UBC Theses and Dissertations
A cogging-torque-assisted motor drive for internal combustion engine valves Reinholz, Bradley
Internal combustion engine valve trains form the interface between the intake and exhaust systems and largely contribute to the overall engine performance, emissions and efficiency. Most modern engines use a camshaft to operate the valve train, but suffer from suboptimal performance since valve events cannot be dynamically altered during transient engine operation. Electromechanical valve actuation is a type of variable valve actuation that uses electromechanical actuators to replace the camshaft in an internal combustion engine. Electromechanical valve actuation promises to improve engine performance, reduce fuel consumption and lower harmful emissions by allowing for fully-independent control of the intake and exhaust valves. A major goal of electromechanical valve actuation is to achieve fully-independent valve control while minimizing the impact on concomitant systems, such as the charging and cooling systems. A new type of electromagnetic actuator is presented in this thesis, which uses cogging torque to recover kinetic energy in the form of a magnetic field. Cogging torque allows the presented actuator to be much more efficient and compact compared to other electromechanical valve actuators that use external mechanical spring systems. To utilize cogging torque effectively, design motivations are initially established and used to conceptualize a practical and efficient design. The proposed design is first simulated to predict its performance and later is experimentally validated using a fabricated prototype. The results of the experiments reveal a highly efficient and fast actuator design compared to other electromechanical actuators found in literature. The energy loss is further reduced by generating an optimal kinematic trajectory using the Nelder-Mead algorithm. The optimal kinematic trajectory enabled the proposed actuator design to be the most efficient electromechanical valve actuator found in literature. The results presented show the novel actuator design reduced losses by over 40% when compared with the most efficient electromechanical valve actuator published in literature and by over 70% when compared with a conventional camshaft. The conclusions of this thesis suggest a cogging-torque-assisted actuator could be feasibly retrofitted into an existing engine with only minor modifications due to its compact and highly efficient nature.
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