allow significant benefits under transient operation with regards to emission and fuel consumption reduction that are specifically dominant under dynamic operation (RDE). This system can flexibly be optimized for different applications with software adaptions and does not require structural changes to the engine layout of modular platforms. This paper describes the latest evolution of the UniAir system from both, the design and layout perspective as well as the latest developments in the available control functions and strategies.

Number of pages

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