Cam phasers allow improvements to the efficiency and emissions of internal combustion engines. The usage of hydraulic vane type cam phasers for heavy-duty applications have shown problems with oscillations during testing at Scania CV. To investigate the root cause of the oscillations a detailed 1-d simulation model has been created. The 1-d simulation model was calibrated and compared against measurements of a cam phaser system mounted on a physical engine. The 1-d simulation model of the cam phaser system was shown to be able to reproduce the oscillatory behavior seen in engine tests. But there are some concerns regarding the model's reliability, due to its dependence on the integration time step. It was determined that free air in the phaser chambers is causing the excessive oscillations. The source of the free air present in physical phasers are not yet fully understood, but the movement of the phaser control valve, opening and closing of the phaser chamber vents, in conjunction with motion of the phase oscillations has a significant effect on the phaser's chamber pressure, resulting in reduce pressures. The reduced pressures result in air being sucked in to the phaser, form both the oil control valve vent and external chamber leakages. Another potential sources of free air is dissolved air in the oil supply being released due to low pressures from oil pressure fluctuations. A potential solution to increase the stability of the phaser is to reduce the sources of air, by having an oil accumulator at the vent, limiting leakage, having a high and steady oil supply pressure, modifying the oil control valve ports to have a more gradual initial opening area and controlling the oil control valve appropriately. How to implement these implementations and evaluate them are left as future work. Potential improvements to get rid of the 1-d simulation model's dependence on the time step, increasing the model's reliability, are discussed, but not tested.

The ability to control engine valve timing has the potential to alter the engine performance over the entire operating range. The outcome of valve timing technology enables the possibility to increase efficiency, lowering emissions, increase engine torque, etc. One of the simplest ways to obtain a variable valve timing is to use cam phasers. The dynamics of a hydraulic cam phaser has been studied, three concepts with the purpose to control such an element has been developed using simulation driven product development. Focus have been on robustness, simplicity and implementation. A final concept using on/off solenoids to control a torque driven cam phaser has been designed and simulated in GT-SUITE which validated its performance and functionality. A dynamic model was built in Simulink which simulated the behaviour of the cam phaser and provided tools for optimizing the rotor design. By combining the knowledge of mechanical- and control engineering at Scania, the development process of such machine elements was effective. The outcome of this thesis has given a new perspective in understanding these components and their potentials.